Citation
Petrogenesis of Andesites and Dacites from the Southern Juan de Fuca Ridge

Material Information

Title:
Petrogenesis of Andesites and Dacites from the Southern Juan de Fuca Ridge
Creator:
COTSONIKA, LAURIE ANN ( Author, Primary )
Copyright Date:
2008

Subjects

Subjects / Keywords:
Basalt ( jstor )
Crystallization ( jstor )
Crystals ( jstor )
Geologic fissures ( jstor )
Lava ( jstor )
Olivine ( jstor )
Oxygen ( jstor )
Pillows ( jstor )
Plagioclase ( jstor )
Pyroxenes ( jstor )

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright Laurie Ann Cotsonika. Permission granted to University of Florida to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Embargo Date:
3/1/2007
Resource Identifier:
649815577 ( OCLC )

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Full Text





PETROGENESIS OF ANDESITES AND DACITES
FROM THE SOUTHERN JUAN DE FUCA RIDGE




















By

LAURIE ANN COTSONIKA


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2006

































Copyright 2006

by

Laurie A. Cotsonika


































To my family.









ACKNOWLEDGMENTS

I would like to thank my advisor, Dr. Michael Perfit, for his patience and guidance

throughout this proj ect, and Dr. Matthew Smith for the support and help he' s given me in order

to complete this. I would also like to thank the Monterey Bay Research Aquarium Institute for

providing use of their equipment and facilities and the crew and officers of the Western Flyer, as

well as the pilots of the ROV Tiburon, for the hard work they put in during the cruise to the Juan

de Fuca Ridge. I would like to thank Dr. Debra Stakes and Dr. Jim Gill for lending their support

and expertise on the cruise and with interpreting my data. Dr. W. Ian Ridley deserves my thanks

for all the help and analytical support provided in Denver and Dr. Paul Wallace for providing the

volatile data. I would also like to thank George Kamenov for the help and analytical support

given while processing my trace element data.

I would like to thank my family, especially my parents, Art and Linda, and my brother and

sister, Nick and Elizabeth, who provided much needed emotional support and understanding. I

would also like to thank all my friends in the Geological Sciences department at University of

Florida.












TABLE OF CONTENTS


page

ACKNOWLEDGMENTS .............. ...............4.....


LIST OF TABLES .........._.... ...............7....__........


LIST OF FIGURES .............. ...............8.....


AB S TRAC T ............._. .......... ..............._ 10...


CHAPTER


1 INTRODUCTION ................. ...............12.......... ......


Regional G eology ................. .... ... .... ........... ...............1
Previous Studies of Highly Fractionated Suites Recovered at MOR ................ ..................14


2 STUDY AREA AND SAMPLE RECOVERY ................. ...............20...............


T73 5 Dive Ob servations ................. ...............21........... ...


3 ANALYTICAL METHODS .............. ...............27....


Maj or Elements ................. ...............27........... ....
Trace Elements .............. ...............28....


4 PETROGRAPHY AND MINERAL CHEMISTRY .............. ...............32....


Basalts ................. ........... ...............32.......
Andesites and Dacites ................. ...............32........... ....


5 MAJOR AND TRACE ELEMENTS .............. ...............48....


Basalts ............... .. ....._ ...............48...

Maj or and Minor Elements ........._...... ...............48..__... ....
Trace Elements .............. ...............50....
Andesites and Dacites ........._...... ...............52...__........

Maj or and Minor Elements ........._._.. ..... .___ ...............53....
Trace Elements .............. ...............53....


6 DI SCUS SSION ........._._.. ..... .___ ...............62.....


Comparison to Other Evolved Suites .............. ...............62....
Dive T73 5 S ampl es............... ...............64
Fractional Cry stallization............... ............6
M agm a M ixing ................ .. .. ... .... ............ ...............7
Partial Melting/Assimilation Fractional Crystallization (AFC) .............. ....................7












7 CONCLUSIONS .............. ...............84....


APPENDIX


A T73 5 DIVE LOGS ............ ..... ._ ...............86..


B PHASE CHEMISTRY FOR T735 LAVAS ...._.. ...._._._._ ......._.__. ...........0


C MAJOR AND TRACE ELEMENT DATA FOR T73 5 LAVAS ........._._ ..... ....._..........159


D PETROLOG RESULT S .............. ...............165....


LIST OF REFERENCES ............ ..... ..__ ...............178..


BIOGRAPHICAL SKETCH ............ _...... ._ ...............188...










LIST OF TABLES


Table page

1: Accepted values for maj or element standards. ................ ......... ...................3

2: ICP Trace element standards. 2005-2006 analyses of ENDV (ran as sample) together
with other MORB samples (drift 1 first sample after the standards)............... ...............3

B-1: Pyroxene compositions determined from microprobe analyses. ............. ....................10

B-2: Plagioclase compositions determined from microprobe analyses. .................. ...............132

B-3: Olivine compositions determined from microprobe analyses. ............. ......................154

C-1: Maj or and trace element data for Dive T73 5 samples ................. ............... 160..........

D-1: Results from Petrolog. Results assume QFM at 200 bars of pressure and sample T73 5-
G35 as the parent composition............... ..............16










LIST OF FIGURES


Figure page

1 Map of the Juan de Fuca Ridge ................. ...............17..............

2 Overview of MBARI dives and rock cores on the southern Cleft segment since 2000. ...18

3 Overview of the dive track taken during Tiburon Dive 73 5 ................ .. ......_. ........24

4 Profile map of dacite dome morphologies and evolved sample locations............._._.. ......26

5 Examples of basaltic lava morphologies seen during dive T73 5........._.. ..........._.......3 6

6 Plain polarized and cross polar views of glomeroporphyritic texture in T73 5-G23..........36

7 Dacite dome lava morphologes............... ..............3

8 Plagioclase oikocryst surrounding several randomly oriented clinopyroxene
chadacrysts in sample T73 5-G10 ........._._.._......_.. ...............37..

9 Element map of poikilitic texture seen in T73 5-G10, in this case, a plagioclase
oikocryst surrounding low-Ca pyroxenes .............. ...............38....

10 Point compositions of pyroxene phenocrysts in T73 5-G9 and T73 5-Gl2 are plotted
to show zoning patterns. ............. ...............39.....

11 Oscillatory zoned clinopyroxene in sample T73 5-G9. ....._.._.._ ......_.._ ........._.....40

12 Skeletal clinopyroxene grain with a lacey reaction rim surrounding the crystal, this is
also indicative of rapid crystal growth. ....__ ......_____ .......__ ...........4

13 Populations of zoned pyroxenes ................ ......................... .................42

14 Olivine and plagioclase glomerophyric cluster ................. ...............43...............

15 Element map of skeletal fayalite crystal in sample T73 5-Gl2 ........._.._.. ....._.._.........43

16 Rare (<1% of the sample) euhedral zircon phenocrysts seen in samples T73 5-Gl2
and T73 5-Gl9 were discovered through microprobe analyses ................. ................ ...44

17 Plain polarized light (left) and crossed polarized light (right) views of a basaltic
xenolith in sample T73 5-Gl l....._.. ............... ...............45. ...

18 Element maps of a basaltic xenolith in sample T73 5-Gl2 .........._.._.. .......__. ..........45

19 A coarser grained xenolith, found in T73 5-G10, is composed of plagioclase, An34 -
An35, and fayalitic olivine, Fols............... ...............46..










20 Myrmekitic intergrowth of quartz and plagioclase .................... ............... 4

21 AFM Diagram comparing Smith, 1994 and Stakes, 2006 samples to dive T735
samples............... ...............55

22 Maj or element plots comparing previous studies of the Cleft segment (Smith et al.,
1994; Stakes et al., 2006) to dive T735 samples............... ...............56

23 Trace element plots comparing previous studies of the Cleft segment (Smith et al.,
1994; Perfit, unpublished) to dive T735 samples. ............. ...............58.....

24 The primitive mantle normalized (McDonough and Sun, 1995) spider diagram
displays the depletion of several key trace elements in the evolved glasses compared
to the basalt compositions. .............. ...............60....

25 The primitive mantle normalized (McDonough and Sun, 1995) REE plot shows the
two distinct groupings within the sample group. .............. ...............61....

26 Comparing maj or element variations in the T73 5 lavas to other evolved suites ..............75

27 Maj or element liquid lines of descent. .............. ...............77.....__.__ ..

28 Cumulative percentage of phases plotted against melt temperature (oC). .................. .......79

29 Trace element liquid lines of descent ................. ...............81........... ..

30 Mixing models calculated using a standard mass balance equation (Langmuir et al.,
1978). ............. ...............8 2....

31 Comparison of T73 5 C1V and Cl/K ratios versus MgO. ........._._......___ ........._....83









Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

PETROGENESIS OF ANDESITES AND DACITES
FROM THE SOUTHERN JUAN DE FUCA RIDGE

By

Laurie A. Cotsonika

December 2006

Chair: Michael R. Perfit
Major: Geology

The Cleft segment and the ridge-transform intersection (RTI) of the Southern Juan de Fuca

Ridge have been investigated during three cruises of Monterey Bay Aquarium Research

Institutes' (MBARI) Research Vessel (R/V) Western Flyer beginning in 2000. A total of 53 rock

cores and 276 precisely located rock or glass samples were collected during sixteen dives with

the remotely operated vehicle (ROV) Tiburon. These ROV dive samples and observations allow

us to test models regarding the magmatic evolution of this segment and the relationships between

specific tectonic and morphologic features and magmatic processes. An extremely wide range of

N-type mid-ocean ridge basalt (MORB) lavas were recovered which are, on average, more

evolved (lower MgO) off-axis, away from the present neovolcanic zone, and towards the RTI.

During dive T73 5 we investigated a region of unfaulted, curved volcanic ridges that overshoot

the Blanco Transform and 39 samples of lava ranging from ferrobasalt to andesite and dacite

(SiO2 = 50.1 to 66.9 wt.%; Mg# = 49.9 to 9.7) were recovered. The highly evolved lavas were

recovered from two large constructional domes comprised of unusually large pillow flows, and

extremely blocky, vesicular flows similar to some terrestrial silicic domes. Some of the

andesite-dacite hand samples are extremely vesicular with elongate vesicles (1-10 cm) in a

glassy matrix. Mineral assemblages are dominated by microphenocrysts of ferroaugite and









ferropigeonite, with lesser amounts of sodic plagioclase and FeTi oxides. Rare zircon, fayalite

and myrmekitic intergrowths of plagioclase and quartz are present. A few of the more magnesian

phenocrysts (xenocrysts?) exhibit fine normal zoning whereas more Fe-rich crystals exhibit fine

reverse zoning. Additionally, inclusions of quenched basaltic material appear within some of the

evolved lavas. These samples represent an extensive and unique set of some of the most highly

fractionated ocean floor rocks that have ever been recovered; particularly from such a well-

documented setting. Fractional crystallization models which predict over 80% crystallization do

not adequately explain the maj or element chemistry of the silicic lavas and most incompatible

trace elements exhibit significant enrichments relative to predicted concentrations. The highly

evolved nature of the dacites, crystal zoning patterns and the presence of basaltic inclusions

suggest the lavas are the result of mixing between two crystal bearing end-members, i.e. a typical

basalt and a rhyolite likely generated by extreme amounts of fractional crystallization. The

andesitic and dacitic lavas also have elevated C1f levels that range from 4000-6000 ppm. While

the Cl-/K levels are enriched they do not indicate that significant amounts of crustal assimilation

have occurred.









CHAPTER 1
INTTRODUCTION



Over 60% of the Earth' s magma flux, > 21 km3/yr, ~3 km3/yr extrusive and ~18 km3/yr

intrusive, takes place at mid-ocean ridges (MOR) (Chadwick and Embley, 1994; Perfit, 2001),

however less than 1% of the total seafloor total area has been sampled or studied in much detail

(Perfit and Chadwick, 1998) and that 1% has been concentrated upon ridge crests. Only a few

studies have focused on the broader area surrounding the immediate region of the ridge axis, and

therefore most investigations have been focused within a narrow neovolcanic zone centered at

the ridge axis. Studies centered on the ridge axis have generally not directly addressed the

processes that occur away from the ridge axis and at ridge-transform intersections (RTI). It has

recently been hypothesized that the areas 5-20 km off of the ridge axis possibly make a greater

contribution to the overall magma flux than previously thought (Goldstein et al., 1994; Graham

et al., 1996; Hekinian et a., 1999; Johnson et al., 2000; Klingelhofer et al., 2001; Zou et al.,

2002). Though published data regarding lavas erupted off-axis and at RTI's is sparse, it has been

suggested that greater amounts of fractional crystallization and assimilation can occur at these

locations. Limited magma recharge can lead to less homogenization of magmas at these

locations compared to the main axial magma body, allowing for more diverse and evolved lava

compositions to be erupted onto the oceanic floor (Christie and Sinton, 1981; Fomari et al.,

1983; Perfit and Fomari, 1983; Perfit and Fomari, 1983; Juster et al., 1989; Perfit et al.., 1994;

Perfit et al.., 1999; Stoffers et al., 2002).

In this thesis, field observations together with petrologic, major and trace element data are

utilized to determine the geochemical characteristics and petrogenesis of highly evolved lavas

recovered from the region of the intersection of the Juan de Fuca Ridge (JdFR) with Blanco









Fracture Zone (BFZ) (Figure 1). Lava samples recovered in 2004 during dive T735 of the ROV

Tiburon operated by the Monterey Bay Aquarium Research Institute (MBARI) represent an

extensive and unique set of some of the most highly fractionated oceanic rocks that have been

recovered from such a well-documented setting. This, in conjunction with the extensive

sampling of the Cleft segment of the southern JdFR and the associated geochemical database,

make it an ideal sample set to explore the magmatic processes involved in the petrogenesis of

samples from the RTI.

Regional Geology

The JdFR in the northeast Pacific is an intermediate spreading rate ridge (56 mm/yr full

rate) that has been extensively studied beginning in the 1960s (Raff et al., 1961; Johnson and

Holmes, 1989; Embley et al., 1991; Smith, 1993; Perfit et al., 1994; Smith et al., 1994; Perfit et

al., 1998; Perfit, 2001; Karson et al., 2002; Tiemey, 2003; Stakes et al., 2006). It is located

approximately 440 km (~23 8 nm) off of the coast of Washington and Oregon and spans almost

500 km between the Blanco and Sovanco Fracture Zones.

The JdFR has been divided into seven second-order ridge segments that have distinct

morphological characteristics (Embley et al., 1991; Embley et al., 2000; Smith et al., 1994;

Chadwick et al., 2005). The Cleft segment (Figure 2) is the southernmost segment with its

northern terminus at ~45003'N and its southern terminus at 44027'N where it intersects the

Blanco Fracture Zone (BFZ) (Embley et al., 1991; Smith et al., 1994). The Cleft segment has

recently been volcanically active and has proved to be an important area for detailed

investigations of submarine volcanology, hydrothermal activity, eruption rates, and MOR

petrogenetic processes. Chadwick and Embley (1994) summarized studies of several mid-ocean

ridge basalt (MORB) lava flows believed to have erupted in 1983 and 1987 along the axis of the

Cleft segment and estimated, following Crisp, (1984) that the average extrusive output along the









whole Cleft segment is 0.003 km3/yr. Extrusive activity was determined to be bimodal with

sheet flows preceding a voluminous eruption of pillow flows (Embley and Chadwick, 1994).

The overall extrusive layer of the Cleft segment has an average thickness of 3 50 m and varies

from 200 to 550 m in thickness (McDonald et al., 1994) while depth to the axial magma chamber

(AMC) varies from 1.9 km under the southern Cleft hydrothermal vent systems to 2.23 km under

the northern hydrothermal fields (Canales, 2006). There is a strong correlation in the Cleft

segment between degree of fractionation and latitude, as lavas are generally more mafic to the

north and more evolved toward the southern terminus (Christie and Sinton, 1981; Smith et al.,

1994, Stakes et al.. 2006).

Since 2000, 53 rock cores and 276 rock and glass samples have been recovered from the

Cleft segment using the Remotely Operated Vehicle (ROV) Tiburon (Stakes et al., 2006; Figure

2). Overall, a wide range of normal incompatible element depleted MORB (N-MORB) lavas

were recovered from the entire length of the Cleft segment. The most highly evolved basalts and

a few high-silica lavas were recovered off-axis, away from the neovolcanic zone, and near the

RTI. In 2000, a sample of MOR, low-potassium dacite was recovered by rock core from a small

topographic dome in an area of the Cleft segment characterized by what appear to be curved

ridges and volcanic cones that overlap the westernmost part of the Blanco Transform and appear

to extend on to the Pacific plate. The extremely rare occurrence (or at least recovery) of dacite in

a MOR setting was the impetus for a ROV dive in 2004 that explored these features at the RTI,

in a common yet poorly studied MOR setting.

Previous Studies of Highly Fractionated Suites Recovered at MOR

Highly fractionated suites of atypically high silica MOR lavas have been recovered in few

other locations around the globe; these include the Galapagos Spreading Center (GSC), Iceland,

the Pacific-Antarctic Ridge and a few places on the East Pacific Rise. Hypotheses put forth to










explain the formation of these petrologically evolved suites on the oceanic floor include the

"cold edge effect" (Christie and Sinton, 1981; Fornari et al., 1983; Perfit et al., 1983; Johnson

and Holmes, 1989; Juster et al., 1989; Embley et al., 1991; Smith, 1993; Smith et al., 1994;

Juteau et al., 1995; Tiemey, 2003; Herzburg, 2004), bimodal volcanism, similar to that occurring

in intrusive suites in the western United States (Reid et al., 1982; Barbarin, 1990; Ratajeski et al.,

2001), and, more recently, crustal assimilation (Kerr et al., 1996; Bohrson and Reid, 1998;

Garcia et al., 1998; Gee et al., 1998; Hoernle, 1998; O'Hara, 1998; Weis et al., 1998; Perfit et

al.., 1999).

The eastern GSC at ~850W has been extensively studied since the late seventies (Christie

and Sinton, 1981; Anderson et al., 1982; Fornari et al., 1983; Perfit and Fornari, 1983; Perfit and

Fomari, 1983; Juster et al., 1989). The discovery of chemically fractionated (high-silica) lavas

along the GSC first led to the development of the "cold edge effect" hypothesis (Christie and

Sinton, 1981; Fornari et al., 1983; Perfit et al., 1983; Juster et al., 1989). This type of "cold edge

effect" occurs along a propagating ridge axis as the advancing ridge magmatic system intersects

older, relatively cool oceanic lithosphere located on the opposite side of a fracture zone. This

intrusion presumably leads to greater extents of cooling in magma bodies causing the magma to

undergo more extensive crystallization than would occur in typical ridge axis settings where

magma chambers are believed to be more steady-state. This hypothesis is proposed to account

for the common occurrence of MOR ferrobasalts and FeTi basalts at propagating rift tips in the

Galapagos Spreading Center (Christie and Sinton, 1981) and lavas as evolved as andesites at the

RTI at ~850W (Fomari et al., 1983; Perfit et al., 1983; Juster et al., 1989).

Silicic volcanism has also recently been documented on the Pacific Antarctic Ridge (PAR)

(Hekinian et al., 1997, 1999; Stoffers et al., 2002; Haase et al., 2005). Stoffers and others (2002)









discovered different populations of evolved lavas, some consistent with crystal fractionation at

low and high oxygen fugacities, and others resulting from the magma mixing of highly

fractionated magmas and unevolved basaltic melts. They hypothesize that extensive crystal

fractionation occurred in a solidification zone surrounding a magma chamber (e.g. Nielson and

Delong, 1992). Residual silicic magma is proposed to migrate upward along the margin of the

magma chamber and assimilate altered basaltic wall-rock, increasing its oxidation state (Stoffers

et al., 2002). Haase and others (2005), associate the silicic lavas with a ridge axial high; a

location where large volumes of magma are found and where there is associated hydrothermal

venting. They further hypothesize that extensive fractional crystallization, facilitated by cooling

from the hydrothermal vent fields, as well as assimilation of hydrothermally altered crustal

material is responsible for the petrogenesis of the andesites and dacites found on the Pacific-

Antarctic Rise.

Recent studies have also considered the roles of fractional crystallization and crustal

assimilation in hotspot environments such as the Galapagos Islands (Geist et al., 1998) and

Iceland where crustal assimilation has been hypothesized to, in part, contribute for the

heterogeneous nature of Icelandic volcanism (Nicholson et al., 1991; Furman et al., 1995; Gee et

al., 1998).


















































Figure 1: Map of the Juan de Fuca Ridge. The Juan de Fuca medium-rate spreading ridge in
located between the Pacific Plate and Juan de Fuca. It is located approximately 440 km (~23 8
nm) off of the coast of Washington and Oregon and spans almost 500 km between the Blanco
and Sovanco Fracture Zones. The samples described in the thesis were recovered from the
southern intersection of the Juan de Fuca Ridge with the Blanco Fracture Zone, as highlighted by
the yellow box. Map created using the open source java application at www.geomapapp.org.













13?94' 130"52' 131~SO'


O hm

13WB' ~30r6' ~50114'


Figure 2: Overview of MBARI dives and rock cores on the southern Cleft segment since 2000.
53 rock cores and 276 rock and glass samples have been recovered from the Cleft segment using
the Remotely Operated Vehicle (ROV) Tiburon (Stakes et al., 2006). In 2000, a sample of dacite









was recovered by rock core from a small topographic dome in an area of the Cleft segment
characterized by what appear to be curved ridges and volcanic cones that overlap the
westernmost part of the Blanco Transform. Dive T73 5 covered the area where the dacite rock
core was taken (Stakes et al., 2006).









CHAPTER 2
STUDY AREA AND SAMPLE RECOVERY



In 1998 the Cleft segment was surveyed using a hull-mounted 30 k
multibeam sonar and using 2 degree by 2 degree beam resolution, the EM300 achieved a ~30 m

lateral resolution over a 3 km swath width (Stakes et al., 2006). The mapping program was

supplemented by a series of in situ observations made from the ROV Tiburon, operated from the

Research Vessel Western Flyer, during July 2000, August 2002 and August 2004 (Stakes et al.,

2006). A total of 16 ROV dives were completed across the Cleft spreading center; Hyve dives

across the axis near the South Cleft hydrothermal Hields; Hyve dives on the southernmost part of

the segment; two dives on the northern wall of the intersection with the BFZ and dive T73 5, the

focus of this thesis, on the hooked ridges that define the western side of the nodal basin where

the ridge axis intersects the BFZ (Figure 2).

Dive T73 5 utilized the ROV Tiburon in order to observe and sample the area where a

dacitic glass was recovered by piston core in 2000 (Figure 3). The dive was dedicated to

investigating the dome-like features observed in the bathymetry and recovering samples along a

dive traverse that began south of the core location and ended to the west of the southernmost

portion of the Cleft axial valley. A detailed sampling program was carried out as part of the

ROV and surface ship operations during the dive. Lava samples were recovered with the

Tiburon manipulator and details of each sampling locality were documented by the scientists in

charge of observations and sampling during each dive. The ROV observations, contemporaneous

magnetic field measurements, digital still and video images and geologic samples were all

located with respect to the EM300 bathymetry through a real-time ArcView-based navigation

and GIS system using the EM300 bathymetric basemap (Stakes et al., 2006). The bathymetric










data, ship locations and ROV USBL (ultra-short baseline) navigation used a common GPS data-

stream with real-time depth (from the ROV) providing consistent position information within 10-

20 meters of bathymetric features on the EM300 bathymetry. Below, the bathymetric,

observational and sample data are integrated to provide a detailed account of the geology along

dive T735.

T735 Dive Observations

Dive T73 5 began at 14:49 Greenwich Mean Time (GMT) on a talus slope at the southern

end of the dive track (Figure 4) but soon crossed an area dominated by lightly sedimented, intact,

basaltic pillow flows, crosscut by several N-S trending fissures. Basalt samples T735-Gl, at

2187 m, through T73 5-G6, at 2216 m, were recovered from this area, before Tiburon began to

traverse upslope. At 16:05 GMT an area of lava drain-back was observed, with moderate

sediment cover in between the pillows and lobate flows. At 16: 13 an area of more blocky flows

was observed and sample T745-G7, a basalt, was recovered from the top of a small knoll (2213

m). At 16:25 GMT Tiburon dropped over the edge of a fissure and moved into an area of thick

sediment cover with isolated pillows basalts. Sample T73 5-G8 was recovered from this area at

16:39 GMT at 2232 m depth. Tiburon then moved through an area of isolated pillows with <50%

sediment cover, before reaching an area of lightly sediment covered, large striated pillows and

associated sheet flows.

Sample T73 5-G9, a dacite, was recovered at 16:45 GMT from a friable sheet flow at the

base of the first of the domes. Samples T73 5-G10 and G11i, both dacitic in composition, were

recovered from large (> Im in diameter), glassy, striated pillows lightly covered with sediment

observed in conjunction in the sheet flows that flowed down the slope to the southwest. As

Tiburon continued to traverse upslope the flows became more blocky and massive, with vapor

pockets and cavities observed between the layers of rock and very little sediment cover. T73 5-










Gl2, one of the most evolved dacitic samples, was collected at 16:59 GMT from one of the

vapor pockets observed in the area at 2211 m depth and was extremely glassy in appearance.

Tiburon then passed over an area with more local relief, in the form of big, sediment-coated

pillows with bread-crust textures surrounded by smoother pillow tubes.

At 17:06 GMT Tiburon moved into an area of fractured sheet flows where andesite

samples T735-Gl3 (17:09 GMT) and Gl4 (17:22 GMT) were collected. At 17:27 GMT,

smoother pillow forms and tube morphologies dominate with more massive flows between.

Then sample T73 5-Gl5, another andesite, was recovered from a region of highly vesicular (10-

15% vesicles), blocky flows on top of what appeared to be a constructional dome at 17:32 GMT.

The interior of the blocky flows was sampled at 17:46 GMT (T745-Gl6) at 2216 m and is dacitic

in composition. After collecting T735-Gl6 Tiburon began to traverse down-slope to the east.

Pillows with bread-crust texture were observed under moderate (<30%) sediment cover. Down

the slope of the dome at 18:06 GMT sample T735-Gl7, a dacitic pillow fragment, was recovered

from a saddle at 2221 m.

To the east, up, out of the saddle, another dome structure was encountered. At 18:16 GMT,

two small pieces of andesitic pillow crust were collected at 2206 m. Continuing upslope, smaller

pillow forms (< 1 m in diameter) were observed up to the top of the dome at 2198 m where the

morphology was dominated by flattened lobate tubes, some of which appeared to flow down-

slope to the south. Sample T73 5-Gl9, an andesite was recovered from the top of the dome

construct at 18:25 GMT.

At 18:29 GMT Tiburon began the slow descent down-slope over a structurally undisturbed

area consisting of well-formed pillows and tubes with only moderate sediment cover. At 18:36

GMT blockier, broken pillows and tubes were observed along a shallow slope. At 2234 m,









18:3 5 GMT, sample T73 5-G20, a dacite, was recovered from a small pile of talus near an in situ

pillow flow. This flow front of pillows over talus continued for a few 10's of meters before the

slope began to steepen towards the east.

Sample T73 5-G21, a large basaltic fragment from an intact pillow, was recovered from the

base of the steep slope at a depth of 2275 m at 19:01 GMT. A region of heavy sediment cover

with isolated pillows was then traversed. Sample T735-G22, was recovered at 19:16 GMT, 2256

m, from an area of extensive collapse (likely drainback) that was associated with sheet flows

under moderate sediment cover. A sample of an isolated basaltic pillow, T735-G23, was

recovered at 19:26 GMT from 2250 m in depth. Afterwards, pillows began to dominate the

landscape once more; recovery of samples G24 and G25 began at 19:37 GMT and they were

both collected from a haystack at a depth of 2249 m. The northern portion of the dive covered

much more tectonized terrain within a zone of pillow ridges separated by N-S trending fissures.

Samples T73 5-G26 through G39, all basalts, were recovered from pillow to lobate flows within

this region.













DIVE T735 (Cleft Dive #1) AUGUST 31, 2004
13P28'30" 130~'2BDD 1305t730' 13057'00'


13P28'31"


1302B'00" 1302730" 130'27'00"


Figure 3: Overview of the dive track taken during Tiburon Dive 735. Yellow dots denote sample
locations, while yellow bulls' eyes denote the 2000 rock cores. The 2000 rock core was









recovered near the T735-Gl5 sample site. The evolved sample set is represented by samples
T73 5-G9 through T73 5-G20.




















B*























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Figure 4:Poiempo aiedm opooie n vle apelctos rfl
esimte frmt edetofteR VBaatsmlsaedsgaebyteludi ons

andeiti sape r eintdb rng rage n aie yre icewt vr it

sample ben nubrd ag hne nth O shaigaentd









CHAPTER 3
ANALYTICAL METHODS



Thirty-nine lava samples were collected from the RTI of the JdFR and the BFZ during dive

T73 5 of the ROV Tiburon during the MBARI research cruise in 2004. Thin-sections were made

of a representative suite of the evolved samples and one basalt recovered during the dive.

Natural glasses were separated and coarsely crushed, and crystal-free glass separates were hand-

picked under a binocular microscope. Evolved lavas had fairly crystalline glass and in picking

those glass chips, crystal clots and phenocrysts were avoided and the least crystalline chips were

chosen for analysis. The crushed glass chips were then ultrasonically cleaned for 10-20 minutes,

in a solution made from equal parts 2.5N reagent grade HCI and 30% H202 in Order to remove

any surficial coatings, such as MnO, adhered to the sample.

Major Elements

Clean glass chips were mounted to thin sections for microprobe analysis, with glass from

UJF internal standard 2392-9, an N-MORB from the East Pacific Rise at 90 50' N, included on

each slide. Major element concentrations were determined on natural glasses using JOEL

electron microprobes at the United States Geological Survey (USGS) in Denver, CO, with the

help of Dr. Ian Ridley, and at Florida International University (FIU) by Dr. Michael Perfit.

Traditional mineral standards were used to calibrate the microprobe analyses and secondary (off-

line) normalizations were completed using the UF standard 2392-2, and the USGS standard

GSC, a synthetic andesite microbeam glass (Riehle et al., 1999). Accepted values for these

standards are given in Table 1. Operating conditions for the microprobe were an accelerating

voltage of 15 keV and a beam current of 20 nA. Probe diameter for mineral analyses was set to

<10 pm and defocused to 20 pm for glass analyses.










Typical precision was evaluated by comparing repeat analysis of UF standard glass 2392-9

(Table 1) which was mounted and analyzed on every probe slide. Percent variation in the 2392-9

analytical values was low, ranging from a one-sigma standard deviation of 6.4% in K20 to

0.13% in the SiO2. SiO2 ValUeS showed strong linear correlations with analysis total and were

corrected to using the following formula, [raw SiO2 value + ((99.7 raw total)*0.4505)], where

the raw silica value has an additional factor added to it consisting of an assumed total (99.7)

minus the raw total multiplied by the slope of the trend-line of raw SiO2 VeTSus the raw total

(0.4505).

Trace Elements

Trace element concentrations were determined at the University of Florida using an

Element 2 Inductively Coupled Plasma- Mass Spectrometer (ICP-MS). Dr. George Kamenov

developed the dissolution and analytical procedures (see below). Sample preparation was

performed at UF in a class 1000 clean lab facility. Standards used included the well-

characterized internal UF standards 2392-9 and ENDV, as well as the USGS standard BHVO-1,

the surface layer of a 1919 Hawaiian pahoehoe flow (Flanagan, 1976). Trace elements measured

by the UF ICP-MS have been determined to be accurate and precise to better than 15% of their

concentration (Table 2).

Phase one of the dissolution process requires that two to three standards encompassing

the likely potential range of the unknown sample concentrations be chosen; for the T735 run

AGV-1 and BCR-2 were used and compared along with two in-house standards, ENDV and

2392-9. Next, tall, clean, hex-cap Savillex Teflon vials were labeled for each sample, including

one blank. Two drops of 4x water were placed in each vial and the scale was zeroed before ~.04

g of either clean glass chips were added to each vial and the precise weight was recorded. In the

clean lab, 1 mL of optima grade HF and 2 mL of optima grade HNO3 were added to each vial









and then the vials were tightly capped and placed in a 1000C oven for approximately 48 hours.

Samples were then dried down on a hot plate (carefully rinsing the caps into the vials with 4x

water) for 12 to 24 hours.

In phase two of the dissolution process, 4 mL of an internal standard (5%HNO3, with Re

and Rh) was measured into each vial. The vials were then capped and heated on the hot plate

overnight.

In order to dilute the samples for analysis 200 CLL of solution was pipetted from each vial

and transferred to a clean auto sampler tube and weighed. Four mL of the same internal standard

was added to each tube and the samples were weighed again. The final dilution factor was

approximately 2000x.

Samples were introduced into the ICP-MS in one-minute uptake times followed by two-

minute washes for each sample. The specific isotopes analyzed were: Sc45, V 1, Cr52, CO59, Ni60,

Cu63, Zn66, Ga69, RbsS, Srss, Y89, Zr90 N 93, Rhl03, Bal137, Lal139, C140, Prl41, Ndl43, Sml49, Eul53,

Gd 5, Tbl59, Dyl63, Hol65, Erl66, Tml69 ybl72, Lu 7, Hf 7, Ta s, Re s, Pb208, Th232 and U238

Four runs were made with four passes per analysis in Medium Resolution mode.

Data were reduced on-line using calibration curves of the standard data acquired during

analyses and drift corrections were mathematically calculated off-line. The ENDV standard was

used for drift corrections during each analytical run; one measurement was taken at the

beginning of the sample series, one in the middle and one at the end of the series. Accuracy and

precision for the T735 analytical run was evaluated by analyzing ENDV standard as a sample

and comparing the results to recent runs of the standard using the same ICP-MS instrumentation

(Table 2). One-sigma standard deviations from the accepted values were less than or equal to

3.6% during these analyses.











Table 1: Accepted values for maj or element standards.


Internal UF Standard 2392-9 Correction Factors


SiO2 SiO2 TiO2 Al203 FeO MnO


MgO CaO Na20 K20 P205


for the averages of each group
average 50 49.49
std dev 0 0.20
% var 0 0.41
2392-9 50.04 50.04
correction
factor 1.00 1.01


for all analyses together
average 50 49.52
std dev 0 0.29


1.28 15.41 8.99 0.15
0.02 0.19 0.05 0.01
1.57 1.22 0.50 5.13
1.31 15.48 9.38 0.18

1.03 1.00 1.04 1.18



1.28 15.41 8.99 0.15
0.04 0.20 0.10 0.02
0.04 1.32 1.07 14.73
1.31 15.48 9.38 0.18


8.23 12.04
0.08 0.06
0.96 0.53
8.50 12.15

1.03 1.01



8.24 12.05
0.14 0.13
1.69 1.06
8.50 12.15

1.03 1.01


2.62 0.10 0.11 0.004
0.03 0.01 0.01 0.001
1.33 6.43 5.59 22.79
2.56 0.09 0.12

0.98 0.92 1.07



2.62 0.10 0.11 0.004
0.06 0.01 0.03 0.003
2.39 11.77 27.06 71.99
2.56 0.09 0.12

0.98 0.92 1.07


% var
2392-9
correction
factor


1 0.58
50.04 50.04


1.01 1.01 1.03 1.00 1.04 1.17


GSC Andesitic Glass Correction Factors


SiO2 TiO2 Al203 FeO MnO MgO CaO Na20 K20 P205 C1V
average 62.11 0.01 13.71 6.27 0.02 3.77 4.99 3.58 3.63 0.04 0.01
std dev 0.45 0.02 0.21 0.10 0.01 0.07 0.05 0.33 0.05 0.02 0.00
% var 0.73 146.27 1.56 1.57 56.90 1.73 1.10 9.11 1.30 49.46 73.04
GSC 62.05 0.01 14.20 6.33 0.03 3.89 5.00 4.06 3.60
correction
factor 1.00 0.85 1.04 1.01 1.75 1.03 1.00 1.13 0.99


Final Correction Factors Used


SiO2 TiO2 Al203 FeO MnO MgO CaO Na20 K20 P205


Evolved
RX
Basalts


1.1
0.97


1.04 1.1 1.03


1.07











Table 2: ICP Trace element standards. 2005-2006 analyses of ENDV (ran as sample) together
with other MORB samples (drift 1 first sample after the standards).



Std %~
ENDV Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Avg dev error
(ppm) (g/mL) (g/mL) (g/mL) (g/mL) (pLg/mL) (pLg/mL) (pLg/mL)
Sc 38.00 39.20 39.30 37.63 38.41 37.55 36.66 39.18 38.27 1.02 2.67
V 275.60 278.82 278.53 269.72 268.44 268.33 262.17 275.48 271.64 6.17 2.27
Cr 290.20 297.94 292.23 279.24 285.96 264.80 262.94 277.86 280.14 13.13 4.69
Co 34.40 35.06 34.82 34.32 35.28 35.06 34.74 35.84 35.02 0.48 1.36
Ni 76.20 77.93 77.24 75.36 76.13 76.13 75.21 78.85 76.69 1.36 1.77
Cu 72.40 72.86 73.02 70.64 72.69 71.41 70.83 72.38 71.98 1.00 1.39
Zn 73.15 78.03 79.20 78.95 78.93 77.45 78.75 77.78 2.13 2.74
Ga 17.20 17.19 16.76 16.91 16.73 17.07 16.86 17.02 16.93 0.17 0.99
Rb 4.38 4.54 4.40 4.37 4.53 4.24 4.26 4.38 4.39 0.12 2.68
Sr 155.80 162.21 156.59 155.15 154.02 153.99 155.42 154.84 156.03 2.87 1.84
Y 32.40 31.65 32.62 32.47 31.96 31.31 31.23 32.81 32.01 0.64 1.99
Zr 113.40 112.58 114.04 112.39 111.96 110.72 110.07 105.06 110.98 2.91 2.62
Nb 6.46 6.62 6.47 6.39 6.34 6.29 6.26 6.46 6.40 0.12 1.93
Ba 64.20 69.90 73.28 70.87 72.80 71.86 71.27 68.19 71.17 1.74 2.44
La 6.02 6.01 6.02 5.97 5.92 5.93 5.90 6.00 5.96 0.05 0.78
Ce 15.60 15.90 15.69 15.40 15.41 15.49 15.52 15.72 15.59 0.18 1.18
Pr 2.46 2.52 2.53 2.44 2.44 2.46 2.44 2.49 2.47 0.04 1.59
Nd 12.60 12.63 12.56 12.60 12.43 12.49 12.21 12.78 12.53 0.18 1.43
Sm 3.76 3.85 3.78 3.76 3.75 3.79 3.74 3.78 3.78 0.04 0.94
Eu 1.34 1.36 1.33 1.33 1.32 1.34 1.33 1.33 1.34 0.01 0.92
Gd 4.88 4.80 4.94 4.88 4.83 4.77 4.76 4.97 4.85 0.08 1.71
Tb 0.86 0.84 0.86 0.86 0.85 0.84 0.83 0.86 0.85 0.01 1.54
Dy 5.28 5.31 5.35 5.29 5.21 5.18 5.21 5.36 5.27 0.07 1.41
Ho 1.10 1.13 1.13 1.10 1.09 1.13 1.11 1.13 1.12 0.02 1.75
Er 2.98 3.13 3.08 2.97 3.03 2.99 2.99 3.02 3.03 0.06 1.84
Tm 0.48 0.48 0.50 0.48 0.49 0.48 0.48 0.49 0.48 0.01 1.51
Yb 3.12 3.12 3.14 3.11 3.15 3.10 3.05 3.12 3.11 0.03 1.03
Lu 0.48 0.49 0.47 0.49 0.49 0.46 0.46 0.48 0.48 0.01 2.83
Hf 2.88 2.85 2.95 2.88 2.83 2.79 2.78 2.63 2.81 0.10 3.56
Ta 0.38 0.37 0.37 0.39 0.37 0.38 0.38 0.39 0.38 0.01 2.34
Pb 2.00 2.06 2.05 1.97 1.97 1.97 1.99 2.07 2.01 0.05 2.26
Th 0.46 0.47 0.46 0.46 0.46 0.46 0.46 0.45 0.46 0.01 1.45
U 0.19 0.20 0.19 0.18 0.19 0.19 0.19 0.19 0.19 0.00 2.07









CHAPTER 4
PETROGRAPHY AND MINERAL CHEMISTRY

Basalts

Approximately two thirds of the samples recovered from dive T73 5 were basaltic in

composition, although all are moderately to highly evolved compared to previously published

Cleft MORB lava compositions. Basaltic lava morphologies ranged from pillow tubes to sheet

flows (Figure 5). Basalt hand samples have a thin glass rind with a microcrystalline interior

containing macroscopic plagioclase laths and pyroxene crystals.

A thin section was made of sample T73 5-G23 going from the surface of the hand sample

into the microcrystalline interior. The thin section average ~80% glass with ~20% quenched

microphenocrysts of plagioclase, ranging from 2 3 CL to 2 mm in length, with the average being

~ Imm in the groundmass. Larger glomeroporphyritic clusters comprised of euhedral to

subhedral, Imm long plagioclase laths, An64-An7o, with simple Carlsbad twins and stepped,

irregularly spaced twinning, and inter-grown anhedral crystals of augitic clinopyroxene (Figure

6) are present, with an Mg# of~-81.3, with the Mg# being defined as 100* [Mg/[Mg+Fe]].

Andesites and Dacites

Of the 39 lava samples collected, 12 were found to be high-silica lavas, five of which are

andesitic (52% < SiO2 <63%) and seven are dacitic (63%
lavas were recovered from two large constructional domes, approximately 34m in height, ~200

to 500 m in diameter, comprised of atypically large vesicular pillow flows, and extremely

blocky, vesicular flows (Figure 7). The flows appeared to be fresh, due to the lack of significant

sediment cover and the thinness of the manganese coating on the recovered hand samples. Some

of the andesite-dacite hand samples are extremely vesicular (10 15%) with elongate vesicles

(1-10 cm) in a glassy matrix. In hand specimen, the samples are composed of a glassy matrix









with small crystals and crystallites (~20 30%) of swallowtail plagioclase, pyroxene and

fayalitic olivine as well as larger semi-circular fragments of darker basaltic xenoliths scattered

throughout. Phase chemical data are presented in Appendix 2. Andesite and dacite assemblages

are dominated by microphenocrysts of ferroaugite and ferropigeonite, lesser amounts of sodic

plagioclase and FeTi oxides, and rare fayalite, zircon and myrmekitic intergrowths of plagioclase

and quartz. Fine-grained basaltic xenoliths are included within all of the evolved lavas.

Matrix glass is variable in color ranging from light to dark brown, nearly opaque, in

proximity to the basaltic xenoliths. Individual euhedral to rounded, subhedral plagioclase laths,

Anls An59, WeTO found scattered throughout the thin-sections and comprise ~5 10% of the

volume of the samples. Crystals have lower first order colors and simple Carlsbad twins or

stepped, irregularly spaced twins. Rare plagioclase oikocrysts with clinopyroxene chadacrysts

are present in one sample, T735-G10 (Figure 8, 9). Plagioclase crystals have two distinct

compositional groupings in the evolved samples. Plagioclase ranging from An69 to An83, OCCUT

in xenolithic clots and as large xenocrysts that appear to be in disequilibrium. More sodic

plagioclase, An38 An66, Occurs in the smaller, equilibrium crystals and in the myrmekitic clot.

Most individual clinopyroxene crystals exhibit finely zoned rims surrounding a more

massive core. Several examples of both normal and reverse zoning are observed in the

clinopyroxene grains in the evolved rocks (Figure 10). Rare clinopyroxene crystals with

oscillatory zoning, or hourglass sector zoning were also observed in these samples, a

phenomenon that has been associated with rapid crystal growth (Carpenter, 1980; Shelley, 1993).

Additionally, the observed sector zoning is commonly combined with fine concentric zoning of

crystal rims (Figure 11). Skeletal clinopyroxene crystals, also indicative of rapid crystal growth,

exhibit lacey, almost spongy, reaction rims (Figure 12). The cores of the pyroxene crystals fall









into two distinct groupings, with one group exhibiting cores that range from Mg# of 56.0 58.6,

and the other range in core Mg# from 8.24 12.6. In addition to these two groupings, there is

also a population of individual pyroxenes, Mg# ranging from 29.3 30.21, whose compositions

correspond with those of the rims in the zoned pyroxenes (Figure 13).

Rare fayalite crystals, Fos Fols, were found in several of the evolved lavas. In plain

polarized light (PPL) these crystals are rounded or embayed and have a deep green color (Figure

14). In crossed polars (XPL) the fayalite crystals displayed high second order colors and a low

2V angle of ~500. Skeletal fayalite crystals have lacey to spongy reaction rims similar to those

seen on the quenched clinopyroxene crystals (Figure 15).

Rare (occurring <1% by volume of the sample) subhedral zircon crystals were found in

several of the dacitic to rhyodacitic samples (Figure 16). Zircons were first discovered through

microprobe analyses and later identified by their high relief and very high birefringence in thin

section. Zircon grains occur almost exclusively as individual grains with no apparent connection

to xenoliths or crystal clots.

Two populations of xenoliths were found in the evolved samples. Rounded xenoliths of

basaltic composition with chilled margins and microcrystalline interiors (Figure 17; Fiigure 18)

and coarse-grained xenoliths composed entirely of large crystals, > 1mm, with rough, irregular

shaped edges. The basaltic xenoliths are composed of plagioclase, An32 An71, and pyroxene,

Mg# ranging from 56.7 to 80.9, and range in size from <1 mm to several mm in diameter.

Larger crystals (>0.5 mm in length) are usually confined to the center of the xenoliths and can

become subophitic in texture with large pyroxene crystals partially enclosing smaller plagioclase

laths. Basaltic xenolithic inclusions have very dark, glassy to microcrystalline interior edges that









extend around the circumference of the inclusions. An optically clearer (PPL) and less

crystalline and darker zone, ~. 1-.5 mm thick, surrounds many of the xenoliths.

The coarser grained xenolith, found in T73 5-G10, an andesite, is composed of plagioclase,

An34 An35, and fayalitic olivine, Fols (Figure 19). It exhibits no mineralogical reactions along

the margin, but the edges of the xenolith are ragged and look like they were ripped from the

country rock.

A single, resorbed myrmekite of plagioclase, An27 An30, and quartz was found in sample

T735-Gl9 (Figure 20). This is typically a plutonic texture that occurs primarily through grain-

boundary reactions in slowly changing conditions (Shelley, 1993). The myrmekite is rounded

and ~1 mm in diameter, with worm-like intertwining of plagioclase and quartz.

























Figure 5: Examples of basaltic lava morphologies seen during dive T73 5. Left: Lobate flows at
the top of a fissure. Lobates usually form at the edges of sheet flows when the lava flow slows
enough to form a fluid core under a solid crust. Right: Pillows, ~lm or less in diameter, and
pillow buds under moderate sediment cover. Pillows form when the extrusion rate of the lava is
slow enough to form a thick outer crust around the erupting lava.



















Figure 6: Plain polarized and cross polar views of glomeroporphyritic texture in T73 5-G23.
Thin sections average ~80% glass with quenched microphenocrysts of plagioclase scattered
throughout the groundmass. The larger glomeroporphyritic clusters were comprised of euhedral
to subhedral, Imm long plagioclase laths, An64-An70, and inter-grown anhedral crystals of augitic
clinopyroxene, with an Mg# of ~81.3.

























Figure 7: Dacite dome lava morphologies. The dacite domes display much different types of lava
morphologies then those seen where basaltic samples were recovered. Left: Blocky, vesicular
flow at the edge of one of the dacite domes. The large amount of vesicles seen is a by-product of
the degassing lava. Right: Extremely large pillow tubes (>1.5m in diameter) were also noted
cascading down-slope on the domes.




















Figure 8: Plagioclase oikocryst surrounding several randomly oriented clinopyroxene
chadacrysts in sample T73 5-G10. This poikilitic texture can be indicative of plutonic origins and
it indicates that the oikocryst mineral had a much more rapid growth rate then the enclosed
chadacrysts (Shelley, 1983; Higgins, 1998).







































Figure 9: Element map of poikilitic texture seen in T73 5-G10, in this case, a plagioclase
oikocryst surrounding low-Ca pyroxenes. Element map were completed using X-ray imaging on
the JOEL microprobe. Element labels are under each picture and count scales are located on the
right-hand side of the images. Brighter colors indicate higher concentrations of a particular
element. The gray-scale image is the backscatter image in which elements with higher mass are
displayed brighter.





Zoning Patterns

40
35
30
25


15


10

0 0.2 0.4 0.6 0.8 1 1.2
Relative Distance from Core to Rim



Figure 10: Point compositions of pyroxene phenocrysts in T735S-G9 and T735S-Gl2 are plotted to
show zoning patterns. Oscillatory (points 1-4; blue line) and reverse (points Sand 6; pink line)
zoning can be seen in the pyroxene from T735S-Gl2 (right). The pyroxene from sample T735S-G9
(left) also demonstrates compositional zoning through its hourglass pattern.





































Figure 11: Oscillatory zoned clinopyroxene in sample T735-G9. This crystal texture is indicative
of rapid crystal growth. Note the fine concentric zoning on the edges of the crystal and the
reversely zoned pyroxene to the upper left of the large crystal. Mapping details in Figure 9.







































Figure 12: Skeletal clinopyroxene grain with a lacey reaction rim surrounding the crystal, this is
also indicative of rapid crystal growth. Mapping details in Figure 9.





fU
60
50

403

20
10

0 0.2 0.4 0.6 0.8 1 1.2
Relative Distance from Core to Rim



Figure 13: Populations of zoned pyroxenes. There are two distinct populations of zoned
pyroxenes. One group exhibits cores that range from Mg# of 56.0 58.6, and the other range in
core Mg# from 8.24 12.6. In addition to these two groupings, there is also a population of
individual pyroxenes, Mg# ranging from 29.3 30.21, whose compositions correspond with
those of the rims in the zoned pyroxenes.


T735-12


Relative Distance from Core to Rim


T735-9

























Figure 14: Olivine and plagioclase glomerophyric cluster. Olivine is fayalitic in composition.


Figure 15: Element map of skeletal fayalite crystal in sample T73 5-Gl2. Note the lacey reaction
rim. Mapping details in Figure 9.





Figure 16: Rare (<1% of the sample) euhedral zircon phenocrysts seen in samples T735-Gl2 and
T73 5-Gl9 were discovered through microprobe analyses. Zirconium concentrations in the
evolved samples range from 397 to 672 ppm. They were later able to be recognized in thin
section due to their high relief and birefringence.









;"I (gFi~hq" ~ *:i~Cr Q1;
't-r~rl r
.ei'?
.SC1~X:~
r
,2 \ \-~51''57~

:uF
~ilj
-r ~;PI LS~
? g-r
.r
!:I
r$,
_X;I Y:~1 r
r ; '1/+

Figure 17. PPL (left) and XPL (right) views of a basaltic xenolith in sample T73 5-G1 i. Basaltic
xenoliths typically are rounded with slightly coarse grained interiors and chilled margins.


Figure 18: Element maps of a basaltic xenolith in sample T73 5-Gl2. Note the high Mg content,
indicating the basaltic nature of the xenolith. Mapping details in Figure 9.








































Figure 19: A coarser grained xenolith, found in T73 5-G10, is composed of plagioclase, An34 -
An3 5, and fayalitic olivine, Fols. The edges of the coarse grained xenolith are rough and there
are no signs of mineralogical reactions. Mapping details in Figure 9.






















































Figure 20: Myrmekitic intergrowth of quartz and plagioclase. The PPL view of myrmekitic
intergrowth of plagioclase, An27 SO, and quartz found in sample T73 5-Gl9. Element maps
of the myrmekite display the wormy intergrown texture of the quartz and sodic plagioclase.
Mapping details in Figure 9.





47









CHAPTER 5
MAJOR AND TRACE ELEMENTS

Basalts

Mid-ocean rdge basalts recovered from the Cleft segment exhibit geochemical

characteristics consistent with typical normal, incompatible element-depleted MORB (N-

MORB). Representative basaltic glass compositions are given in Table 3, with the complete data

presented in Appendix 3.

Major and Minor Elements

Basalt compositions are fairly evolved overall with nineteen of the twenty-three basalts

recovered being ferrobasalts (FeOT > 12.0 wt.%). Basalt compositions are tightly grouped with

MgO ranging from 7.55 weight % in the most primitive basalts to 6.29 wt% in the most evolved

basalt recovered (Table 3). The Al203 ValUeS decrease from 13.8 wt%, in the most primitive

basalt sampled, to 12.8 wt% in the most evolved. The CaO concentrations also fall, with

abundances decreasing from 11.8 wt% to 10.9 with decreasing MgO. The FeOT and TiO2 ValUeS

increase with decreasing MgO from 10.8 to 12.9 wt% and 1.61 to 2.26 wt% respectively.

Concentrations of Na20, K20 and P20s also increase with decreasing MgO, rising from 2.45 to

2.69 wt%, 0.12 to 0.20 wt% and 0. 14 to 0.25 wt% respectively. Lastly, MnO shows a loose

overall decline, from 0.24 to 0.18 wt% with decreasing MgO, the trend is scattered due to the

low concentration of the oxide in the samples. The maj or elements within the recovered basalt

suite all plot smoothly relative to MgO (and each other) with no maj or inflection points.

The T735 basalts have compositions similar to other southern JdF basalts but have limited

variation compared to the all of Cleft segment basalts, of which two hundred and eighty-six

samples were analyzed for major elements (Smith, 1994; Stakes et al., 2006; Figure 21).

Overall, Cleft segment MORB show relatively little maj or element chemical variation at any









given MgO content, forming well-defined geochemical trends consistent with differentiation via

low-pressure fractional crystallization of similar parental lavas (Smith, 1994; Figure 22).

Previously published data for Cleft segment lavas range in MgO from 10.5 wt%/ in the most

primitive basalts, to 4.41 wt% in the most evolved samples and reported Mg#'s range from 70.8

to 32.6. However, the maj ority of reported data exhibit MgO contents greater than 6 wt%, with

sixty samples extending the compositional range to the more evolved compositions. The maj or

elements for the T73 5 basalts all plot near the center of the overall range of MgO values (Figure

22).

The Al203 ValUeS of the T73 5 basalts are lower at a given MgO than in the existing Cleft

data set which ranges from 17.7 to 12.2 wt% with falling MgO (Smith, 1994; Stakes et al.,

2006). For example, at an MgO of ~7 wt% Cleft basalts range from 13.5 to 14.9 wt%, whereas

T735 samples range from 13.1 to 13.3 wt%. Similarly, FeOT COncentrations of T735 samples,

which range from 12.9 to 10.8 wt%, form a trend within the Cleft data trend which ranges form

7.92 to 16.3 wt% with falling MgO (Smith, 1994; Stakes et al., 2006). At an MgO of ~7 wt%

FeO ranges from 11.5 to 13.1 wt% in Cleft basalts, while T735 samples have a range of 11.07 to

1 1.22 wt%. Within the overall Cleft segment data, a group of 2 basalts, 8 ferrobasalts and one

andesite form an apparent subsidiary trend towards lower FeOT COncentrations, from 13.4 to 11.6

wt%, at values of MgO, ranging from 5.98 to 4.46 wt. % (Figure 22) while most of the Cleft data

exhibits an increase in FeO to~-16 wt%. It is important to note that the group of low FeO

samples exhibits a trend with decreasing MgO towards the compositions of the andesite and

dacite samples described below.

The TiO2 ValUeS for dive T73 5 basalts and ferrobasalts are relatively high particularly the

more evolved end of the ferrobasalts, which have values from 1.60 to 1.99 wt% TiO2 at a MgO









value of ~7 wt% and ranges from 2.02 to 2. 18 in the T73 5 dive samples. In both the Cleft

basalts, which range from 0.89 to 3.15 wt% TiO2 with falling MgO, and the T73 5 samples the

TiO2 trend in the basalts is one of increasing concentration with decreasing MgO. As with the

FeO data discussed above, there are several Cleft samples in the ferro-basalt/andesite range that

display relatively low TiO2 concentrations trending towards the compositions of andesites and

dacites recovered in dive T735. The CaO and Na20 data for T735 basalts and ferrobasalts fall

in the center of the data trends established by the Cleft samples, which range from 12.6 to 8.47

and 2. 11 to 3.38, respectively, with decreasing MgO. The observed trends of decreasing CaO and

increasing Na20 with decreasing MgO are also smooth, without inflection points.

Overall, the maj or element trends observed in the data support fractional crystallization of

plagioclase and olivine, indicated by the trend of decreasing Al203, with decreasing MgO

coupled with a trend of increasing CaO/Al203 with decreasing MgO observed in the most mafic

samples. It is likely that clinopyroxene enters as a crystallizing phase when the magma reached

approximately 7.9 wt% MgO, as indicated by the inflection point in CaO/Al203 (Figure 22)

which steadily decreases thereafter.

Water and CO2 COncentrations for two of the T73 5 basaltic lavas, T73 5-G23, and T73 5-

G35, the most mafic sample recovered, are 0.27 and 0. 17 wt. % and 118 and 101 ppm,

respectively. Chlorine concentrations for the T735 basalts range from 90 to 410 ppm with

decreasing MgO.

Trace Elements

Trace element concentrations in the T735 basaltic lavas lie within the compositional ranges

of other Cleft basalts (Figure 23). While the T73 5 basalts display little to no trend on their own,

when included with the reported Cleft data overall trends are apparent. Zirconium increases in a

tight, smooth pattern with decreasing MgO from 102 to 142 ppm in the T735 basalts and from









51.4 to 607 ppm in the Cleft samples (Smith, 1994; Perfit, unpublished). Yttrium also displays

an increasing concentration with decreasing MgO ranging from 37.6 to 53.4 ppm in the T73 5

samples and from 21 to 220 in the Cleft samples. Tantalum values plot in a tight group ranging

from 0. 15 to 0.29 ppm in the T735 data with a slight, but poorly defined, increasing trend vs.

decreasing MgO while the Cleft samples range in Ta concentration from 0. 11 to 0.90 ppm, with

most samples plotting within ~.1 ppm at given MgO contents. Lanthanum, Sm and Lu all show

well defined increasing trends plotted against decreasing MgO when included with the Cleft

samples. Lanthanum ranges from 3.40 to 5.24 ppm in the T735 samples and from 1.9 to 21 ppm

in the Cleft samples, respectively, Samarium ranges from 3.49 to 4.87 ppm and from 1.8 to 17.6

ppm respectively, and Lu ranges from 0.58 to 0.81 ppm in the T735 basaltic samples and from

0.30 to 3.44 ppm in the Cleft samples (Smith, 1994; Perfit, unpublished). Rubidium and Nb

show increasing trends that are less well-defined and show greater scatter than the trace elements

discussed above (Figure 23) when plotted against decreasing MgO. Rubidium ranges from 0.73

to 1.3 1 pmm in the T73 5 basaltic samples, while ranging from 0.24 to 5.8 ppm in the Cleft

samples and vary by ~2 pmm at ~7 wt% MgO ~2.7 ppm at an MgO of ~5 wt%. Niobium ranges

from 2.88 to 4.76 ppm in the T735 basalts and from 1.4 to 18.7 ppm in the Cleft samples (Smith,

1994; Perfit, unpublished).

Strontium and Cr both decrease in concentration with decreasing MgO (Figure 23).

Strontium shows an overall decrease with decreasing MgO, ranging from 118 to 99.7 ppm in the

T735 basalts and from 150 to 82.4 ppm in the Cleft samples (Smith, 1994; Perfit, unpublished).

The spread of the main body of data is fairly wide with the Sr ranging from 98 to 128 ppm at an

MgO of ~7.2 wt. percent. Chromium shows a clearer trend ranging from 287 to 98.3 ppm with









decreasing MgO in the T735 samples and from 584 to 11 ppm in the Cleft samples (Smith, 1994;

Perfit, unpublished).

Vanadium shows an increasing trend in the Cleft data until ~6 wt. percent MgO (full range:

8.69 to 3.41 wt. percent MgO) when there is an inflection point and a downward trend toward the

more evolved compositions. Vanadium ranges from 395 to 330 ppm in the T735 basalts and

from 569 to 185 in the Cleft samples (Smith, 1994; Perfit, unpublished). The inflection point

seen is consistent with the introduction of titano-magnetite as a crystallizing phase.

On a trace element primitive mantle-normalized plot (McDonough and Sun, 1995; Figure

24), the samples show highly incompatible element depletions and negative Sr (4.73 to 5.6 times

primitive mantle) and Pb (6.44 to 9.26 times primitive mantle) anomalies. Concentrations of the

most highly incompatible trace elements are at 10 times primitive mantle or below.

Primitive mantle-normalized Rare Earth Elements (REE) diagrams (Figure 25),

(McDonough and Sun, 1995), show that the samples have Light Rare Earth Element depleted

smooth patterns with concentrations at about 5 to 10 times primitive mantle. The light REE

show a slight depletion in relation to the heavy REE, and slight Eu anomalies, attributed to

plagioclase crystallization. Lanthanum/Samarium ratios range from 0.63 to 0.74 in the MORB

samples recovered, while Ce/Yb ranges from 0.78 to 0.89. Overall, there is an increase in total

REE with decreasing MgO content.

Andesites and Dacites

The more evolved rocks create an extension of the tholeiitic differentiation trend seen in

the recovered MORB. Representative evolved glass compositions are given in Table 3, with the

complete data presented in Appendix 3.










Major and Minor Elements

In the chemically fractionated lava suite, SiO2 TangeS from 62.0 to 66.9 wt%, over an

MgO wt% range from 1.94 to 0.6, with an Mg # range of 15.9 to 6.1; significantly lower than the

nearby basalts and all of the previously recovered samples from the Cleft ridge axis. Aluminum

oxide values range from 13.6 to 12.2 wt% with decreasing MgO and are slightly scattered

(Figure 22). Titanium oxide values range from 1.4 to 0.81 wt% and FeOT TangeS from 7.28 to

10.3 wt%, both oxides falling in loosely constrained trends with MgO content. The offshoots

from the FeTi-basalts found in the overall Cleft dataset, are most pronounced in the TiO2 and

FeOT variation diagrams as they trend towards the more evolved compositions. Calcium oxide

falls from 5.4 to 3.4 wt%/ with MgO, in a very tight trend along the same line as the basalts. The

Na20 also has a tightly constrained grouping with a range in weight percent from 4.36 to 5.07

that plots very smoothly along the same trend line as the basalt values. The K20 values increase

from 1.02 to 1.30 wt% with falling MgO concentration.

H20 concentrations in the evolved samples range from 1.5 to 2.0 wt% while CO2

concentrations were below detectable limits. Chlorine concentrations range from 4100 to 6100

ppm with decreasing MgO.

Trace Elements

Incompatible trace elements increase in concentration in the evolved lava samples as

MgO concentrations fall and form a trend wherein the single dacite glass, that was recovered in a

rock core taken in 2000 (RC 10) is comparable and is therefore included in the discussion of the

evolved samples from Dive T735. Zirconium rises from 397 to 737 ppm in evolved samples

with decreasing MgO. Yttrium rises from 158 to 240 ppm and Ta concentrations rise from 0.927

to 1.6 ppm with falling MgO in the evolved samples. Lanthanum concentrations rise with falling

MgO from 22.4 to 33.8 ppm in the evolved lavas. The concentration of Sm ranges from 13.8 to









21.1 ppm with falling MgO and Lu ranges from 2.38 to 3.65 ppm in the evolved lavas. The Rb

and Nb concentrations increase as well with falling MgO in the evolved samples with Rb rising

from 9.17 to 12.7 ppm and Nb rising from 14.0 to 21.2 ppm in the samples.

Strontium and Cr concentrations both decrease with decreasing MgO in the T735 samples

(Figure 23). Strontium falls from 92 to 67.4 in a loosely defined trend and Cr falls from 54.1 to

1.84 ppm in the evolved lavas, overall the trend is much tighter and more distinct then seen in the

Sr. Scandium and V both decrease in concentration in well-defined trends and extend the trends

in the Cleft samples after the inflection point at ~6 wt. percent MgO. Scandium falls from 23.4

to 15.9 ppm in the T73 5 samples, and the V falls from 178 to 47.6 ppm.

Trace element concentrations show much more variation in the mantle-normalized and

REE diagrams than observed in the T73 5 basalts, consistent with certain phases differentiating

out of the melt (Figure 24). Large negative anomalies in Sr (3.19 to 4. 12 times primitive

mantle), P (5.13 to 19.3 times primitive mantle) and Ti (3.62 to 6.21 times primitive mantle) are

consistent with the crystallization of plagioclase, apatite and titanomagnetite, respectively, from

the melt. All of these phases are present in the evolved samples.

The primitive mantle-normalized REE diagram displays an overall smooth, flat pattern

within the evolved samples (Figure 25). Lanthanum/Samarium ratios range from 0.98 to 1.12,

while Ce/Y ranges from 1.0 to 1.1. Europium displays an increasing negative anomaly (7.03 to

9. 16 times primitive mantle) as MgO decreases which is consistent with the continued

crystallization of plagioclase out of the magma.











































*Smith, 1994; Stakes, 2006
O Dive T735


0 10 20 30 40 50 60 70 80 90 100 MgO


Na20+K20


Figure 21: AFM Diagram comparing Smith, 1994 and Stakes, 2006 samples to dive T735
samples. Basalts follow a typical tholeiitic differentiation trend. The evolved samples from dive
T73 5 form an extension of the tholeiitic trend taken to >80% crystallization, after a gap of no
data. The evolved samples have lower concentrations of FeO due to the crystallization of FeTi
oxides out of the melt.


AFM Diagram
FeO

o














0 Smith, 1994
SStakes,2006
+ Elve 735

















0 2 6 8 10 1:

MgO


S2 4 6 8 0 1

MgO

















+'i I f


S2 6 8 10 1:

MgO


70









45





.55














0.5


rl
+~-

'-

I
~:i

"""""""'""'"""'~

"""""""'""'"""'~


2


2


Figure 22: Maj or element plots comparing previous studies of the Cleft segment (Smith et al.,

1994; Stakes et al., 2006) to dive T735 samples.


______I______


______I______

______I______


______I______
*i
t
~......*...j..............

Pi


I:


C

fC
h

i~* '































2 6 8 10 12
MgO


















2 6 8 10 1;


) 2 4 6 8 10 12
MgO















Si .


Srnith, 1994
SStakes, 006
+ Elve 735
14

12 -- -- --

1 0 .. .. .. .. ..


L


1.4



1

O .8

0.6

0 .4


a.
D


2


Figure 22: Continued.


...


I
-


-~*........i..............

-I~F~:j~~~~~~~~~~~~~~
i


_............1............r

-17


I

I

______I_____

.~C..........i..............


bP~ ~il*



















E~mith,. 1994; Perfi unpublished
*Dhre T735


D 2 6 8 10 12








igo



















D 2 6 8 10 12


i 2 6 8 ID 12











oc k
















] 2 6 B 10 12

Mo






















It


~""""""'"""""""

rl
~""~"''""""""~

I


-*i







-~


I_







I_







I_
~C tt


7CQ


as


gg(


~Ug

XB


aB


Im


p





+s


xl


y


in


Is


ro





o





as



as


um






aB



ICCI



Ct


aJ



Is

E

Icl



s



o






xcl






Im



z 1~4L1


Im






o


D 2 6 B 10 12


Figure 23: Trace element plots comparing previous studies of the Cleft segment (Smith et al.,

1994; Perfit, unpublished) to dive T735 samples.


I


I


'P""""""""""""

*r' I
,~
























-C


1~~~ ....BII I









++





32 6 8 10 12


70



so


D 2 6 B 109 12


en








2m





IED


+5
















D


P 2


8 Io 12


Figure 23: Continued.


Smith, 194; Perfit unpublished





lma41






m
E
m
.L
;f: Clb~
.=
L



E


Rb Ba Th U K Nb Ta La Ce Pb Sr Nd P Hf 1 Sen Ti Tb Y MD


Figure 24: The primitive mantle normalized (McDonough and Sun, 1995) spider diagram
displays the depletion of several key trace elements in the evolved glasses compared to the basalt
compositions. Strontium is incorporated into the structure of plagioclase crystals, while the Ti
depletion is due to the crystallization of titanomagnetite. The P depletion is due to the
crystallization of apatite in the evolved samples. Sample 99RC99 (-) is an andesite recovered
from the coaxial segment and shows the same trend as the evolved samples recovered from the
RTI.


Spider Diagram



















REE Diagram


100 000


,---


_;,--------~ -"=;
C~' .. -==cc-
--h -
h_


_--+


~T~I-l i'jjf
iu --~ rjj
?7; 11 _rri' --i~jjl~~
?7:) i7ii


3'-13 i~3j I~ i-3ii
I~ -- i7 ~i i~~~ J
i c i-


1.000


I La 1.e Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu Y




Figure 25: The primitive mantle normalized (McDonough and Sun, 1995) REE plot shows the

two distinct groupings within the sample group. The basalt samples show the typical flat REE

pattern while the evolved glasses have a characteristic Eu depletion from plagioclase

crystallization. The black outline displays the REE range of the Smith, 1994, samples. The

LREE in the evolved glasses are slightly enriched compared to the basalt glasses. Sample

99RC99 shows a similar enrichment trend.


ly
C
m
E
ru
.I:
- 10000
E
e

E
f,









CHAPTER 6
DISCUSSION



The lavas recovered during dive T73 5 represent one of the most complete and evolved

suites recovered from a MOR environment. The atypical composition of the T73 5 suite provides

an opportunity to investigate petrogenetic processes of MORB evolution that have been well

addressed by traditional magma chamber models created for on-axis volcanism that do not fully

explain the petrogenesis of these andesites and dacites. Here we explore several hypotheses in an

attempt to constrain the potential petrogenetic history of this unique suite.

One of the prevailing hypotheses for the petrogenesis of evolved MOR lavas is that they

are formed by extreme fractional crystallization of basaltic magmas, in part due to the "cold edge

effect", an effect associated with MOR lavas erupted close to an oceanic transform fault or an

area where a ridge is propagating into older oceanic crust (Christie and Sinton, 1981; Fornari et

al., 1983; Perfit et al., 1983; Johnson and Holmes, 1989; Juster et al., 1989; Embley et al., 1991;

Smith, 1993; Smith et al., 1994; Juteau et al., 1995; Tierney, 2003; Herzburg, 2004). The ridge-

transform intersection (RTI) of the JdFR and the BFZ is an area where the cold edge effect is

likely to affect the petrogenesis of MOR lavas (Stakes et al., 2006). The Blanco Transform is

approximately ~345 km long from the southern terminus of the JdFR to the northern terminus of

the Gorda Ridge (Chadwick et al., 1998) that results in the axis of the southern Cleft segment

abutting old and cold lithosphere that is approximately 6.3 million years old; hence providing an

environment for extensive cooling.

Comparison to Other Evolved Suites

Although relatively rare in MOR environments, highly evolved lavas and plutonic rocks

(generally known as plagiogranites) have been found in a number of diverse environments that









include fast, intermediate and slow spreading ridges, back-arc basins, and quite a few ophiolites.

A wide range of samples from these environments are compared to the T73 5 suite in Figure 26.

These samples include lavas from the Galapagos Rift (Fornari et al., 1983) volcanic samples

from the Mid-Atlantic Ridge (Hekinian et al., 1997) back arc basin (BAB) samples from the

Southwest Pacific (Nakada et al., 1994), the Lau Basin (Falloon et al., 1992) and the western

Pacific (Bloomer, Smithsonian Institution Volcanic Glass Individual Analysis File, VG no# 9772

9777). Geochemical comparisons have also been made with evolved plutonic samples from

supra-subduction zone ophiolites from California (Beard, 1998), Greece (Tsikouras and

Hatzipanagiotou, 1998; Bebien, 1991), Norway (Pedersen and Malpas, 1984), Newfoundland

(Malpas, 1979), Oregon (Phelps and Ave Lallemant, 1980), Chile (Saunders et al., 1979), Crete

(Koepke, 1986), and Canada (Flagler and Spray, 1991). Four experimental plagiograntic

residual melt compositions were also compared to the T73 5 samples; residual melts from a

gabbro heated to 900 OC and 940 oC (Koepke et al., 2004) the partial melt of a MORB protolith

heated to 955 OC (Dixon-Spulber and Rutherford, 1983) and the partial melt from a hydrous

MORB heated to 950 OC (Berndt, 2002).

SiO2 ValUeS for the T73 5 lavas are generally lower those of plagiogranite compositions at

similar MgO concentrations (Figure 26). SiO2 ValUeS of the evolved T73 5 suite range from 62.0

to 66.9 wt% in samples containing less than 2 wt% MgO compared to plagiogranite samples that

have values that mostly range from 64.5 to 68.13 wt% SiO2. Experimental partial melts of wet

and dry MORB protoliths (~ 9000 9550C) have quite variable SiO2 ValUeS, (60.9 to 65.8 wt%

SiO2) but they all generally display higher MgO then the T735 evolved lavas, with the lowest

MgO value, 1.29 wt%, in the partial melt generated from the dry MORB parent.









In general the T73 5 evolved lavas have lower concentrations of Al203 COmpared to the

maj ority of evolved samples. The T73 5 evolved lavas have a very limited range of Al203 frOm

13.6 to 12.23 wt% compared the global volcanic suite that has values ranging 16.0 to 11.4 wt%,

including some subvolcanic rocks having the highest values at 16.0 and 15.83 wt%. Al203 in the

plutonic suite ranges from 18.1 to 10.4 wt%/. The experimentally derived melts all have

comparatively high concentrations of Al203 Tanging fTOm 20. 1 (gabbro protolith) to 15.41 (dry

MORB protolith) wt% Al203.

The T73 5 evolved lavas are enriched in TiO2 relative to the bulk of the compared evolved

samples. The T735 evolved lavas range from 1.39 to 0.81 wt%/ TiO2 while within the volcanic

suites, the only one with samples of higher value, range from 2.44 to 0.34 wt%. The plutonic

suite displays very low TiO2 ValUeS, which range from 0.84 to 0.30 wt%. Such low TiO2 ValUeS

could be indicative of an island arc signal given that many of these rocks were believed have

been formed in supra-subduction zone environments. The evolved liquid from the MORB

protoliths have TiO2 ValUeS of 1.25 and 1.17 wt%, which lie within the field outlined by the T735

evolved lavas. The gabbroic protoliths both have very low TiO2 ValUeS, 0.36 and 0.12 wt% TiO2.

K20 is extremely enriched in the T73 5 evolved lavas relative to any of the plagiogranite

comparison suites, ranging from 1.02 to 1.30 wt%. Only one sample, a volcanic sample from the

MAR (Hekinian et al., 1997), lies within the field created by the T73 5 samples, with its value

being 1.09 wt% K20.

Dive T735 Samples

During dive T73 5, we documented the presence of two constructive volcanic mounds that

are comprised of massive pillows to blocky, vesicular, silicic lavas. Morphology ranges from

large (>2 m in diameter) pillow tubes, to extremely vesicular (~20% elongate vesicles), blocky









flows, a drastic change in morphology from the small (~lm in diameter), rounded non-vesicular

pillows observed in the surrounding areas where only basalts were recovered.

The petrography and phase chemistry of the evolved samples recovered are indicative of a

complex petrogenetic process. Two populations of phenocrysts were found within the evolved

samples, each exhibiting chemical zoning. Iron-rich pyroxenes, that have core Mg# from 8.24 to

12.6, were reversely zoned while those with Mg-rich cores, ~Mg# of 57.2, exhibit normal

zoning. The rims of both populations approach similar compositions with Mg# ranging from

27.7 to 37.5. Significantly, the rims approach the microphenocryst compositions in the glass

matrix. This petrographic evidence suggests two things;

Mixing between a relatively mafic basalticc) magma and a highly evolved magma, likely

rhyodacitic, each of which crystallized pyroxene before mixing occurred (Barbarin, 1990;

Furman et al., 1995; Perfit et al., 1999; Grove, 2000; Ratajeski et al., 2001). The silicic magma

was relatively dry when it erupted, indicated by the presence of fayalite and Fe-rich pyroxene in

the recovered rocks rather than amphibole (Dixon-Spulber and Rutherford, 1983; Koepke et al.,

2004; Berndt et al., 2005).

Several xenoliths with coarser-grained textures, indicative of slower, crystallization

conditions, are also present in the andesites and dacites. These include rare plagioclase

oikocrysts containing low-Ca pyroxene chadacrysts as well as a coarse-grained xenolith

comprised of plagioclase (An34 An35) and fayalitic olivine, (Fols), present in sample T73 5-G10.

A quartz-plagioclase myrmekitic intergrowth is present in sample T735-Gl9. The presence of

these textural features indicates that that the erupted lava interacted with an evolved plutonic

body or mush zone.









Rounded basalt xenoliths are also present in the evolved lavas. They range in size from <1

mm to several mm in diameter, and have fine-grained to opaque rims. These presence and

texture of these xenoliths basaltic magma intruded/recharged an evolving magma body. The

fresh, mafic material would have been at a much higher temperature then the evolved, viscous

melt it intruded into/mixed with. The high viscosity of the evolved melts would have inhibited

large scale mixing with the fresh mafic material and the temperature difference between the

melts basalticc >1200 oC; dacitic <1000 oC) could explain the fine-grained textures of the

basaltic xenoliths and chilled margins.

Maj or and trace element variations observed in the entire T73 5 suite indicate a bimodal

sample set, that has no samples of intermediate composition (Figure 22; Figure 23) although it

should be noted that most of the basaltic samples recovered around the andesite/dacite domes

have fairly fractionated compositions with many being ferrobasalts (FeO >12 wt.%).

There are a number of different ways that these kinds of rock suites have been

hypothesized to form;

* the extreme fractional crystallization of a MOR magma (Fornari et al., 1983; Perfit et al.,
1983; Juster et al., 1989; Geist et al., 1998; Perfit et al., 1999; Grove, 2000);

* magma mixing between an extremely evolved, possibly rhyodacitic end-member and a
ferrobasalt (Barbarin, 1990; Perfit et al., 1983; Furman et al., 1995; Hekinian et al., 1999;
Perfit et al., 1999; Grove, 2000; Ratajeski et al., 2001);

* partial melting of the hydrated oceanic crust (Dixon et al., 1995; Brandriss et al., 1999;
Berndt et al., 2005);

* assimilation of oceanic crust and assimilation fractional crystallization (AFC) (Bohrson et
al., 1998; Garcia et al., 1998; Gee et al., 1998; Hornle et al., 1998; Grove, 2000).









Fractional Crystallization

Silica rich rocks found in oceanic environments may be formed by extreme amounts of

fractional crystallization (Perfit et al., 1983, Juster et al.., 1989). The Galapagos are a prime

example of an area where the evolved lavas recovered fit the extreme fractional crystallization

model well. Juster et al., 1989, used experimentally determined phase boundaries to model the

fractionation of lavas recovered at 850 W. The results of the experiments determined that the

range of compositions found there were the result of shallow-level differentiation processes and

the higher levels of fractionation and silica enrichment were due to the higher fO2, which allowed

for a titanomagnetite bearing assemblage to begin to crystallize earlier, driving the

concentrations of SiO2 up and FeO and TiO2 down.

To test a fractional crystallization model for the Cleft suite, liquid lines of decent (LLD)

(Appendix 4) were calculated using the program Petrolog (Danyushevsky, 2001) under various

starting conditions (e.g. pressure, oxygen fugacity, different mineral assemblages). Sample

T73 5-G3 5 was chosen as the composition of the parent melt because it is the most mafic sample

recovered in the area were the evolved samples were recovered. The mineral-melt models of

Danyushevsky (1999) were chosen for calculating the compositions of olivine, plagioclase and

clinopyroxene; Ariskin (1993) for orthopyroxene and Ariskin and Barmina (1999) were used for

magnetite compositions. Melt oxidation states along the QFM buffer were determined using the

conditions of Borisov and Shapkin, 1990. Calculations were run at 200 bars and 1 kb of pressure,

in order to simulate the pressure at the seafloor and within the shallow crust (~3 km). All

calculations were executed assuming perfect fractional crystallization in 0.1 wt% incremental

crystallization steps and were typically terminated ~88% total crystallization when certain

components were expended. Using the 200 bar model, which started at 1185 oC and was run at

QFM, the calculated maj or element trends (Figure 27) are fairly smooth with a maj or inflection









point seen in SiO2, Al203, TiO2, and FeO at an MgO of ~3 wt% when titanomagnetite enters as a

crystallizing phase, after ~65% crystallization of the parental melt. Oxidation state affects the

temperature and composition at which titanomagnetite (and ilmenite) crystallizes; higher oxygen

fugacity causes earlier (higher T, less total crystallization) stabilization of oxide phases.

Consequently, the modeled inflection point occurs earlier in the chemical evolution when using

an oxygen buffer higher than QFM. Figure 28 shows the relationship between temperature and

percentages of mineral phases in the crystallizing assemblage from a successful model.

The modeled order of crystallization along a QFM buffer at 200 bars is olivine -olivine +

clinopyroxene -olivine + plagioclase + clinopyroxene -plagioclase + clinopyroxene +

orthopyroxene -plagioclase + clinopyroxene + orthopyroxene + magnetite (Figure 28). The

modeled LLD at QFM corresponds well to the interpreted crystallization order based on

petrographic examination of sample thin sections. The order of crystallization is olivine +

plagioclase -plagioclase + clinopyroxene 1 olivine -plagioclase + clinopyroxene + FeTi

oxides & olivine -plagioclase + pigeonite (or orthopyroxene) + FeTi oxides.

Dacite compositions are predicted to form after approximately 80% crystallization, even

though the phase equilibria used in the Petrolog program are not very well constrained in such

evolved compositions. The results of the models generally agree with the maj or element trends

observed in the dacites. SiO2 ValUeS in the evolved rocks are slightly higher than model

predictions and K20 is over-enriched, while TiO2, Al203 and P20s are lower relative to the

calculated abundances (Figure 27).

Variations in the trace element abundances were modeled for selected elements using the

Raleigh fractionation equation, phase proportions predicted by the maj or element models and

published trace element Kd's (Bougault and Hekinian, 1974; Shimizu and Kushiro, 1975; Duke,










1976; Matsui et al., 1977; Mysen, 1978; Kravuchuk, 1981; Villemant et al., 1981; Colson et al.,

1988; Kloeck and Palme, 1988; Agee, 1990; McKenzie and O'Nions, 1991; Keleman and Dunn,

1992; Hart and Dunn, 1993; Hauri et al., 1994; Nikogosian and Sobolev, 1997; Bindeman et al.,

1998) and also by assuming Kd's of zero for the most incompatible elements. Calculated trends

for several of the incompatible trace elements also seem to follow calculated fractional

crystallization trends (Figure 29) although in order to reach the concentration levels of the most

evolved compositions greater than ~90% crystallization is required. The enrichments observed

in some of the most incompatible trace elements could not be modeled even if the bulk

distribution coefficient was assumed to be zero.

Trace element variations generated with published Kd's are only slightly below the actual

trends of the lavas recovered (Figure 29). Zr, Y and Sm concentrations are well-modeled using

the Rayleigh fractionation equation with a D of zero and the proportions of minerals determined

from the Petrolog models. The La, K and Rb values of the evolved lavas, on the other hand, are

significantly higher than the calculated abundances even using an assumed D of zero, which

would give the maximum enrichment. Modeled variations for Cr, Ni and V compare favorably to

the actual evolved compositions, but the Cr and Ni concentrations of some intermediate to

evolved basalt samples are lower than those in the calculated model. Kd's for Ni and Cr are not

well-constrained for basaltic systems though. Sr and Sc are significantly lower in the evolved

samples when compared to the modeled concentrations.

In general, fractional crystallization seems to adequately (though not entirely) explain the

elemental trends, although models suggest extreme amounts of crystallization (>80%) of an

already evolved basalt parent in order to duplicate the maj or element compositions of the dacites.

With such extreme amounts of crystallization needed in order to model the evolved










compositions, there would be a problem with a crystal-laden melt being able to erupt, as the melt

has progressed well past the solidification front predicted at 40% crystallization (Marsh, 2000).

Magma Mixing

Petrographic evidence supports magma mixing was involved in the petrogenesis of the

evolved suite, and might help to explain some of the discrepancies in the elemental trends as well

as the compositions of some basaltic andesites recovered along the axis of the Cleft segment

north of this study area. Clearly the bimodal pyroxene compositions and extensive amounts of

zoning, as well as chilled basaltic xenoliths observed in all of the evolved samples, point to some

type of magma mixing event or events. The phase chemical variations suggest there was mixing

between a basaltic end-member, possibly as evolved as a ferrobasalt, and a very evolved magma,

possibly as evolved as a rhyodacite or rhyolite, to create the andesitic and dacitic lava samples

recovered. There is no evidence of evolved magma mixing with mafic basaltic liquids.

In order to evaluate the potential role of magma mixing, mass balance mixing calculations

were performed between likely mixing end-member compositions. As the most evolved silicic

end-member(s) is unknown, all mixing lines were calculated using the composition of dacite

sample T73 5-Gl2 (Mg# of 6. 14), the most evolved lava recovered. The three basaltic end-

members chosen were T73 5-G3 5 (Mg# of 37.5, MgO = 7.55 wt%), the most mafic basalt

recovered during the dive, T73 5-G7 (Mg# of 32.3, MgO = 6.79 wt%), a moderately evolved

basalt and T73 5-G32 (Mg# of 29.8, MgO = 6.29 wt%), the most evolved basalt recovered on the

dive. Increments of mixing were calculated for every 10% portion (i.e. 10% of A and 90% of B,

20% of A and 80% of B, etc.) using a standard mass balance equation (Langmuir et al., 1978).

The calculated mixing lines (Figure 30) represent a few of the potential mixing models that are

possible.









Results of the mixing calculations show that the compositions of some of the outlying

samples on the major element plots that did not fit the fractional crystallization models are better

explained by magma mixing. In part, the group of 2 basalts, 8 ferrobasalts and one andesite from

the entire S. Cleft suite that show a trend of decreasing FeO concentrations with decreasing MgO

fall along the mixing line from T73 5-G7 to T73 5-Gl2. Mixing lines calculated using the two

more mafic basalt samples as end-members don't seem to include any outlying basaltic and

andesitic samples in their trends. It could be interpreted that, if mixing was involved in creating

these intermediate outliers, and the evolved compositions they trend towards, that one of the end-

members involved in the mixing would have to be a fairly evolved ferrobasalt or FeTi-basalt,

since the most evolved sample recovered provides the best end-member to explain elemental

trends in the full dataset.

The mixing calculations suggest a mix of 30 40% of the ferrobasalt (T73 5-G32) with 60

- 70% of the dacite (T73 5-Gl2) would be required in order to create the observed evolved

compositions in the T735 suite. The moderately evolved andesites observed in the larger Cleft

dataset would require only about 30% of the dacitic end-member to be mixed with the

ferrobasaltic liquid. The petrology of the samples, and the presence of the myrmekite, zircons,

fayalite as well as sodic plagioclase (Anls) and iron-rich pyroxene (Mg# of 8.24) crystals, as

well as the fine magnesian rims surround Fe-rich pyroxene (Figures 11 and 12) and fayalite

(Figure 15) cores, strongly suggest that there is the possibility of an even more evolved end-

member then T73 5-Gl2 was involved that was mixed back to create the compositions recovered.

Based upon the traj ectory of the mixing lines drawn between the evolved samples and possible

basaltic end-members, the proj ected evolved end member might be expected to have a

composition similar to this: ~67 wt% SiO2, ~12 wt% Al203, 0.75 wt% TiO2, 7.5 wt% FeOT, ~3.0









wt% CaO, ~5.2 wt% Na20 and K20 ~1.4 wt%. All these values were estimated by extrapolating

the current mixing model to an MgO of almost zero.

The trace element compositions also seem to be more supportive of a mixing model, as

crystal fractionation cannot account for over-enrichments seen in highly incompatible elements

such as La, Sm, Zr, and Y where a Kd of zero is needed to approximate the observed values in

the most fractionated lavas (Figure 29). This would however, require that the evolved end-

member was formed by extreme amounts of fractional crystallization (>90%).

Partial Melting/Assimilation Fractional Crystallization (AFC)

Another hypothesis for generating highly evolved melts is to partially melt the basaltic

crust (Petford et al., 2001; Castillo et al., 2002; Coogan et al., 2003) or assimilate country rock

into the melt (Nicholson et al., 1991; Bohrson et al., 1998; Garcia et al., 1998; Gee, 1998;

Hoernle, 1998; O'Hara et al., 1998; Weis et al., 1998; Grove, 2000).

Several studies have shown it possible to produce silicic melts from partially melting

hydrous mafic protoliths (Holloway and Burnham, 1972; Helz, 1973; Beard and Lofgren, 1991;

Kawamoto, 1996, Koepke et al., 2003; Koepke et al., 2004). There is also evidence of anatexis in

plagiogranitic rocks found in ophiolite sequences (Malpas, 1979; Pederson and Malpas, 1984;

Flagler and Spray, 1991) as well young oceanic crst (Mevel, 1988) although the exact

compositions of the protoliths in these studies has not been well constrained and may include

gabbros and sheeted dikes that may have been altered due to hydrothermal activity. Water is

usually assumed to be a component of the melting process due to the presence of amphibole

found in samples of felsic oceanic crust (Bebien, 1991; Beard, 1998; Tsikouras and

Hatzipanagiotou, 1998; Koepke et al., 2002), often in poikilitic textures, suggesting a magmatic

origin (Koepke, 1986).









Phase chemical data from melting experiments (Koepke,. 2004) also demonstrated an

increase in olivine Fo content in the restite due to increasing temperature and the influence of

water. Residual plagioclase were also more An-rich in the experiments due to the effect of water

(Sisson and Grove, 1993; Berndt, 2002) and amphibole was present in all systems at

temperatures <~-980 oC.

Assimilation of crustal material has also been hypothesized as a method to create evolved

compositions. Assimilation in a MOR regime most likely involves oceanic crust that has been

hydrothermally altered and this has been substantiated by direct field observations of xenolithic

basaltic material in ophiolites (Castillo, 2002). The addition of altered material into a MORB

magma results in an over-enrichment of chlorine, relative to other incompatible elements such as

K20 and TiO2 (Jambon et al., 1985; Michael and Schilling, 1989; Michael and Cornell, 1998;

Castillo, 2002; Coogan, 2003).

When compared with the phase chemistry of the resulting melts from the Koepke, 2004,

experiments, the phase chemistries of evolved lavas from dive T73 5 are conspicuously free of

any signal of water activity. No evidence of amphibole is present in the T73 5 lavas, nor is there

evidence that amphibole was present in the residue of melting due to the absence of a LREE to

HREE enrichment in the REE pattern of the T73 5 glasses, as the Kd values for REE in

amphiboles decrease in value for the lighter elements (McKenzie et al., 1991). The phase

compositions of the T73 5 lavas and the absence of evidence of hydrous phases would seem to

preclude the notion of the silicic end-member being the result of a partial melt of hydrous

oceanic crust. While small batches of xenolith material are present in the T73 5 evolved lavas

none contain amphibole. In addition, there is no elevated chlorine signal (Cl/K ratios remain









fairly constant; Figure 31), precluding large amounts of assimilation of altered crust taking place

in the petrogenesis of the evolved lavas.

Strontium and oxygen isotope values for the evolved T735 are identical to those in MORB

from the Cleft segment, consistent with a lack of any seawater alteration or contamination

(Perfit, personal communication). If high-temperature altered crust were melted to form dacitic

partial melts, the values of sSr/86Sr would be higher than fresh basalts and oxygen isotopic

values would be lower. In both cases this is not true instead values well within the range of JdFR

fresh, unaltered lavas.














70
68 m1

66
64 q
62 x + Volcanic
60~ m Putonic
Experimental
58
m T735 samples
56
54
52

0 1 2 3 4 5 6 7 8
MgO


Comparison of TiO2 Values

2.5




1.5 Volcanic
o"~ Plutonic
Experimental
1-
I ~ I T735 evolved lavas

0.5


0 0.5 1 1 .5 2 2.5 3 3.5
MgO


Com prison of SiO2 ValUsS


Figure 26: Comparing maj or element variations in the T73 5 lavas to other evolved suites. Other
suites are from varied locations and petrogenetic origins, including lavas from the Galapagos Rift
(Fornari et al., 1983) and Mid-Atlantic Ridge (Hekinian et al., 1997), back arc basin (BAB)
samples from the Southwest Pacific (Nakada et al., 1994), the Lau Basin (Falloon et al., 1992)
and the western Pacific (Bloomer, Smithsonian Institution Volcanic Glass Individual Analysis
File, VG no# 9772 9777), plutonic samples from supra-subduction zone ophiolites in California
(Beard, 1998), Greece (Tsikouras and Hatzipanagiotou, 1998; Bebien, 1991), Norway (Pedersen
and Malpas, 1984), Newfoundland (Malpas, 1979), Oregon (Phelps and Ave Lallemant, 1980),
Chile (Saunders et al., 1979), Crete (Koepke, 1986), and Canada (Flagler and Spray, 1991). The
experimental plagiograntic residual melt compositions compared were from a gabbro taken to
900 oC and 940 oC (Koepke et al., 2004) the partial melt of a MORB protolith taken to 955 OC
(Dixon-Spulber and Rutherford, 1983) and the partial melt from a hydrous MORB heated to 950
oC (Berndt, 2002). SiO2 values were plotted with the recovered T73 5 basalt as well as the
evolved samples in order to demonstrate the amount of differentiation.























I +




.


Comparison of K20 values


1.1

1.2

1
Volcanic
O0.81 m Plutonic
0.6 m1 m &perimental
m T735 evohred lavas
0.4

0.2m


0 0.5 1 1 .5 2 2.5 3 3.5

MgO


22









1 4




10


S0.5 1 1.5 2 2.5 3 35

ht10


Figure 26: Continued.


Comparison of~ AIO, valus


* Vosican
5 Aulenic


* T735-evolved lave

















Ib


46




3.5





1.5


D 2 4 6
MgO


8 10 12


MgO


MgO


Figure 27: Maj or element liquid lines of descent. Liquid lines of decent are modeled using
Petrolog (Danyushevsky, 2001) using a QFM buffer at 200 bars of pressure and were run to
~88% crystallization. Sample T73 5-G3 5 was used as the starting composition, as it was the most
mafic sample recovered during the dive. Sio2 ValUeS in the evolved rocks are slightly higher than
model predictions and K20 is over-enriched, while TiO2, Al203 and P20s are lower relative to
the calculated abundances.





























X


0 2 4 6 8 10 12
MgO






$*














a 2 4 6 8 10 12
MgO


D 2 4 B 8 10 12


a Srnith, 1994
4 Stakes,2006
+ Eive T735
x Petr~log LLD


8

7







4

3 -

2
0 2 4 6 8 10 12


~P I


D


Y
I


2


1.4

1.2

1


r
a.B

a.4

0.2

a


Figure 27: Continued.






















S 60-






O + : +;



BOO 850 900 950 1000 1050 1100 1150 1200

T~oC)


Figure 28: Cumulative percentage of phases plotted against melt temperature (oC). This figure
illustrates the changing mineral assemblage as the modeled parent composition cools. Model
assumes QFM and 200 bars of pressure.


































































































Figure 29: Trace element liquid lines of descent. Liquid lines of decent are modeled using

calculated Kd's and the results of a Petrolog model run using a QFM buffer at 200 bars of

pressure, run to ~88% crystallization. Sample T735-G35 was used as the starting composition, as

it was the most mafic sample recovered during the dive. While most trace elements follow the

calculated trends, La and Lu show over-enrichments, even when LLD's are calculated using a

Kd of zero. Zr and Sm also show slight enrichments relative to the calculated Kd' s, but can be

predicted using a D of zero.


a


c


c

t


Cl 2 46 8 10 12






0


g


a


a


a


a


a


o


lg(


8 10 12


D 2 4 6


B ID 12


0240


2 6 g 10 12


ag


4~0


um


uxo


st


rm


D2r


nE


458


D 2


+6


ID1 I


B 1012

















SSmith, 1994; Perit, nulse
* Eiv T735
El Calculated Kd's


U ~O
Cr,


02+6SB


ID I2


Eon


aon


ucon


>son


D 2 + 9


ID 12


2 6 8 10 12


Figure 29: Cotinued.

























Ix
t


o Sm ith, 1994
+- Stakes, 2006
* Dive T735
x G35to 012
7 G32 to 012
= G7 inG1 2


-0


0 24 6
Mg O


8 10 12


0 2 46

Mg O


8 10 12


0 .5 i

OM O M O ~


Figure 30: Mxing modelscaluae sigasadadms alneeutin(aguita.
197).Figre26:Miinglies er cacuate t T735--Gl2, th ---e most evolve end-membe

reoerdduigthe die h he ai ndmmescoe eeT75G5(lc ') h










822

















EPR 9 10N (le Rour at al.)
SS. Cleft (StakeE, eat .)
.. ....... .. .......... .. T7 35 R TI
8 GSC BSiW Perrit etal.)














:I '




0 2 4 6 8 10~ 1;


mooewt%


14 ,





CI ~111.i


* EPR 9-10N (le Roux atal.)
S S. Cleft (Stakes 81 l.)
+ 735 RTI
O SC Bli W (Fedit aet al.}


O.B t


S2 4 6


8 10


Figure 3 1: Comparison of T73 5 Cl~ and Cl/K ratios versus MgO. The Cl/K ratio of entire T73 5
suite remains fairly constant over the full range of MgO. While the Cl- concentration increases

with decreasing MgO the ratio of Cl-/K in the T735 samples (green diamonds) does not show the

same rate of increase seen in the Southern Cleft samples (Stakes et al., 2006), the GSC (Perfit et

al., 1999) and the EPR (le Roux et al., 2006) where assimilation takes on a much larger role.


b
-e- ----a-- -- -- ---- -- -- -- --- -



I i

111 1~
............,.... ...........,...









CHAPTER 7
CONCLUSIONS

* Low pressure fractional crystallization models adequately reproduce the observed trends in
major elements and some of the minor/trace elements. There are slight discrepancies
between the predicted and observed compositions though, most notably with K20 being
very over enriched, while TiO2, Al203 and P20s are lower relative to the predicted
abundances (Figure 20). Calculated trace element LLDs for La, Rb and K, even assuming
Kd's of zero, do not fully predict the concentrations seen in the evolved samples, which are
over-enriched to models values.

* The calculated models require fractional crystallization of greater than 80% in order to
duplicate the evolved lava compositions recovered on Dive T73 5; well past the amount of
crystallization required to form an impermeable solidification front predicted by Marsh,
2000.

* Petrographic evidence strongly supports mixing as a significant petrogenetic process that
created the evolved lavas. Chilled basaltic xenoliths as well as disequilibrium crystals are
prolific in all the evolved samples, as well as complex normal and reverse zoning seen in
pyroxene and plagioclase crystals. The petrography and chemistry suggest that that a
possible recharge event between and evolved, rhyodacitic melt and a ferrobasalt created
the andesitic and dacitic lavas recovered.

* Large amounts of assimilation or partial melting of altered oceanic crust do not seem to be
involved in the petrogenesis of these evolved lavas. Signals expected from the
assimilation/incorporation of hydrothermally altered oceanic crust, such as over
enrichment of C1F, due to the interaction of seawater with the crust (Coogan2 et al. 1, 2003),
or a sloped REE pattern, due to the lower Kd' s of the LREE in amphiboles causing an
enrichment of them in the melt (M~cKenzie et al., 1991), are not seen in the T73 5 evolved
lavas.



The evolved lavas recovered from dive T73 5, at the southern terminus of the JdFR, have

had an extremely complex petrogenesis. While large scale amounts of assimilation and/or partial

melting of hydrous crust can be ruled out as methods of creating this particular suite of rocks

magma mixing between two distinct magma types that formed by different amounts of fractional

crystallization is certain. The ferrobasaltic xenoliths provide a good estimate as to what the more

mafic end-member composition might be, but the extremely evolved end-member is much more

difficult to constrain.









These highly evolved melts would have been extremely viscous and had very limited

mobility. Due to the fact they the lavas were located at the RTI, propagating dikes, composed of

much hotter, ferrobasaltic material, from the larger magma bodies found up-ridge could have

provided the necessary heat to mobilize the dacitic melts, allowing them to exsolve H20 and CO2

through decompression, lowering the density enough to allow them to erupt on the ocean floor.









APPENDIX A
T73 5 DIVE LOGS









DATE: 31AUGO4

J-Day: 244



Dive objectives: Explore RTI near southern Cleft



13:31 Om rov entered water, start dive T735

14:51 2192m on bottom for past 2 minutes, talus slope

14:55 setting down to sample, pillow fragments, some microbial growth on fragments

14:57 2190m sample T73 5-Gl, from pile of pillow debris, placed in S3 in rov drawer, slightly

Mn coated

15:00 2190 looking around, some possibly intset pilows present

15:01 2187m starting traverse along curved ridge

15:03 2187m pillow talus, crossing dome summit

15:06 2187m can see glassy remains on many of the fragments

15:08 2193m larger pillows here, no convincing in-place pillows

15:11 2200m possible in-place mound, looking for place to sample

15:12 2202m small pillow fragment, T735-G2, brownish, placed in S3

15:13 see flows pointing downhill, pillows appear vesicular, small hornito in area, turning

around to look at hornito

15:16 2201m spatter mound-tube thing, or vapor escape tube??,

15:19 trying to grab sample, fractured in place, highly altered, glassy

15:22 2202m grab samplefrom tube thing, T73 5-G3, placed in S3, broken off from top of tube

15:23 underway again, some flows appear inplace, heading 341

15:24 2205m crossing partially covered fissure by pillows









15:25 contact to almost all intact flows

15:26 2204m intact pillow flows, slight sed covered, flows appear to be draping topography,

glassy

15:27 2202m collapse features, mod sed cover in interstices of flows

15:28 2203m stop to sample

15:31 2205m looking for piece to pickup

15:33 2205m collected sample of crust, T735-G4, in S3 again thin piece from lobate flow

15:36 2201m stepping down to west going to look at rigde in sonar, crossing faultsteps,

15:38 2201m fault scarp, razorback ridge series separate by crevasses slightly wider than the

rov, flows on top are intact, heading 336, pie shape wedge of crust between fissures, flattened

lobates, this is the wall from the sonar

15:42 2200m fissures seemed to j oin, its much wider here, about as deep as it is wide, fissure

wall has clean surface, appears pulled apart

15:43 2199m two Hissure walls are closing in according to the sonar

15:51 2220m stopping for sample from lobates

15:54 2221m smal pillow wedge collected, sample T735-G5, also in S3

15:57 2217m another fissure, buried by overlying pillows, hard to tell if flowing in or out

15:59 2215m another fissure, pillows neatly broken along edge

16:03 2216m collect sample of pillow crust, intact?, T73 5-G6, placed in S3, blocky reddish

sample

16:05 2214m drainback, area of pillows, mod sed between pillows, very plastic flows covering

Ider terrain










16:06 2210m crack fissure starting here, pillows are knobby, older terrain appeared to be large

pillows

16:09 2215m still intact flows, fissure off to port

16:13 2212m stopping for sample, different looking stuff, more blocky

16: 18 2213m collected grab sample T73 5-G7, from flat area at near top of knoll, placed in front

of S7

16:20 2209m intact pillows, mod sed cover between

16:22 2207m appears more constructional, fissure to west side, sharp drop, bottom a few meters

down, approx. 5m wide

16:23 2207m dropping down over edge of fissure, top of wall is intact, base has lots of debris,

appears sed covered even on talus and pillows, appears old

16:25 2214m thick sed cover, few pillows sticking up from sed

16:27 2216m mixture of intact pillows and broken pilow debris

16:34 2225m 50-60% sed cover, good sed cover on pillows too

16:36 2231Im more pillows, tubular, somewhat smaller than previous, stopping for sample

16:39 2232m sample T73 5-G8, blocky pillow frag, placed in S4

16:41 2229m scattered pillows, <50%s sed cover

16:42 2231Im tube and sheet flow down to SW, stopping to sample

16:44 2232m sampling sheet, too friable need to put in biotube, must be glassy

16:45 2232m sample sheet flow?, T73 5-G9, fragments placed in BT5

16:48 2227m pillow tubes appear different, very large well formed tubes, striations

16:50 2226m stopped to sample

16:52 2226m collected sample T73 5-G1 1 from large pillows, very glassy, placed in S4










16:54 2219m very well formed pillows flowing downslope, very little sed on top, very glassy

surface

16:57 -2213m

16:58 2212m, vapor pockets and cavities between layers of basalt

16:59 2211Im, picking sample of vapor pocket, T73 5-Gl2

17:02- 2213m, sample looked glassy, still passing over breadcrust texture, sed coating on all

17:03 2211m, lots of local relief, big pillows surrounding by smoother tubes

17:06 2211m, twrining on to next line, sheetier appearance

17:07 2209m, large flat broken up sheet flow, perhaps a silicic constructional dome

17:08 2210m, trying to sample at top of constructional feature, slabby flow

17:09 2210m, collected sample of striated top of slabby flow, in BT4, T73 5-Gl3

17: 12 2211m, was broken from beneath, top is flat but sides are tilted

17:13 2214m, still same flow, very straited, blocky iand angular n some places, plus few big

pillows

17:16 lost my comment

17:18 2214m, turned to the left, and are back in the straited, sheety thick flow

17:19 2214m, collecting another piece of striated flow

17:20 2214m, sample of sheet flow, won't fit into bio tube

17:22 2214m, sample was collected in between the P/S boxes, T73 5 Gl4, another piece

collected at same time

17:24 2213m, finished collecting another sample of what is hopefully a dacite flow

17:26 2214m, nav jumpy because we're tunring, lots of pillows

17:27 2216m, large broken pillows, tubular










17:28 2209m, between the tubes and pillows still getting massive flows (layered)

17:30 2209m, pillow texture is smoother

17:3 1 2212m, stopping to collect another sample, lots of gas cavities

17:32 2212m, sample going into biotube 3, T735 Gl5

17:34 2211Im, back on the line, hdg 62, this area had lots of vesicles, and dome-like feature had

both angular blocky rocks and pillows

17:38 2213m, tilted slab block, probably from eruption

17:40 2219m, still in the same general area of geology and morphology, still looking at dome-

like structure, probably not basalt

17:42 -2215m

17:44 2215m, going to sample in this area

17:45 2216m, sample will be taken from the interior, more broken

17:46 2216m, sample T735-Gl6, from interior of flow, S5, should be smallest piece in S5

17:50 2215m, coming down slope of construct, hdg back to line

17:52 2216m, still at pillows with breadcrust texture, moderate sed cover

17:53 2218m, very evolved rocks, broken up large pillow, no tectonic fissures on sonar

17:57 octopod, red Dumbo

17:58 2216m, large striated pillow, broken down the middle

18:00- 2216m, heading back to line, irregualr terrain

18:01- 2216m, irregular terrain, with broken up blocky lava

18:04- 2221Im, collect a sample of broken pillow, to see if it's the same as the previous samples

or it it's less viscous

18:06 2221m, taking a pillow sample










18:06 2221m, S1 pillow sample with lots of vesicles, T735-Gl7

18:09 2221m, at bottom of saddle, will soon be heading upslope

18:10 2214m, coming up constructional slope, pillows flowing downhill radially

18:12 2207m, attempting to sample the crust of these pillows, looking for small piece

18:14 2205m, continued to move upslope looking for a breakable pillow crust

18:16 2206m, collected two pieces of pillow crust, small, in S1, T73 5-Gl8,

18:17 2192m, moving upslope, smaller pillows, reached a bench

18:19 2199m, moving up feature, more relief than dacite mound

18:21 2198m, tublar, flattened pillows, probably at top

18:22 2198m, much less blocky than last dome, collecting sample

18:25 2198m, picking up sample previously dropped, near top of slope, PS, T73 5-Gl9

18:26 2198m, this may have been sample site, nav jump

18:28 2199m, tubes flowing off to right, south

18:29 2201m, crabbing downslope, very little tectonic features

18:31 2208m, well-formed pillows and tubes, heading downslope to south

18:33 2205m, stepping downslope, mod sediment on pillows

18:34 2206m, elongate tubes look like they're flowing south

18:35 -2199m

18:36 2199m, tubes and broken pillows, pillows are more fragmented

18:40 2203m, still see some blocky, angular flows, on shallow slope

18:41 2204m, slow progress on hdg because of current

18:43 -2205m

18:45 -2209m









18:46 2216m, heading downslope, flattened tubular pillows

18:49 2216m, still elongate tubes

18:50 2234m, looking at in place pillows, attempting to sample, also smaller rubble

18:52 223 5m, collected rock sample from talus near in place pillows

18:35 -2234m, T735- G20, P5

18:57 2258m flow fron talus, large bocky boulders

19:01 2275m collect large fragment of intact pillow, T73 5-G21, from base of steep slope, slope

continues down to east, skinny pillows

19:07 2263m heavy sed cover in gully between two knolls, isolated exposed pillows

19:08 2258m heading 93 degrees

19: 10 2256m much less sed cover, pillows sticking out of mod sed cover

19:13 2254m pillows with heavy sed cover

19:14 2252m collapse feature showing sheet flows beneath pillows

19: 16 2256m collect sheet flow sample T73 5-G22 from collapse feature

19: 18 2251m large pillow with inner drain features, pillows more bulbous, mod sed

19:21 2249m picking of fragment of pillow from top of sed, too big!

19:24 2249m looking for sample to collect, pillows in thick sed cover

19:26 2250m collect large pillow fragment from top of sed, T73 5-G23, put in P5

19:28 2247m constructional pillows in sed cover

19:29 2246m veered off course to NE, heading back S to top of knoll

19:31 2249m closer pillows, everything appears intact, possibly big hornito, all pillows flow

downhill from top of mound

19:37 2249m collect sample T735-G24 in S2, greenish-white looking inside










19:41 2250m collect basalt sample from same area, T735-G25

19:44 2248m heading down mound to north, bulbous pillows poking up through sed

19:45 2249m Hield of unsedimented pillow surfaces, slightly more gentle slope than the west

slope

19:49 2252m mostly jumbled rubble, some intact pillows heading downslope to saddle between

knolls, 50% sed cover with equal amounts of pillow rubble

19:53 2254m crossing Eissure almost N-S several meters deep, broken pillow pieces, appears

tectonic, sed on walls and at base, all pillows exposed in fissure wall

19:56 2260m following same fissure to north along trackline, starting to shallow out

20:03 2266m collect grab sample from more massive unit, T735-G26, in S5

20:05 2265m massive flow overlain by pillow, lowest most exposed unit, well fissured with

pillows on top, pillows appears to possibly flow inside indicating pillows post-date fissure, N-S

fissure

20:07 2264m crossing massive flow, large fissure also to righ of ROV (east), possibly moving

into the transition from hooked ridge to normal ridge morphology

2008 2265m following fissure, series of fissures N-S cutting massive flow, columnar talus in

fissure

20:09 2265m some evidence of uplift along this section of fissure

20:13 2258m very heavy sed cover

20:16 2265m more pillows, less sed

20:22 2271m thick sed cover, large pilows sticking up

20:24 stopped for sample, cow patty looking pillow

20:26 2271m sample from cowpatty pillow, crust, T735-G27, in P2










20:31 2274m drifting to port towards large depression, some broken pillows with spill-outs,

some tubular

20:32 2275m fissure heading N-S, shows well on sonar, looks deep, tectonic

20:35 2268m, mound in depression near fisure, constructional

20:38 2275m small hornito, drippy flows, ~lm relief on structure

20:39 2271m appears like old fissure, sed filled, some truncated pillows???, narrow

constructional ridge???

20:42 2270m crossing fissure, just past linear series of small constructs, ~lm in relief, dropped

down crossing fissure to west

20:45 2272m shallow fissure, sed covering talus, orientation ~340

20:46 2271m another fissure, slight downdrop to east

20:48 2269m possible emuptive fissure, N-S, east side dropped down

20:50 2269m sample from pillow along fissure, T735-G28, pie shaped, in P2

20:57 2268m, hdg to east, 100% sediment cover

20:58 2267m, crossed a fissure trending N-S

20:59 2267m, still in region of pillow and heavy sediment

21:01 2270m, sparse pillow/lobate outcrops with heavy sed between

21:02 lost comment

21:05 2272m, moved over small fissure trace, pillows

21:07 2274m, typical deep sea biology

21:09 2268m, many more outcrops right now, small ridge of broken pillows

21:11 2264m, many more broken pillow outcrops

21:12 2259m, slope is shallowing to the north










21:15 2261m, on edge of slope with pillows outcropping, slope steepens to S

21:17 2261m, on the edge of large escarpment

21:18 2263m, fissure runs N-S, regional fissure system

2: 120 2266m, lots of broken pillows exposed here, much less sediment

21:22 2264m, back to isloated pillows and heavy sediment, flat

21:24 2259m, climbing toward top of dome, pillows loo tectonized, but broken in place

21:25 2258m, shallow depression filled in partially

21:27 2260m, at 2257m, maybe reached the summit of this feature, as bathy dropped off

afterward

21:29 2254m, pillow tubes, many going downslope to N(?)

21:30 2253m, crossing over smaller N-S fissure, can see both sides, sedimented on inside

21:32 2249m, continuing to move upward, most pillow tubes in place, plus rubble

21:33 2248m, in place pillows and a small rubble-filled fissure

21:35 2249m, collecting pieces of pillow crust near top of dome

21:36 2246m, T73 5-G29 will be in P3, looks old and oxidized

21:39 2242m, at top of mound, several fissures dissecting the top, running NS

21:42 2246m, running along a small N-S fissure, many on sonar, hdg is now 345ish

21:43 2251m, inside fissure, blocky and talus inside fissure, 20-30m wide

21:45 2250m, flying along the fissure, walls on both sides, small fissures wihtin main wall

21:47- 2252m

21:49 2257m, irregular, tectonized terrain, lots of rubble, some intact pillows on edge of small

fisure

21:50 2264m, mod sediment covered, more fractured terrain, filled in fissures









21:53 2270m, vehicle depth has been consistently 10m shallow than bathy

21:54 collection a sample for biotube 2, T73 5-G30, hopefully at intersection bewteen regional

fabric and local valley fabric

21:57 2272m, dropped first sample, looking for another piece of pillow crust

21:58 got another sample T73 5-G30, triangular piece of pillow crust, into biottube2

22:01 2272m, back to heavy sediment, flat, small isolated outcrops

22:03- 2270m, 40m to E is a fissure, flat-lying, 100% sed cover

22:05 2272m, 100% sed cover, isolated pillow outcrop

22:07 2276m, more of the same

22:09 2285m, more exposure of small bulbous pillows, still lots of sed

22:11 2293m, continuing to get deeper, still heavily sed

22: 17 2294 heading to the ridge parallel wall, sediments 100%

22:19 2294 sed. continue, tape change, type 8

22:24 2295 pilow ridges, about to get sample

22:24 same depth, sample T73 5-G3 1 taken from the pillow ridge

22:29 2296, sed. again, some pillow ridges again

22:29 2296, sed. again, some pillow ridges again

22:34 2296 still 90% sed. some flow tos broken

22:36 2290 fissure 337 orientation, talus on the sides on the fissure,

22:39 2287, more pillow terrane, heavily fissured

22:41 2289, still fissures, heavily sed. between issues

22:43 2280, compl. tectonized big pile of debrii pillows

22:46 2291 old fault (fault sliver) heavily tectonised









22:47 2290 approaching the opposite wall, covered with talus, another fault sliver

22:49 2287 wedging out fault sliver, two intersecting faults

22:51 2294 still old tectonized terrane

22:53 2297 materail changes, more collapsed pillows

22:54 2298 about to get sample

22:56 2298 sample G32 from the base of the wall

22:59 2296 ROV loosing main comp. going toward the wall

23:01 2291 base of the wall flat sheets, tectonised ridge

23:03 2291 small pillows with buds on the side base of the wall

23:04 2294 moderate sed. cover, lobates, pillows with buds, still intact, gradually going uphill

23:05 2293, fissure parallel to the wall

23:07 2293 first ridge parellel tectonised zone

23:08 2290 into the real fault, big step up

23:10 2288 intact collapse pit, not consistent wall

23:12 2281 change headings to 300 up the fault

23:14 2276 intact pillows and lobate flows downhill from us,

23:15 2274 remarkably little fractionation on pillows, constractional part of the wall?

23:17 2269 tectonised area

23:19 2263 heavily tectonized zone, small fragments nothing intact

23:20 2260 coming to relative. flat artea, sedimented

23:23 2257 continue flat area, covered with sheety flow debri

23:25 2257 sample from the sheety glassy flow -G33

23:26 2257 sample G33 very altered glassy, taken another piece









23:31 2248 intact flows and lobates, going down parallel to the wall

23:33 2244 half-way up the wall, flows align down

23:34 2242 sedim. area, covered with thin sheeted flows, contiune up the wall

23:36 2239 approaching steep wall..

23:3 8 2239 escarpment pillow debrii, series of fault stpes, broken sheets

23:40 2233 moving into area of intact lobate flows

23:40 2232 still intact flow

23:41 2225 alteranting talus and flows

23:42 2226 samples from the flow sheet and lobate flows

23:45 2228 sample G34 from lobate flow

23:45 2228 second sample G35 from the same area

23:48 2230 near the top of the wall coherent flows

23:50 2231 sample G36

23:53 2231 G37 and G 38 samples

23:55 2231 G 39 sample

23:59 ROV is coming up

01:26 Om end dive T735









APPENDIX B
PHASE CHEMISTRY FOR T73 5 LAVAS




Full Text

PAGE 1

1 PETROGENESIS OF ANDESITES AND DACITES FROM THE SOUTHERN JUAN DE FUCA RIDGE By LAURIE ANN COTSONIKA A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2006

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2 Copyright 2006 by Laurie A. Cotsonika

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3 To my family.

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4 ACKNOWLEDGMENTS I would like to thank my advisor, Dr. Mi chael Perfit, for his patience and guidance throughout this project, and Dr. Ma tthew Smith for the support and help hes given me in order to complete this. I would also like to thank th e Monterey Bay Research Aquarium Institute for providing use of their equipment and fac ilities and the crew and officers of the Western Flyer as well as the pilots of the ROV Tiburon for the hard work they put in during the cruise to the Juan de Fuca Ridge. I would like to thank Dr. Debr a Stakes and Dr. Jim Gill for lending their support and expertise on the cruise and with interpreting my data. Dr. W. Ian Ridley deserves my thanks for all the help and analytical support provided in Denver and Dr. Paul Wallace for providing the volatile data. I would also like to thank George Kamenov for th e help and analytical support given while processing my trace element data. I would like to thank my famil y, especially my parents, Art and Linda, and my brother and sister, Nick and Elizabeth, who provided much needed emotional support and understanding. I would also like to thank all my friends in the Geological Sciences depart ment at University of Florida.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........7 LIST OF FIGURES................................................................................................................ .........8 ABSTRACT....................................................................................................................... ............10 CHAPTER 1 INTRODUCTION..................................................................................................................12 Regional Geology............................................................................................................... ....13 Previous Studies of Highly Fracti onated Suites Recovered at MOR.....................................14 2 STUDY AREA AND SAMPLE RECOVERY......................................................................20 T735 Dive Observations.........................................................................................................21 3 ANALYTICAL METHODS..................................................................................................27 Major Elements................................................................................................................. ......27 Trace Elements................................................................................................................. ......28 4 PETROGRAPHY AND MINERAL CHEMISTRY..............................................................32 Basalts........................................................................................................................ .............32 Andesites and Dacites.......................................................................................................... ...32 5 MAJOR AND TRACE ELEMENTS.....................................................................................48 Basalts........................................................................................................................ .............48 Major and Minor Elements..............................................................................................48 Trace Elements................................................................................................................50 Andesites and Dacites.......................................................................................................... ...52 Major and Minor Elements..............................................................................................53 Trace Elements................................................................................................................53 6 DISCUSSION..................................................................................................................... ....62 Comparison to Other Evolved Suites.....................................................................................62 Dive T735 Samples.............................................................................................................. ...64 Fractional Crystallization..................................................................................................... ...67 Magma Mixing................................................................................................................... ....70 Partial Melting/Assimilation Frac tional Crystallization (AFC).............................................72

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6 7 CONCLUSIONS....................................................................................................................84 APPENDIX A T735 DIVE LOGS................................................................................................................. .86 B PHASE CHEMISTRY FOR T735 LAVAS.........................................................................100 C MAJOR AND TRACE ELEMENT DATA FOR T735 LAVAS.........................................159 D PETROLOG RESULTS.......................................................................................................165 LIST OF REFERENCES.............................................................................................................178 BIOGRAPHICAL SKETCH.......................................................................................................188

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7 LIST OF TABLES Table page 1: Accepted values for ma jor element standards...........................................................................30 2: ICP Trace element standards. 2005-2006 an alyses of ENDV (ran as sample) together with other MORB samples (d rift 1 first sample after the standards)...............................31 B-1: Pyroxene compositions determ ined from microprobe analyses..........................................101 B-2: Plagioclase compositions determ ined from microprobe analyses.......................................132 B-3: Olivine compositions determin ed from microprobe analyses.............................................154 C-1: Major and trace element data for Dive T735 samples.........................................................160 D-1: Results from Petrolog. Results assume QF M at 200 bars of pressure and sample T735G35 as the parent composition.........................................................................................166

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8 LIST OF FIGURES Figure page 1 Map of the Juan de Fuca Ridge..........................................................................................17 2 Overview of MBARI dives and rock core s on the southern Cleft segment since 2000....18 3 Overview of the dive trac k taken during Tiburon Dive 735..............................................24 4 Profile map of dacite dome morphol ogies and evolved sample locations.........................26 5 Examples of basaltic lava mo rphologies seen during dive T735.......................................36 6 Plain polarized and cross polar views of glomeroporphyritic texture in T735-G23..........36 7 Dacite dome lava morphologes..........................................................................................37 8 Plagioclase oikocryst surrounding seve ral randomly orient ed clinopyroxene chadacrysts in sample T735-G10.......................................................................................37 9 Element map of poikilitic texture seen in T735-G10, in this case, a plagioclase oikocryst surrounding low-Ca pyroxenes..........................................................................38 10 Point compositions of pyroxene phenocrysts in T735-G9 and T735-G12 are plotted to show zoning patterns.....................................................................................................39 11 Oscillatory zoned clinopyr oxene in sample T735-G9.......................................................40 12 Skeletal clinopyroxene grain with a lacey reaction rim surrounding th e crystal, this is also indicative of rapid crystal growth...............................................................................41 13 Populations of zoned pyroxenes........................................................................................42 14 Olivine and plagioclas e glomerophyric cluster..................................................................43 15 Element map of skeletal fayalite crystal in sample T735-G12..........................................43 16 Rare (<1% of the sample) euhedral zi rcon phenocrysts seen in samples T735-G12 and T735-G19 were discovered th rough microprobe analyses..........................................44 17 Plain polarized light (left) and crossed polarized light (right) views of a basaltic xenolith in sample T735-G11............................................................................................45 18 Element maps of a basaltic xenolith in sample T735-G12................................................45 19 A coarser grained xenolith, found in T735G10, is composed of plagioclase, An34 An35, and fayalitic olivine, Fo15........................................................................................46

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9 20 Myrmekitic intergrowth of quartz and plagioclase............................................................47 21 AFM Diagram comparing Smith, 1994 and Stakes, 2006 samples to dive T735 samples........................................................................................................................ .......55 22 Major element plots comparing previous st udies of the Cleft segment (Smith et al., 1994; Stakes et al., 2006) to dive T735 samples................................................................56 23 Trace element plots comparing previous studi es of the Cleft segment (Smith et al., 1994; Perfit, unpublished) to dive T735 samples..............................................................58 24 The primitive mantle normalized (McDonough and Sun, 1995) spider diagram displays the depletion of several key trace elements in the evolved glasses compared to the basalt compositions..................................................................................................60 25 The primitive mantle normalized (McDonough and Sun, 1995) REE plot shows the two distinct groupings within the sample group................................................................61 26 Comparing major element variations in the T735 lavas to other evolved suites...............75 27 Major element liquid lines of descent................................................................................77 28 Cumulative percentage of phases plot ted against melt temperature (C)..........................79 29 Trace element liquid lines of descent.................................................................................81 30 Mixing models calculated using a standa rd mass balance equation (Langmuir et al., 1978).......................................................................................................................... ........82 31 Comparison of T735 Cland Cl/K ratios versus MgO......................................................83

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10 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science PETROGENESIS OF ANDESITES AND DACITES FROM THE SOUTHERN JUAN DE FUCA RIDGE By Laurie A. Cotsonika December 2006 Chair: Michael R. Perfit Major: Geology The Cleft segment and the ridge-transform inters ection (RTI) of the Southern Juan de Fuca Ridge have been investigated during three cruises of Mont erey Bay Aquarium Research Institutes (MBARI) Research Vessel (R/V) Western Flyer beginning in 2000. A total of 53 rock cores and 276 precisely located ro ck or glass samples were colle cted during sixteen dives with the remotely operated vehicle (ROV) Tiburon These ROV dive samples and observations allow us to test models regarding the magmatic evolut ion of this segment and the relationships between specific tectonic and morphologic feat ures and magmatic processes. An extremely wide range of N-type mid-ocean ridge basalt (MORB) lavas were recovered which are, on average, more evolved (lower MgO) off-axis, away from the present neovolcanic zone, and towards the RTI. During dive T735 we investigated a region of unfaulted, curved volcanic ridges that overshoot the Blanco Transform and 39 samples of lava ra nging from ferrobasalt to andesite and dacite (SiO2 = 50.1 to 66.9 wt.%; Mg# = 49.9 to 9.7) were recovered. The highly evolved lavas were recovered from two large constructional domes co mprised of unusually large pillow flows, and extremely blocky, vesicular flows similar to so me terrestrial silicic domes. Some of the andesite-dacite hand samples are extremely vesicu lar with elongate vesicles (1-10 cm) in a glassy matrix. Mineral assemblages are dom inated by microphenocrysts of ferroaugite and

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11 ferropigeonite, with lesser amounts of sodic plag ioclase and FeTi oxides. Rare zircon, fayalite and myrmekitic intergrowths of plagioclase and qua rtz are present. A few of the more magnesian phenocrysts (xenocrysts?) exhibit fine normal zoni ng whereas more Fe-rich crystals exhibit fine reverse zoning. Additionally, inclusions of quenched basaltic material appear within some of the evolved lavas. These samples represent an extens ive and unique set of so me of the most highly fractionated ocean floor rocks that have ever be en recovered; particularly from such a welldocumented setting. Fractional crystallization m odels which predict over 80% crystallization do not adequately explain the major element chemistry of the silicic lavas and most incompatible trace elements exhibit significant enrichments relative to predicted c oncentrations. The highly evolved nature of the dacites, crystal zoning pa tterns and the presence of basaltic inclusions suggest the lavas are the result of mixing between two crystal bear ing end-members, i.e. a typical basalt and a rhyolite likely generated by extreme amounts of fractional crystallization. The andesitic and dacitic lavas also have elevated Cllevels that range from 4000-6000 ppm. While the Cl-/K levels are enriched they do not indicat e that significant amounts of crustal assimilation have occurred.

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12 CHAPTER 1 INTRODUCTION Over 60% of the Earths magma flux, > 21 km 3/yr, ~3 km3/yr extrusive and ~18 km3/yr intrusive, takes place at mi d-ocean ridges (MOR) (Chadwick and Embley, 1994; Perfit, 2001), however less than 1% of the total seafloor tota l area has been sampled or studied in much detail (Perfit and Chadwick, 1998) and that 1% has been concentrated upon ridge crests. Only a few studies have focused on the broader area surroundi ng the immediate region of the ridge axis, and therefore most investigations ha ve been focused within a narrow neovolcanic zone centered at the ridge axis. Studies centered on the ridge ax is have generally not directly addressed the processes that occur away from the ridge axis and at ridge-transform intersections (RTI). It has recently been hypothesized that the areas 5-20 km off of the ridge axis possibly make a greater contribution to the overall magma flux than previ ously thought (Goldstein et al., 1994; Graham et al., 1996; Hekinian et a., 1999; Johnson et al., 2000; Klingel hofer et al., 2001; Zou et al., 2002). Though published data regarding lavas erupted off-axis and at RTIs is sparse, it has been suggested that greater amounts of fractional crystallization and assimilation can occur at these locations. Limited magma recharge can lead to less homogenization of magmas at these locations compared to the main axial magma bod y, allowing for more diverse and evolved lava compositions to be erupted onto the oceanic fl oor (Christie and Sinton, 1981; Fornari et al., 1983; Perfit and Fornari, 1983; Perfit and Fornari, 1983; Juster et al., 1989; Perfit et al.., 1994; Perfit et al.., 1999; St offers et al., 2002). In this thesis, field observations together with petrologic, ma jor and trace element data are utilized to determine the geochemical character istics and petrogenesis of highly evolved lavas recovered from the region of the intersection of the Juan de Fuca Ridge (JdFR) with Blanco

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13 Fracture Zone (BFZ) (Figure 1). Lava sample s recovered in 2004 during dive T735 of the ROV Tiburon operated by the Monterey Bay Aquarium Research Institute (MBARI) represent an extensive and unique set of some of the most hi ghly fractionated oceanic rocks that have been recovered from such a well-documented setting. This, in conjunction with the extensive sampling of the Cleft segment of the southern JdFR and the associated geochemical database, make it an ideal sample set to explore the magm atic processes involved in the petrogenesis of samples from the RTI. Regional Geology The JdFR in the northeast Pacific is an inte rmediate spreading rate ridge (56 mm/yr full rate) that has been extensively studied begi nning in the 1960s (Raff et al., 1961; Johnson and Holmes, 1989; Embley et al., 1991; Smith, 1993; Pe rfit et al., 1994; Smith et al., 1994; Perfit et al., 1998; Perfit, 2001; Karson et al., 2002; Tierney, 2003; Stakes et al., 2006). It is located approximately 440 km (~238 nm) off of the coas t of Washington and Oregon and spans almost 500 km between the Blanco and Sovanco Fracture Zones. The JdFR has been divided into seven secondorder ridge segments that have distinct morphological characteristics (Embley et al., 199 1; Embley et al., 2000; Smith et al., 1994; Chadwick et al., 2005). The Cleft segment (Figur e 2) is the southernmost segment with its northern terminus at ~45N and its southern terminus at 44N where it intersects the Blanco Fracture Zone (BFZ) (Embley et al., 199 1; Smith et al., 1994). The Cleft segment has recently been volcanically active and has prove d to be an important area for detailed investigations of submarin e volcanology, hydrothermal activ ity, eruption rates, and MOR petrogenetic processes. Chadwick and Embley (1994) summarized studies of several mid-ocean ridge basalt (MORB) lava flow s believed to have erupted in 1983 and 1987 along the axis of the Cleft segment and estimated, following Crisp, (1984) that the average extrusive output along the

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14 whole Cleft segment is 0.003 km3/yr. Extrusive activity was determined to be bimodal with sheet flows preceding a voluminous eruption of pillow flows (Embley and Chadwick, 1994). The overall extrusive layer of the Cleft segment has an averag e thickness of 350 m and varies from 200 to 550 m in thickness (McDonald et al., 1994) while depth to the axial magma chamber (AMC) varies from 1.9 km under the southern Cl eft hydrothermal vent systems to 2.23 km under the northern hydrothermal fields (Canales, 2006). There is a st rong correlation in the Cleft segment between degree of fractionation and latit ude, as lavas are generally more mafic to the north and more evolved toward the southern te rminus (Christie and Sinton, 1981; Smith et al., 1994, Stakes et al.. 2006). Since 2000, 53 rock cores and 276 rock and glas s samples have been recovered from the Cleft segment using the Remotely Operated Ve hicle (ROV) Tiburon (Stake s et al., 2006; Figure 2). Overall, a wide range of normal incomp atible element depleted MORB (N-MORB) lavas were recovered from the entire length of the Cl eft segment. The most highly evolved basalts and a few high-silica lavas were recovered off-axis, away from the neovolcanic zone, and near the RTI. In 2000, a sample of MOR, low-potassium d acite was recovered by rock core from a small topographic dome in an area of the Cleft segmen t characterized by what appear to be curved ridges and volcanic cones that overlap the wester nmost part of the Blanco Transform and appear to extend on to the Pacific plate. The extremely ra re occurrence (or at least recovery) of dacite in a MOR setting was the impetus for a ROV dive in 2004 that explored these features at the RTI, in a common yet poorly studied MOR setting. Previous Studies of Highly Frac tionated Suites Recovered at MOR Highly fractionated suites of at ypically high silica MOR lavas have been recovered in few other locations around the globe; these include the Galapagos Spreading Center (GSC), Iceland, the Pacific-Antarctic Ridge and a few places on th e East Pacific Rise. Hypotheses put forth to

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15 explain the formation of these petrologically ev olved suites on the oceanic floor include the cold edge effect (Christie a nd Sinton, 1981; Fornari et al., 1983; Perfit et al., 1983; Johnson and Holmes, 1989; Juster et al., 1989; Embley et al., 1991; Smith, 1993; Smith et al., 1994; Juteau et al., 1995; Tierney, 2003; Herzburg, 2004), bimodal volcanism, similar to that occurring in intrusive suites in the western United States (Reid et al., 1982; Barbarin, 1990; Ratajeski et al., 2001), and, more recently, crustal assimilation (Kerr et al., 1996; Bohrson and Reid, 1998; Garcia et al., 1998; Gee et al ., 1998; Hoernle, 1998; OHara, 1998; Weis et al., 1998; Perfit et al.., 1999). The eastern GSC at ~85W has been extensivel y studied since the late seventies (Christie and Sinton, 1981; Anderson et al., 1982; Fornari et al ., 1983; Perfit and Forn ari, 1983; Perfit and Fornari, 1983; Juster et al., 1989). The discovery of chemically fractionated (high-silica) lavas along the GSC first led to the development of the cold edge effect hypothesis (Christie and Sinton, 1981; Fornari et al., 1983; Perf it et al., 1983; Juster et al., 1989). This type of cold edge effect occurs along a propagating ri dge axis as the advancing ridge magmatic system intersects older, relatively cool oceanic lithosphere locat ed on the opposite side of a fracture zone. This intrusion presumably leads to greater extents of cooling in magma bodi es causing the magma to undergo more extensive crystallization than woul d occur in typical ridge axis settings where magma chambers are believed to be more steady-state. This hypothesis is proposed to account for the common occurrence of MOR fe rrobasalts and FeTi basalts at propagating rift tips in the Galapagos Spreading Center (Chris tie and Sinton, 1981) and lavas as evolved as andesites at the RTI at ~85W (Fornari et al., 1983; Perf it et al., 1983; Juster et al., 1989). Silicic volcanism has also recently been doc umented on the Pacific Antarctic Ridge (PAR) (Hekinian et al., 1997, 1999; Stoffe rs et al., 2002; Haase et al., 2005). Stoffers and others (2002)

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16 discovered different populations of evolved lavas, some consistent with crystal fractionation at low and high oxygen fugacities, and others resulting from the magma mixing of highly fractionated magmas and unevolved basaltic melt s. They hypothesize that extensive crystal fractionation occurred in a so lidification zone surrounding a ma gma chamber (e.g. Nielson and Delong, 1992). Residual silicic magma is proposed to migrate upward along the margin of the magma chamber and assimilate al tered basaltic wall-rock, increas ing its oxidation state (Stoffers et al., 2002). Haase and others (2005), associate the silicic lavas with a ridge axial high; a location where large volumes of magma are found and where ther e is associated hydrothermal venting. They further hypothesize that extensive fractional crystallizati on, facilitated by cooling from the hydrothermal vent fields, as well as assimilation of hydrotherm ally altered crustal material is responsible for the petrogenesis of the andesites and dacites found on the PacificAntarctic Rise. Recent studies have also considered the ro les of fractional crysta llization and crustal assimilation in hotspot environments such as the Galapagos Islands (Geist et al., 1998) and Iceland where crustal assimilation has been hypothesized to, in part, contribute for the heterogeneous nature of Icelandic volcanism (N icholson et al., 1991; Furman et al., 1995; Gee et al., 1998).

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17 Figure 1: Map of the Juan de Fuca Ridge. The Juan de Fuca medium-rate spreading ridge in located between the Pacific Plate and Juan de Fuca. It is located approximately 440 km (~238 nm) off of the coast of Washington and Oregon and spans almost 500 km between the Blanco and Sovanco Fracture Zones. The samples descri bed in the thesis were recovered from the southern intersection of the Juan de Fuca Ridge with the Blanco Fracture Zone, as highlighted by the yellow box. Map created using the open s ource java application at www.geomapapp.org.

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18 Figure 2: Overview of MBARI dives and rock cores on the southern Cleft segment since 2000. 53 rock cores and 276 rock and glass samples have been recovered from the Cleft segment using the Remotely Operated Vehicle (R OV) Tiburon (Stakes et al., 2006). In 2000, a sample of dacite

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19 was recovered by rock core from a small topogr aphic dome in an area of the Cleft segment characterized by what appear to be curved ridges and volcanic c ones that overlap the westernmost part of the Blanco Transform. Di ve T735 covered the area where the dacite rock core was taken (Stakes et al., 2006).

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20 CHAPTER 2 STUDY AREA AND SAMPLE RECOVERY In 1998 the Cleft segment was surveyed us ing a hull-mounted 30 kHz Simrad EM300 multibeam sonar and using 2 degree by 2 degree beam resolution, the EM300 achieved a ~30 m lateral resolution over a 3 km swath width (Stakes et al ., 2006). The mapping program was supplemented by a series of in situ observations made from the ROV Tiburon, operated from the Research Vessel Western Flyer during July 2000, August 2002 and August 2004 (Stakes et al., 2006). A total of 16 ROV dives were completed acr oss the Cleft spreadin g center; five dives across the axis near the South Cleft hydrothermal fields; five dives on the southernmost part of the segment; two dives on the northern wall of the intersection with the BFZ and dive T735, the focus of this thesis, on the hooked ridges that de fine the western side of the nodal basin where the ridge axis intersects the BFZ (Figure 2). Dive T735 utilized the ROV Tiburon in order to observe and sample the area where a dacitic glass was recovered by piston core in 2000 (Figure 3). The dive was dedicated to investigating the dome-like featur es observed in the bathymetry and recovering samples along a dive traverse that began south of the core location a nd ended to the west of the southernmost portion of the Cleft axial valley. A detailed sa mpling program was carried out as part of the ROV and surface ship operations during the dive Lava samples were recovered with the Tiburon manipulator and details of each sampling locality were documented by the scientists in charge of observations and sampling during ea ch dive. The ROV observations, contemporaneous magnetic field measurements, digital still and video images and geologic samples were all located with respect to the EM300 bathymetry through a real-time ArcView-based navigation and GIS system using the EM300 bathymetric base map (Stakes et al., 2006). The bathymetric

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21 data, ship locations and ROV US BL (ultra-short baseline) navi gation used a common GPS datastream with real-time depth (from the ROV) pr oviding consistent positio n information within 1020 meters of bathymetric features on the EM300 bathymetry. Below, the bathymetric, observational and sample data are integrated to provide a detailed acc ount of the geology along dive T735. T735 Dive Observations Dive T735 began at 14:49 Greenwich Mean Ti me (GMT) on a talus sl ope at the southern end of the dive track (Figure 4) but soon crossed an area dominated by lightly sedimented, intact, basaltic pillow flows, crosscut by several N-S trending fissures. Basalt samples T735-G1, at 2187 m, through T735-G6, at 2216 m, were recovered from this area, before Tiburon began to traverse upslope. At 16:05 GMT an area of la va drain-back was observed, with moderate sediment cover in between the pillows and lobate flows. At 16:13 an area of more blocky flows was observed and sample T745-G7, a basalt, wa s recovered from the top of a small knoll (2213 m). At 16:25 GMT Tiburon dropped over the edge of a fissure and moved into an area of thick sediment cover with isolated pillows basalts. Sample T735-G8 was recovered from this area at 16:39 GMT at 2232 m depth. Tiburon then moved through an area of isolated pillows with <50% sediment cover, before reaching an area of light ly sediment covered, large striated pillows and associated sheet flows. Sample T735-G9, a dacite, was recovered at 16:45 GMT from a friable sheet flow at the base of the first of the domes. Samples T 735-G10 and G11, both dacitic in composition, were recovered from large (> 1m in diameter), glassy, striated pillows lightly covered with sediment observed in conjunction in the sh eet flows that flowed down the slope to the southwest. As Tiburon continued to traverse upslope the flows became more blocky and massive, with vapor pockets and cavities observed between the layers of rock and very little sediment cover. T735-

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22 G12, one of the most evolved dacitic samples, was collected at 16:59 GMT from one of the vapor pockets observed in the area at 2211 m dept h and was extremely glassy in appearance. Tiburon then passed over an area with more local re lief, in the form of big, sediment-coated pillows with bread-crust textures surrounded by smoother pillow tubes. At 17:06 GMT Tiburon moved into an area of fractur ed sheet flows where andesite samples T735-G13 (17:09 GMT) and G14 ( 17:22 GMT) were collected. At 17:27 GMT, smoother pillow forms and tube morphologies do minate with more massive flows between. Then sample T735-G15, another andesite, was re covered from a region of highly vesicular (1015% vesicles), blocky flows on top of what appear ed to be a constructional dome at 17:32 GMT. The interior of the blocky flows was sampled at 17:46 GMT (T745-G16) at 2216 m and is dacitic in composition. After collecting T735-G16 Tiburon began to traverse down-slope to the east. Pillows with bread-crust texture were observed under moderate (<30%) sediment cover. Down the slope of the dome at 18:06 GMT sample T735 -G17, a dacitic pillow fragment, was recovered from a saddle at 2221 m. To the east, up, out of the sa ddle, another dome structure wa s encountered. At 18:16 GMT, two small pieces of andesitic pillo w crust were collected at 2206 m. Continuing upslope, smaller pillow forms (< 1 m in diameter) were observed up to the top of the dome at 2198 m where the morphology was dominated by flattened lobate tube s, some of which appeared to flow downslope to the south. Sample T735-G19, an andes ite was recovered from the top of the dome construct at 18:25 GMT. At 18:29 GMT Tiburon began the slow descent down-slope over a structurally undisturbed area consisting of well-formed pillows and tubes with only moderate sediment cover. At 18:36 GMT blockier, broken pillows and tubes were observed along a shallow slope. At 2234 m,

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23 18:35 GMT, sample T735-G20, a dacite, was recovered from a small pile of talus near an in situ pillow flow. This flow front of pillows over talu s continued for a few 10s of meters before the slope began to steepen towards the east. Sample T735-G21, a large basaltic fragment fr om an intact pillow, was recovered from the base of the steep slope at a depth of 2275 m at 19:01 GMT. A region of heavy sediment cover with isolated pillows was then traversed. Sample T735-G22, was recovered at 19:16 GMT, 2256 m, from an area of extensive collapse (likely drainback) that was associ ated with sheet flows under moderate sediment cover. A sample of an isolated basaltic pillow, T735-G23, was recovered at 19:26 GMT from 2250 m in depth. Afterwards, pillows began to dominate the landscape once more; recovery of samples G24 and G25 began at 19:37 GMT and they were both collected from a haystack at a depth of 2249 m. The northern portio n of the dive covered much more tectonized terrain with in a zone of pillow ridges sepa rated by N-S trending fissures. Samples T735-G26 through G39, all basalts, were r ecovered from pillow to lobate flows within this region.

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24 Figure 3: Overview of the dive track taken during Tiburon Dive 735. Yellow dots denote sample locations, while yellow bulls eyes denote th e 2000 rock cores. The 2000 rock core was

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25 recovered near the T735-G15 sample site. The evolved sample set is represented by samples T735-G9 through T735-G20.

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26 Figure 4: Profile map of dacite dome morphol ogies and evolved sample locations. Profile estimated from the depth of the ROV. Basa lt samples are designated by the blue diamonds, andesitic samples are designated by orange triangles and dacites by red circles, with every fifth sample being numbered. Large changes in the ROVs heading are noted.

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27 CHAPTER 3 ANALYTICAL METHODS Thirty-nine lava samples were collected from the RTI of the JdFR and the BFZ during dive T735 of the ROV Tiburon during th e MBARI research cruise in 2004. Thin-sections were made of a representative suite of the evolved samp les and one basalt recovered during the dive. Natural glasses were separated and coarsely cr ushed, and crystal-free glass separates were handpicked under a binocular microscope. Evolved lava s had fairly crystalline glass and in picking those glass chips, crystal clots and phenocrysts were avoided and the least crystalline chips were chosen for analysis. The crushed glass chips we re then ultrasonically cleaned for 10-20 minutes, in a solution made from equal part s 2.5N reagent grade HCl and 30% H2O2 in order to remove any surficial coatings, such as MnO, adhered to the sample. Major Elements Clean glass chips were mounted to thin sec tions for microprobe anal ysis, with glass from UF internal standard 2392-9, an N-MORB from th e East Pacific Rise at 9 50 N, included on each slide. Major element concentrations we re determined on natural glasses using JOEL electron microprobes at the United States Geologi cal Survey (USGS) in Denver, CO, with the help of Dr. Ian Ridley, and at Florida Internat ional University (FIU) by Dr. Michael Perfit. Traditional mineral standards were used to calib rate the microprobe analyses and secondary (offline) normalizations were completed using the UF standard 2392-2, and the USGS standard GSC, a synthetic andesite microbeam glass (Rie hle et al., 1999). Accepted values for these standards are given in Table 1. Operating condi tions for the microprobe were an accelerating voltage of 15 keV and a beam current of 20 nA. Probe diameter for mineral analyses was set to <10 m and defocused to 20 m for glass analyses.

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28 Typical precision was evaluated by comparing re peat analysis of UF standard glass 2392-9 (Table 1) which was mounted and analyzed on ev ery probe slide. Percen t variation in the 2392-9 analytical values was low, ranging from a one-sigma standard deviation of 6.4% in K2O to 0.13% in the SiO2. SiO2 values showed strong linear correlati ons with analysis total and were corrected to using the foll owing formula, [raw SiO2 value + ((99.7 raw total)*0.4505)], where the raw silica value has an addi tional factor added to it consis ting of an assumed total (99.7) minus the raw total multiplied by the slope of the trend-line of raw SiO2 versus the raw total (0.4505). Trace Elements Trace element concentrations were determined at the University of Florida using an Element 2 Inductively Coupled PlasmaMass Spectrometer (ICP-MS). Dr. George Kamenov developed the dissolution and analytical proced ures (see below). Sa mple preparation was performed at UF in a class 1000 clean lab f acility. Standards used included the wellcharacterized internal UF standards 2392-9 and ENDV, as well as the USGS standard BHVO-1, the surface layer of a 1919 Hawaiian pahoehoe fl ow (Flanagan, 1976). Trace elements measured by the UF ICP-MS have been determined to be accurate and precise to be tter than % of their concentration (Table 2). Phase one of the dissolution process require s that two to three standards encompassing the likely potential range of the unknown sample concentrations be chosen; for the T735 run AGV-1 and BCR-2 were used and compared alon g with two in-house standards, ENDV and 2392-9. Next, tall, clean, hex-cap Savillex Teflon vials were labeled for each sample, including one blank. Two drops of 4x water were placed in each vial and the scale was zeroed before ~.04 g of either clean glass chips were added to each vial and the precise weight was recorded. In the clean lab, 1 mL of optima grade HF and 2 mL of optima grade HNO3 were added to each vial

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29 and then the vials were tightly capped and pl aced in a 100C oven for approximately 48 hours. Samples were then dried down on a hot plate (car efully rinsing the caps into the vials with 4x water) for 12 to 24 hours. In phase two of the dissolution process, 4 mL of an internal standard (5%HNO3, with Re and Rh) was measured into each vial. The vials were then capped and heated on the hot plate overnight. In order to dilute the samples for analysis 200 L of solution was pipetted from each vial and transferred to a clean auto sampler tube and we ighed. Four mL of the same internal standard was added to each tube and the samples were weighed again. The final dilution factor was approximately 2000x. Samples were introduced into the ICP-MS in one-minute uptake times followed by twominute washes for each sample. The specific isotopes analyzed were: Sc45, V51, Cr52, Co59, Ni60, Cu63, Zn66, Ga69, Rb85, Sr88, Y89, Zr90, Nb93, Rh103, Ba137, La139, Ce140, Pr141, Nd143, Sm149, Eu153, Gd157, Tb159, Dy163, Ho165, Er166, Tm169, Yb172, Lu175, Hf178, Ta181, Re185, Pb208, Th232 and U238. Four runs were made with four passes pe r analysis in Medium Resolution mode. Data were reduced on-line using calibration cu rves of the standard data acquired during analyses and drift corrections were mathematica lly calculated off-line. The ENDV standard was used for drift corrections duri ng each analytical run; one measurement was taken at the beginning of the sample series, one in the middle and one at the end of the series. Accuracy and precision for the T735 analytical run was evaluated by analyzi ng ENDV standard as a sample and comparing the results to rece nt runs of the standard using the same ICP-MS instrumentation (Table 2). One-sigma standard deviations from the accepted values were less than or equal to 3.6% during these analyses.

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30 Table 1: Accepted values for major element standards. Internal UF Standard 2392-9 Correction Factors SiO2 SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 Clfor the averages of each group average 50 49.49 1.28 15.41 8.99 0.15 8.23 12.04 2.62 0.10 0.11 0.004 std dev 0 0.20 0.02 0.19 0.05 0.01 0.08 0.06 0.03 0.01 0.01 0.001 % var 0 0.41 1.57 1.22 0.50 5.13 0.96 0.53 1.33 6.43 5.59 22.79 2392-9 50.04 50.04 1.31 15.48 9.38 0.18 8.50 12.15 2.56 0.09 0.12 correction factor 1.00 1.01 1.03 1.00 1.04 1.18 1.03 1.01 0.98 0.92 1.07 for all analyses together average 50 49.52 1.28 15.41 8.99 0.15 8.24 12.05 2.62 0.10 0.11 0.004 std dev 0 0.29 0.04 0.20 0.10 0.02 0.14 0.13 0.06 0.01 0.03 0.003 % var 1 0.58 0.04 1.32 1.07 14.73 1.69 1.06 2.39 11.77 27.06 71.99 2392-9 50.04 50.04 1.31 15.48 9.38 0.18 8.50 12.15 2.56 0.09 0.12 correction factor 1.01 1.01 1.03 1.00 1.04 1.17 1.03 1.01 0.98 0.92 1.07 GSC Andesitic Glass Correction Factors SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 Claverage 62.11 0.01 13.71 6.27 0.02 3.77 4.99 3.58 3.63 0.04 0.01 std dev 0.45 0.02 0.21 0.10 0.01 0.07 0.05 0.33 0.05 0.02 0.00 % var 0.73 146.27 1.56 1.57 56.90 1.73 1.10 9.11 1.30 49.46 73.04 GSC 62.05 0.01 14.20 6.33 0.03 3.89 5.00 4.06 3.60 correction factor 1.00 0.85 1.04 1.01 1.75 1.03 1.00 1.13 0.99 Final Correction Factors Used SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 ClEvolved RX 1.01 1.1 Basalts 1.03 1.04 1.1 1.03 0.97 1.07

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31 Table 2: ICP Trace element standards. 2005-2006 analyses of ENDV (ran as sample) together with other MORB samples (drift 1 first sample after the standards). ENDV Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Avg Std dev % error (ppm) (g/mL) (g/mL) (g/mL) ( g/mL) (g/mL) (g/mL) (g/mL) Sc 38.00 39.20 39.30 37.63 38.41 37.55 36.66 39.18 38.27 1.02 2.67 V 275.60 278.82 278.53 269.72 268.44 268.33 262.17 275.48 271.64 6.17 2.27 Cr 290.20 297.94 292.23 279.24 285.96 264.80 262.94 277.86 280.14 13.13 4.69 Co 34.40 35.06 34.82 34.32 35.28 35.06 34.74 35.84 35.02 0.48 1.36 Ni 76.20 77.93 77.24 75.36 76.13 76.13 75.21 78.85 76.69 1.36 1.77 Cu 72.40 72.86 73.02 70.64 72.69 71.41 70.83 72.38 71.98 1.00 1.39 Zn 73.15 78.03 79.20 78.95 78.93 77.45 78.75 77.78 2.13 2.74 Ga 17.20 17.19 16.76 16.91 16.73 17.07 16.86 17.02 16.93 0.17 0.99 Rb 4.38 4.54 4.40 4.37 4.53 4.24 4.26 4.38 4.39 0.12 2.68 Sr 155.80 162.21 156.59 155.15 154.02 153.99 155.42 154.84 156.03 2.87 1.84 Y 32.40 31.65 32.62 32.47 31.96 31.31 31.23 32.81 32.01 0.64 1.99 Zr 113.40 112.58 114.04 112.39 111.96 110.72 110.07 105.06 110.98 2.91 2.62 Nb 6.46 6.62 6.47 6.39 6.34 6.29 6.26 6.46 6.40 0.12 1.93 Ba 64.20 69.90 73.28 70.87 72.80 71.86 71.27 68.19 71.17 1.74 2.44 La 6.02 6.01 6.02 5.97 5.92 5.93 5.90 6.00 5.96 0.05 0.78 Ce 15.60 15.90 15.69 15.40 15.41 15.49 15.52 15.72 15.59 0.18 1.18 Pr 2.46 2.52 2.53 2.44 2.44 2.46 2.44 2.49 2.47 0.04 1.59 Nd 12.60 12.63 12.56 12.60 12.43 12.49 12.21 12.78 12.53 0.18 1.43 Sm 3.76 3.85 3.78 3.76 3.75 3.79 3.74 3.78 3.78 0.04 0.94 Eu 1.34 1.36 1.33 1.33 1.32 1.34 1.33 1.33 1.34 0.01 0.92 Gd 4.88 4.80 4.94 4.88 4.83 4.77 4.76 4.97 4.85 0.08 1.71 Tb 0.86 0.84 0.86 0.86 0.85 0.84 0.83 0.86 0.85 0.01 1.54 Dy 5.28 5.31 5.35 5.29 5.21 5.18 5.21 5.36 5.27 0.07 1.41 Ho 1.10 1.13 1.13 1.10 1.09 1.13 1.11 1.13 1.12 0.02 1.75 Er 2.98 3.13 3.08 2.97 3.03 2.99 2.99 3.02 3.03 0.06 1.84 Tm 0.48 0.48 0.50 0.48 0.49 0.48 0.48 0.49 0.48 0.01 1.51 Yb 3.12 3.12 3.14 3.11 3.15 3.10 3.05 3.12 3.11 0.03 1.03 Lu 0.48 0.49 0.47 0.49 0.49 0.46 0.46 0.48 0.48 0.01 2.83 Hf 2.88 2.85 2.95 2.88 2.83 2.79 2.78 2.63 2.81 0.10 3.56 Ta 0.38 0.37 0.37 0.39 0.37 0.38 0.38 0.39 0.38 0.01 2.34 Pb 2.00 2.06 2.05 1.97 1.97 1.97 1.99 2.07 2.01 0.05 2.26 Th 0.46 0.47 0.46 0.46 0.46 0.46 0.46 0.45 0.46 0.01 1.45 U 0.19 0.20 0.19 0.18 0.19 0.19 0.19 0.19 0.19 0.00 2.07

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32 CHAPTER 4 PETROGRAPHY AND MINERAL CHEMISTRY Basalts Approximately two thirds of the samples re covered from dive T735 were basaltic in composition, although all are moderately to highly evolved compared to previously published Cleft MORB lava compositions. Basaltic lava morphologies ranged from pillow tubes to sheet flows (Figure 5). Basalt hand samples have a th in glass rind with a microcrystalline interior containing macroscopic plagioclase laths and pyroxene crystals. A thin section was made of sample T735G23 going from the surface of the hand sample into the microcrystalline interior. The thin section average ~80% glass with ~20% quenched microphenocrysts of plagioclase, ranging from 2 3 to 2 mm in length, with the average being ~ 1mm in the groundmass. Larger glomeroporphyr itic clusters comprised of euhedral to subhedral, 1mm long plagioclase laths, An64-An70, with simple Carlsbad twins and stepped, irregularly spaced twinning, and inter-grown anhedr al crystals of augitic clinopyroxene (Figure 6) are present, with an Mg# of ~81.3, with the Mg# being defined as 100*[Mg/[Mg+Fe]]. Andesites and Dacites Of the 39 lava samples collected, 12 were found to be high-silica lavas, five of which are andesitic (52% < SiO2 <63%) and seven are da citic (63%
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33 with small crystals and crystallites (~20 30 %) of swallowtail plagioclase, pyroxene and fayalitic olivine as well as larger semi-circular fragments of darker basa ltic xenoliths scattered throughout. Phase chemical data are presented in Appendix 2. Andesite and dacite assemblages are dominated by microphenocrysts of ferroaugite and ferropigeonite, lesser amounts of sodic plagioclase and FeTi oxides, and rare fayalite, zircon and myrmekitic intergrowths of plagioclase and quartz. Fine-grained basaltic xenoliths ar e included within all of the evolved lavas. Matrix glass is variable in color ranging fr om light to dark brown, nearly opaque, in proximity to the basaltic xenolit hs. Individual euhedral to rou nded, subhedral plagioclase laths, An18 An59, were found scattered throughout the thin-s ections and comprise ~5 10% of the volume of the samples. Crystals have lower fi rst order colors and simp le Carlsbad twins or stepped, irregularly spaced twins. Rare plagioclase oikocrysts with clinopyroxe ne chadacrysts are present in one sample, T735-G10 (Figure 8, 9) Plagioclase crystals have two distinct compositional groupings in the evolved samples. Plagioclase ranging from An69 to An83, occur in xenolithic clots and as large xenocrysts that appear to be in disequilibrium. More sodic plagioclase, An38 An66, occurs in the smaller, equilibrium crystals and in the myrmekitic clot. Most individual clinopyroxene crystals ex hibit finely zoned rims surrounding a more massive core. Several examples of both nor mal and reverse zoning are observed in the clinopyroxene grains in the e volved rocks (Figure 10). Rare clinopyroxene crystals with oscillatory zoning, or hourgla ss sector zoning were also obs erved in these samples, a phenomenon that has been associated with rapid crystal growth (Carpenter, 1980; Shelley, 1993). Additionally, the observed sector zoning is commonly combined with fine concentric zoning of crystal rims (Figure 11). Skelet al clinopyroxene crystals, also i ndicative of rapid crystal growth, exhibit lacey, almost spongy, reaction rims (Figur e 12). The cores of the pyroxene crystals fall

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34 into two distinct groupings, with one group exhi biting cores that range from Mg# of 56.0 58.6, and the other range in core Mg# from 8.24 12.6. In addition to these two groupings, there is also a population of individual pyroxenes, Mg# ranging from 29.3 30.21, whose compositions correspond with those of the rims in the zoned pyroxenes (Figure 13). Rare fayalite crystals, Fo5 Fo15, were found in several of the evolved lavas. In plain polarized light (PPL) these crysta ls are rounded or embayed and have a deep green color (Figure 14). In crossed polars (XPL) the fayalite crysta ls displayed high second order colors and a low 2V angle of ~50. Skeletal fayalite crystals ha ve lacey to spongy reaction rims similar to those seen on the quenched clinopyroxe ne crystals (Figure 15). Rare (occurring <1% by volume of the sample ) subhedral zircon crystals were found in several of the dacitic to rhyodacitic samples (Figure 16). Zircons were first discovered through microprobe analyses and later identified by their hi gh relief and very high birefringence in thin section. Zircon grains occur almost exclusively as individual grains with no apparent connection to xenoliths or crystal clots. Two populations of xenoliths were found in th e evolved samples. Rounded xenoliths of basaltic composition with chilled margins and microcrystalline interiors (Figure 17; Fiigure 18) and coarse-grained xenoliths composed entirely of large crystals, 1mm, with rough, irregular shaped edges. The basaltic xenoliths are composed of plagioclase, An32 An71, and pyroxene, Mg# ranging from 56.7 to 80.9, and range in size from <1 mm to several mm in diameter. Larger crystals (>0.5 mm in length) are usually confined to the center of the xenoliths and can become subophitic in texture with large pyroxene crystals partially enclosing smaller plagioclase laths. Basaltic xenolithic inclusions have very dark, glassy to microcryst alline interior edges that

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35 extend around the circumference of the inclusio ns. An optically clearer (PPL) and less crystalline and darker zone, ~.1-.5 mm thick, surrounds many of the xenoliths. The coarser grained xenolith, found in T735-G10, an andesite, is composed of plagioclase, An34 An35, and fayalitic olivine, Fo15 (Figure 19). It exhibits no mineralogical reactions along the margin, but the edges of the xenolith are ragg ed and look like they were ripped from the country rock. A single, resorbed myrmekite of plagioclase, An27 An30, and quartz was found in sample T735-G19 (Figure 20). This is typically a pluton ic texture that occurs primarily through grainboundary reactions in slowly changing condition s (Shelley, 1993). The myrmekite is rounded and ~1 mm in diameter, with worm-like intertwining of plag ioclase and quartz.

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36 Figure 5: Examples of basaltic lava morphologies seen during dive T735. Left: Lobate flows at the top of a fissure. Lobates usually form at the edges of sheet flows when the lava flow slows enough to form a fluid core under a solid crust. Right: Pillows, ~1m or less in diameter, and pillow buds under moderate sediment cover. Pillows form when the extrusion rate of the lava is slow enough to form a thick outer crust around the erupting lava. Figure 6: Plain polarized and cross polar views of glomeropor phyritic texture in T735-G23. Thin sections average ~80% glass with quenc hed microphenocrysts of plagioclase scattered throughout the groundmass. The larger glomeroporphyri tic clusters were comprised of euhedral to subhedral, 1mm long plagioclase laths, An64-An70, and inter-grown anhedral crystals of augitic clinopyroxene, with an Mg# of ~81.3.

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37 Figure 7: Dacite dome lava morphologies. The dacite domes display much different types of lava morphologies then those seen where basaltic samples were recovered. Left: Blocky, vesicular flow at the edge of one of the dacite domes. Th e large amount of vesicles seen is a by-product of the degassing lava. Right: Extremely large pillow tubes (>1.5m in diameter) were also noted cascading down-slope on the domes. Figure 8: Plagioclase oikocryst surrounding several randomly oriented clinopyroxene chadacrysts in sample T735-G10. This poikilitic texture can be indicative of plutonic origins and it indicates that the oikocryst mineral had a much more rapid growth rate then the enclosed chadacrysts (Shelle y, 1983; Higgins, 1998).

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38 Figure 9: Element map of poikilitic texture s een in T735-G10, in this case, a plagioclase oikocryst surrounding low-Ca pyroxenes. Element map were completed using X-ray imaging on the JOEL microprobe. Element labels are under each picture and count scales are located on the right-hand side of the images. Brighter colors indicate higher concentrat ions of a particular element. The gray-scale image is the backscatter image in whic h elements with higher mass are displayed brighter.

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39 Zoning Patterns0 5 10 15 20 25 30 35 40 00.20.40.60.811.2 Relative Distance from Core to RimMg# Figure 10: Point compositions of pyroxene phenocr ysts in T735-G9 and T735-G12 are plotted to show zoning patterns. Oscillatory (points 1-4; blue line) and re verse (points 5and 6; pink line) zoning can be seen in the pyr oxene from T735-G12 (right). The pyroxene from sample T735-G9 (left) also demonstrates compositi onal zoning through its hourglass pattern.

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40 Figure 11: Oscillatory zoned clinopy roxene in sample T735-G9. This crystal texture is indicative of rapid crystal growth. Note the fine concen tric zoning on the edges of the crystal and the reversely zoned pyroxene to the upper left of the large crystal. Mapping details in Figure 9.

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41 Figure 12: Skeletal clinopyroxene grain with a lacey reaction rim surrounding the crystal, this is also indicative of rapid crystal growth. Mapping details in Figure 9.

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42 T735-120 10 20 30 40 50 60 70 00.20.40.60.811.2 Relative Distance from Core to RimMg# T735-90 10 20 30 40 50 60 70 00.20.40.60.811.2 Relative Distance from Core to RimMg# Figure 13: Populations of zoned pyroxenes. Th ere are two distinct populations of zoned pyroxenes. One group exhibits co res that range from Mg# of 56.0 58.6, and the other range in core Mg# from 8.24 12.6. In addition to these two groupings, there is also a population of individual pyroxenes, Mg# ranging from 29.3 30.21, whose compositions correspond with those of the rims in the zoned pyroxenes.

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43 Figure 14: Olivine and plagioclase glomerophyric cluster. Olivine is fayalitic in composition. Figure 15: Element map of skeletal fayalite crystal in sample T735-G12. Note the lacey reaction rim. Mapping details in Figure 9.

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44 Figure 16: Rare (<1% of the sample) euhedral zircon phenocrysts seen in samples T735-G12 and T735-G19 were discovered thr ough microprobe analyses. Zirconium concentrations in the evolved samples range from 397 to 672 ppm. They were later able to be recognized in thin section due to their high re lief and birefringence.

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45 Figure 17: PPL (left) and XPL (right) views of a ba saltic xenolith in sample T735-G11. Basaltic xenoliths typically are rounded w ith slightly coarse grained interiors and chilled margins. Figure 18: Element maps of a basaltic xenolith in sample T735-G12. Note the high Mg content, indicating the basaltic na ture of the xenolith. Mapping details in Figure 9.

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46 Figure 19: A coarser grained xenolith, found in T735-G10, is composed of plagioclase, An34 An35, and fayalitic olivine, Fo15. The edges of the coarse grai ned xenolith are rough and there are no signs of mineralo gical reactions. Mapping details in Figure 9.

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47 Figure 20: Myrmekitic intergrowth of quartz an d plagioclase. The PPL view of myrmekitic intergrowth of plagioclase, An27 An30, and quartz found in sample T735-G19. Element maps of the myrmekite display the wormy intergrown texture of the quartz a nd sodic plagioclase. Mapping details in Figure 9.

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48 CHAPTER 5 MAJOR AND TRACE ELEMENTS Basalts Mid-ocean rdge basalts recovered from the Cleft segment exhibit geochemical characteristics consistent with typical normal, incompatible element-depleted MORB (NMORB). Representative basaltic glass compositions are given in Table 3, with the complete data presented in Appendix 3. Major and Minor Elements Basalt compositions are fairly evolved overall with nineteen of the twenty-three basalts recovered being ferrobasalts (FeOT > 12.0 wt.%). Basalt compositions are tightly grouped with MgO ranging from 7.55 weight % in the most pr imitive basalts to 6.29 wt% in the most evolved basalt recovered (Table 3). The Al2O3 values decrease from 13.8 wt%, in the most primitive basalt sampled, to 12.8 wt% in the most evolve d. The CaO concentrations also fall, with abundances decreasing from 11.8 wt% to 10.9 with decreasing MgO. The FeOT and TiO2 values increase with decreasing MgO from 10.8 to 12.9 wt% and 1.61 to 2.26 wt% respectively. Concentrations of Na2O, K2O and P2O5 also increase with decrea sing MgO, rising from 2.45 to 2.69 wt%, 0.12 to 0.20 wt% and 0.14 to 0.25 wt% resp ectively. Lastly, MnO shows a loose overall decline, from 0.24 to 0.18 wt% with decr easing MgO, the trend is scattered due to the low concentration of the oxide in the samples. The major elements within the recovered basalt suite all plot smoothly relative to MgO (a nd each other) with no major inflection points. The T735 basalts have compositions similar to other southern JdF basalts but have limited variation compared to the all of Cleft segment basalts, of which two hundred and eighty-six samples were analyzed for major elements (S mith, 1994; Stakes et al., 2006; Figure 21). Overall, Cleft segment MORB show relatively lit tle major element chemical variation at any

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49 given MgO content, forming welldefined geochemical trends cons istent with differentiation via low-pressure fractional crystall ization of similar parental lavas (Smith, 1994; Figure 22). Previously published data for Cleft segment la vas range in MgO from 10.5 wt% in the most primitive basalts, to 4.41 wt% in the most evol ved samples and reported Mg#s range from 70.8 to 32.6. However, the majority of reported data exhibit MgO contents greater than 6 wt%, with sixty samples extending the compositional range to the more evolved compositions. The major elements for the T735 basalts all plot near the center of the overa ll range of MgO values (Figure 22). The Al2O3 values of the T735 basalts are lower at a given MgO than in the existing Cleft data set which ranges from 17.7 to 12.2 wt% with falling MgO (Smith, 1994; Stakes et al., 2006). For example, at an MgO of ~7 wt% Clef t basalts range from 13.5 to 14.9 wt%, whereas T735 samples range from 13.1 to 13.3 wt%. Similarly, FeOT concentrations of T735 samples, which range from 12.9 to 10.8 wt%, form a trend w ithin the Cleft data trend which ranges form 7.92 to 16.3 wt% with falling MgO (Smith, 1994; Stak es et al., 2006). At an MgO of ~7 wt% FeO ranges from 11.5 to 13.1 wt% in Cleft basalts, while T735 samples have a range of 11.07 to 11.22 wt%. Within the overall Cleft segment data a group of 2 basalts, 8 ferrobasalts and one andesite form an apparent subs idiary trend towards lower FeOT concentrations, from 13.4 to 11.6 wt%, at values of MgO, ranging from 5.98 to 4.46 wt % (Figure 22) while most of the Cleft data exhibits an increase in FeO to ~16 wt%. It is important to note th at the group of low FeO samples exhibits a trend with decreasing MgO towards the compositions of the andesite and dacite samples described below. The TiO2 values for dive T735 basalts and ferroba salts are relatively high particularly the more evolved end of the ferrobasalts, wh ich have values from 1.60 to 1.99 wt% TiO2 at a MgO

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50 value of ~7 wt% and ranges from 2.02 to 2.18 in the T735 dive samples. In both the Cleft basalts, which range from 0.89 to 3.15 wt% TiO2 with falling MgO, and the T735 samples the TiO2 trend in the basalts is one of increasing concentration with decreasing MgO. As with the FeO data discussed above, there are several Cleft samples in the ferro-basalt/andesite range that display relatively low TiO2 concentrations tr ending towards the compositions of andesites and dacites recovered in dive T735. The CaO and Na2O data for T735 basalts and ferrobasalts fall in the center of the data trends established by the Cleft samples, which range from 12.6 to 8.47 and 2.11 to 3.38, respectively, with decreasing MgO. The observed trends of decreasing CaO and increasing Na2O with decreasing MgO are also sm ooth, without inflection points. Overall, the major element trends observed in the data support fractiona l crystallization of plagioclase and olivine, indicate d by the trend of decreasing Al2O3, with decreasing MgO coupled with a trend of increasing CaO/Al2O3 with decreasing MgO obser ved in the most mafic samples. It is likely that clinopyroxene enters as a crystallizing phase when the magma reached approximately 7.9 wt% MgO, as indicat ed by the inflection point in CaO/Al2O3 (Figure 22) which steadily decreases thereafter. Water and CO2 concentrations for two of the T 735 basaltic lavas, T735-G23, and T735G35, the most mafic sample recovered, are 0.27 and 0.17 wt. % and 118 and 101 ppm, respectively. Chlorine concentrations for th e T735 basalts range from 90 to 410 ppm with decreasing MgO. Trace Elements Trace element concentrations in the T735 basal tic lavas lie within the compositional ranges of other Cleft basalts (Figure 23) While the T735 basalts displa y little to no trend on their own, when included with the reported Cl eft data overall trends are apparent. Zirconium increases in a tight, smooth pattern with decreasing MgO from 102 to 142 ppm in the T735 basalts and from

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51 51.4 to 607 ppm in the Cleft samples (Smith, 1994; Perfit, unpublished). Yttrium also displays an increasing concentration with decreasi ng MgO ranging from 37.6 to 53.4 ppm in the T735 samples and from 21 to 220 in the Cleft samples. Tantalum values plot in a tight group ranging from 0.15 to 0.29 ppm in the T735 data with a sl ight, but poorly define d, increasing trend vs. decreasing MgO while the Cleft sa mples range in Ta concentration from 0.11 to 0.90 ppm, with most samples plotting within ~.1 ppm at given Mg O contents. Lanthanum, Sm and Lu all show well defined increasing trends plotted against decr easing MgO when incl uded with the Cleft samples. Lanthanum ranges from 3.40 to 5.24 ppm in the T735 samples and from 1.9 to 21 ppm in the Cleft samples, respectively, Samarium ranges from 3.49 to 4.87 ppm and from 1.8 to 17.6 ppm respectively, and Lu ranges from 0.58 to 0.81 ppm in the T735 basaltic samples and from 0.30 to 3.44 ppm in the Cleft samples (Smith, 1994; Perfit, unpublished). Rubidium and Nb show increasing trends that are le ss well-defined and show greater scatter than the trace elements discussed above (Figure 23) when plotted against decreasing Mg O. Rubidium ranges from 0.73 to 1.31 pmm in the T735 basaltic samples, wh ile ranging from 0.24 to 5.8 ppm in the Cleft samples and vary by ~2 pmm at ~7 wt% MgO ~ 2.7 ppm at an MgO of ~5 wt%. Niobium ranges from 2.88 to 4.76 ppm in the T735 basalts and from 1.4 to 18.7 ppm in the Cleft samples (Smith, 1994; Perfit, unpublished). Strontium and Cr both decrease in concen tration with decreasing MgO (Figure 23). Strontium shows an overall decrease with decr easing MgO, ranging from 118 to 99.7 ppm in the T735 basalts and from 150 to 82.4 ppm in the Cl eft samples (Smith, 1994; Perfit, unpublished). The spread of the main body of data is fairly wi de with the Sr ranging from 98 to 128 ppm at an MgO of ~7.2 wt. percent. Chromium shows a clearer trend ranging from 287 to 98.3 ppm with

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52 decreasing MgO in the T735 samples and from 584 to 11 ppm in the Cleft samples (Smith, 1994; Perfit, unpublished). Vanadium shows an increasing trend in the Cl eft data until ~6 wt. pe rcent MgO (full range: 8.69 to 3.41 wt. percent MgO) when there is an in flection point and a downward trend toward the more evolved compositions. Vanadium ranges from 395 to 330 ppm in the T735 basalts and from 569 to 185 in the Cleft samples (Smith, 1994; Perfit, unpublished). The inflection point seen is consistent with the introduction of titano-magnetite as a crystallizing phase. On a trace element primitive mantle-nor malized plot (McDonough and Sun, 1995; Figure 24), the samples show highly incompatible elemen t depletions and negative Sr (4.73 to 5.6 times primitive mantle) and Pb (6.44 to 9.26 times primitiv e mantle) anomalies. Concentrations of the most highly incompatible trace elements ar e at 10 times primitive mantle or below. Primitive mantle-normalized Rare Earth Elements (REE) diagrams (Figure 25), (McDonough and Sun, 1995), show that the samples ha ve Light Rare Earth Element depleted smooth patterns with concentrations at about 5 to 10 times primitive mantle. The light REE show a slight depletion in rela tion to the heavy REE, and slight Eu anomalies, attributed to plagioclase crystallization. Lanthanum/Samarium ratios rang e from 0.63 to 0.74 in the MORB samples recovered, while Ce/Yb ranges from 0.78 to 0.89. Overall, there is an increase in total REE with decreasing MgO content. Andesites and Dacites The more evolved rocks create an extension of the tholeiitic differentiation trend seen in the recovered MORB. Representative evolved gl ass compositions are given in Table 3, with the complete data presented in Appendix 3.

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53 Major and Minor Elements In the chemically fractionated lava suite, SiO2 ranges from 62.0 to 66.9 wt%, over an MgO wt% range from 1.94 to 0.6, with an Mg # ra nge of 15.9 to 6.1; significantly lower than the nearby basalts and all of the previously recovere d samples from the Cleft ridge axis. Aluminum oxide values range from 13.6 to 12.2 wt% with decreasing MgO and are slightly scattered (Figure 22). Titanium oxide values range from 1.4 to 0.81 wt% and FeOT ranges from 7.28 to 10.3 wt%, both oxides falling in loosely constraine d trends with MgO content. The offshoots from the FeTi-basalts found in the overall Cl eft dataset, are most pronounced in the TiO2 and FeOT variation diagrams as they trend towards the more evolved compositions. Calcium oxide falls from 5.4 to 3.4 wt% with MgO, in a very tig ht trend along the same line as the basalts. The Na2O also has a tightly constrai ned grouping with a range in we ight percent from 4.36 to 5.07 that plots very smoothly along the same trend line as the basalt values. The K2O values increase from 1.02 to 1.30 wt% with falling MgO concentration. H2O concentrations in the evolved samp les range from 1.5 to 2.0 wt% while CO2 concentrations were below det ectable limits. Chlorine concen trations range from 4100 to 6100 ppm with decreasing MgO. Trace Elements Incompatible trace elements increase in c oncentration in the evol ved lava samples as MgO concentrations fall and form a trend wherein th e single dacite glass, that was recovered in a rock core taken in 2000 (RC10) is comparable and is therefore in cluded in the discussion of the evolved samples from Dive T735. Zirconium rises from 397 to 737 ppm in evolved samples with decreasing MgO. Yttrium rises from 158 to 240 ppm and Ta concentr ations rise from 0.927 to 1.6 ppm with falling MgO in the evolved samples. Lanthanum concentrations rise with falling MgO from 22.4 to 33.8 ppm in the evolved lavas. The concentration of Sm ranges from 13.8 to

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54 21.1 ppm with falling MgO and Lu ranges from 2.38 to 3.65 ppm in the evolved lavas. The Rb and Nb concentrations increase as well with fal ling MgO in the evolved samples with Rb rising from 9.17 to 12.7 ppm and Nb rising from 14.0 to 21.2 ppm in the samples. Strontium and Cr concentrations both decr ease with decreasing Mg O in the T735 samples (Figure 23). Strontium falls from 92 to 67.4 in a loosely defined trend an d Cr falls from 54.1 to 1.84 ppm in the evolved lavas, overall the trend is much tighter and mo re distinct then seen in the Sr. Scandium and V both decrease in concentrati on in well-defined trends and extend the trends in the Cleft samples after the inflection point at ~6 wt. percent MgO. Scandium falls from 23.4 to 15.9 ppm in the T735 samples, and the V falls from 178 to 47.6 ppm. Trace element concentrations show much mo re variation in the mantle-normalized and REE diagrams than observed in the T735 basalts, consistent with certa in phases differentiating out of the melt (Figure 24). Large negativ e anomalies in Sr (3 .19 to 4.12 times primitive mantle), P (5.13 to 19.3 times primitive mantle) and Ti (3.62 to 6.21 times primitive mantle) are consistent with the crystallization of plagiocl ase, apatite and titanomagnetite, respectively, from the melt. All of these phases are present in the evolved samples. The primitive mantle-normalized REE diagram displays an overall smooth, flat pattern within the evolved samples (Figure 25). La nthanum/Samarium ratios range from 0.98 to 1.12, while Ce/Y ranges from 1.0 to 1.1. Europium di splays an increasing negative anomaly (7.03 to 9.16 times primitive mantle) as MgO decreases which is consistent with the continued crystallization of plagio clase out of the magma.

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55 AFM Diagram MgO 0102030405060708090100 FeO 0 10 20 30 40 50 60 70 80 90 100 Na2O+K2O 0 10 20 30 40 50 60 70 80 90 100 Smith, 1994; Stakes, 2006 Dive T735 Figure 21: AFM Diagram comparing Smith, 1994 and Stakes, 2006 samples to dive T735 samples. Basalts follow a typical tholeiitic diffe rentiation trend. The evolved samples from dive T735 form an extension of the t holeiitic trend taken to >80% cr ystallization, after a gap of no data. The evolved samples have lower concentrati ons of FeO due to the cr ystallization of FeTi oxides out of the melt.

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56 Figure 22: Major element plots co mparing previous studies of th e Cleft segment (Smith et al., 1994; Stakes et al., 2006) to dive T735 samples.

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57 Figure 22: Continued.

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58 Figure 23: Trace element plots comparing previous studies of the Cleft segment (Smith et al., 1994; Perfit, unpublished) to dive T735 samples.

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59 Figure 23: Continued.

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60 Figure 24: The primitive mantle normalized (McDonough and Sun, 1995) spider diagram displays the depletion of severa l key trace elements in the evolve d glasses compared to the basalt compositions. Strontium is incorporated into the structure of plagioclase crystals, while the Ti depletion is due to the crystallization of titanomagnetite. The P depletion is due to the crystallization of apatite in the evolved sample s. Sample 99RC99 (-) is an andesite recovered from the coaxial segment and shows the same trend as the evolved samples recovered from the RTI.

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61 Figure 25: The primitive mantle normalized (McDonough and Sun, 1995) REE plot shows the two distinct groupings within th e sample group. The basalt sample s show the typical flat REE pattern while the evolved glasses have a ch aracteristic Eu depletion from plagioclase crystallization. The black outline displays th e REE range of the Smith, 1994, samples. The LREE in the evolved glasses are slightly enriched compared to the basalt glasses. Sample 99RC99 shows a similar enrichment trend.

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62 CHAPTER 6 DISCUSSION The lavas recovered during dive T735 repres ent one of the most complete and evolved suites recovered from a MOR environment. The atypical composition of the T735 suite provides an opportunity to investigate petrogenetic proces ses of MORB evolution that have been well addressed by traditional magma chamber models cr eated for on-axis volcanism that do not fully explain the petrogenesis of these andesites and dacites. Here we explore several hypotheses in an attempt to constrain the potential petroge netic history of this unique suite. One of the prevailing hypotheses for the petroge nesis of evolved MOR lavas is that they are formed by extreme fractional crystallization of basaltic magmas, in part due to the cold edge effect, an effect associated with MOR lavas er upted close to an oceanic transform fault or an area where a ridge is propagati ng into older oceanic crust (Chr istie and Sinton, 1981; Fornari et al., 1983; Perfit et al., 1983; J ohnson and Holmes, 1989; Juster et al., 1989; Embley et al., 1991; Smith, 1993; Smith et al., 1994; Juteau et al ., 1995; Tierney, 2003; He rzburg, 2004). The ridgetransform intersection (RTI) of the JdFR and the BF Z is an area where the cold edge effect is likely to affect the petrogenesis of MOR lavas (Stakes et al., 2006). The Blanco Transform is approximately ~345 km long from the southern term inus of the JdFR to the northern terminus of the Gorda Ridge (Chadwick et al., 1998) that results in the axis of the southern Cleft segment abutting old and cold lithosphere that is approximately 6.3 million years old; hence providing an environment for extensive cooling. Comparison to Other Evolved Suites Although relatively rare in MOR environments highly evolved lavas and plutonic rocks (generally known as plagiogranite s) have been found in a number of diverse environments that

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63 include fast, intermediate and sl ow spreading ridges, back-arc ba sins, and quite a few ophiolites. A wide range of samples from these environments are compared to the T735 suite in Figure 26. These samples include lavas from the Galapagos Rift (Fornari et al ., 1983) volcanic samples from the Mid-Atlantic Ridge (Hekinian et al., 1997) back arc basin (BAB) samples from the Southwest Pacific (Nakada et al., 1994), the La u Basin (Falloon et al., 1992) and the western Pacific (Bloomer, Smithsonian Institution Volcan ic Glass Individual An alysis File, VG no# 9772 9777). Geochemical comparisons have also been made with evolved plutonic samples from supra-subduction zone ophiolites from California (Beard, 1998), Greece (Tsikouras and Hatzipanagiotou, 1998; Bbien, 1991), Norway (Pedersen and Malpas, 1984), Newfoundland (Malpas, 1979), Oregon (Phelps and Ave Lallema nt, 1980), Chile (Saunder s et al., 1979), Crete (Koepke, 1986), and Canada (Flagler and Spra y, 1991). Four experimental plagiograntic residual melt compositions were also compared to the T735 samples; residual melts from a gabbro heated to 900 C and 940 C (Koepke et al., 2004) the partial me lt of a MORB protolith heated to 955 C (Dixon-Spul ber and Rutherford, 1983) and th e partial melt from a hydrous MORB heated to 950 C (Berndt, 2002). SiO2 values for the T735 lavas are generally lo wer those of plagiogranite compositions at similar MgO concentrations (Figure 26). SiO2 values of the evolved T735 suite range from 62.0 to 66.9 wt% in samples containing less than 2 wt% MgO compared to plagiogranite samples that have values that mostly ra nge from 64.5 to 68.13 wt% SiO2. Experimental partial melts of wet and dry MORB protoliths (~ 900 955C) have quite variable SiO2 values, (60.9 to 65.8 wt% SiO2) but they all generally display higher MgO then the T735 evolved lavas, with the lowest MgO value, 1.29 wt%, in the partial me lt generated from the dry MORB parent.

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64 In general the T735 evolved lavas have lower concentrations of Al2O3 compared to the majority of evolved samples. The T735 evol ved lavas have a very limited range of Al2O3 from 13.6 to 12.23 wt% compared the global volcanic su ite that has values ranging 16.0 to 11.4 wt%, including some subvolcanic rocks having the highest values at 16.0 and 15.83 wt%. Al2O3 in the plutonic suite ranges from 18.1 to 10.4 wt%. Th e experimentally derived melts all have comparatively high concentrations of Al2O3 ranging from 20.1 (gabbro protolith) to 15.41 (dry MORB protolith) wt% Al2O3. The T735 evolved lavas are enriched in TiO2 relative to the bulk of the compared evolved samples. The T735 evolved lavas range from 1.39 to 0.81 wt% TiO2 while within the volcanic suites, the only one with samples of higher value, range from 2.44 to 0.34 wt%. The plutonic suite displays very low TiO2 values, which range from 0.84 to 0.30 wt%. Such low TiO2 values could be indicative of an island arc signal given that many of these rocks were believed have been formed in supra-subduction zone envi ronments. The evolved liquid from the MORB protoliths have TiO2 values of 1.25 and 1.17 wt%, which lie within the field outlined by the T735 evolved lavas. The gabbroic prot oliths both have very low TiO2 values, 0.36 and 0.12 wt% TiO2. K2O is extremely enriched in the T735 evolved lavas relative to any of the plagiogranite comparison suites, ranging from 1.02 to 1.30 wt%. Only one sample, a volcanic sample from the MAR (Hekinian et al 1997), lies within the field create d by the T735 samples, with its value being 1.09 wt% K2O. Dive T735 Samples During dive T735, we documented the presence of two constructive volcanic mounds that are comprised of massive pillow s to blocky, vesicular, silicic lavas. Morphology ranges from large (>2 m in diameter) pillow tubes, to extr emely vesicular (~20% elongate vesicles), blocky

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65 flows, a drastic change in morphology from the small (~1m in diameter), rounded non-vesicular pillows observed in the surrounding areas where only basalts were recovered. The petrography and phase chemistry of the e volved samples recovered are indicative of a complex petrogenetic process. Two populations of phenocrysts were found within the evolved samples, each exhibiting chemical zoning. Iron-ri ch pyroxenes, that have core Mg# from 8.24 to 12.6, were reversely zoned while those with Mg-rich cores, ~Mg# of 57.2, exhibit normal zoning. The rims of both populations approach similar compositions with Mg# ranging from 27.7 to 37.5. Significantly, the rims approach th e microphenocryst compositions in the glass matrix. This petrographic evid ence suggests two things; Mixing between a relatively mafic (basaltic ) magma and a highly evolved magma, likely rhyodacitic, each of which crystallized pyroxene before mixing occurred (Barbarin, 1990; Furman et al., 1995; Perfit et al., 1999; Grove, 20 00; Ratajeski et al., 2001 ). The silicic magma was relatively dry when it erupted, indicated by the presence of fayalite and Fe-rich pyroxene in the recovered rocks rather than amphibole (Dixon-Spulber and Ru therford, 1983; Koepke et al., 2004; Berndt et al., 2005). Several xenoliths with coarser-grained textures, indicative of slower, crystallization conditions, are also present in the andesites a nd dacites. These include rare plagioclase oikocrysts containing low-Ca pyroxene chadacrysts as well as a coarse-grained xenolith comprised of plagioclase (An34 An35) and fayalitic olivine, (Fo15), present in sample T735-G10. A quartz-plagioclase myrmekitic intergrowth is present in sample T735-G19. The presence of these textural features indicates that that the erupted lava interacted with an evolved plutonic body or mush zone.

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66 Rounded basalt xenoliths are also present in the evolved lavas. They range in size from <1 mm to several mm in diameter, and have fine-g rained to opaque rims. These presence and texture of these xenoliths basa ltic magma intruded/recharged an evolving magma body. The fresh, mafic material would have been at a much higher temperature then the evolved, viscous melt it intruded into/mixed with. The high viscos ity of the evolved melts would have inhibited large scale mixing with the fresh mafic materi al and the temperature difference between the melts (basaltic >1200 C; dacitic <1000 C) coul d explain the fine-grained textures of the basaltic xenoliths and chilled margins. Major and trace element variations observed in the entire T735 suite indicate a bimodal sample set, that has no samples of intermed iate composition (Figure 22; Figure 23) although it should be noted that most of the basaltic sa mples recovered around the andesite/dacite domes have fairly fractionated compositions with many being ferrobasalts (FeO >12 wt.%). There are a number of different ways that these kinds of rock suites have been hypothesized to form; the extreme fractional crystallization of a MO R magma (Fornari et al., 1983; Perfit et al., 1983; Juster et al., 1989; Geist et al ., 1998; Perfit et al., 1999; Grove, 2000); magma mixing between an extremely evolve d, possibly rhyodacitic end-member and a ferrobasalt (Barbarin, 1990; Perf it et al., 1983; Furman et al., 1995; Hekinian et al., 1999; Perfit et al., 1999; Grove, 2000; Ratajeski et al., 2001); partial melting of the hydrated oceanic crust (Dixon et al., 1995; Brandriss et al., 1999; Berndt et al., 2005); assimilation of oceanic crust and assimilation fractional crystallization (AFC) (Bohrson et al., 1998; Garcia et al., 1998; Gee et al ., 1998; Hornle et al., 1998; Grove, 2000).

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67 Fractional Crystallization Silica rich rocks found in oceanic environm ents may be formed by extreme amounts of fractional crystallization (Perfit et al., 1983, Juster et al.., 1989). The Galapagos are a prime example of an area where the ev olved lavas recovered fit the extreme fractional crystallization model well. Juster et al., 1989, used experimentally determined phase boundaries to model the fractionation of lavas recovered at 85 W. The results of the experiments determined that the range of compositions found there were the result of shallow-leve l differentiation processes and the higher levels of fracti onation and silica enrichment were due to the higher fO2, which allowed for a titanomagnetite bearing assemblage to begin to crystallize earlier, driving the concentrations of SiO2 up and FeO and TiO2 down. To test a fractional crystallization model fo r the Cleft suite, liquid lines of decent (LLD) (Appendix 4) were calculated using the progr am Petrolog (Danyushevsky, 2001) under various starting conditions (e.g. pressure, oxygen fugaci ty, different mineral assemblages). Sample T735-G35 was chosen as the composition of the pa rent melt because it is the most mafic sample recovered in the area were the evolved samples were recovered. The mineral-melt models of Danyushevsky (1999) were chosen for calculating th e compositions of olivine, plagioclase and clinopyroxene; Ariskin (1993) fo r orthopyroxene and Ariskin and Barmina (1999) were used for magnetite compositions. Melt oxidation states along the QFM buffer were determined using the conditions of Borisov and Shapkin, 1990. Calculations were run at 200 bars and 1 kb of pressure, in order to simulate the pressure at the seafl oor and within the shallow crust (~3 km). All calculations were executed assuming perfect frac tional crystallization in 0.1 wt% incremental crystallization steps and were typically termin ated ~88% total crys tallization when certain components were expended. Using the 200 bar mode l, which started at 1185 C and was run at QFM, the calculated major element trends (Figur e 27) are fairly smooth with a major inflection

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68 point seen in SiO2, Al2O3, TiO2, and FeO at an MgO of ~3 wt% when titanomagnetite enters as a crystallizing phase, after ~65% cr ystallization of the parental melt. Oxidation state affects the temperature and composition at which titanomagne tite (and ilmenite) crystallizes; higher oxygen fugacity causes earlier (higher T, less total cr ystallization) stabilizat ion of oxide phases. Consequently, the modeled inflection point occurs earlier in the chemical evolution when using an oxygen buffer higher than QFM. Figure 28 show s the relationship between temperature and percentages of mineral phases in the crystall izing assemblage from a successful model. The modeled order of crystallization al ong a QFM buffer at 200 bars is olivine olivine + clinopyroxene olivine + plagiocl ase + clinopyroxene plagioclase + clinopyroxene + orthopyroxene plagioclase + clinopyroxene + ort hopyroxene + magnetite (Figure 28). The modeled LLD at QFM corresponds well to the interpreted crystallization order based on petrographic examination of sample thin sectio ns. The order of crysta llization is olivine + plagioclase plagioclase + clinopyroxene olivine plagioclase + clinopyroxene + FeTi oxides olivine plagioclase + pigeonite (or orthopyroxene) + FeTi oxides. Dacite compositions are predic ted to form after approximately 80% crystallization, even though the phase equilibria used in the Petrolog pr ogram are not very well constrained in such evolved compositions. The results of the models generally agree with the major element trends observed in the dacites. SiO2 values in the evolved rocks ar e slightly higher than model predictions and K2O is over-enriched, while TiO2, Al2O3 and P2O5 are lower relative to the calculated abundances (Figure 27). Variations in the trace element abundances were modeled for selected elements using the Raleigh fractionation equation, pha se proportions predicted by the major element models and published trace element Kds (Bougault and Heki nian, 1974; Shimizu and Kushiro, 1975; Duke,

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69 1976; Matsui et al., 1977; Mysen, 1978; Kravuch uk, 1981; Villemant et al., 1981; Colson et al., 1988; Kloeck and Palme, 1988; Agee, 1990; Mc Kenzie and ONions, 1991; Keleman and Dunn, 1992; Hart and Dunn, 1993; Hauri et al., 1994; Nikogosian and S obolev, 1997; Bindeman et al., 1998) and also by assuming Kds of zero for the mo st incompatible elements. Calculated trends for several of the incompatible trace elements also seem to follow calculated fractional crystallization trends (Figure 29) although in order to re ach the concentration levels of the most evolved compositions greater than ~90% crystallization is requi red. The enrichments observed in some of the most incompatible trace elem ents could not be mode led even if the bulk distribution coefficient was assumed to be zero. Trace element variations generated with publishe d Kds are only slightly below the actual trends of the lavas recovered (Figure 29). Zr, Y and Sm concentrations are well-modeled using the Rayleigh fractionation equati on with a D of zero and the propor tions of minerals determined from the Petrolog models. The La, K and Rb values of the evolved lavas, on the other hand, are significantly higher than the calculated abundances even using an assumed D of zero, which would give the maximum enrichment. Modeled vari ations for Cr, Ni and V compare favorably to the actual evolved compositions, but the Cr and Ni concentrations of some intermediate to evolved basalt samples are lower than those in th e calculated model. Kds for Ni and Cr are not well-constrained for basaltic systems though. Sr and Sc are significantly lower in the evolved samples when compared to the modeled concentrations. In general, fractional crystal lization seems to adequately (t hough not entirely) explain the elemental trends, although mode ls suggest extreme amounts of crystallization (>80%) of an already evolved basalt parent in order to duplicat e the major element compos itions of the dacites. With such extreme amounts of crystallizat ion needed in order to model the evolved

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70 compositions, there would be a problem with a crys tal-laden melt being able to erupt, as the melt has progressed well past the soli dification front predicted at 40 % crystallization (Marsh, 2000). Magma Mixing Petrographic evidence supports magma mixing was involved in the petrogenesis of the evolved suite, and might help to explain some of the discrepancies in the elemental trends as well as the compositions of some basaltic andesites recovered along the axis of the Cleft segment north of this study area. Clear ly the bimodal pyroxene compos tions and extensive amounts of zoning, as well as chilled basaltic xenoliths observed in all of the evolved samples, point to some type of magma mixing event or events. The phase chemical variations suggest there was mixing between a basaltic end-member, possibly as evolve d as a ferrobasalt, and a very evolved magma, possibly as evolved as a rhyodacite or rhyolite, to create the an desitic and dacitic lava samples recovered. There is no evidence of evolved magma mixing with mafic basaltic liquids. In order to evaluate the potential role of magma mixing, mass bala nce mixing calculations were performed between likely mixing end-member compositions. As the most evolved silicic end-member(s) is unknown, all mixing lines were calculated using the composition of dacite sample T735-G12 (Mg# of 6.14), the most evolve d lava recovered. The three basaltic endmembers chosen were T735-G35 (Mg# of 37.5, MgO = 7.55 wt%), the most mafic basalt recovered during the dive, T735-G7 (Mg# of 32.3, MgO = 6.79 wt%), a moderately evolved basalt and T735-G32 (Mg# of 29.8, MgO = 6.29 wt%), the most evolved basalt recovered on the dive. Increments of mixing were calculated for every 10% portion (i.e. 10% of A and 90% of B, 20% of A and 80% of B, etc.) using a standard mass balance equation (Langmuir et al., 1978). The calculated mixing lines (Figur e 30) represent a few of the pot ential mixing models that are possible.

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71 Results of the mixing calculations show that the compositions of some of the outlying samples on the major element plots that did not fit the fractional crystallization models are better explained by magma mixing. In pa rt, the group of 2 basalts, 8 ferr obasalts and one andesite from the entire S. Cleft suite that show a trend of decreasing FeO concentrations with decreasing MgO fall along the mixing line from T735-G7 to T735G12. Mixing lines calculated using the two more mafic basalt samples as end-members don t seem to include any outlying basaltic and andesitic samples in their trends. It could be in terpreted that, if mixing was involved in creating these intermediate outliers, and the evolved compos itions they trend towards, that one of the endmembers involved in the mixing woul d have to be a fairly evolve d ferrobasalt or FeTi-basalt, since the most evolved sample recovered provid es the best end-member to explain elemental trends in the full dataset. The mixing calculations suggest a mix of 30 40% of the ferrobasalt (T735-G32) with 60 70% of the dacite (T735-G12) would be requ ired in order to crea te the observed evolved compositions in the T735 suite. The moderately evolved andesites observed in the larger Cleft dataset would require only about 30% of the dacitic end-member to be mixed with the ferrobasaltic liquid. The petrology of the samples, and the presence of the myrmekite, zircons, fayalite as well as sodic plagioclase (An18 ) and iron-rich pyroxene (Mg# of 8.24) crystals, as well as the fine magnesian rims surround Fe-rich pyroxene (Figures 11 and 12) and fayalite (Figure 15) cores, strongly sugge st that there is the possibility of an even more evolved endmember then T735-G12 was involved that was mixe d back to create the compositions recovered. Based upon the trajectory of the mixing lines dr awn between the evolved samples and possible basaltic end-members, the projected evolved end member might be expected to have a composition similar to this: ~67 wt% SiO2, ~12 wt% Al2O3, 0.75 wt% TiO2, 7.5 wt% FeOT, ~3.0

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72 wt% CaO, ~5.2 wt% Na2O and K2O ~1.4 wt%. All these values were estimated by extrapolating the current mixing model to an MgO of almost zero. The trace element compositions also seem to be more supportive of a mixing model, as crystal fractionation cannot accoun t for over-enrichments seen in highly incompatible elements such as La, Sm, Zr, and Y where a Kd of zero is needed to approximate the observed values in the most fractionated lavas (Figure 29). This would however, require that the evolved endmember was formed by extreme amounts of fractional crysta llization (>90%). Partial Melting/Assimilation Fr actional Crystallization (AFC) Another hypothesis for generating highly evolve d melts is to partially melt the basaltic crust (Petford et al., 2001; Cast illo et al., 2002; Coogan et al., 2003) or assimilate country rock into the melt (Nicholson et al ., 1991; Bohrson et al., 1998; Garc ia et al., 1998; Gee, 1998; Hoernle, 1998; OHara et al., 1998 ; Weis et al., 1998; Grove, 2000). Several studies have shown it possible to produce silicic melts from partially melting hydrous mafic protoliths (Holloway and Bur nham, 1972; Helz, 1973; Beard and Lofgren, 1991; Kawamoto, 1996, Koepke et al., 2003; Koepke et al., 2004). There is also evidence of anatexis in plagiogranitic rocks found in ophiolite sequences (Malpas, 1979; Pederson and Malpas, 1984; Flagler and Spray, 1991) as well young oceanic crust (Mvel, 1988) although the exact compositions of the protoliths in these studies has not been well constrained and may include gabbros and sheeted dikes that may have been altered due to hydrotherm al activity. Water is usually assumed to be a component of the melting process due to the presence of amphibole found in samples of felsic oceanic crus t (Bbien, 1991; Beard, 1998; Tsikouras and Hatzipanagiotou, 1998; Koepke et al., 2002), often in poikilitic textures, suggesting a magmatic origin (Koepke, 1986).

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73 Phase chemical data from melting experime nts (Koepke,. 2004) also demonstrated an increase in olivine Fo content in the restite due to increasing temperatur e and the influence of water. Residual plagioclase were also more An-rich in the experiments due to the effect of water (Sisson and Grove, 1993; Berndt, 2002) and am phibole was present in all systems at temperatures < ~980 C. Assimilation of crustal material has also been hypothesized as a method to create evolved compositions. Assimilation in a MOR regime most likely involves oceanic crust that has been hydrothermally altered and this has been substant iated by direct field obs ervations of xenolithic basaltic material in ophiolites (Castillo, 2002). The addition of altered material into a MORB magma results in an over-enrichmen t of chlorine, relative to other incompatible elements such as K2O and TiO2 (Jambon et al., 1985; Michael and Schill ing, 1989; Michael and Cornell, 1998; Castillo, 2002; Coogan, 2003). When compared with the phase chemistry of the resulting melts from the Koepke, 2004, experiments, the phase chemistries of evolved la vas from dive T735 are conspicuously free of any signal of water activity. No evidence of amphibole is present in the T735 lavas, nor is there evidence that amphibole was present in the residu e of melting due to the absence of a LREE to HREE enrichment in the REE pattern of the T 735 glasses, as the Kd values for REE in amphiboles decrease in value for the lighter elements (McKenzie et al., 1991). The phase compositions of the T735 lavas and the absence of evidence of hydrous phases would seem to preclude the notion of the silicic end-member being the result of a partial melt of hydrous oceanic crust. While small batches of xenolith material are present in the T735 evolved lavas none contain amphibole. In addition, there is no elevated chlorine signal (Cl/K ratios remain

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74 fairly constant; Figure 31), prec luding large amounts of assimila tion of altered crust taking place in the petrogenesis of the evolved lavas. Strontium and oxygen isotope values for the e volved T735 are identical to those in MORB from the Cleft segment, consistent with a lack of any seawater alteration or contamination (Perfit, personal communication). If high-temperat ure altered crust were melted to form dacitic partial melts, the values of 87Sr/86Sr would be higher than fr esh basalts and oxygen isotopic values would be lower. In both cases this is not tr ue instead values well within the range of JdFR fresh, unaltered lavas.

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75 Comparison of SiO2 values 50 52 54 56 58 60 62 64 66 68 70 012345678 MgOSiO2 Volcanic Plutonic Experimental T735 samples Comparison of TiO2 values0 0.5 1 1.5 2 2.5 00.511.522.533.5 MgOTiO2 Volcanic Plutonic Experimental T735 evolved lavas Figure 26: Comparing major element variations in the T735 lavas to other evolved suites. Other suites are from varied locations a nd petrogenetic origins, including lavas from the Galapagos Rift (Fornari et al., 1983) an d Mid-Atlantic Ridge (Hekinian et al., 1997), back arc basin (BAB) samples from the Southwest Pacific (Nakada et al., 1994), the Lau Basi n (Falloon et al., 1992) and the western Pacific (Bloomer, Smithsonian In stitution Volcanic Glass Individual Analysis File, VG no# 9772 9777), plutonic samples from supr a-subduction zone ophiol ites in California (Beard, 1998), Greece (Tsikouras and Hatzipanagio tou, 1998; Bbien, 1991), Norway (Pedersen and Malpas, 1984), Newfoundland (Malpas, 1979) Oregon (Phelps and Ave Lallemant, 1980), Chile (Saunders et al., 1979), Cr ete (Koepke, 1986), and Canada (F lagler and Spray, 1991). The experimental plagiograntic residual melt compositions compared were from a gabbro taken to 900 C and 940 C (Koepke et al., 2004) the part ial melt of a MORB protolith taken to 955 C (Dixon-Spulber and Rutherford, 1983) and the partial melt from a hydrous MORB heated to 950 C (Berndt, 2002). SiO2 values were plotted with the recovered T735 basalt as well as the evolved samples in order to demons trate the amount of differentiation.

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76 Comparison of K2O values0 0.2 0.4 0.6 0.8 1 1.2 1.4 00.511.522.533.5 MgOK2O Volcanic Plutonic Experimental T735 evolved lavas Figure 26: Continued.

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77 Figure 27: Major element liquid lines of descen t. Liquid lines of decent are modeled using Petrolog (Danyushevsky, 2001) using a QFM buffer at 200 bars of pressure and were run to ~88% crystallization. Sample T735-G35 was used as the starting composition, as it was the most mafic sample recovered during the dive. SiO2 values in the evolved rock s are slightly higher than model predictions and K2O is over-enriched, while TiO2, Al2O3 and P2O5 are lower relative to the calculated abundances.

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78 Figure 27: Continued.

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79 Figure 28: Cumulative percentage of phases plot ted against melt temperature (C). This figure illustrates the changing mineral assemblage as the modeled parent composition cools. Model assumes QFM and 200 bars of pressure.

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80 Figure 29: Trace element liquid lines of descent. Liquid lines of dece nt are modeled using calculated Kds and the results of a Petrolog model run using a QFM buffer at 200 bars of pressure, run to ~88% crystallization. Sample T735-G35 was used as the starting composition, as it was the most mafic sample recovered during th e dive. While most trace elements follow the calculated trends, La and Lu show over-enrichmen ts, even when LLDs are calculated using a Kd of zero. Zr and Sm also show slight enrichme nts relative to the calculated Kds, but can be predicted using a D of zero.

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81 Figure 29: Cotinued.

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82 Figure 30: Mixing models calculated using a st andard mass balance equation (Langmuir et al., 1978). Figure 26: Mixing lines we re calculated to T735-G12, th e most evolved end-member recovered during the dive, the three mafic end-me mbers chosen were T735-G35 (black Xs), the most mafic end-member recovered during the di ve, T735-G32 (pink triangles), a member of intermediate basaltic composition recovered during dive T735 and T735-G7 (orange circles), the most evolved basalt recovered on the dive. Ou tlying samples from Stakes, 2006, which are well constrained in a fractional crystallization model, can be predicted usi ng the dacite (T735-12) ferrobasalt (T735-G7) mixing model.

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83 Figure 31: Comparison of T735 Cland Cl/K ratios versus MgO. The Cl/K ratio of entire T735 suite remains fairly constant over the full range of MgO. While the Clconcentration increases with decreasing MgO the ratio of Cl-/K in the T735 samples (green diamonds) does not show the same rate of increase seen in the Southern Clef t samples (Stakes et al., 2006), the GSC (Perfit et al., 1999) and the EPR (le Roux et al., 2006) wher e assimilation takes on a much larger role.

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84 CHAPTER 7 CONCLUSIONS Low pressure fractional crystallization models adequately reproduce th e observed trends in major elements and some of the minor/trace elements. There are slight discrepancies between the predicted and observed co mpositions though, most notably with K2O being very over enriched, while TiO2, Al2O3 and P2O5 are lower relative to the predicted abundances (Figure 20). Calculated trace el ement LLDs for La, Rb and K, even assuming Kd's of zero, do not fully predict the concentrat ions seen in the evol ved samples, which are over-enriched to models values. The calculated models require fractional crystallization of gr eater than 80% in order to duplicate the evolved lava compositions recove red on Dive T735; well past the amount of crystallization required to form an imperm eable solidification front predicted by Marsh, 2000. Petrographic evidence strongly s upports mixing as a significant petrogenetic process that created the evolved lavas. Chilled basaltic xenol iths as well as disequilibrium crystals are prolific in all the evolved samples, as well as complex normal and reverse zoning seen in pyroxene and plagioclase crystals. The petrog raphy and chemistry suggest that that a possible recharge event between and evolve d, rhyodacitic melt and a ferrobasalt created the andesitic and dacitic lavas recovered. Large amounts of assimilation or partial melting of altered oceanic crust do not seem to be involved in the petrogenesis of these e volved lavas. Signals expected from the assimilation/incorporation of hydrothermally altered oceanic crust, such as over enrichment of Cl-, due to the interaction of seawater with the crust ( Coogan et al.l 2003), or a sloped REE pattern, due to the lower Kds of the LREE in amphiboles causing an enrichment of them in the melt ( McKenzie et al. 1991), are not seen in the T735 evolved lavas. The evolved lavas recovered from dive T735, at the southern terminus of the JdFR, have had an extremely complex petrogenesis. While la rge scale amounts of assimilation and/or partial melting of hydrous crust can be ruled out as met hods of creating this part icular suite of rocks magma mixing between two distinct magma types that formed by different amounts of fractional crystallization is certain. The fe rrobasaltic xenoliths pr ovide a good estimate as to what the more mafic end-member composition might be, but the extremely evolved end-member is much more difficult to constrain.

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85 These highly evolved melts would have been extremely viscous and had very limited mobility. Due to the fact they the lavas were loca ted at the RTI, propagating dikes, composed of much hotter, ferrobasaltic material, from the larger magma bodies found up-ridge could have provided the necessary heat to mobilize the dacitic melts, allowing them to exsolve H2O and CO2 through decompression, lowering the density enough to allow them to erupt on the ocean floor.

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86 APPENDIX A T735 DIVE LOGS

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87 DATE: 31AUG04 J-Day: 244 Dive objectives: Explore RTI near southern Cleft 13:31 0m rov entered water, start dive T735 14:51 2192m on bottom for past 2 minutes, talus slope 14:55 setting down to sample, pillow fragme nts, some microbial growth on fragments 14:57 2190m sample T735-G1, from pile of pillow debris, placed in S3 in rov drawer, slightly Mn coated 15:00 2190 looking around, some po ssibly intsct pilows present 15:01 2187m starting traver se along curved ridge 15:03 2187m pillow talus, crossing dome summit 15:06 2187m can see glassy remains on many of the fragments 15:08 2193m larger pillows here, no convincing in-place pillows 15:11 2200m possible in-place mo und, looking for place to sample 15:12 2202m small pillow fragment, T735-G2, brownish, placed in S3 15:13 see flows pointing downhill, pillows appear vesicular, small hornito in area, turning around to look at hornito 15:16 2201m spatter mound-tube th ing, or vapor escape tube??, 15:19 trying to grab sample, fractured in place, highly altered, glassy 15:22 2202m grab samplefrom tube thing, T735-G3, placed in S3, broken off from top of tube 15:23 underway again, some flow s appear inplace, heading 341 15:24 2205m crossing partially covered fissure by pillows

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88 15:25 contact to almost all intact flows 15:26 2204m intact pillow flows, slight sed covered, flows appe ar to be draping topography, glassy 15:27 2202m collapse features, mod se d cover in interstices of flows 15:28 2203m stop to sample 15:31 2205m looking for piece to pickup 15:33 2205m collected sample of crust, T735-G4, in S3 again thin piece from lobate flow 15:36 2201m stepping down to west going to look at rigde in s onar, crossing faultsteps, 15:38 2201m fault scarp, razorback ridge series separate by crevas ses slightly wider than the rov, flows on top are intact, head ing 336, pie shape wedge of crust betrween fissures, flattened lobates, this is the wall from the sonar 15:42 2200m fissures seemed to join, its much wide r here, about as deep as it is wide, fissure wall has clean surface, apears pulled apart 15:43 2199m two fissure walls are cl osing in according to the sonar 15:51 2220m stopping for sample from lobates 15:54 2221m smal pillow wedge collected, sample T735-G5, also in S3 15:57 2217m another fissure, buried by overlying p illows, hard to tell if flowing in or out 15:59 2215m another fissure, pillows neatly broken along edge 16:03 2216m collect sample of p illow crust, intact?, T735-G6, placed in S3, blocky reddish sample 16:05 2214m drainback, area of pillows, mod sed between pillows, very plastic flows covering lder terrain

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89 16:06 2210m crack fissure starting here, pillows are knobby, older terrain a ppeared to be large pillows 16:09 2215m still intact flows, fissure off to port 16:13 2212m stopping for sample, differe nt looking stuff, more blocky 16:18 2213m collected grab sample T735-G7, from fl at area at near top of knoll, placed in front of S7 16:20 2209m intact pillows, mod sed cover between 16:22 2207m apears more constructional, fissure to west side, sharp drop, bottom a few meters down, approx. 5m wide 16:23 2207m dropping down over edge of fissure, top of wall is intact, base has lots of debris, appears sed covered even on talus and pillows, appears old 16:25 2214m thick sed cover, few pillows sticking up from sed 16:27 2216m mixture of intact pillows and broken pilow debris 16:34 2225m 50-60% sed cover, good sed cover on pillows too 16:36 2231m more pillows, tubular, somewhat smaller than previous, stopping for sample 16:39 2232m sample T735-G8, blocky pillow frag, placed in S4 16:41 2229m scattered pillows, <50%s sed cover 16:42 2231m tube and sheet flow down to SW, stopping to sample 16:44 2232m sampling sheet, too friable need to put in biotube, must be glassy 16:45 2232m sample sheet flow?, T735-G9, fragments placed in BT5 16:48 2227m pillow tubes appear different, ve ry large well formed tubes, striations 16:50 2226m stopped to sample 16:52 2226m collected sample T735-G11 from la rge pillows, very glassy, placed in S4

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90 16:54 2219m very well formed pillows flowing dow nslope, very little sed on top, very glassy surface 16:57 2213m 16:58 2212m, vapor pockets and cav ities between layers of basalt 16:59 2211m, picking sample of vapor pocket, T735-G12 17:022213m, sample looked glassy, still passi ng over breadcrust texture, sed coating on all 17:03 2211m, lots of local relief, big pillows surrounding by smoother tubes 17:06 2211m, turining on to ne xt line, sheetier appearance 17:07 2209m, large flat broken up sheet fl ow, perhaps a silicic constructional dome 17:08 2210m, trying to sample at top of constructional feature, slabby flow 17:09 2210m, collected sample of striat ed top of slabby flow, in BT4, T735-G13 17:12 2211m, was broken from beneath, top is flat but sides are tilted 17:13 2214m, still same flow, very straited, bl ocky iand angular n some places, plus few big pillows 17:16 lost my comment 17:18 2214m, turned to the left, and are back in the straited, sheety thick flow 17:19 2214m, collecting another piece of striated flow 17:20 2214m, sample of sheet fl ow, won't fit into bio tube 17:22 2214m, sample was collected in betw een the P/S boxes, T735 G14, another piece collected at same time 17:24 2213m, finished collecting another samp le of what is hopefully a dacite flow 17:26 2214m, nav jumpy because we're tunring, lots of pillows 17:27 2216m, large broken pillows, tubular

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91 17:28 2209m, between the tubes and pillows still getting massive flows (layered) 17:30 2209m, pillow texture is smoother 17:31 2212m, stopping to collect anot her sample, lots of gas cavities 17:32 2212m, sample going into biotube 3, T735 G15 17:34 2211m, back on the line, hdg 62, this area had lots of vesicles, and dome-like feature had both angular blocky rocks and pillows 17:38 2213m, tilted slab block, probably from eruption 17:40 2219m, still in the same general area of geology and morphology, still looking at domelike structure, probably not basalt 17:42 2215m 17:44 2215m, going to sample in this area 17:45 2216m, sample will be taken from the interior, more broken 17:46 2216m, sample T735-G16, from interior of flow, S5, should be smallest piece in S5 17:50 2215m, coming down slope of construct, hdg back to line 17:52 2216m, still at pillows with bread crust texture, moderate sed cover 17:53 2218m, very evolved rocks, broken up large pillow, no tectonic fissures on sonar 17:57 octopod, red Dumbo 17:58 2216m, large striated pillow, broken down the middle 18:002216m, heading back to line, irregualr terrain 18:012216m, irregular terrai n, with broken up blocky lava 18:042221m, collect a sample of broken pillow, to see if it's the same as the previous samples or it it's less viscous 18:06 2221m, taking a pillow sample

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92 18:06 2221m, S1 pillow sample with lots of vesicles, T735-G17 18:09 2221m, at bottom of saddle, will soon be heading upslope 18:10 2214m, coming up constructional slop e, pillows flowing downhill radially 18:12 2207m, attempting to sample the crus t of these pillows, looking for small piece 18:14 2205m, continued to move upslope looking for a breakable pillow crust 18:16 2206m, collected two pieces of p illow crust, small, in S1, T735-G18, 18:17 2192m, moving upslope, smaller pillows, reached a bench 18:19 2199m, moving up feature, more relief than dacite mound 18:21 2198m, tublar, flattene d pillows, probably at top 18:22 2198m, much less blocky than last dome, collecting sample 18:25 2198m, picking up sample previously dsropped, near top of slope, P5, T735-G19 18:26 2198m, this may have been sample site, nav jump 18:28 2199m, tubes flowing off to right, south 18:29 2201m, crabbing downslope, ve ry little tectonic features 18:31 2208m, well-formed pillows and tubes, heading downslope to south 18:33 2205m, stepping downslope mod sediment on pillows 18:34 2206m, elongate tubes look like they're flowing south 18:35 2199m 18:36 2199m, tubes and broken pillows pillows are more fragmented 18:40 2203m, still see some blocky, angular flows, on shallow slope 18:41 2204m, slow progress on hdg because of current 18:43 2205m 18:45 2209m

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93 18:46 2216m, heding downslope, flattened tubular pillows 18:49 2216m, still elongate tubes 18:50 2234m, looking at in place pillows, attempting to sample, also smaller rubble 18:52 2235m, collected rock sample from talus near in place pillows 18:35 2234m, T735 G20, P5 18:57 2258m flow fron talu s, large bocky boulders 19:01 2275m collect large fragment of intact p illow, T735-G21, from base of steep slope, slope continues down to east, skinny pillows 19:07 2263m heavy sed cover in gully betw en two knolls, isolated exposed pillows 19:08 2258m heading 93 degrees 19:10 2256m much less sed cover, pillows sticking out of mod sed cover 19:13 2254m pillows with heavy sed cover 19:14 2252m collapse feature showing sheet flows beneath pillows 19:16 2256m collect sheet flow samp le T735-G22 from collapse feature 19:18 2251m large pillow with inner drain features, pillows more bulbous, mod sed 19:21 2249m picking of fragment of pillow from top of sed, too big! 19:24 2249m looking for sample to collect, pillows in thick sed cover 19:26 2250m collect large pill ow fragment from top of sed, T735-G23, put in P5 19:28 2247m constructional pillows in sed cover 19:29 2246m veered off course to NE heading back S to top of knoll 19:31 2249m closer pillows, everything appears intact, possibly big hornito, all pillows flow downhill from top of mound 19:37 2249m collect sample T735-G24 in S2, greenish-white looking inside

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94 19:41 2250m collect basalt sample from same area, T735-G25 19:44 2248m heading down mound to nort h, bulbous pillows poking up through sed 19:45 2249m field of unsedimented pillow surfaces slightly more gentle slope than the west slope 19:49 2252m mostly jumbled rubble, some intact pillows heading downslope to saddle between knolls, 50% sed cover with e qual amounts of pillow rubble 19:53 2254m crossing fissure almost N-S severa l meters deep, broken pillow pieces, appears tectonic, sed on walls and at base, all pillows exposed in fissure wall 19:56 2260m folowing same fissure to north along trackline, star ting to shallow out 20:03 2266m collect grab sample from more massive unit, T735-G26, in S5 20:05 2265m massive flow overlain by pillow, lo west most exposed unit, well fissured with pillows on top, pillows appears to possibly flow inside indicating pillows post-date fissure, N-S fissure 20:07 2264m crossing massive flow, large fissure also to righ of ROV (east), possibly moving into the transition from hooked ridge to normal ridge morphology 2008 2265m following fissure, series of fissures N-S cutting massive flow, columnar talus in fissure 20:09 2265m some evidence of uplif t along this section of fissure 20:13 2258m very heavy sed cover 20:16 2265m more pillows, less sed 20:22 2271m thick sed cover, large pilows sticking up 20:24 stopped for sample, cow patty looking pillow 20:26 2271m sample from cowpatty pillow, crust, T735-G27, in P2

PAGE 95

95 20:31 2274m drifting to port towards large depr ession, some broken pillows with spill-outs, some tubular 20:32 2275m fissure heading N-S, shows well on sonar, looks deep, tectonic 20:35 2268m, mound in depression near fisure, constructional 20:38 2275m small hornito, drippy fl ows, ~1m relief on structure 20:39 2271m appears like old fissure, sed f illed, some truncated pillows???, narrow constructional ridge??? 20:42 2270m crossing fissure, just pa st linear series of small constructs, ~1m in relief, dropped down crossing fissure to west 20:45 2272m shallow fissure, sed co vering talus, orientation ~340 20:46 2271m another fissure, slight downdrop to east 20:48 2269m possible eruptive fissu re, N-S, east side dropped down 20:50 2269m sample from pillow along fissure, T735-G28, pie shaped, in P2 20:57 2268m, hdg to east, 100% sediment cover 20:58 2267m, crossed a fissure trending N-S 20:59 2267m, still in region of pillow and heavy sediment 21:01 2270m, sparse pillow/lobate outcrops with heavy sed between 21:02 lost comment 21:05 2272m, moved over small fissure trace, pillows 21:07 2274m, typical deep sea biology 21:09 2268m, many more outcrops right now, small ridge of broken pillows 21:11 2264m, many more broken pillow outcrops 21:12 2259m, slope is shallowing to the north

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96 21:15 2261m, on edge of slope with pillows outcropping, slope steepens to S 21:17 2261m, on the edge of large escarpment 21:18 2263m, fissure runs N-S, regional fissure system 2:120 2266m, lots of broken pillows exposed here, much less sediment 21:22 2264m, back to isloated pillows and heavy sediment, flat 21:24 2259m, climbing toward top of dome, pillows loo tectonized, but broken in place 21:25 2258m, shallow depresion filled in partially 21:27 2260m, at 2257m, maybe reached the summ it of this feature, as bathy dropped off afterward 21:29 2254m, pillow tubes, many going downslope to N(?) 21:30 2253m, crossing over smaler N-S fissure, can see both si des, sedimented on inside 21:32 2249m, continuing to move upward, most pillow tubes in place, plus rubble 21:33 2248m, in place pillows and a small rubble-filled fissure 21:35 2249m, collecting pieces of pillow crust near top of dome 21:36 2246m, T735-G29 will be in P3, looks old and oxidized 21:39 2242m, at top of mound, several fi ssures dissecting the top, running NS 21:42 2246m, running along a small N-S fi ssure, many on sonar, hdg is now 345ish 21:43 2251m, inside fissure, blocky and talus inside fissure, 20-30m wide 21:45 2250m, flying along the fissure, walls on bot h sides, small fissures wihtin main wall 21:47 2252m 21:49 2257m, irregular, tectonized terrain, lots of rubble, some in tact pillows on edge of small fisure 21:50 2264m, mod sediment covered, more fractured terrain, filled in fissures

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97 21:53 2270m, vehicle depth has been c onsistent;y 10m shallow than bathy 21:54 collectin a sample for biotube 2, T735-G30, hopefully at intersection bewteen regional fabric and local valley fabric 21:57 2272m, dropped first sample, looking for another piece of pillow crust 21:58 got another sample T735-G30, triangular piece of pillow crust, into biottube2 22:01 2272m, back to heavy sediment, flat, small isolated outcrops 22:032270m, 40m to E is a fissu re, flat-lying, 100% sed cover 22:05 2272m, 100% sed cover, isolated pillow outcrop 22:07 2276m, more of the same 22:09 2285m, more exposure of small bulbous pillows, still lots of sed 22:11 2293m, continuing to get deeper, still heavily sed 22:17 2294 heading to the ridge parallel wall, sediments 100% 22:19 2294 sed. continue, tape change, type 8 22:24 2295 pilow ridges, about to get sample 22:24 same depth, sample T735-G31 taken from the pillow ridge 22:29 2296, sed. again, some pillow ridges again 22:29 2296, sed. again, some pillow ridges again 22:34 2296 still 90% sed. some flow tos brocken 22:36 2290 fissure 337 orientation, ta lus on the sides on the fissure, 22:39 2287, more pillow terrane, heavily fissured 22:41 2289, still fissures, h eavily sed. between fissues 22:43 2280, compl. tectonized big pile of debrii pillows 22:46 2291 old fault (fault sl iver) heavily tectonised

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98 22:47 2290 approaching the oppposite wall, cove red with talus, another fault sliver 22:49 2287 wedging out fault sliver, two intersecting faults 22:51 2294 still old tectonized terrane 22:53 2297 materail changes, more collapsed pillows 22:54 2298 about to get sample 22:56 2298 sample G32 from the base of the wall 22:59 2296 ROV loosing main comp. going toward the wall 23:01 2291 base of the wall fl at sheets, tectonised ridge 23:03 2291 small pillows with buds on the side base of the wall 23:04 2294 moderate sed. cover, lobates, pillows with buds, still intact, gradually going uphill 23:05 2293, fissure parallel to the wall 23:07 2293 first ridge pare llel tectonised zone 23:08 2290 into the real fault, big step up 23:10 2288 intact colapse pit, not consistent wall 23:12 2281 change headings to 300 up the fault 23:14 2276 intact pillows and lobate flows downhill from us, 23:15 2274 remarkably little fractionation on pillows, constractional part of the wall? 23:17 2269 tectonised area 23:19 2263 heavily tectonized zone, small fragments nothing intact 23:20 2260 coming to relativ. flat artea, sedimented 23:23 2257 continue flat area, c overed with sheety flow debri 23:25 2257 sample from the sheety glassy flow -G33 23:26 2257 sample G33 very altered glassy, taken another piece

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99 23:31 2248 intact flows and lobate s, going down parallel to the wall 23:33 2244 half-way up the wall, flows align down 23:34 2242 sedim. area, covered with th in sheeted flows, contiune up the wall 23:36 2239 approaching steep wall.. 23:38 2239 escarpment pillow debrii, series of fault stpes, brocken sheets 23:40 2233 moving into area of intact lobate flows 23:40 2232 still intact flow 23:41 2225 alteranting talus and flows 23:42 2226 samples from the flow sheet and lobate flows 23:45 2228 sample G34 from lobate flow 23:45 2228 second sample G35 from the same area 23:48 2230 near the top of the wall coherent flows 23:50 2231 sample G36 23:53 2231 G37 and G 38 samples 23:55 2231 G 39 sample 23:59 ROV is coming up 01:26 0m end dive T735

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100 APPENDIX B PHASE CHEMISTRY FOR T735 LAVAS

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101 Table B-1: Pyroxene compositions de termined from microprobe analyses. Phase chemistry for lavas re covered during Dive T735. Pyroxenes Sample T735-G9 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 Analy. Loc. core rim interior in terior rim interior interior xeno/pheno? pheno xeno pheno pheno pheno pheno q pheno SiO2 51.15 51.82 50.67 51.69 50.33 50.26 52.34 TiO2 0.48 0.93 1.34 0.97 0.94 0.36 0.80 Al2O3 0.92 4.13 3.59 2.68 1.97 0.73 1.73 FeO 26.34 9.14 11.18 10.17 17.57 24.01 15.72 MnO 0.68 0.24 0.29 0.30 0.45 0.58 0.44 MgO 13.82 16.55 14.82 15.34 10.83 6.51 16.50 CaO 7.31 17.44 17.96 18.60 18.03 18.16 12.93 K2O 0.01 0.00 0.00 0.00 0.01 0.00 0.00 Na2O 0.11 0.34 0.31 0.25 0.29 0.24 0.19 P2O5 Cl Total 100.83 100.79 100.22 100.11 100.48 100.90 100.67 Number of cations per 6 oxygens Si 1.97 1.88 1.88 1.91 1.92 1.98 1.94 Ti 0.01 0.03 0.04 0.03 0.03 0.01 0.02 Al 0.05 0.21 0.19 0.14 0.11 0.04 0.09 Fe 0.85 0.28 0.35 0.31 0.56 0.79 0.49 Mn 0.02 0.01 0.01 0.01 0.01 0.02 0.01 Mg 0.79 0.90 0.82 0.85 0.62 0.38 0.91 Ca 0.30 0.68 0.71 0.74 0.74 0.77 0.51 Na 0.01 0.02 0.02 0.02 0.02 0.02 0.01 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 4.00 4.01 4.00 4.01 4.00 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xeno-xenocryst; phenol-phenocryst

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102 Table B-1: Continued. Pyroxenes Sample T735G10 T735-G10 T735-G10 T735-G 10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? q pheno xeno xeno xeno xeno xeno xeno SiO2 49.90 51.50 50.70 53.39 51.52 51.36 53.91 TiO2 1.33 1.10 1.11 0.58 1.10 1.09 0.42 Al2O3 2.56 3.00 3.34 1.30 3.32 2.78 1.32 FeO 16.37 12.02 13.04 11.94 9.04 10.94 16.25 MnO 0.42 0.34 0.31 0.34 0.23 0.28 0.41 MgO 12.74 17.04 16.85 18.79 16.27 15.38 22.84 CaO 15.42 14.80 14.48 13.95 18.55 18.10 4.87 K2O 0.01 0.00 0.00 0.00 0.00 0.00 0.00 Na2O 0.27 0.25 0.26 0.16 0.26 0.29 0.11 P2O5 Cl Total 99.06 100.11 100.22 100. 55 100.41 100.33 100.25 Number of cations per 6 oxygens Si 1.91 1.90 1.88 1.96 1.89 1.90 1.97 Ti 0.04 0.03 0.03 0.02 0.03 0.03 0.01 Al 0.14 0.15 0.17 0.07 0.17 0.14 0.07 Fe 0.52 0.37 0.40 0.37 0.28 0.34 0.50 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mg 0.73 0.94 0.93 1.03 0.89 0.85 1.24 Ca 0.63 0.58 0.57 0.55 0.73 0.72 0.19 Na 0.02 0.02 0.02 0.01 0.02 0.02 0.01 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 4.00 4.02 4.00 4.01 4.01 3.99 interiorinterior of crystal; q phenoquen ched phenocryst; xeno-xenocryst; phenol-phenocryst

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103 Table B-1: Continued. Pyroxenes Sample T735G10 T735-G10 T735-G10 T735-G 10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior interior interior core core core rim xeno/pheno? xeno xeno pheno quench pheno quench pheno quench pheno quench pheno SiO2 51.06 50.99 50.61 49.71 53.38 53.33 51.93 TiO2 1.06 0.50 0.47 0.90 0.84 1.03 0.88 Al2O3 3.09 1.49 0.95 2.77 2.66 2.98 1.86 FeO 11.13 18.61 25.24 10.67 10.44 10.05 16.24 MnO 0.32 0.37 0.68 0.27 0.25 0.22 0.36 MgO 15.84 21.12 8.73 16.70 15.96 15.10 11.39 CaO 16.74 5.86 14.15 15.91 17.28 18.66 17.46 K2O 0.00 0.00 0.03 0.00 0.02 0.00 0.00 Na2O 0.25 0.09 0.21 0.27 0.26 0.31 0.24 P2O5 Cl Total 99.63 99.16 101.10 97. 19 101.08 101.68 100.35 Number of cations per 6 oxygens Si 1.90 1.92 1.97 1.89 1.94 1.93 1.96 Ti 0.03 0.01 0.01 0.03 0.02 0.03 0.03 Al 0.16 0.08 0.05 0.15 0.13 0.15 0.10 Fe 0.35 0.59 0.82 0.34 0.32 0.30 0.51 Mn 0.01 0.01 0.02 0.01 0.01 0.01 0.01 Mg 0.88 1.18 0.51 0.95 0.86 0.81 0.64 Ca 0.67 0.24 0.59 0.65 0.67 0.72 0.71 Na 0.02 0.01 0.02 0.02 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 4.03 4.00 4.02 3.98 3.98 3.97 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 104

104 Table B-1: Continued. Pyroxenes Sample T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 Analy. Loc. core rim core rim core interior rim xeno/pheno? quench pheno quench pheno quench pheno quench pheno pheno pheno pheno SiO2 48.16 51.18 53.99 51.34 50.71 51.34 50.22 TiO2 2.57 0.75 0.66 1.07 0.62 0.49 0.99 Al2O3 5.27 1.61 1.59 2.59 1.54 1.23 2.27 FeO 16.68 21.45 17.65 16.31 18.56 17.35 18.03 MnO 0.39 0.49 0.43 0.36 0.47 0.40 0.47 MgO 12.09 12.14 20.33 13.75 11.51 10.99 10.22 CaO 14.51 12.94 5.71 15.15 16.13 17.96 17.65 K2O 0.04 0.01 0.02 0.01 0.00 0.00 0.02 Na2O 0.41 0.22 0.10 0.27 0.25 0.24 0.34 P2O5 Cl Total 100.12 100.79 100.47 100.84 99.79 99.99 100.20 Number of cations per 6 oxygens Si 1.81 1.95 1.98 1.92 1.95 1.97 1.92 Ti 0.07 0.02 0.02 0.03 0.02 0.01 0.03 Al 0.28 0.09 0.08 0.14 0.08 0.07 0.12 Fe 0.52 0.68 0.54 0.51 0.60 0.56 0.58 Mn 0.01 0.02 0.01 0.01 0.02 0.01 0.02 Mg 0.68 0.69 1.11 0.77 0.66 0.63 0.58 Ca 0.58 0.53 0.22 0.61 0.66 0.74 0.72 Na 0.03 0.02 0.01 0.02 0.02 0.02 0.03 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.99 3.99 3.97 4.00 4.00 4.00 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 105

105 Table B-1: Continued. Pyroxenes Sample T735G10 T735-G10 T735-G10 T735-G 10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 51.68 52.32 51.05 52.53 52.01 52.29 52.15 TiO2 0.66 0.31 0.15 0.29 0.16 0.38 0.30 Al2O3 1.22 1.03 0.43 0.42 0.54 1.00 0.57 FeO 17.21 19.98 30.66 30.85 29.53 17.69 28.96 MnO 0.35 0.51 0.70 0.77 0.75 0.38 0.70 MgO 12.00 12.26 13.98 14.41 14.27 11.36 13.81 CaO 16.77 14.14 3.20 3.30 3.75 17.76 4.57 K2O 0.00 0.01 0.00 0.01 0.00 0.02 0.00 Na2O 0.26 0.23 0.03 0.05 0.06 0.25 0.04 P2O5 Cl Total 100.16 100.76 100.20 102.62 101.07 101.13 101.10 Number of cations per 6 oxygens Si 1.97 1.99 1.99 2.00 2.00 1.98 2.00 Ti 0.02 0.01 0.00 0.01 0.00 0.01 0.01 Al 0.06 0.05 0.02 0.02 0.03 0.05 0.03 Fe 0.55 0.63 1.00 0.98 0.95 0.56 0.93 Mn 0.01 0.02 0.02 0.02 0.02 0.01 0.02 Mg 0.68 0.69 0.81 0.82 0.82 0.64 0.79 Ca 0.68 0.58 0.13 0.13 0.15 0.72 0.19 Na 0.02 0.02 0.00 0.00 0.00 0.02 0.00 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.99 3.99 3.99 3.99 3.98 3.99 3.98 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 106

106 Table B-1: Continued. Pyroxenes Sample T735G10 T735-G10 T735-G10 T735-G 10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno chadacryst SiO2 52.90 51.76 51.91 52.11 48.79 51.93 50.81 TiO2 0.20 0.28 0.40 0.51 0.49 0.36 0.18 Al2O3 0.32 0.73 1.21 1.11 1.33 1.08 0.32 FeO 30.76 21.42 16.67 17.70 17.26 18.21 30.11 MnO 0.70 0.49 0.39 0.42 0.48 0.42 0.69 MgO 14.85 12.53 11.34 11.70 11.47 11.57 14.49 CaO 3.26 13.05 18.39 16.68 17.29 17.02 3.08 K2O 0.00 0.01 0.00 0.00 0.00 0.00 0.00 Na2O 0.08 0.20 0.24 0.23 0.25 0.28 0.00 P2O5 Cl Total 103.06 100.45 100.56 100.45 97.36 100.87 99.67 Number of cations per 6 oxygens Si 2.00 1.98 1.97 1.98 1.93 1.97 1.99 Ti 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Al 0.02 0.04 0.06 0.06 0.07 0.06 0.02 Fe 0.97 0.69 0.53 0.56 0.57 0.58 0.99 Mn 0.02 0.02 0.01 0.01 0.02 0.01 0.02 Mg 0.84 0.72 0.64 0.66 0.68 0.66 0.85 Ca 0.13 0.54 0.75 0.68 0.73 0.69 0.13 Na 0.01 0.01 0.02 0.02 0.02 0.02 0.00 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.99 4.00 3.99 3.99 4.03 4.00 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 107

107 Table B-1: Continued. Pyroxenes Sample T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior core core core core core interior xeno/pheno? chadacryst pheno pheno pheno pheno pheno pheno SiO2 52.18 49.21 49.31 49.14 49.78 50.24 49.95 TiO2 0.09 0.29 0.23 0.46 0.43 0.42 0.45 Al2O3 0.33 0.60 0.61 0.76 0.76 0.90 1.09 FeO 29.92 33.11 32.74 29.70 29.89 24.26 22.94 MnO 0.73 0.83 0.75 0.69 0.75 0.58 0.56 MgO 14.72 8.48 8.42 8.18 8.43 7.43 8.20 CaO 3.26 7.75 8.00 10.25 10.66 15.80 16.38 K2O 0.00 0.00 0.01 0.00 0.02 0.00 0.00 Na2O 0.00 0.08 0.10 0.11 0.10 0.22 0.23 P2O5 Cl Total 101.23 100.35 100.16 99.29 100.81 99.85 99.80 Number of cations per 6 oxygens Si 2.00 1.97 1.98 1.98 1.97 1.98 1.97 Ti 0.00 0.01 0.01 0.01 0.01 0.01 0.01 Al 0.02 0.03 0.03 0.04 0.04 0.05 0.06 Fe 0.96 1.11 1.10 1.00 0.99 0.80 0.75 Mn 0.02 0.03 0.03 0.02 0.03 0.02 0.02 Mg 0.84 0.51 0.50 0.49 0.50 0.44 0.48 Ca 0.13 0.33 0.34 0.44 0.45 0.67 0.69 Na 0.00 0.01 0.01 0.01 0.01 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.99 4.00 4.00 3.99 4.00 3.99 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 108

108 Table B-1: Continued. Pyroxenes Sample T735G10 T735-G10 T735-G10 T735-G 10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior rim rim interi or interior interior interior xeno/pheno? pheno pheno pheno xeno xeno xeno xeno SiO2 50.20 49.63 50.43 51.53 49.95 50.57 50.45 TiO2 0.46 0.51 0.49 1.03 1.22 0.92 0.88 Al2O3 1.14 1.03 0.92 3.09 3.98 4.02 3.77 FeO 22.99 22.75 26.34 8.56 8.95 9.30 9.70 MnO 0.50 0.59 0.71 0.19 0.22 0.23 0.24 MgO 8.13 8.25 8.68 16.33 14.78 15.56 15.63 CaO 16.58 15.53 13.34 17.47 18.52 16.81 17.22 K2O 0.00 0.01 0.02 0.00 0.00 0.00 0.00 Na2O 0.18 0.17 0.19 0.21 0.25 0.27 0.23 P2O5 Cl Total 100.17 98.46 101.12 98.41 97.86 97.68 98.12 Number of cations per 6 oxygens Si 1.97 1.97 1.97 1.91 1.87 1.89 1.89 Ti 0.01 0.02 0.01 0.03 0.03 0.03 0.02 Al 0.06 0.06 0.05 0.16 0.21 0.21 0.20 Fe 0.75 0.76 0.86 0.27 0.28 0.29 0.30 Mn 0.02 0.02 0.02 0.01 0.01 0.01 0.01 Mg 0.47 0.49 0.51 0.90 0.83 0.87 0.87 Ca 0.70 0.66 0.56 0.69 0.74 0.67 0.69 Na 0.01 0.01 0.01 0.02 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 3.99 4.00 3.99 4.00 3.99 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 109

109 Table B-1: Continued. Pyroxenes Sample T735G10 T735-G10 T735-G11 T735-G 11 T735-G11 T735-G11 T735-G11 Analy. Loc. rim rim interior interior interior core rim xeno/pheno? xeno pheno xeno xeno pheno pheno pheno SiO2 49.43 50.27 51.40 50.30 49.35 50.71 50.11 TiO2 1.22 1.14 0.86 1.30 1.51 1.11 0.90 Al2O3 2.88 2.12 3.05 3.96 3.10 2.24 1.82 FeO 18.23 16.70 10.77 9.20 15.78 16.52 17.65 MnO 0.46 0.38 0.28 0.20 0.38 0.45 0.43 MgO 14.28 10.19 18.65 15.87 14.14 15.88 11.10 CaO 12.21 17.19 14.58 18.54 15.09 13.11 17.92 K2O 0.02 0.01 0.00 0.01 0.01 0.01 0.02 Na2O 0.24 0.30 0.23 0.27 0.26 0.20 0.31 P2O5 0.00 0.01 0.10 0.00 0.06 Cl 0.00 0.00 0.00 0.01 0.01 Total 98.97 98.29 99.81 99. 65 99.72 100.22 100.32 Number of cations per 6 oxygens Si 1.89 1.95 1.89 1.86 1.87 1.90 1.92 Ti 0.04 0.03 0.02 0.04 0.04 0.03 0.03 Al 0.15 0.11 0.16 0.20 0.16 0.12 0.10 Fe 0.58 0.54 0.33 0.28 0.50 0.52 0.57 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mg 0.81 0.59 1.02 0.87 0.80 0.89 0.63 Ca 0.50 0.71 0.57 0.73 0.61 0.53 0.74 Na 0.02 0.02 0.02 0.02 0.02 0.01 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.01 3.97 4.02 4.01 4.02 4.01 4.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 110

110 Table B-1: Continued. Pyroxenes Sample T735G11 T735-G12 T735-G12 T735-G 12 T735-G12 T735-G12 T735-G12 Analy. Loc. core interior inte rior rim rim interior core xeno/pheno? xeno pheno pheno pheno pheno pheno pheno SiO2 53.52 49.25 50.98 49.34 49.90 50.32 49.83 TiO2 0.38 0.41 1.18 1.83 0.78 0.88 1.05 Al2O3 0.72 0.77 2.14 3.38 1.39 1.25 1.55 FeO 19.13 28.53 13.31 19.91 22.08 21.46 19.94 MnO 0.46 0.74 0.35 0.54 0.59 0.57 0.47 MgO 21.45 4.45 13.31 10.31 11.13 12.12 11.81 CaO 4.54 16.35 18.72 14.87 13.04 12.82 13.62 K2O 0.01 0.00 0.00 0.04 0.02 0.01 0.00 Na2O 0.06 0.24 0.29 0.30 0.16 0.17 0.22 P2O5 Cl Total 100.34 100.75 100.37 100.56 99.09 99.64 98.49 Number of cations per 6 oxygens Si 1.98 1.98 1.91 1.88 1.95 1.95 1.94 Ti 0.01 0.01 0.03 0.05 0.02 0.03 0.03 Al 0.04 0.04 0.11 0.18 0.08 0.07 0.08 Fe 0.59 0.96 0.42 0.64 0.72 0.69 0.65 Mn 0.01 0.03 0.01 0.02 0.02 0.02 0.02 Mg 1.18 0.27 0.74 0.59 0.65 0.70 0.69 Ca 0.18 0.70 0.75 0.61 0.55 0.53 0.57 Na 0.00 0.02 0.02 0.02 0.01 0.01 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 4.00 4.01 3.99 4.00 4.00 3.99 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 111

111 Table B-1: Continued. Pyroxenes Sample T735G12 T735-G12 T735-G12 T735-G 12 T735-G12 T735-G12 T735-G12 Analy. Loc. core rim core co re rim interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 50.12 52.52 48.79 49.49 50.93 50.96 50.42 TiO2 1.13 0.60 0.53 0.36 0.95 1.04 1.27 Al2O3 1.78 2.61 1.09 0.72 1.65 2.42 2.99 FeO 20.64 17.64 25.64 27.49 16.76 13.92 13.51 MnO 0.54 0.46 0.59 0.73 0.44 0.36 0.30 MgO 12.65 9.77 4.66 5.12 12.96 14.69 14.36 CaO 12.65 16.25 18.19 16.74 16.11 16.03 16.52 K2O 0.00 0.11 0.00 0.01 0.00 0.00 0.01 Na2O 0.21 0.41 0.24 0.19 0.26 0.26 0.36 P2O5 Cl Total 99.75 100.45 99.78 100.90 100.07 99.76 99.85 Number of cations per 6 oxygens Si 1.93 1.98 1.96 1.97 1.93 1.91 1.89 Ti 0.03 0.02 0.02 0.01 0.03 0.03 0.04 Al 0.10 0.14 0.06 0.04 0.09 0.13 0.16 Fe 0.66 0.56 0.86 0.92 0.53 0.44 0.42 Mn 0.02 0.01 0.02 0.02 0.01 0.01 0.01 Mg 0.73 0.55 0.28 0.30 0.73 0.82 0.80 Ca 0.52 0.66 0.78 0.72 0.66 0.64 0.66 Na 0.02 0.03 0.02 0.01 0.02 0.02 0.03 K 0.00 0.01 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 3.95 4.00 4.00 4.00 4.00 4.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 112

112 Table B-1: Continued. Pyroxenes Sample T735G12 T735-G12 T735-G12 T735-G 12 T735-G12 T735-G12 T735-G12 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 50.93 52.00 51.85 51.17 51.83 51.68 51.40 TiO2 1.21 0.88 0.82 1.13 0.95 1.02 1.16 Al2O3 2.83 2.65 2.94 3.54 3.26 3.25 3.55 FeO 13.42 9.60 8.85 9.48 9.54 9.69 9.97 MnO 0.34 0.27 0.26 0.29 0.21 0.26 0.27 MgO 14.65 16.85 17.33 16.70 17.27 17.16 17.36 CaO 16.25 17.51 17.28 17.18 16.53 16.92 16.06 K2O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Na2O 0.26 0.23 0.24 0.28 0.27 0.29 0.26 P2O5 Cl Total 100.01 100.29 99.80 99.93 100.07 100.44 100.30 Number of cations per 6 oxygens Si 1.90 1.91 1.91 1.88 1.90 1.89 1.88 Ti 0.03 0.02 0.02 0.03 0.03 0.03 0.03 Al 0.15 0.14 0.15 0.18 0.17 0.17 0.18 Fe 0.42 0.30 0.27 0.29 0.29 0.30 0.31 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mg 0.82 0.92 0.95 0.92 0.94 0.94 0.95 Ca 0.65 0.69 0.68 0.68 0.65 0.66 0.63 Na 0.02 0.02 0.02 0.02 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 4.00 4.01 4.01 4.00 4.01 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 113

113 Table B-1: Continued. Pyroxenes Sample T735G12 T735-G12 T735-G12 T735-G 12 T735-G12 T735-G12 T735-G12 Analy. Loc. interior interior interi or interior interior rim interior xeno/pheno? pheno xeno xeno xeno xeno xeno xeno SiO2 52.57 49.17 50.75 49.98 49.01 52.80 52.86 TiO2 0.75 2.06 1.18 1.52 1.64 0.99 0.67 Al2O3 2.89 4.00 2.71 3.15 3.34 5.49 2.28 FeO 11.65 16.48 11.93 14.56 15.82 20.53 10.70 MnO 0.31 0.37 0.32 0.35 0.41 0.51 0.28 MgO 20.06 12.10 14.21 14.11 14.79 5.18 19.09 CaO 12.16 16.43 18.40 15.78 13.79 13.02 14.49 K2O 0.00 0.01 0.01 0.00 0.01 0.27 0.01 Na2O 0.15 0.42 0.31 0.28 0.23 0.99 0.22 P2O5 0.00 Cl 0.00 Total 100.72 101.10 99.86 99.74 99.06 101.25 100.58 Number of cations per 6 oxygens Si 1.91 1.84 1.90 1.88 1.86 1.99 1.92 Ti 0.02 0.06 0.03 0.04 0.05 0.03 0.02 Al 0.15 0.21 0.14 0.17 0.18 0.29 0.12 Fe 0.35 0.52 0.37 0.46 0.50 0.65 0.33 Mn 0.01 0.01 0.01 0.01 0.01 0.02 0.01 Mg 1.08 0.68 0.79 0.79 0.84 0.29 1.04 Ca 0.47 0.66 0.74 0.64 0.56 0.53 0.57 Na 0.01 0.03 0.02 0.02 0.02 0.07 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.01 0.00 Total Cation 4.00 4.01 4.01 4.00 4.01 3.88 4.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 114

114 Table B-1: Continued. Pyroxenes Sample T735G12 T735-G12 T735-G12 T735-G 12 T735-G12 T735-G13 T735-G13 Analy. Loc. interior interior co re rim interior interior core xeno/pheno? xeno pheno pheno pheno pheno pheno pheno SiO2 51.13 49.50 48.92 51.01 50.69 51.52 48.50 TiO2 1.18 0.34 0.40 0.78 0.87 0.68 0.86 Al2O3 3.39 0.57 0.98 1.39 1.81 1.27 2.11 FeO 9.41 28.27 28.35 17.40 20.86 17.39 13.33 MnO 0.25 0.69 0.66 0.53 0.57 0.39 0.38 MgO 16.48 5.26 3.29 12.47 12.01 18.96 15.56 CaO 18.47 16.15 18.51 16.22 13.17 8.01 14.48 K2O 0.00 0.00 0.00 0.02 0.04 0.01 0.02 Na2O 0.25 0.17 0.27 0.25 0.21 0.16 0.22 P2O5 0.00 0.02 0.01 0.02 0.02 Cl 0.00 0.00 0.00 0.00 0.00 Total 100.55 100.97 101.39 100.07 100.24 98.38 95.44 Number of cations per 6 oxygens Si 1.87 1.98 1.96 1.95 1.94 1.95 1.90 Ti 0.03 0.01 0.01 0.02 0.03 0.02 0.03 Al 0.17 0.03 0.05 0.07 0.10 0.07 0.12 Fe 0.29 0.94 0.95 0.56 0.67 0.55 0.44 Mn 0.01 0.02 0.02 0.02 0.02 0.01 0.01 Mg 0.90 0.31 0.20 0.71 0.69 1.07 0.91 Ca 0.72 0.69 0.79 0.66 0.54 0.32 0.61 Na 0.02 0.01 0.02 0.02 0.02 0.01 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.02 4.00 4.01 4.00 3.99 4.00 4.03 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 115

115 Table B-1: Continued. Pyroxenes Sample T735G13 T735-G13 T735-G13 T735-G 13 T735-G13 T735-G13 T735-G13 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? xeno xeno xeno xeno xeno xeno pheno SiO2 48.50 47.10 48.98 52.33 48.79 54.38 50.04 TiO2 1.11 1.96 0.81 0.90 0.88 0.87 0.28 Al2O3 3.26 5.22 2.35 2.34 3.28 4.09 0.96 FeO 10.94 9.85 10.90 11.17 10.61 16.31 25.77 MnO 0.23 0.20 0.31 0.28 0.25 0.45 0.63 MgO 17.62 14.87 15.59 14.97 15.85 10.66 6.29 CaO 14.44 16.93 17.59 17.39 14.01 12.91 16.49 K2O 0.00 0.01 0.01 0.00 0.00 0.07 0.04 Na2O 0.24 0.37 0.31 0.24 0.25 1.22 0.22 P2O5 Cl Total 96.34 96.49 96.84 99. 61 93.91 100.94 100.74 Number of cations per 6 oxygens Si 1.86 1.80 1.89 1.94 1.90 1.99 1.98 Ti 0.03 0.06 0.02 0.03 0.03 0.02 0.01 Al 0.17 0.28 0.13 0.12 0.18 0.21 0.05 Fe 0.35 0.31 0.35 0.35 0.35 0.50 0.85 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.02 Mg 1.01 0.85 0.89 0.83 0.92 0.58 0.37 Ca 0.59 0.69 0.73 0.69 0.59 0.51 0.70 Na 0.02 0.03 0.02 0.02 0.02 0.09 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.03 4.02 4.04 3.98 3.99 3.92 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 116

116 Table B-1: Continued. Pyroxenes Sample T735G13 T735-G13 T735-G13 T735-G 13 T735-G13 T735-G13 T735-G13 Analy. Loc. core rim inte rior core core rim rim xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 50.13 49.50 51.21 52.17 53.61 49.97 50.63 TiO2 0.57 0.36 1.10 1.13 0.29 0.79 1.50 Al2O3 1.55 0.94 1.98 3.02 0.45 2.25 3.27 FeO 25.00 25.19 17.47 14.86 22.78 19.87 13.93 MnO 0.53 0.57 0.43 0.37 0.51 0.48 0.36 MgO 6.23 6.07 16.47 14.90 19.65 12.94 14.80 CaO 17.84 16.51 10.36 12.18 3.90 12.11 15.11 K2O 0.00 0.01 0.46 0.05 0.02 0.02 0.01 Na2O 0.33 0.27 0.27 0.27 0.11 0.23 0.33 P2O5 Cl Total 102.18 99.44 99.73 98.95 101.32 98.66 99.93 Number of cations per 6 oxygens Si 1.95 1.98 1.93 1.95 1.99 1.93 1.89 Ti 0.02 0.01 0.03 0.03 0.01 0.02 0.04 Al 0.08 0.05 0.10 0.16 0.02 0.12 0.17 Fe 0.81 0.84 0.55 0.46 0.71 0.64 0.43 Mn 0.02 0.02 0.01 0.01 0.02 0.02 0.01 Mg 0.36 0.36 0.92 0.83 1.09 0.75 0.82 Ca 0.74 0.71 0.42 0.49 0.16 0.50 0.60 Na 0.03 0.02 0.02 0.02 0.01 0.02 0.02 K 0.00 0.00 0.02 0. 00 0.00 0.00 0.00 Total Cation 4.01 3.99 4.01 3.95 4.00 4.00 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 117

117 Table B-1: Continued. Pyroxenes Sample T735G13 T735-G13 T735-G13 T735-G 13 T735-G13 T735-G14 T735-G14 Analy. Loc. rim core rim ri m interior interior core xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 50.83 50.74 51.05 49.92 49.11 49.29 49.41 TiO2 0.68 0.52 0.49 0.38 0.38 0.49 0.46 Al2O3 1.86 1.24 1.18 0.91 0.81 1.00 0.79 FeO 15.12 18.75 19.49 24.62 28.03 26.19 26.67 MnO 0.37 0.46 0.42 0.58 0.72 0.67 0.62 MgO 13.09 8.33 8.58 9.47 4.52 4.35 6.14 CaO 17.10 17.30 18.93 13.01 16.72 18.47 16.88 K2O 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Na2O 0.27 0.26 0.25 0.25 0.19 0.24 0.16 P2O5 0.00 Cl 0.00 Total 99.32 97.60 100.38 99. 14 100.51 100.71 101.13 Number of cations per 6 oxygens Si 1.93 2.00 1.97 1.97 1.97 1.97 1.96 Ti 0.02 0.02 0.01 0.01 0.01 0.01 0.01 Al 0.10 0.07 0.06 0.05 0.05 0.06 0.04 Fe 0.48 0.62 0.63 0.81 0.94 0.87 0.88 Mn 0.01 0.02 0.01 0.02 0.02 0.02 0.02 Mg 0.74 0.49 0.49 0.56 0.27 0.26 0.36 Ca 0.70 0.73 0.78 0.55 0.72 0.79 0.72 Na 0.02 0.02 0.02 0.02 0.01 0.02 0.01 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.01 3.96 3.99 4.00 4.00 4.00 4.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 118

118 Table B-1: Continued. Pyroxenes Sample T735G14 T735-G14 T735-G14 T735-G 14 T735-G14 T735-G14 T735-G14 Analy. Loc. rim core rim co re core core interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 50.51 49.12 49.93 52.13 50.94 50.89 51.80 TiO2 0.66 1.86 1.45 0.92 0.88 0.87 0.70 Al2O3 1.36 4.99 6.73 3.35 1.84 1.87 1.66 FeO 20.33 11.64 16.70 14.45 17.65 17.04 15.73 MnO 0.51 0.29 0.38 0.35 0.44 0.42 0.43 MgO 12.46 15.62 6.83 16.67 14.13 14.61 15.15 CaO 14.19 15.88 15.79 11.82 14.27 14.09 14.58 K2O 0.03 0.02 0.24 0.07 0.02 0.00 0.01 Na2O 0.24 0.31 1.03 0.33 0.20 0.19 0.24 P2O5 0.00 0.05 0.11 0.00 0.01 0.00 0.05 Cl 0.01 0.00 0.09 0. 04 0.00 0.00 0.01 Total 100.29 99.77 99.24 100. 11 100.38 99.97 100.35 Number of cations per 6 oxygens Si 1.94 1.82 1.89 1.92 1.93 1.92 1.94 Ti 0.02 0.05 0.04 0.03 0.03 0.02 0.02 Al 0.07 0.26 0.36 0.17 0.10 0.10 0.09 Fe 0.65 0.36 0.53 0.44 0.56 0.54 0.49 Mn 0.02 0.01 0.01 0.01 0.01 0.01 0.01 Mg 0.71 0.86 0.38 0.91 0.80 0.82 0.85 Ca 0.58 0.63 0.64 0.47 0.58 0.57 0.59 Na 0.02 0.02 0.08 0.02 0.01 0.01 0.02 K 0.00 0.00 0.01 0. 00 0.00 0.00 0.00 Total Cation 4.02 4.01 3.94 3.98 4.01 4.01 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 119

119 Table B-1: Continued. Pyroxenes Sample T735G15 T735-G15 T735-G15 T735-G 15 T735-G15 T735-G15 T735-G15 Analy. Loc. interior interior inte rior interior core interior rim xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 49.73 50.88 50.01 54.15 51.22 49.33 49.40 TiO2 0.33 1.09 1.41 0.58 0.95 0.37 0.20 Al2O3 0.54 3.47 3.45 2.12 2.29 0.73 0.63 FeO 29.42 8.99 12.29 13.51 12.08 26.66 28.05 MnO 0.79 0.22 0.31 0.33 0.32 0.57 0.66 MgO 4.68 15.89 16.38 23.86 16.05 5.00 5.05 CaO 15.61 19.32 15.43 5.92 16.59 17.82 16.60 K2O 0.00 0.00 0.00 0.01 0.00 0.00 0.01 Na2O 0.19 0.28 0.28 0.14 0.25 0.20 0.20 P2O5 0.00 0.02 0.02 0.00 0.01 0.00 Cl 0.00 0.00 0. 00 0.00 0.00 0.00 Total 101.31 100.13 99.58 100.66 99.77 100.69 100.80 Number of cations per 6 oxygens Si 1.99 1.87 1.86 1.94 1.91 1.97 1.98 Ti 0.01 0.03 0.04 0.02 0.03 0.01 0.01 Al 0.03 0.18 0.18 0.11 0.12 0.04 0.04 Fe 0.98 0.28 0.38 0.41 0.38 0.89 0.94 Mn 0.03 0.01 0.01 0.01 0.01 0.02 0.02 Mg 0.28 0.87 0.91 1.28 0.89 0.30 0.30 Ca 0.67 0.76 0.62 0.23 0.66 0.76 0.71 Na 0.02 0.02 0.02 0.01 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 4.02 4.02 3.99 4.01 4.01 4.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 120

120 Table B-1: Continued. Pyroxenes Sample T735G15 T735-G15 T735-G16 T735-G 16 T735-G16 T735-G16 T735-G16 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno clot clot clot SiO2 50.62 50.88 52.56 47.74 51.08 48.96 48.50 TiO2 1.10 1.10 0.60 2.29 0.97 0.60 0.58 Al2O3 3.19 3.02 1.71 4.27 3.32 1.02 1.07 FeO 8.84 10.60 18.74 16.34 10.70 25.87 28.21 MnO 0.18 0.26 0.47 0.43 0.26 0.56 0.68 MgO 15.98 17.37 20.58 12.73 16.58 5.57 5.87 CaO 19.16 16.44 5.47 15.51 17.15 17.60 15.28 K2O 0.00 0.00 0.01 0.00 0.00 0.00 0.00 Na2O 0.27 0.25 0.10 0.35 0.28 0.23 0.21 P2O5 0.01 0.03 0.00 0.14 0.03 0.03 0.00 Cl 0.02 0.01 0.00 0. 00 0.00 0.00 0.00 Total 99.36 99.94 100.23 99. 79 100.37 100.44 100.38 Number of cations per 6 oxygens Si 1.88 1.88 1.94 1.81 1.88 1.95 1.95 Ti 0.03 0.03 0.02 0.07 0.03 0.02 0.02 Al 0.17 0.16 0.09 0.23 0.17 0.06 0.06 Fe 0.27 0.33 0.58 0.52 0.33 0.86 0.95 Mn 0.01 0.01 0.01 0.01 0.01 0.02 0.02 Mg 0.88 0.96 1.13 0.72 0.91 0.33 0.35 Ca 0.76 0.65 0.22 0.63 0.68 0.75 0.66 Na 0.02 0.02 0.01 0.03 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.02 4.02 4.00 4.02 4.02 4.01 4.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 121

121 Table B-1: Continued. Pyroxenes Sample T735G16 T735-G16 T735-G16 T735-G 16 T735-G17 T735-G17 T735-G17 Analy. Loc. interior core rim core core interior interior xeno/pheno? clot pheno pheno pheno pheno pheno pheno SiO2 48.81 50.73 49.62 49.31 51.52 49.72 47.86 TiO2 0.47 1.04 1.25 1.74 1.05 1.33 1.98 Al2O3 0.89 1.89 2.16 3.25 2.61 2.78 4.65 FeO 29.06 16.72 20.60 15.60 11.18 16.15 15.42 MnO 0.75 0.44 0.55 0.42 0.25 0.41 0.36 MgO 5.71 15.53 11.83 12.16 16.00 13.29 12.10 CaO 14.58 13.08 14.07 17.37 17.20 15.84 16.98 K2O 0.01 0.00 0.01 0.00 0.01 0.00 0.00 Na2O 0.16 0.20 0.22 0.34 0.23 0.28 0.32 P2O5 0.03 0.04 0.00 0.03 0.06 Cl 0.00 0.00 0.00 0.00 0.00 Total 100.45 99.67 100.30 100.28 100.18 99.82 99.73 Number of cations per 6 oxygens Si 1.96 1.92 1.91 1.87 1.91 1.89 1.82 Ti 0.01 0.03 0.04 0.05 0.03 0.04 0.06 Al 0.05 0.10 0.12 0.17 0.13 0.15 0.25 Fe 0.98 0.53 0.66 0.49 0.35 0.51 0.49 Mn 0.03 0.01 0.02 0.01 0.01 0.01 0.01 Mg 0.34 0.88 0.68 0.69 0.88 0.75 0.68 Ca 0.63 0.53 0.58 0.70 0.68 0.64 0.69 Na 0.01 0.01 0.02 0.03 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.01 4.01 4.01 4.01 4.01 4.01 4.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 122

122 Table B-1: Continued. Pyroxenes Sample T735G17 T735-G17 T735-G17 T735-G 17 T735-G17 T735-G17 T735-G17 Analy. Loc. core rim interior core interior rim interior xeno/pheno? pheno pheno pheno pheno pheno pheno xeno SiO2 49.48 50.71 50.96 51.82 51.82 47.87 48.18 TiO2 0.23 0.59 0.64 0.76 0.83 1.31 2.31 Al2O3 0.36 1.11 1.04 2.50 2.10 2.62 5.72 FeO 36.78 25.05 21.93 10.58 12.75 22.50 12.67 MnO 0.93 0.72 0.59 0.27 0.35 0.50 0.29 MgO 8.29 14.57 15.24 18.17 17.82 10.36 14.25 CaO 4.56 6.95 9.43 15.37 13.91 13.65 16.93 K2O 0.00 0.01 0.02 0.00 0.01 0.02 0.00 Na2O 0.04 0.10 0.13 0.20 0.21 0.26 0.40 P2O5 0.00 0.06 0.00 0.00 0.01 0.00 0.02 Cl 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total 100.67 99.86 99.98 99.67 99.80 99.09 100.77 Number of cations per 6 oxygens Si 1.99 1.96 1.95 1.91 1.92 1.88 1.78 Ti 0.01 0.02 0.02 0.02 0.02 0.04 0.06 Al 0.02 0.06 0.06 0.13 0.11 0.14 0.30 Fe 1.24 0.81 0.70 0.33 0.40 0.74 0.39 Mn 0.03 0.02 0.02 0.01 0.01 0.02 0.01 Mg 0.50 0.84 0.87 1.00 0.98 0.61 0.78 Ca 0.20 0.29 0.39 0.61 0.55 0.57 0.67 Na 0.00 0.01 0.01 0.01 0.02 0.02 0.03 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.99 4.00 4.01 4.01 4.01 4.02 4.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 123

123 Table B-1: Continued. Pyroxenes Sample T735G17 T735-G18 T735-G18 T735-G 18 T735-G18 T735-G18 T735-G18 Analy. Loc. interior core rim core interior rim interior xeno/pheno? xeno pheno pheno pheno pheno pheno xeno SiO2 48.90 50.83 52.89 54.30 51.50 52.03 51.84 TiO2 2.20 0.21 0.50 0.45 1.02 0.79 0.75 Al2O3 5.55 0.56 1.46 1.83 3.99 2.95 3.04 FeO 12.37 23.10 11.69 11.58 9.48 12.60 8.51 MnO 0.28 0.57 0.29 0.31 0.30 0.33 0.21 MgO 14.55 7.16 15.98 25.06 18.27 15.35 17.48 CaO 17.16 18.56 17.79 6.73 15.72 16.13 18.20 K2O 0.01 0.00 0.00 0.00 0.00 0.05 0.01 Na2O 0.35 0.21 0.20 0.09 0.22 0.32 0.23 P2O5 0.08 0.00 0.00 0.00 0.00 0.01 0.00 Cl 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total 101.44 101.20 100.81 100.34 100.50 100.56 100.28 Number of cations per 6 oxygens Si 1.79 1.98 1.95 1.94 1.87 1.92 1.89 Ti 0.06 0.01 0.01 0.01 0.03 0.02 0.02 Al 0.28 0.03 0.08 0.09 0.20 0.15 0.16 Fe 0.38 0.75 0.36 0.35 0.29 0.39 0.26 Mn 0.01 0.02 0.01 0.01 0.01 0.01 0.01 Mg 0.79 0.42 0.88 1.34 0.99 0.84 0.95 Ca 0.67 0.78 0.70 0.26 0.61 0.64 0.71 Na 0.02 0.02 0.01 0.01 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.02 4.00 4.00 4.00 4.01 4.00 4.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 124

124 Table B-1: Continued. Pyroxenes Sample T735G18 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. interior core interior interior rim interior interior xeno/pheno? xeno pheno pheno pheno pheno pheno pheno SiO2 48.28 48.80 50.79 50.91 52.08 50.75 49.36 TiO2 1.72 0.40 0.11 0.18 0.44 0.12 0.28 Al2O3 5.83 0.86 0.39 0.35 1.48 0.30 0.93 FeO 13.05 25.57 22.85 22.70 10.48 22.77 25.11 MnO 0.29 0.68 0.66 0.67 0.30 0.60 0.61 MgO 15.18 6.33 7.20 7.18 16.36 7.35 6.51 CaO 15.10 16.02 18.28 18.29 17.02 18.44 16.38 K2O 0.01 0.00 0.00 0.02 0.00 0.00 0.00 Na2O 0.25 0.26 0.17 0.17 0.23 0.18 0.21 P2O5 0.07 Cl 0.00 Total 99.77 98.91 100.45 100.47 98.39 100.51 99.39 Number of cations per 6 oxygens Si 1.79 1.97 2.00 2.00 1.96 1.99 1.97 Ti 0.05 0.01 0.00 0.01 0.01 0.00 0.01 Al 0.30 0.05 0.02 0.02 0.08 0.02 0.05 Fe 0.41 0.86 0.75 0.75 0.33 0.75 0.84 Mn 0.01 0.02 0.02 0.02 0.01 0.02 0.02 Mg 0.84 0.38 0.42 0.42 0.92 0.43 0.39 Ca 0.60 0.69 0.77 0.77 0.68 0.78 0.70 Na 0.02 0.02 0.01 0.01 0.02 0.01 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.02 4.01 4.00 3.99 4.00 4.00 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 125

125 Table B-1: Continued. Pyroxenes Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. rim interior interior interior interior core interior xeno/pheno? pheno q pheno q pheno xeno xeno xeno xeno SiO2 52.20 47.68 51.23 51.22 51.80 52.90 50.71 TiO2 0.42 1.91 0.71 0.74 0.63 0.60 0.98 Al2O3 1.73 8.07 3.18 3.09 3.39 2.68 3.60 FeO 10.99 9.99 8.98 7.18 7.22 7.87 8.17 MnO 0.32 0.21 0.20 0.24 0.22 0.20 0.20 MgO 15.48 13.84 17.98 15.98 15.83 16.14 15.77 CaO 17.18 17.04 15.47 18.52 19.64 18.68 18.43 K2O 0.00 0.01 0.00 0.16 0.03 0.04 0.01 Na2O 0.20 0.31 0.20 0.40 0.30 0.26 0.34 P2O5 Cl Total 98.52 99.05 97.96 97.52 99.04 99.37 98.22 Number of cations per 6 oxygens Si 1.96 1.76 1.90 1.92 1.91 1.94 1.89 Ti 0.01 0.05 0.02 0.02 0.02 0.02 0.03 Al 0.09 0.42 0.16 0.16 0.17 0.14 0.19 Fe 0.35 0.31 0.28 0.22 0.22 0.24 0.25 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mg 0.87 0.76 1.00 0.89 0.87 0.88 0.88 Ca 0.69 0.67 0.62 0.74 0.78 0.73 0.74 Na 0.01 0.02 0.01 0.03 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 01 0.00 0.00 0.00 Total Cation 3.99 3.99 4.00 4.00 4.00 3.98 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 126

126 Table B-1: Continued. Pyroxenes Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. rim core rim core core core core xeno/pheno? xeno xeno xeno pheno pheno pheno pheno SiO2 52.71 53.85 46.83 51.83 51.37 51.39 51.35 TiO2 0.31 0.56 2.51 0.53 0.67 0.69 0.92 Al2O3 2.12 1.84 7.67 2.02 1.79 3.41 3.24 FeO 7.93 7.32 11.05 10.52 10.13 9.70 9.63 MnO 0.25 0.21 0.21 0.26 0.26 0.18 0.22 MgO 17.88 17.26 13.92 14.49 14.58 17.10 15.40 CaO 16.49 18.11 16.56 18.71 18.55 15.57 17.86 K2O 0.00 0.01 0.03 0.00 0.00 0.03 0.01 Na2O 0.24 0.26 0.40 0.25 0.24 0.30 0.30 P2O5 Cl Total 97.91 99.42 99.17 98.61 97.59 98.37 98.94 Number of cations per 6 oxygens Si 1.96 1.97 1.74 1.95 1.95 1.91 1.91 Ti 0.01 0.02 0.07 0.02 0.02 0.02 0.03 Al 0.11 0.09 0.40 0.11 0.10 0.18 0.17 Fe 0.25 0.22 0.34 0.33 0.32 0.30 0.30 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mg 0.99 0.94 0.77 0.81 0.83 0.95 0.85 Ca 0.66 0.71 0.66 0.75 0.75 0.62 0.71 Na 0.02 0.02 0.03 0.02 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.99 3.98 4.01 3.99 3.99 4.00 3.99 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 127

127 Table B-1: Continued. Pyroxenes Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. interior interior interior core interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 51.91 50.90 52.09 51.89 51.06 51.49 51.92 TiO2 0.57 0.61 0.81 0.58 0.66 0.61 0.74 Al2O3 2.02 2.08 3.55 2.70 2.74 2.25 1.57 FeO 9.10 11.21 12.96 7.38 7.70 8.86 12.37 MnO 0.29 0.31 0.29 0.22 0.18 0.24 0.29 MgO 16.03 14.02 12.54 16.90 16.11 16.23 14.58 CaO 17.96 18.03 16.94 17.68 18.15 17.27 17.00 K2O 0.00 0.00 0.06 0.00 0.00 0.00 0.00 Na2O 0.23 0.29 0.31 0.29 0.23 0.22 0.22 P2O5 Cl Total 98.12 97.45 99.55 97.64 96.83 97.18 98.67 Number of cations per 6 oxygens Si 1.94 1.94 1.94 1.93 1.93 1.94 1.96 Ti 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Al 0.11 0.11 0.19 0.14 0.14 0.12 0.08 Fe 0.28 0.36 0.40 0.23 0.24 0.28 0.39 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mg 0.90 0.80 0.70 0.94 0.91 0.91 0.82 Ca 0.72 0.74 0.68 0.71 0.73 0.70 0.69 Na 0.02 0.02 0.02 0.02 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.99 4.00 3.96 3.99 3.99 3.99 3.99 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 128

128 Table B-1: Continued. Pyroxenes Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. interior interior interi or interior interior interior rim xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 48.32 50.33 50.43 50.19 49.99 50.22 50.17 TiO2 0.66 0.24 0.26 0.31 0.32 0.31 0.33 Al2O3 2.20 0.66 0.70 0.64 0.80 0.82 0.84 FeO 14.15 24.54 24.38 23.71 25.01 24.90 24.82 MnO 0.37 0.63 0.61 0.60 0.66 0.62 0.64 MgO 14.94 6.71 6.69 6.79 6.27 5.92 5.74 CaO 14.21 17.00 17.28 18.04 17.28 17.65 17.61 K2O 0.01 0.00 0.00 0.00 0.00 0.00 0.00 Na2O 0.28 0.19 0.22 0.21 0.22 0.21 0.23 P2O5 Cl Total 95.13 100.31 100.55 100. 54 100.56 100.72 100.38 Number of cations per 6 oxygens Si 1.91 1.99 1.99 1.98 1.98 1.98 1.99 Ti 0.02 0.01 0.01 0.01 0.01 0.01 0.01 Al 0.12 0.04 0.04 0.04 0.04 0.05 0.05 Fe 0.47 0.81 0.80 0.78 0.83 0.82 0.82 Mn 0.01 0.02 0.02 0.02 0.02 0.02 0.02 Mg 0.88 0.39 0.39 0.40 0.37 0.35 0.34 Ca 0.60 0.72 0.73 0.76 0.73 0.75 0.75 Na 0.02 0.01 0.02 0.02 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.03 3.99 3.99 4.00 4.00 3.99 3.99 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 129

129 Table B-1: Continued. Pyroxenes Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. rim interior core inte rior interior in terior interior xeno/pheno? pheno xeno xeno pheno pheno pheno pheno SiO2 50.36 53.21 50.25 51.80 52.40 50.49 52.45 TiO2 0.34 0.09 1.10 0.83 0.72 0.73 0.66 Al2O3 0.80 28.20 3.28 2.74 2.50 3.53 1.75 FeO 23.18 1.00 11.66 8.57 7.80 7.70 11.02 MnO 0.64 0.00 0.31 0.19 0.19 0.20 0.34 MgO 7.28 0.16 15.14 16.84 16.88 16.63 16.47 CaO 17.55 12.84 17.64 18.61 18.79 18.05 16.83 K2O 0.02 0.08 0.00 0.00 0.00 0.00 0.01 Na2O 0.21 4.26 0.24 0.24 0.23 0.24 0.22 P2O5 Cl Total 100.36 99.87 99. 78 99.99 99.70 97.87 99.82 Number of cations per 6 oxygens Si 1.98 1.73 1.88 1.90 1.92 1.89 1.94 Ti 0.01 0.00 0.03 0.02 0.02 0.02 0.02 Al 0.04 1.28 0.17 0.14 0.13 0.18 0.09 Fe 0.76 0.03 0.36 0.26 0.24 0.24 0.34 Mn 0.02 0.00 0.01 0.01 0.01 0.01 0.01 Mg 0.43 0.01 0.84 0.92 0.92 0.93 0.91 Ca 0.74 0.45 0.71 0.73 0.74 0.72 0.67 Na 0.02 0.27 0.02 0.02 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 3.76 4.02 4.01 4.00 4.01 4.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 130

130 Table B-1: Continued. Pyroxenes Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G23 T735-G23 T735-G23 Analy. Loc. core core interior inte rior interior in terior interior xeno/pheno? pheno pheno xeno xeno pheno pheno pheno SiO2 51.29 51.74 49.16 52.41 51.21 52.12 51.56 TiO2 0.88 0.78 1.74 0.51 0.79 0.75 0.86 Al2O3 2.21 2.21 5.71 1.03 3.38 3.26 3.31 FeO 12.60 12.90 11.69 14.24 6.78 7.89 6.83 MnO 0.37 0.35 0.27 0.39 0.18 0.21 0.18 MgO 15.00 15.38 14.98 15.75 16.71 18.14 16.55 CaO 16.88 16.63 16.53 14.87 19.42 17.44 20.18 K2O 0.00 0.01 0.01 0.02 0.00 0.00 0.00 Na2O 0.25 0.25 0.32 0.18 0.24 0.25 0.26 P2O5 0.02 0.02 0.00 Cl 0.00 0.00 0.00 Total 99.54 100.32 100.54 99.40 98.72 100.07 99.72 Number of cations per 6 oxygens Si 1.92 1.92 1.81 1.97 1.89 1.90 1.89 Ti 0.02 0.02 0.05 0.01 0.02 0.02 0.02 Al 0.12 0.12 0.29 0.05 0.17 0.17 0.17 Fe 0.39 0.40 0.36 0.45 0.21 0.24 0.21 Mn 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mg 0.84 0.85 0.82 0.88 0.92 0.98 0.90 Ca 0.68 0.66 0.65 0.60 0.77 0.68 0.79 Na 0.02 0.02 0.02 0.01 0.02 0.02 0.02 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.00 4.01 4.01 3.99 4.01 4.01 4.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 131

131 Table B-1: Continued. Pyroxenes Sample T735G23 T735-G23 Analy. Loc. interior interior xeno/pheno? pheno pheno SiO2 51.69 51.76 TiO2 0.64 0.71 Al2O3 2.91 3.18 FeO 6.88 6.74 MnO 0.18 0.18 MgO 17.32 16.87 CaO 19.13 19.78 K2O 0.00 0.00 Na2O 0.24 0.23 P2O5 0.00 0.00 Cl 0.00 0.00 Total 98.99 99.46 Number of cations per 6 oxygens Si 1.90 1.90 Ti 0.02 0.02 Al 0.15 0.16 Fe 0.21 0.21 Mn 0.01 0.01 Mg 0.95 0.92 Ca 0.75 0.78 Na 0.02 0.02 K 0.00 0.00 Total Cation 4.01 4.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 132

132 Table B-2: Plagioclase compositions de termined from microprobe analyses. Phase chemistry for lavas recovered during Dive T735. Plagioclase Sample T735-G9 T735-G9 T735-G9 T735-G9 T735-G9 T735-G9 T735-G9 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 54.47 58.12 57.75 57.6858.2658.02 58.30 TiO2 0.04 0.06 0.08 0.050.050.02 0.09 Al2O3 28.84 25.43 25.38 26.0025.5125.01 25.51 FeO 0.54 0.46 0.55 0.430.560.46 0.42 MnO 0.02 0.01 0.01 0.000.010.03 0.02 MgO 0.03 0.03 0.03 0.010.020.01 0.02 CaO 9.08 8.81 9.25 9.569.039.06 8.93 Na2O 5.96 6.42 6.31 6.126.426.42 6.40 K2O 0.13 0.12 0.11 0.100.130.15 0.15 P2O5 Cl Total 99.14 99.50 99.48 99.95100.0299.20 99.85 Number of cations per 8 oxygens Si 2.35 2.50 2.49 2.472.502.51 2.50 Ti 0.00 0.00 0.00 0.000.000.00 0.00 Al 1.74 1.53 1.53 1.561.531.51 1.53 Fe 0.02 0.02 0.02 0.020.020.02 0.02 Mn 0.00 0.00 0.00 0.000.000.00 0.00 Mg 0.00 0.00 0.00 0.000.000.00 0.00 Ca 0.42 0.41 0.43 0.440.420.42 0.41 Na 0.50 0.54 0.53 0.510.530.54 0.53 K 0.01 0.01 0.010. 010.010.01 0.01 Total Cation 5.03 5.00 5.015.005.015.01 5.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 133

133 Table B-2: Continued. Plagioclase Sample T735G9 T735-G9 T735-G10 T735-G 10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? xeno pheno xeno xeno xeno pheno pheno SiO2 51.66 61.25 59.36 62.23 61.01 57.74 59.82 TiO2 0.06 0.01 0.03 0.00 0.08 0.06 0.00 Al2O3 28.54 23.49 25.74 25.42 25.97 27.79 26.81 FeO 0.73 0.36 0.36 0.32 0.40 0.48 0.37 MnO 0.00 0.00 0.02 0.00 0.02 0.00 0.00 MgO 0.19 0.00 0.01 0.00 0.00 0.02 0.03 CaO 14.11 6.39 7.40 6.43 7.11 8.80 8.22 Na2O 3.63 7.85 7.66 8.03 7.57 5.46 6.98 K2O 0.03 0.23 0.19 0.17 0.20 0.15 0.19 P2O5 Cl Total 98.98 99.57 100.77 102. 60 102.37 100.50 102.41 Number of cations per 8 oxygens Si 2.26 2.63 2.52 2.58 2.54 2.44 2.49 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.75 1.41 1.53 1.47 1.51 1.64 1.56 Fe 0.03 0.01 0.01 0.01 0.01 0.02 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.01 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.66 0.29 0.34 0.29 0.32 0.40 0.37 Na 0.31 0.65 0.63 0.65 0.61 0.45 0.56 K 0.00 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.02 5.00 5.04 5.01 5.01 4.96 5.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 134

134 Table B-2: Continued. Plagioclase Sample T735G10 T735-G10 T735-G10 T735-G 10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 59.67 57.47 58.43 58.27 57.30 57.56 57.64 TiO2 0.00 0.07 0.08 0.00 0.05 0.00 0.00 Al2O3 26.12 27.13 27.58 27.78 27.47 27.75 27.33 FeO 0.38 0.46 0.32 0.43 0.43 0.54 0.47 MnO 0.01 0.00 0.00 0.00 0.00 0.00 0.00 MgO 0.04 0.04 0.05 0.04 0.02 0.03 0.02 CaO 7.69 8.88 9.23 9.38 9.22 9.15 8.94 Na2O 7.21 6.90 6.42 6.47 6.45 6.60 6.58 K2O 0.18 0.13 0.17 0.16 0.14 0.14 0.18 P2O5 Cl Total 101.29 101.08 102.27 102.53 101.08 101.77 101.18 Number of cations per 8 oxygens Si 2.51 2.44 2.44 2.43 2.43 2.42 2.44 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.54 1.61 1.61 1.62 1.63 1.63 1.62 Fe 0.01 0.02 0.01 0.02 0.02 0.02 0.02 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.35 0.40 0.41 0.42 0.42 0.41 0.41 Na 0.59 0.57 0.52 0.52 0.53 0.54 0.54 K 0.01 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.02 5.04 5.01 5.02 5.03 5.03 5.03 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 135

135 Table B-2: Continued. Plagioclase Sample T735G10 T735-G10 T735-G10 T735-G 10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior interior interi or interior interior interior rim xeno/pheno? pheno pheno pheno q pheno q pheno q pheno q pheno SiO2 59.16 56.47 57.33 59.64 60.28 60.97 62.05 TiO2 0.09 0.00 0.00 0.04 0.45 0.08 0.24 Al2O3 27.01 27.46 27.74 26.16 21.93 25.56 22.55 FeO 0.47 0.48 0.47 0.96 2.00 0.92 1.69 MnO 0.02 0.00 0.03 0.01 0.00 0.00 0.02 MgO 0.04 0.03 0.03 0.00 0.08 0.08 0.12 CaO 8.33 9.15 9.49 7.62 5.58 6.81 6.07 Na2O 6.94 6.50 6.37 7.51 7.03 7.76 6.95 K2O 0.16 0.11 0.14 0.17 0.35 0.19 0.27 P2O5 Cl Total 102.21 100.21 101.62 102.10 97.71 102.35 99.96 Number of cations per 8 oxygens Si 2.47 2.41 2.42 2.50 2.65 2.55 2.66 Ti 0.00 0.00 0.00 0.00 0.02 0.00 0.01 Al 1.58 1.64 1.64 1.54 1.35 1.49 1.35 Fe 0.02 0.02 0.02 0.03 0.07 0.03 0.06 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.01 Ca 0.37 0.42 0.43 0.34 0.26 0.30 0.28 Na 0.56 0.54 0.52 0.61 0.60 0.63 0.58 K 0.01 0.01 0.01 0. 01 0.02 0.01 0.01 Total Cation 5.02 5.04 5.03 5.04 4.97 5.02 4.96 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 136

136 Table B-2: Continued. Plagioclase Sample T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? coarse xeno coarse xeno coarse xeno pheno pheno xeno xeno SiO2 58.95 60.83 60.88 60.10 59.59 54.71 56.90 TiO2 0.04 0.03 0.00 0.03 0.04 0.08 0.12 Al2O3 26.97 24.00 24.34 24.62 25.30 27.57 26.50 FeO 0.34 0.32 0.31 0.50 0.33 0.91 1.05 MnO 0.00 0.00 0.01 0.00 0.00 0.00 0.00 MgO 0.00 0.00 0.01 0.00 0.00 0.16 0.09 CaO 7.23 7.11 7.12 7.67 7.94 11.86 10.36 Na2O 7.31 7.47 7.58 7.27 6.95 4.78 5.83 K2O 0.15 0.18 0.17 0.15 0.16 0.07 0.09 P2O5 Cl Total 101.00 99.95 100.44 100. 36 100.32 100.16 100.98 Number of cations per 8 oxygens Si 2.49 2.60 2.59 2.56 2.54 2.36 2.43 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.59 1.43 1.45 1.47 1.51 1.66 1.58 Fe 0.01 0.01 0.01 0.02 0.01 0.03 0.04 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.01 0.01 Ca 0.33 0.33 0.32 0.35 0.36 0.55 0.47 Na 0.60 0.62 0.62 0.60 0.57 0.40 0.48 K 0.01 0.01 0.01 0. 01 0.01 0.00 0.01 Total Cation 5.02 5.00 5.01 5.01 5.00 5.01 5.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 137

137 Table B-2: Continued. Plagioclase Sample T735G10 T735-G10 T735-G 10 T735-G10 T735-G10 735-11 clot1 plag1 735-11 clot1 plag2 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? xeno xeno xeno xeno xeno xeno xeno SiO2 53.48 53.45 53.55 54.38 54.26 52.88 52.56 TiO2 0.07 0.08 0.08 0.10 0.09 0.08 0.06 Al2O3 27.01 28.07 27.89 27.00 27.53 29.29 29.59 FeO 0.84 0.73 0.84 0.97 0.92 0.88 0.88 MnO 0.01 0.02 0.02 0.02 0.00 0.01 0.01 MgO 0.15 0.19 0.21 0.21 0.24 0.19 0.18 CaO 12.32 12.81 12.78 12.41 12.40 12.98 13.29 Na2O 4.66 4.37 4.42 4.66 4.65 4.28 4.12 K2O 0.07 0.05 0.04 0.05 0.05 0.05 0.05 P2O5 0.05 0.02 Cl 0.00 0.00 Total 98.62 99.77 99.81 99. 79 100.16 100.69 100.75 Number of cations per 8 oxygens Si 2.35 2.31 2.32 2.36 2.34 2.27 2.25 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.66 1.70 1.69 1.64 1.66 1.76 1.77 Fe 0.03 0.03 0.03 0.04 0.03 0.03 0.03 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.01 0.01 0.01 0.01 0.02 0.01 0.01 Ca 0.58 0.59 0.59 0.58 0.57 0.60 0.61 Na 0.40 0.37 0.37 0.39 0.39 0.36 0.34 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 5.02 5.02 5.02 5.02 5.02 5.03 5.03 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 138

138 Table B-2: Continued. Plagioclase Sample T735G11* T735-G11* T735-G 11* T735-G11* T735-G11* T735-G11* T735-G11* Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 58.14 58.27 57.78 58.20 58.30 58.50 57.85 TiO2 0.05 0.02 0.06 0.01 0.00 0.05 0.01 Al2O3 25.93 26.02 26.11 25.85 25.98 25.81 25.86 FeO 0.44 0.48 0.46 0.42 0.47 0.41 0.39 MnO 0.01 0.00 0.00 0.00 0.02 0.01 0.01 MgO 0.02 0.03 0.00 0.02 0.03 0.02 0.03 CaO 8.51 8.59 8.69 8.54 8.52 8.45 8.71 Na2O 6.75 6.62 6.67 6.59 6.72 6.54 6.59 K2O 0.13 0.14 0.11 0.13 0.13 0.13 0.14 P2O5 0.01 0.00 0.00 0.01 0.03 0.02 0.00 Cl 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total 99.99 100.17 99.86 99.78 100.18 99.95 99.59 Number of cations per 8 oxygens Si 2.49 2.49 2.48 2.49 2.49 2.50 2.49 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.55 1.55 1.56 1.55 1.55 1.54 1.55 Fe 0.02 0.02 0.02 0.02 0.02 0.01 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.39 0.39 0.40 0.39 0.39 0.39 0.40 Na 0.56 0.55 0.55 0.55 0.56 0.54 0.55 K 0.01 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.02 5.01 5.02 5.01 5.01 5.00 5.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 139

139 Table B-2: Continued. Plagioclase Sample T735G11* T735-G11* T735-G 11* T735-G11* T735-G11* T735-G11* T735-G11* Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 58.00 58.33 56.84 51.43 58.09 57.96 57.06 TiO2 0.00 0.03 0.08 0.05 0.02 0.07 0.00 Al2O3 25.97 25.86 26.33 24.31 25.72 25.96 26.34 FeO 0.42 0.40 0.44 0.55 0.46 0.46 0.46 MnO 0.00 0.00 0.00 0.02 0.00 0.03 0.00 MgO 0.01 0.03 0.04 0.04 0.03 0.02 0.01 CaO 8.74 8.57 8.27 7.49 8.52 8.63 8.81 Na2O 6.64 6.60 6.45 5.99 6.74 6.70 6.48 K2O 0.11 0.13 0.13 0.14 0.11 0.13 0.13 P2O5 0.03 0.01 0.02 0.03 0.03 0.02 0.04 Cl 0.00 0.00 0.00 0. 05 0.00 0.00 0.01 Total 99.91 99.97 98.59 90.10 99.73 99.98 99.34 Number of cations per 8 oxygens Si 2.49 2.50 2.46 2.44 2.49 2.48 2.46 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.56 1.55 1.59 1.61 1.54 1.55 1.59 Fe 0.01 0.01 0.02 0.02 0.02 0.02 0.02 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.40 0.39 0.38 0.38 0.39 0.40 0.41 Na 0.55 0.55 0.54 0.55 0.56 0.56 0.54 K 0.01 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.02 5.01 5.01 5.03 5.02 5.02 5.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 140

140 Table B-2: Continued. Plagioclase Sample T735G11* T735-G11* T735-G11* T735-G 11* T735-G11* T735-G11* T735-G12 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 57.63 58.02 58.01 57.91 57.84 57.69 61.33 TiO2 0.05 0.00 0.02 0.04 0.05 0.05 0.02 Al2O3 26.19 25.93 26.14 25.88 26.02 26.11 24.03 FeO 0.41 0.47 0.45 0.44 0.46 0.58 0.48 MnO 0.01 0.02 0.00 0.01 0.00 0.01 0.00 MgO 0.03 0.03 0.03 0.02 0.07 0.01 0.00 CaO 8.81 8.61 8.66 8.69 8.70 8.56 6.40 Na2O 6.43 6.69 6.52 6.61 6.43 6.66 7.94 K2O 0.15 0.14 0.14 0.13 0.14 0.13 0.20 P2O5 0.06 0.03 0.00 0.02 0.00 0.01 0.02 Cl 0.00 0.00 0.00 0. 00 0.00 0.01 0.00 Total 99.75 99.93 99.98 99.75 99.72 99.82 100.42 Number of cations per 8 oxygens Si 2.47 2.49 2.48 2.49 2.48 2.48 2.61 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.57 1.55 1.56 1.55 1.56 1.57 1.43 Fe 0.01 0.02 0.02 0.02 0.02 0.02 0.02 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.41 0.40 0.40 0.40 0.40 0.39 0.29 Na 0.54 0.56 0.54 0.55 0.53 0.55 0.65 K 0.01 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.01 5.02 5.01 5.01 5.01 5.02 5.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 141

141 Table B-2: Continued. Plagioclase Sample T735G12 T735-G12 T735-G12 T735-G12 T735-G12 T735-G12 T735-G12 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno xeno xeno pheno pheno SiO2 61.29 61.03 60.88 53.32 52.22 59.69 61.28 TiO2 0.06 0.02 0.02 0.08 0.05 0.02 0.01 Al2O3 23.78 24.13 24.29 27.88 29.74 25.41 24.34 FeO 0.50 0.34 0.40 0.82 0.76 0.34 0.38 MnO 0.00 0.00 0.00 0.03 0.00 0.00 0.00 MgO 0.01 0.00 0.00 0.12 0.18 0.00 0.00 CaO 6.59 6.44 6.65 11.69 13.52 7.73 6.61 Na2O 7.49 7.93 7.81 4.79 3.88 7.11 7.69 K2O 0.23 0.17 0.19 0.08 0.05 0.13 0.18 P2O5 0.00 0.09 0.00 0.01 0.00 0.02 0.01 Cl 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total 99.94 100.14 100.24 98.83 100.41 100.46 100.48 Number of cations per 8 oxygens Si 2.62 2.60 2.59 2.33 2.25 2.54 2.60 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.42 1.44 1.45 1.70 1.79 1.51 1.44 Fe 0.02 0.01 0.01 0.03 0.03 0.01 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.01 0.01 0.00 0.00 Ca 0.30 0.29 0.30 0.55 0.62 0.35 0.30 Na 0.62 0.66 0.64 0.41 0.32 0.59 0.63 K 0.01 0.01 0.01 0. 00 0.00 0.01 0.01 Total Cation 4.99 5.01 5.01 5.03 5.02 5.00 5.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 142

142 Table B-2: Continued. Plagioclase Sample T735G12 T735-G12 T735-G12 T735-G 12 T735-G12 T735-G12 T735-G12 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 60.24 59.80 60.21 61.28 60.70 58.58 59.60 TiO2 0.03 0.02 0.00 0.04 0.04 0.05 0.03 Al2O3 24.78 23.70 24.00 23.26 23.89 25.15 24.45 FeO 0.35 0.34 0.39 0.31 0.33 0.53 0.41 MnO 0.01 0.02 0.00 0.03 0.02 0.00 0.03 MgO 0.00 0.00 0.00 0.01 0.00 0.03 0.00 CaO 7.16 6.86 7.37 6.48 6.93 8.73 7.90 Na2O 7.48 7.54 7.54 7.93 7.64 6.56 7.13 K2O 0.17 0.17 0.14 0.17 0.16 0.13 0.16 P2O5 0.00 Cl 0.00 Total 100.22 98.47 99. 68 99.52 99.70 99.81 99.77 Number of cations per 8 oxygens Si 2.57 2.59 2.58 2.63 2.60 2.52 2.56 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.48 1.44 1.44 1.40 1.43 1.51 1.47 Fe 0.01 0.01 0.01 0.01 0.01 0.02 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.33 0.32 0.34 0.30 0.32 0.40 0.36 Na 0.62 0.63 0.63 0.66 0.63 0.55 0.59 K 0.01 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.01 5.01 5.01 5.01 5.01 5.00 5.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 143

143 Table B-2: Continued. Plagioclase Sample T735G12 T735-G12 T735-G12 T735-G 12 T735-G12 T735-G12 T735-G12 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 59.49 59.40 58.51 57.61 61.68 62.09 61.69 TiO2 0.03 0.04 0.00 0.16 0.00 0.02 0.02 Al2O3 24.79 24.73 24.45 24.97 22.78 22.96 23.10 FeO 0.33 0.36 0.38 1.31 0.38 0.38 0.46 MnO 0.00 0.01 0.00 0.00 0.00 0.00 0.00 MgO 0.03 0.00 0.01 0.10 0.00 0.00 0.01 CaO 8.11 8.16 8.45 9.30 6.04 6.07 6.71 Na2O 7.01 6.93 6.88 6.30 8.06 8.10 7.67 K2O 0.12 0.13 0.14 0.12 0.22 0.23 0.23 P2O5 Cl Total 99.94 99.81 98.83 99.89 99.19 99.87 99.89 Number of cations per 8 oxygens Si 2.55 2.55 2.54 2.49 2.65 2.65 2.64 Ti 0.00 0.00 0.00 0.01 0.00 0.00 0.00 Al 1.48 1.48 1.48 1.51 1.37 1.37 1.38 Fe 0.01 0.01 0.01 0.05 0.01 0.01 0.02 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.01 0.00 0.00 0.00 Ca 0.37 0.37 0.39 0.43 0.28 0.28 0.31 Na 0.58 0.58 0.58 0.53 0.67 0.67 0.64 K 0.01 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.00 5.00 5.01 5.02 5.00 5.00 4.99 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 144

144 Table B-2: Continued. Plagioclase Sample T735G13 T735-G13 T735-G13 T735-G 14 T735-G14 T735-G15 T735-G15 Analy. Loc. interior core interior in terior interior in terior interior xeno/pheno? pheno q pheno xeno pheno pheno pheno pheno SiO2 59.40 52.80 52.92 47.07 58.17 53.38 52.00 TiO2 0.01 0.01 0.11 0.05 0.01 0.10 0.03 Al2O3 24.11 28.32 29.04 35.05 25.81 28.75 29.49 FeO 0.31 0.91 0.76 3.66 0.50 0.94 0.76 MnO 0.00 0.00 0.00 0.00 0.00 0.03 0.04 MgO 0.02 0.12 0.23 0.08 0.01 0.16 0.19 CaO 6.14 10.73 12.17 6.55 8.40 12.51 13.31 Na2O 7.89 5.51 4.73 5.06 6.73 4.62 4.00 K2O 0.20 0.10 0.07 0.11 0.12 0.06 0.05 P2O5 0.00 0.04 0.00 0.02 Cl 0.17 0.00 0.00 0.00 Total 98.08 98.50 100.02 97.75 99.79 100.56 99.90 Number of cations per 8 oxygens Si 2.58 2.31 2.28 2.06 2.50 2.29 2.25 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.47 1.73 1.75 2.14 1.55 1.73 1.78 Fe 0.01 0.03 0.03 0.13 0.02 0.03 0.03 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.01 0.01 0.01 0.00 0.01 0.01 Ca 0.29 0.50 0.56 0.31 0.39 0.58 0.62 Na 0.67 0.47 0.40 0.43 0.56 0.39 0.33 K 0.01 0.01 0.00 0. 01 0.01 0.00 0.00 Total Cation 5.02 5.06 5.04 5.09 5.01 5.03 5.03 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 145

145 Table B-2: Continued. Plagioclase Sample T735G15 T735-G15 T735-G15 T735-G 15 T735-G15 T735-G15 T735-G16 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno xeno SiO2 52.53 51.94 61.18 52.46 59.99 60.00 58.02 TiO2 0.06 0.05 0.00 0.09 0.03 0.01 0.00 Al2O3 29.18 29.70 24.17 28.85 24.98 24.67 24.62 FeO 0.81 0.72 0.29 0.83 0.32 0.39 0.55 MnO 0.03 0.00 0.00 0.02 0.01 0.00 0.00 MgO 0.19 0.19 0.00 0.18 0.00 0.01 0.01 CaO 12.94 13.58 6.36 12.67 7.29 6.64 7.34 Na2O 4.21 3.93 7.98 4.31 7.57 7.43 7.17 K2O 0.05 0.06 0.16 0.04 0.16 0.23 0.16 P2O5 0.00 0.01 0.00 0.00 0.04 0.01 0.03 Cl 0.00 0.00 0.00 0. 00 0.00 0.01 0.00 Total 99.99 100.17 100.15 99.45 100.41 99.40 97.89 Number of cations per 8 oxygens Si 2.27 2.24 2.60 2.28 2.55 2.57 2.54 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.76 1.79 1.44 1.75 1.49 1.48 1.50 Fe 0.03 0.03 0.01 0.03 0.01 0.01 0.02 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.01 0.01 0.00 0.01 0.00 0.00 0.00 Ca 0.60 0.63 0.29 0.59 0.33 0.31 0.34 Na 0.35 0.33 0.66 0.36 0.62 0.62 0.61 K 0.00 0.00 0.01 0. 00 0.01 0.01 0.01 Total Cation 5.03 5.03 5.01 5.03 5.02 5.00 5.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 146

146 Table B-2: Continued. Plagioclase Sample T735G16 T735-G16 T735-G16 T735-G 16 T735-G16 T735-G16 T735-G17 Analy. Loc. interior interior interior interior interior interior core xeno/pheno? xeno pheno xeno xeno xeno pheno xeno SiO2 59.61 60.27 59.05 58.39 59.23 60.73 60.32 TiO2 0.00 0.04 0.01 0.04 0.00 0.01 0.00 Al2O3 24.93 24.75 25.29 25.07 25.23 24.58 24.66 FeO 0.40 0.38 0.35 0.46 0.43 0.32 0.53 MnO 0.01 0.00 0.00 0.01 0.00 0.03 0.04 MgO 0.00 0.00 0.01 0.01 0.01 0.01 0.00 CaO 7.17 7.05 7.91 7.73 7.61 7.06 6.78 Na2O 7.59 7.70 7.16 7.16 7.24 7.61 7.74 K2O 0.16 0.17 0.15 0.17 0.14 0.15 0.16 P2O5 0.00 0.02 0.00 0.07 0.04 0.02 0.00 Cl 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total 99.88 100.36 99.93 99.09 99.94 100.52 100.23 Number of cations per 8 oxygens Si 2.55 2.57 2.53 2.52 2.53 2.58 2.57 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.49 1.47 1.51 1.51 1.51 1.46 1.47 Fe 0.01 0.01 0.01 0.02 0.02 0.01 0.02 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.33 0.32 0.36 0.36 0.35 0.32 0.31 Na 0.63 0.64 0.59 0.60 0.60 0.63 0.64 K 0.01 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.02 5.02 5.02 5.02 5.02 5.01 5.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 147

147 Table B-2: Continued. Plagioclase Sample T735G17 T735-G17 T735-G17 T735-G 17 T735-G18 T735-G18 T735-G18 Analy. Loc. rim core interior inte rior interior in terior interior xeno/pheno? xeno xeno xeno xeno xeno xeno xeno SiO2 62.36 60.69 56.47 55.54 53.79 50.78 54.35 TiO2 0.50 0.00 0.15 0.11 0.08 0.08 0.10 Al2O3 20.56 24.94 26.23 27.21 28.62 30.59 27.42 FeO 2.05 0.40 1.29 1.04 1.02 0.66 1.22 MnO 0.03 0.01 0.00 0.00 0.01 0.00 0.02 MgO 0.00 0.00 0.10 0.11 0.11 0.20 0.41 CaO 6.59 7.05 10.13 10.91 12.23 14.65 11.94 Na2O 5.41 7.52 5.47 5.32 4.60 3.23 4.54 K2O 0.38 0.17 0.12 0.09 0.12 0.04 0.07 P2O5 0.03 0.07 0.03 0.02 0.02 0.03 0.03 Cl 0.11 0.00 0.00 0. 00 0.00 0.00 0.00 Total 98.00 100.84 99.98 100. 36 100.60 100.26 100.09 Number of cations per 8 oxygens Si 2.73 2.57 2.43 2.39 2.31 2.19 2.35 Ti 0.02 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.26 1.48 1.58 1.63 1.72 1.84 1.66 Fe 0.07 0.01 0.05 0.04 0.04 0.02 0.04 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.01 0.01 0.01 0.01 0.03 Ca 0.31 0.32 0.47 0.50 0.56 0.68 0.55 Na 0.46 0.62 0.46 0.44 0.38 0.27 0.38 K 0.02 0.01 0.01 0. 00 0.01 0.00 0.00 Total Cation 4.87 5.01 5.00 5.02 5.02 5.02 5.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 148

148 Table B-2: Continued. Plagioclase Sample T735G18 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? xeno xeno xeno xeno xeno xeno xeno SiO2 52.29 78.76 60.05 62.26 78.47 52.82 53.25 TiO2 0.07 0.00 0.00 0.00 0.05 0.08 0.10 Al2O3 29.22 12.07 22.98 24.97 12.07 30.59 30.64 FeO 0.95 1.08 0.29 0.31 1.47 0.86 0.77 MnO 0.00 0.02 0.00 0.00 0.07 0.02 0.00 MgO 0.24 0.15 0.00 0.00 0.17 0.22 0.21 CaO 13.39 1.41 5.42 6.01 1.67 12.79 12.24 Na2O 3.88 0.74 7.68 8.42 0.71 4.23 4.29 K2O 0.05 1.35 0.24 0.20 1.26 0.06 0.04 P2O5 0.00 Cl 0.00 Total 100.07 95.57 96.65 102. 17 95.94 101.67 101.53 Number of cations per 8 oxygens Si 2.26 3.37 2.64 2.60 3.35 2.24 2.25 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.76 0.72 1.41 1.46 0.72 1.81 1.81 Fe 0.03 0.04 0.01 0.01 0.05 0.03 0.03 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.02 0.01 0.00 0.00 0.01 0.01 0.01 Ca 0.62 0.06 0.26 0.27 0.08 0.58 0.55 Na 0.32 0.06 0.65 0.68 0.06 0.35 0.35 K 0.00 0.07 0.01 0. 01 0.07 0.00 0.00 Total Cation 5.02 4.34 4.99 5.02 4.35 5.03 5.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 149

149 Table B-2: Continued. Plagioclase Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. interior interior interi or interior interior interior rim xeno/pheno? xeno q pheno q pheno q pheno pheno pheno pheno SiO2 50.65 55.02 56.21 56.87 62.62 61.92 60.97 TiO2 0.01 0.12 0.13 0.33 0.11 0.12 0.02 Al2O3 31.09 27.30 27.97 25.29 24.89 24.91 25.11 FeO 0.84 1.10 0.86 1.48 0.26 0.31 0.42 MnO 0.05 0.00 0.02 0.02 0.01 0.00 0.00 MgO 0.16 0.18 0.10 0.16 0.00 0.00 0.00 CaO 13.00 9.94 10.26 8.92 5.73 5.53 6.32 Na2O 3.85 5.12 5.55 5.26 8.30 8.63 8.04 K2O 0.03 0.14 0.13 0.27 0.19 0.19 0.16 P2O5 Cl Total 99.69 98.93 101.23 98. 60 102.10 101.60 101.03 Number of cations per 8 oxygens Si 2.19 2.39 2.38 2.48 2.61 2.59 2.57 Ti 0.00 0.00 0.00 0.01 0.00 0.00 0.00 Al 1.88 1.66 1.66 1.54 1.45 1.46 1.48 Fe 0.03 0.04 0.03 0.05 0.01 0.01 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.01 0.01 0.01 0.01 0.00 0.00 0.00 Ca 0.60 0.46 0.47 0.42 0.26 0.25 0.29 Na 0.32 0.43 0.46 0.44 0.67 0.70 0.66 K 0.00 0.01 0.01 0. 02 0.01 0.01 0.01 Total Cation 5.03 5.00 5.01 4.97 5.00 5.03 5.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 150

150 Table B-2: Continued. Plagioclase Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? xeno xeno xeno xeno xeno xeno xeno SiO2 53.21 53.30 59.16 55.08 57.30 52.67 53.28 TiO2 0.09 0.08 0.42 0.18 0.27 0.09 0.10 Al2O3 28.20 28.39 22.56 25.53 23.79 28.58 27.47 FeO 1.00 0.97 2.16 1.23 1.58 0.88 1.07 MnO 0.00 0.00 0.01 0.00 0.00 0.02 0.02 MgO 0.16 0.14 0.29 0.27 0.26 0.16 0.19 CaO 12.84 12.89 8.55 11.00 9.54 12.99 12.61 Na2O 4.26 4.34 4.78 4.66 5.46 4.15 4.34 K2O 0.08 0.07 0.25 0.12 0.17 0.06 0.07 P2O5 Cl Total 99.87 100.17 98. 30 98.10 98.44 99.63 99.15 Number of cations per 8 oxygens Si 2.30 2.30 2.59 2.42 2.52 2.29 2.33 Ti 0.00 0.00 0.01 0.01 0.01 0.00 0.00 Al 1.71 1.71 1.38 1.57 1.46 1.73 1.68 Fe 0.04 0.04 0.08 0.05 0.06 0.03 0.04 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.01 0.01 0.02 0.02 0.02 0.01 0.01 Ca 0.60 0.60 0.40 0.52 0.45 0.60 0.59 Na 0.36 0.36 0.41 0.40 0.46 0.35 0.37 K 0.00 0.00 0.01 0. 01 0.01 0.00 0.00 Total Cation 5.02 5.02 4.91 4.99 4.98 5.02 5.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 151

151 Table B-2: Continued. Plagioclase Sample T735G19 T735-G19 T735-G19 T735-G 19 T735-G19 T735-G19 T735-G19 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? xeno pheno pheno pheno myrmekite myrmekite myrmekite SiO2 51.51 50.64 52.43 52.49 62.50 60.09 62.71 TiO2 0.07 0.04 0.07 0.09 0.02 0.02 0.00 Al2O3 29.18 29.51 28.48 27.39 23.60 24.93 23.11 FeO 0.68 0.63 0.71 0.81 0.33 0.22 0.35 MnO 0.01 0.03 0.04 0.00 0.01 0.00 0.03 MgO 0.20 0.18 0.22 0.22 0.00 0.01 0.00 CaO 14.12 14.71 13.55 13.24 6.35 6.12 5.65 Na2O 3.40 3.18 3.79 4.04 7.75 7.01 8.22 K2O 0.04 0.03 0.04 0.05 0.24 0.25 0.25 P2O5 Cl Total 99.26 98.99 99.37 98. 35 100.84 98.69 100.32 Number of cations per 8 oxygens Si 2.24 2.21 2.28 2.31 2.64 2.58 2.66 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.78 1.80 1.73 1.69 1.39 1.50 1.37 Fe 0.02 0.02 0.03 0.03 0.01 0.01 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.01 0.01 0.01 0.01 0.00 0.00 0.00 Ca 0.66 0.69 0.63 0.62 0.29 0.28 0.26 Na 0.29 0.27 0.32 0.35 0.64 0.58 0.68 K 0.00 0.00 0.00 0. 00 0.01 0.01 0.01 Total Cation 5.01 5.02 5.01 5.02 4.98 4.97 5.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 152

152 Table B-2: Continued. Plagioclase Sample T735G19 T735-G19 T735-G19 T735-G19 T735-G19 T735-G19 T735-G19 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? myrmekite myrmekite myrmekite myrmekite myrmekite myrmekite myrmekite SiO2 62.72 62.21 61.99 61.76 62.22 61.79 62.67 TiO2 0.01 0.00 0.01 0.02 0.02 0.02 0.03 Al2O3 23.42 23.65 23.47 23.69 23.32 23.79 22.27 FeO 0.33 0.31 0.30 0.28 0.25 0.28 0.24 MnO 0.01 0.01 0.00 0.01 0.00 0.02 0.00 MgO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 CaO 5.79 6.10 6.21 6.27 5.80 6.18 5.61 Na2O 8.25 8.06 7.97 7.93 8.26 8.07 8.36 K2O 0.23 0.22 0.23 0.23 0.23 0.23 0.25 P2O5 Cl Total 100.78 100.56 100.20 100.20 100.10 100.39 99.45 Number of cations per 8 oxygens Si 2.65 2.64 2.64 2.63 2.65 2.62 2.69 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.38 1.40 1.40 1.41 1.39 1.41 1.34 Fe 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.26 0.28 0.28 0.29 0.26 0.28 0.26 Na 0.68 0.66 0.66 0.65 0.68 0.66 0.69 K 0.01 0.01 0.01 0. 01 0.01 0.01 0.01 Total Cation 5.00 5.00 5.00 5.00 5.00 5.01 5.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 153

153 Table B-2: Continued. Plagioclase Sample T735G19 T735-G23 T735-G23 T735-G23 T735-G23 T735-G23 T735-G23 Analy. Loc. interior interior interior interior interior interior interior xeno/pheno? myrmekite pheno pheno pheno pheno pheno pheno SiO2 62.88 51.70 52.13 52.50 50.81 51.97 51.31 TiO2 0.00 0.03 0.11 0.04 0.04 0.08 0.11 Al2O3 22.63 29.66 29.50 29.41 30.46 29.53 29.85 FeO 0.29 0.62 0.91 0.63 0.65 0.60 0.60 MnO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 MgO 0.00 0.24 0.26 0.23 0.21 0.23 0.23 CaO 6.09 13.69 13.48 13.15 14.45 13.73 14.10 Na2O 7.80 3.78 3.82 4.01 3.42 3.76 3.46 K2O 0.25 0.06 0.03 0.04 0.04 0.05 0.03 P2O5 0.00 0.02 0.03 0.02 0.04 0.03 Cl 0.00 0.00 0. 00 0.00 0.00 0.00 Total 99.96 99.77 100.27 100.04 100.08 99.99 99.71 Number of cations per 8 oxygens Si 2.68 2.24 2.25 2.26 2.19 2.24 2.22 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 1.35 1.79 1.78 1.77 1.84 1.78 1.81 Fe 0.01 0.02 0.03 0.02 0.02 0.02 0.02 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.02 0.02 0.02 0.01 0.01 0.01 Ca 0.28 0.63 0.62 0.61 0.67 0.64 0.65 Na 0.64 0.32 0.32 0.33 0.29 0.32 0.29 K 0.01 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 4.97 5.03 5.02 5.02 5.03 5.02 5.02 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst *, line of analyses run on same plagioclase crystal

PAGE 154

154 Table B-3: Olivine compositions determined from microprobe analyses. Olivine phase chemistry for lava s recovered during Dive T735. Olivine Sample T735-G9 T735-G9 T735-G9 T735-G9 T735-G9 T735-G9 T735-G9 Analy. Loc. interior interior interi or rim interior interior interior xeno/pheno? pheno pheno pheno pheno pheno pheno pheno SiO2 31.57 31.30 29.25 31.98 31.38 31.32 31.25 TiO2 0.02 0.05 0.00 0.12 0.02 0.00 0.01 Al2O3 0.03 0.02 0.00 0.00 0.00 0.03 0.03 FeO 65.25 65.86 64.31 66.38 66.14 65.94 62.56 MnO 1.28 1.39 1.30 1.38 1.30 1.33 1.34 MgO 3.85 3.93 3.99 3.80 3.88 3.90 6.26 CaO 0.31 0.26 0.36 0.27 0.27 0.32 0.32 Na2O 0.01 0.04 0.01 0.00 0.03 0.00 0.04 K2O 0.01 0.00 0.00 0.00 0.00 0.00 0.01 P2O5 Cl Total 102.32 102.85 99.22 103. 91 103.02 102.84 101.81 Number of cations per 4 oxygens Si 1.01 1.00 0.98 1.01 1.00 1.00 0.99 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe 1.75 1.76 1.80 1.75 1.77 1.76 1.66 Mn 0.03 0.04 0.04 0.04 0.04 0.04 0.04 Mg 0.18 0.19 0.20 0.18 0.18 0.19 0.30 Ca 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Na 0.00 0.00 0.00 0.00 0.00 0.00 0.00 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 2.99 3.00 3.02 2.99 3.00 3.00 3.01 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 155

155 Table B-3: Continuted. Olivine Sample T735-G9 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 Analy. Loc. rim interior interior in terior interior in terior interior xeno/pheno? pheno xeno xeno xeno xeno xeno xeno SiO2 30.88 32.99 32.68 31.72 32.00 31.17 32.14 TiO2 0.00 0.02 0.02 0.06 0.00 0.02 0.08 Al2O3 0.01 0.00 0.00 0.04 0.03 0.04 0.01 FeO 66.30 58.96 63.65 63.47 64.75 62.43 63.59 MnO 1.31 0.99 1.21 1.14 1.14 1.15 1.10 MgO 4.15 5.49 5.84 5.80 5.80 5.72 5.67 CaO 0.28 0.30 0.37 0.29 0.34 0.34 0.32 Na2O 0.00 0.03 0.05 0.00 0.00 0.01 0.06 K2O 0.00 0.00 0.02 0.00 0.00 0.00 0.00 P2O5 Cl Total 102.92 98.79 103.84 102. 53 104.05 100.88 102.95 Number of cations per 4 oxygens Si 0.99 1.06 1.01 1.00 1.00 1.00 1.01 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe 1.78 1.58 1.65 1.68 1.69 1.68 1.67 Mn 0.04 0.03 0.03 0.03 0.03 0.03 0.03 Mg 0.20 0.26 0.27 0.27 0.27 0.27 0.27 Ca 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Na 0.00 0.00 0.00 0.00 0.00 0.00 0.00 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.01 2.94 2.99 3.00 3.00 3.00 2.99 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 156

156 Table B-3: Continuted. Olivine Sample T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 T735-G10 Analy. Loc. rim rim core core interi or interior interior xeno/pheno? xeno xeno xeno xeno xeno xeno xeno SiO2 31.95 31.56 32.20 32. 47 53.22 50.59 32.20 TiO2 0.04 0.09 0.04 0. 00 0.22 0.29 0.02 Al2O3 0.00 0.00 0.03 0. 02 0.30 0.44 0.00 FeO 63.28 63.88 63.87 63. 03 31.50 29.43 62.13 MnO 1.11 1.15 1.20 1. 18 0.74 0.78 1.25 MgO 5.78 6.04 5.64 5. 80 14.27 13.81 6.01 CaO 0.33 0.32 0.31 0. 32 3.12 4.24 0.29 Na2O 0.00 0.00 0.01 0. 03 0.07 0.06 0.00 K2O 0.00 0.00 0.00 0. 00 0.00 0.01 0.00 P2O5 Cl Total 102.49 103.04 103.29 102. 84 103.43 99.64 101.93 Number of cations per 4 oxygens Si 1.01 0.99 1.01 1. 02 1.34 1.32 1.02 Ti 0.00 0.00 0.00 0. 00 0.00 0.01 0.00 Al 0.00 0.00 0.00 0. 00 0.01 0.02 0.00 Fe 1.67 1.68 1.67 1. 65 0.66 0.64 1.64 Mn 0.03 0.03 0.03 0. 03 0.02 0.02 0.03 Mg 0.27 0.28 0.26 0. 27 0.53 0.54 0.28 Ca 0.01 0.01 0.01 0. 01 0.08 0.12 0.01 Na 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 2.99 3.00 2.99 2. 98 2.65 2.67 2.98 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 157

157 Table B-3: Continuted. Olivine Sample T735-G10 T735-G10 T735-G10 T735-G12 T735-G12 T735-G12 T735-G12 Analy. Loc. interior interior inte rior rim rim interior interior xeno/pheno? xeno xeno xeno xeno pheno pheno pheno SiO2 31.79 31.47 31.76 32.55 32.33 31.08 30.94 TiO2 0.03 0.04 0.09 0.05 0.07 0.04 0.02 Al2O3 0.03 1.82 0.00 0.00 0.00 0.00 0.00 FeO 61.70 61.27 61.95 56.46 59.16 65.48 65.65 MnO 1.14 1.23 1.22 1.08 1.23 1.42 1.38 MgO 5.93 5.87 5.89 10.59 8.09 2.86 2.65 CaO 0.26 0.29 0.29 0.35 0.41 0.38 0.39 Na2O 0.01 0.00 0.02 0.03 0.00 0.03 0.00 K2O 0.00 0.00 0.00 0.01 0.01 0.00 0.00 P2O5 Cl Total 100.90 102.00 101.29 101.15 101.34 101.29 101.07 Number of cations per 4 oxygens Si 1.01 0.98 1.01 1.01 1.01 1.01 1.01 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 0.00 0.08 0.00 0.00 0.00 0.00 0.00 Fe 1.65 1.60 1.65 1.46 1.55 1.78 1.79 Mn 0.03 0.03 0.03 0.03 0.03 0.04 0.04 Mg 0.28 0.27 0.28 0.49 0.38 0.14 0.13 Ca 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Na 0.00 0.00 0.00 0.00 0.00 0.00 0.00 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 2.98 2.98 2.99 2.99 2.99 2.99 2.99 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 158

158 Table B-3: Continuted. Olivine Sample T735-G12 T735-G16 T735-G16 T735-G16 T735-G16 T735-G16 T735-G16 Analy. Loc. interior interior inte rior rin rim interior interior xeno/pheno? pheno xeno xeno pheno pheno pheno pheno SiO2 32.34 30.96 29.87 30.88 32.01 30.93 31.03 TiO2 0.02 0.06 0.00 0.04 0.04 0.01 0.07 Al2O3 0.00 0.00 0.01 0.00 0.03 0.00 0.00 FeO 58.60 65.31 64.23 64.91 58.00 65.15 65.39 MnO 1.06 1.24 1.31 1.26 1.05 1.32 1.29 MgO 9.87 3.80 4.04 3.87 9.23 3.82 3.99 CaO 0.29 0.40 0.32 0.36 0.37 0.38 0.36 Na2O 0.02 0.02 0.03 0.00 0.00 0.01 0.02 K2O 0.00 0.00 0.00 0.00 0.01 0.00 0.01 P2O5 0.04 0.03 0.00 0.02 0.00 0.00 0.00 Cl 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total 102.24 101.81 99.80 101. 35 100.72 101.61 102.15 Number of cations per 4 oxygens Si 1.00 1.00 0.99 1.00 1.00 1.00 1.00 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Al 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe 1.51 1.77 1.78 1.76 1.52 1.76 1.76 Mn 0.03 0.03 0.04 0.03 0.03 0.04 0.04 Mg 0.45 0.18 0.20 0.19 0.43 0.18 0.19 Ca 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Na 0.00 0.00 0.00 0.00 0.00 0.00 0.00 K 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 Total Cation 3.00 3.00 3.01 3.00 3.00 3.00 3.00 interiorinterior of crystal; q phenoquen ched phenocryst; xenoxenocryst; phenophenocryst

PAGE 159

159 APPENDIX C MAJOR AND TRACE ELEMENT DATA FOR T735 LAVAS

PAGE 160

160 Table C-1: Major and trace element data for Dive T735 samples. Sample 735-G01 735-G02 735-G03 735-G04 735-G05 735-G06 735-G07 SiO2 50.48 50.39 50.42 50.59 50.47 50.48 TiO2 2.12 2.06 2. 12 1.87 2.09 2.12 Al2O3 13.31 13.32 13. 33 13.48 13.38 13.12 FeOT 12.31 12.30 12. 32 11.96 12.21 12.29 MnO 0.21 0.20 0.21 0.22 0.20 0.20 MgO 6.87 7.04 6.94 6.86 6.94 6.78 CaO 11.27 11.18 11.17 11.25 11.24 11.17 Na2O 2.53 2.51 2.54 2.69 2.56 2.52 K2O 0.17 0.17 0.17 0.18 0.17 0.17 P2O5 0.22 0.22 0.20 0.23 0.22 0.24 Cl 0.02 0.02 0.02 0.03 0.02 0.03 Total (wt.%) 99.81 99. 69 99.74 99.68 99.80 99.41 H2O* CO2 (ppm) Sc 41.18 41.96 41.80 40.38 V 382.11 340.30 390.88 377.74 Cr 173.26 188.16 179.64 169.88 Co 37.56 38.02 38.47 37.19 Ni 57.21 53.81 59.75 57.45 Cu 55.40 64.76 56.20 54.84 Zn 99.24 89.24 101.87 98.31 Ga 18.05 17.40 18.34 17.61 Rb 1.23 1.21 1.23 1.19 Sr 102.40 118.06 104.22 99.75 Y 50.41 44.19 51.22 49.73 Zr 135.84 125.07 136.91 133.86 Nb 4.47 4.34 4.59 4.42 Rh 0.00 0.00 0.00 0.00 Ba 15.10 16.69 15.44 14.92 La 4.93 4.75 5.02 4.87 Ce 15.69 14.74 15.94 15.47 Pr 2.51 2.36 2.54 2.48 Nd 13.80 12.59 13.99 13.46 Sm 4.68 4.18 4.72 4.55 Eu 1.51 1.36 1.52 1.47 Gd 5.46 4.73 5.51 5.34 Tb 1.17 1.04 1.19 1.15 Dy 7.74 6.78 7.82 7.57 Ho 1.80 1.56 1.83 1.77 Er 5.13 4.37 5.21 5.01 Tm 0.69 0.61 0.70 0.67 Yb 4.97 4.34 5.01 4.83 Lu 0.77 0.67 0.77 0.75 Hf 3.80 3.40 3.83 3.72 Ta 0.28 0.24 0.28 0.28 Re 0.00 0.00 0.00 0.00 Pb 0.37 0.35 0.37 0.36 Th 0.27 0.27 0.28 0.27 U 0.11 0.11 0.11 0.11

PAGE 161

161 Table C-1: Continued. Sample 735-G08 735-G09 735-G10 735-G11 735-G12 735-G13 735-G14 SiO2 50.38 63.73 63.98 63.36 66.89 62.82 62.90 TiO2 2.10 1.20 1.17 1.22 0.81 1.39 1.33 Al2O3 13.13 12.42 12. 43 12.38 12.23 12.35 12.36 FeOT 12.22 9.45 9.35 9.87 7.95 9.81 9.80 MnO 0.20 0.17 0. 17 0.19 0.14 0.16 0.19 MgO 6.92 1.04 1. 00 1.03 0.60 1.40 1.38 CaO 11.13 4.39 4. 29 4.43 3.41 4.85 4.80 Na2O 2.54 4.76 4. 76 4.79 5.01 4.52 4.57 K2O 0.17 1.14 1. 15 1.10 1.30 1.09 1.08 P2O5 0.21 0.33 0. 33 0.40 0.18 0.34 0.37 Cl 0.02 0.55 0. 55 0.51 0.61 0.52 0.53 Total (wt.%) 99.33 99.47 99.48 99.56 99. 44 99.55 99.59 H2O* 1.86 1.96 1.73 1.98 1.63 0.35 CO2 (ppm) det det det det det 224.88 Sc 41.09 18.09 21.12 20.09 15.86 19.57 19.95 V 383.67 73.12 108.77 66. 65 48.11 110.02 113.42 Cr 173.32 5.37 20.63 4.10 1.83 10.87 10.89 Co 37.78 12.61 15.86 13.61 10.02 14.95 15.22 Ni 59.28 4.50 10.40 3. 37 1.74 7.92 8.05 Cu 54.96 15.89 23.20 15.92 13.47 18.73 19.02 Zn 99.72 137.90 136.15 152. 33 144.49 134.31 134.59 Ga 18.03 26.62 25.92 27.98 27.62 25.84 26.07 Rb 1.23 10.29 9.40 10.62 12.04 10.25 10.10 Sr 101.96 86.18 90.13 92.94 80.06 86.01 87.26 Y 50.39 214.67 197.17 229.99 240.37 202.57 201.21 Zr 134.66 637.21 585.34 671. 98 663.67 590.09 580.29 Nb 4.49 19.29 17.40 20.10 21.20 17.82 17.72 Rh 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ba 16.23 82.57 77.40 87.69 95.39 83.83 79.17 La 4.98 29.97 26.79 30. 59 33.78 28.28 28.15 Ce 15.63 82.13 74.50 84.39 91.20 77.50 77.34 Pr 2.49 11.33 10.43 11.84 12.79 10.80 10.74 Nd 13.78 64.59 59.10 68.05 72.82 61.17 61.05 Sm 4.64 18.89 17.38 20.19 21.15 17.96 17.73 Eu 1.48 3.94 3.67 4.20 4.15 3.67 3.65 Gd 5.34 20.89 19.08 22.01 23.23 19.72 19.55 Tb 1.17 4.46 4.11 4.75 4.99 4.20 4.16 Dy 7.66 29.37 27.02 31.08 32.88 27.73 27.59 Ho 1.79 7.19 6.61 7.67 8.09 6.81 6.77 Er 5.11 21.99 20.16 23.25 24.87 20.82 20.67 Tm 0.68 2.46 2.29 2.59 2.78 2.35 2.34 Yb 4.94 20.64 19.23 22.00 23.63 19.92 19.55 Lu 0.76 3.19 2.97 3. 41 3.65 3.08 2.99 Hf 3.73 18.32 16.83 19.06 19.62 17.18 16.77 Ta 0.27 1.27 1.14 1.35 1.45 1.22 1.16 Re 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Pb 0.40 2.48 2.29 2.63 2.91 3.11 2.35 Th 0.27 2.82 2.54 2.83 3.28 2.80 2.73 U 0.11 1.07 0.97 1. 07 1.24 1.05 1.03

PAGE 162

162 Table C-1: Continued. Sample 735-G15 735-G16 735-G17 735-G18 735-G19 735-G20 735-G21 735-G22 SiO2 62.70 66.43 64.33 62. 16 61.95 65.75 50.63 50.09 TiO2 1.33 0.85 1.21 1. 26 1.34 0.98 2.26 2.22 Al2O3 12.33 12.44 12.56 13.32 13.59 12. 88 12.89 12.77 FeOT 10.25 8.02 9.16 8. 89 8.94 7.28 12.70 12.79 MnO 0.19 0.16 0.18 0.16 0.16 0.12 0.22 0.22 MgO 1.15 0.60 0.76 1.94 1.73 1.33 6.68 6.69 CaO 4.60 3.57 4.03 5.40 5.38 4. 32 11.11 11.03 Na2O 4.76 5.07 5.04 4.36 4.62 4.71 2.58 2.62 K2O 1.07 1.28 1.17 1.02 1.03 1.28 0.18 0.16 P2O5 0.42 0.30 0.35 0.18 0.17 0.11 0.25 0.23 Cl 0.49 0.61 0.55 0.41 0.42 0.52 0.02 0.03 Total (wt.%) 99.58 99.63 99. 63 99.43 99.65 99. 60 99.80 99.12 H2O* 2.00 1.77 1.97 2.01 1.51 CO2 (ppm) det det det det det Sc 19.52 16.12 18.16 22. 58 23.43 17.15 41.54 41.13 V 70.97 47.59 66.11 178.05 179. 52 123.38 391.22 389.33 Cr 7.42 2.54 5.76 43.90 54.10 31.62 151.73 147.55 Co 13.92 10.39 12.26 19. 13 19.65 14.07 38.83 38.15 Ni 4.27 2.24 3.74 18.94 20.40 13.82 58.50 55.25 Cu 15.36 13.58 14.17 27. 46 27.90 21.70 54.81 54.74 Zn 146.00 144.35 142.37 116.10 116.66 113.45 102.27 102.69 Ga 27.26 27.76 27.17 23. 27 23.06 24.28 18.18 18.21 Rb 9.90 11.83 10.67 9. 37 9.17 12.66 1.27 1.31 Sr 93.34 82.33 87.72 78.97 79.13 67.40 102.48 102.08 Y 212.61 238.81 219.95 160.04 158.38 194.22 52.89 53.37 Zr 636.42 671.63 641.86 440.76 439.80 396.77 140.88 141.97 Nb 18.62 21.01 19.47 14. 09 13.96 17.03 4.68 4.76 Rh 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 0.00 Ba 78.15 93.54 84.95 70. 55 69.20 88.70 16.25 16.50 La 29.13 33.47 30.18 22.60 22.36 29.38 5.21 5.24 Ce 80.08 91.83 83.32 61. 40 60.66 78.75 16.28 16.39 Pr 11.22 12.60 11.59 8. 51 8.41 10.71 2.60 2.61 Nd 64.26 71.67 66.59 47. 36 46.82 59.18 14.31 14.55 Sm 18.89 20.97 19.47 13. 86 13.76 16.98 4.78 4.87 Eu 4.10 4.14 4.05 2. 81 2.79 3.01 1.52 1.54 Gd 20.77 22.82 21.31 15. 10 14.96 18.40 5.48 5.52 Tb 4.43 4.91 4.55 3. 27 3.24 3.97 1.20 1.21 Dy 29.32 32.59 30.13 21. 69 21.56 26.49 7.95 8.01 Ho 7.14 8.02 7.40 5. 31 5.29 6.53 1.86 1.88 Er 21.87 24.58 22.67 16. 26 16.13 19.96 5.26 5.33 Tm 2.46 2.75 2.55 1. 88 1.86 2.29 0.70 0.71 Yb 20.71 23.37 21.52 15. 73 15.57 19.15 5.16 5.22 Lu 3.16 3.56 3.29 2.40 2.38 2.90 0.80 0.81 Hf 18.21 19.71 18.68 13. 00 12.96 13.10 3.89 3.92 Ta 1.23 1.40 1.30 0. 96 0.93 1.17 0.27 0.29 Re 0.00 0.00 0.00 0. 00 0.00 0.00 0.00 0.00 Pb 2.43 2.85 2.59 2. 14 2.07 2.74 0.40 0.41 Th 2.63 3.21 2.85 2. 32 2.29 3.14 0.29 0.29 U 1.02 1.21 1.09 0.87 0.85 1.15 0.12 0.12

PAGE 163

163 Table C-1: Continued. Sample 735-G23 735-G24 735-G25 735-G26 735-G27 735-G28 735-G29 735-G30 SiO2 50.53 50.54 50.46 50. 65 50.46 50.47 50.64 50.66 TiO2 2.19 2.22 2.22 2. 18 2.13 2.13 2.13 2.11 Al2O3 13.02 12.91 13.02 13.08 13.05 13. 11 13.04 12.93 FeOT 12.66 12.78 12.72 12. 64 12.44 12.42 12.90 12.58 MnO 0.22 0.21 0.22 0.23 0.24 0.22 0.24 0.21 MgO 6.74 6.67 6.68 6.92 7.05 7.13 6.82 6.69 CaO 11.17 11.11 11.10 11.19 11.19 11. 20 10.94 10.86 Na2O 2.62 2.57 2.63 2.60 2.53 2.54 2.62 2.57 K2O 0.16 0.17 0.17 0.16 0.16 0.15 0.16 0.17 P2O5 0.23 0.23 0.20 0.22 0.19 0.20 0.23 0.20 Cl 0.02 0.02 0.03 0.02 0.02 0.02 0.02 0.02 Total (wt.%) 99.85 99.72 99.73 100.16 99.76 99.88 100.02 99.28 H2O* 0.27 CO2 (ppm) 117.74 Sc 41.99 41.60 41.09 V 395.07 391.98 387.75 Cr 159.09 169.28 100.59 Co 38.36 37.96 38.28 Ni 54.66 55.89 45.63 Cu 55.48 55.00 53.64 Zn 103.05 100.67 103.36 Ga 18.58 18.27 18.34 Rb 1.28 1.24 1.28 Sr 105.32 103.98 108.60 Y 53.06 51.73 52.31 Zr 142.27 137.85 142.01 Nb 4.71 4.59 4.68 Rh 0.00 0.00 0.00 Ba 15.99 16.17 16.48 La 5.17 5.06 5.19 Ce 16.28 15.89 16.44 Pr 2.61 2.54 2.63 Nd 14.48 14.01 14.40 Sm 4.86 4.73 4.82 Eu 1.53 1.50 1.53 Gd 5.51 5.38 5.49 Tb 1.21 1.19 1.19 Dy 8.02 7.79 7.94 Ho 1.87 1.82 1.85 Er 5.31 5.21 5.22 Tm 0.70 0.69 0.70 Yb 5.21 5.07 5.16 Lu 0.81 0.79 0.79 Hf 3.89 3.76 3.89 Ta 0.27 0.27 0.28 Re 0.00 0.00 0.00 Pb 0.39 0.39 0.41 Th 0.28 0.28 0.29 U 0.12 0.11 0.11

PAGE 164

164 Table C-1: Continued. Sample 735-G31 735-G32 735G33 735-G34 735-G35 735G36 735-G37 735-G38 735G39 SiO2 51.57 50.32 50.46 50.67 50.67 50.72 TiO2 1.67 2.15 1. 61 1.61 2.11 2.09 Al2O3 13.38 12.81 13. 60 13.76 13.05 13.05 FeOT 11.30 12.77 10. 78 10.86 12.76 12.69 MnO 0.20 0.24 0.19 0.19 0.23 0.22 MgO 6.78 6.29 7.43 7.55 6.68 6.70 CaO 10.98 10.92 11.81 11.84 10.95 10.94 Na2O 2.65 2.63 2.45 2.47 2.63 2.61 K2O 0.20 0.15 0.12 0.12 0.15 0.15 P2O5 0.16 0.21 0.16 0.14 0.18 0.18 Cl 0.04 0.02 0.01 0.01 0.02 0.02 Total (wt.%) 99.22 98.78 98.93 99.54 99.71 99.66 H2O* 0.17 CO2 (ppm) 101.00 Sc 40.74 40.52 V 391.91 329.94 Cr 98.28 286.58 Co 39.15 38.03 Ni 46.45 69.96 Cu 53.54 63.30 Zn 105.24 84.75 Ga 18.48 16.59 Rb 1.13 0.73 Sr 101.05 101.07 Y 51.70 37.64 Zr 134.30 101.70 Nb 4.14 2.88 Rh 0.00 0.00 Ba 14.65 11.21 La 4.67 3.40 Ce 15.04 11.43 Pr 2.44 1.92 Nd 13.52 9.98 Sm 4.64 3.49 Eu 1.48 1.18 Gd 5.34 4.00 Tb 1.18 0.88 Dy 7.76 5.88 Ho 1.83 1.35 Er 5.22 3.73 Tm 0.69 0.54 Yb 5.07 3.72 Lu 0.79 0.58 Hf 3.73 2.82 Ta 0.24 0.15 Re 0.00 0.00 Pb 0.37 0.25 Th 0.25 0.17 U 0.10 0.07

PAGE 165

165 APPENDIX D PETROLOG RESULTS

PAGE 166

166 Table D-1: Results from Petrol og. Results assume QFM at 200 bars of pressure and sample T735-G35 as the parent composition. Petrolog Results for sample T735-G35 SiO2 51.58 51.64 51.6451.6451.6651.67 51.68 TiO2 1.64 1.65 1.651.661.671.69 1.70 Al2O3 14.01 14.09 14.1114.1114.0714.04 14.01 FeOT 9.95 9.91 9.929.9410.0010.06 10.12 MnO 0.19 0.19 0.190.190.190.19 0.19 MgO 7.68 7.49 7.467.467.437.40 7.37 CaO 12.05 12.12 12.1012.0912.0512.00 11.96 Na2O 2.52 2.53 2.542.542.552.56 2.57 K2O 0.12 0.12 0.120.120.120.13 0.13 P2O5 0.15 0.15 0.150.150.150.15 0.15 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1185.30 1179.30 1178.801178.701178.101177.50 1176.90 lgfO2 -8.47 -8.54 -8.55-8.55-8.55-8.56 -8.57 Fo 82.69 82.35 -1.00-1.0082.0981.94 81.77 An -1.00 -1.00 70.3470.3070.1169.91 69.72 CpxMG# -1.00 83.91 83.8483.8183.6683.51 83.36 OpxMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 MgtMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 Density 2.68 2.68 2.682.682.682.68 2.68 Ln 7.04 7.13 7.147.147.147.15 7.15 Melt% 100.00 99.45 99.1999.0097.9996.99 95.98 Olv% 0.00 0.55 0.550.550.610.66 0.70 Plg% 0.00 0.00 0.000.090.571.05 1.52 Cpx% 0.00 0.00 0.260.370.831.31 1.79 Opx% 0.00 0.00 0.000.000.000.00 0.00 Mgt% 0.00 0.00 0.000.000.000.00 0.00 inst F 0.99 1.001.000.990.99 0.99 Inst % ol 1.00 0.000.000.060.05 0.04 Inst % plg 0.00 0.000.450.480.48 0.47 Inst % cpx 0.00 1.000.550.460.48 0.48 Inst % opx 0.00 0.000.000.000.00 0.00 Inst % mgt 0.00 0.000.000.000.00 0.00 Ln = viscosity

PAGE 167

167 Table D-1: Continued. SiO2 51.70 51.71 51.7151.7151.7151.71 51.70 TiO2 1.72 1.74 1.751.771.791.80 1.82 Al2O3 13.98 13.94 13.9113.8813.8513.82 13.78 FeOT 10.19 10.27 10.3210.3810.4410.51 10.58 MnO 0.19 0.20 0.200.200.200.20 0.20 MgO 7.33 7.30 7.267.227.177.12 7.08 CaO 11.92 11.86 11.8511.8311.8111.79 11.78 Na2O 2.58 2.59 2.602.612.622.63 2.64 K2O 0.13 0.13 0.130.130.130.14 0.14 P2O5 0.15 0.16 0.160.160.160.16 0.16 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1176.30 1175.60 1175.001174.301173.601172.80 1172.00 lgfO2 -8.57 -8.58 -8.59-8.60-8.61-8.61 -8.62 Fo 81.60 81.39 -1.00-1.00-1.00-1.00 -1.00 An 69.52 69.27 69.1268.9168.7068.49 68.28 CpxMG# 83.20 82.99 82.8682.6882.4882.29 82.09 OpxMG# -1.00 82.76 82.6582.5082.3582.19 82.03 MgtMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 Density 2.68 2.68 2.682.682.682.68 2.68 Ln 7.16 7.16 7.177.177.187.18 7.19 Melt% 94.98 93.72 92.9891.9790.9689.96 88.96 Olv% 0.76 0.82 0.820.820.820.82 0.82 Plg% 2.00 2.59 2.953.443.914.39 4.88 Cpx% 2.26 2.87 3.093.383.693.99 4.30 Opx% 0.00 0.00 0.170.390.610.84 1.05 Mgt% 0.00 0.00 0.000.000.000.00 0.00 inst F 0.99 1.00 0.990.990.990.99 0.99 Inst % ol 0.06 0.04 0.000.000.000.00 0.00 Inst % plg 0.48 0.46 0.480.490.470.48 0.49 Inst % cpx 0.47 0.50 0.290.290.310.30 0.31 Inst % opx 0.00 0.00 0.230.220.220.23 0.21 Inst % mgt 0.00 0.00 0.000.000.000.00 0.00 Ln = viscosity

PAGE 168

168 Table D-1: Continued. SiO2 51.70 51.70 51.7051.6951.6951.69 51.68 TiO2 1.84 1.86 1.901.921.941.96 1.98 Al2O3 13.75 13.71 13.6513.6113.5813.54 13.51 FeOT 10.64 10.71 10.8510.9210.9911.07 11.14 MnO 0.20 0.21 0.210.210.210.21 0.22 MgO 7.03 6.98 6.886.836.786.73 6.67 CaO 11.75 11.73 11.6911.6711.6511.62 11.60 Na2O 2.65 2.66 2.682.692.702.71 2.72 K2O 0.14 0.14 0.140.140.150.15 0.15 P2O5 0.17 0.17 0.170.170.180.18 0.18 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1171.20 1170.40 1168.701167.801166.901166.00 1165.00 lgfO2 -8.63 -8.64 -8.66-8.67-8.68-8.69 -8.71 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 68.07 67.85 67.4167.1966.9666.74 66.51 CpxMG# 81.88 81.67 81.2381.0180.7880.54 80.29 OpxMG# 81.87 81.70 81.3681.1881.0080.81 80.62 MgtMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 Density 2.68 2.69 2.692.692.692.69 2.69 Ln 7.19 7.20 7.217.217.227.23 7.23 Melt% 87.95 86.94 84.9383.9382.9381.92 80.92 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 5.35 5.84 6.787.267.738.20 8.66 Cpx% 4.61 4.93 5.575.896.216.55 6.88 Opx% 1.26 1.47 1.892.102.312.51 2.72 Mgt% 0.00 0.00 0.000.000.000.00 0.00 inst F 0.99 0.99 0.990.990.990.99 0.99 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.47 0.48 0.470.480.470.47 0.46 Inst % cpx 0.31 0.31 0.320.320.320.34 0.33 Inst % opx 0.21 0.21 0.210.210.210.20 0.21 Inst % mgt 0.00 0.00 0.000.000.000.00 0.00 Ln = viscosity

PAGE 169

169 Table D-1: Continued. SiO2 51.68 51.67 51.6751.6651.6651.65 51.65 TiO2 2.01 2.03 2.052.102.122.15 2.18 Al2O3 13.48 13.44 13.4113.3413.3013.27 13.24 FeOT 11.22 11.30 11.3711.5311.6211.70 11.78 MnO 0.22 0.22 0.220.230.230.23 0.23 MgO 6.62 6.56 6.516.396.336.27 6.21 CaO 11.58 11.55 11.5211.4611.4311.40 11.37 Na2O 2.73 2.74 2.762.782.792.81 2.82 K2O 0.15 0.15 0.160.160.160.16 0.17 P2O5 0.18 0.18 0.190.190.190.20 0.20 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1164.10 1163.10 1162.001159.901158.701157.60 1156.40 lgfO2 -8.72 -8.73 -8.74-8.77-8.78-8.79 -8.81 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 66.28 66.04 65.8165.3465.0964.84 64.60 CpxMG# 80.03 79.78 79.5178.9578.6578.35 78.04 OpxMG# 80.43 80.23 80.0379.6179.3979.17 78.93 MgtMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 Density 2.69 2.69 2.692.692.692.69 2.69 Ln 7.24 7.25 7.267.277.287.29 7.30 Melt% 79.91 78.91 77.9175.9074.9073.90 72.89 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 9.13 9.60 10.06 10.9811.4411.90 12.35 Cpx% 7.21 7.55 7.908.618.969.31 9.69 Opx% 2.92 3.11 3.313.703.884.08 4.26 Mgt% 0.00 0.00 0.000.000.000.00 0.00 inst F 0.99 0.99 0.990.990.990.99 0.99 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.47 0.47 0.460.460.460.46 0.45 Inst % cpx 0.33 0.34 0.350.350.350.35 0.38 Inst % opx 0.20 0.19 0.200.200.180.20 0.18 Inst % mgt 0.00 0.00 0.000.000.000.00 0.00 Ln = viscosity

PAGE 170

170 Table D-1: Continued. SiO2 51.64 51.64 51.6351.6251.6151.61 51.60 TiO2 2.20 2.23 2.262.292.352.38 2.41 Al2O3 13.20 13.17 13.1313.1013.0313.00 12.97 FeOT 11.87 11.96 12.0512.1412.3312.42 12.52 MnO 0.23 0.24 0.240.240.250.25 0.25 MgO 6.15 6.08 6.025.955.825.75 5.68 CaO 11.33 11.30 11.2611.2211.1411.09 11.05 Na2O 2.83 2.85 2.862.872.902.92 2.93 K2O 0.17 0.17 0.170.180.180.18 0.19 P2O5 0.20 0.21 0.210.210.220.22 0.22 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1155.20 1153.90 1152.601151.301148.501147.00 1145.50 lgfO2 -8.82 -8.84 -8.85-8.87-8.90-8.92 -8.94 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 64.35 64.10 63.8463.5863.0562.78 62.51 CpxMG# 77.72 77.39 77.0576.7075.9675.57 75.17 OpxMG# 78.70 78.46 78.2177.9677.4377.16 76.87 MgtMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 Density 2.70 2.70 2.702.702.702.70 2.70 Ln 7.31 7.32 7.337.347.377.38 7.40 Melt% 71.88 70.88 69.8768.8766.8665.85 64.85 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 12.80 13.25 13.70 14.1515.0415.48 15.92 Cpx% 10.06 10.44 10.82 11.2012.0012.39 12.80 Opx% 4.43 4.61 4.794.965.295.45 5.62 Mgt% 0.00 0.00 0.000.000.000.00 0.00 inst F 0.99 0.99 0.990.990.990.98 0.98 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.45 0.45 0.450.450.440.44 0.43 Inst % cpx 0.37 0.38 0.380.380.410.39 0.40 Inst % opx 0.17 0.18 0.180.170.160.16 0.17 Inst % mgt 0.00 0.00 0.000.000.000.00 0.00 Ln = viscosity

PAGE 171

171 Table D-1: Continued. SiO2 51.59 51.59 51.5851.5751.5751.55 51.54 TiO2 2.44 2.47 2.512.542.582.65 2.69 Al2O3 12.93 12.90 12.8712.8312.8012.74 12.71 FeOT 12.62 12.72 12.8212.9313.0313.25 13.37 MnO 0.25 0.26 0.260.260.260.27 0.27 MgO 5.60 5.53 5.465.385.315.15 5.07 CaO 11.00 10.95 10.8910.8410.7810.66 10.59 Na2O 2.95 2.97 2.983.003.023.06 3.07 K2O 0.19 0.19 0.200.200.200.21 0.21 P2O5 0.23 0.23 0.230.240.240.25 0.26 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1143.90 1142.40 1140.801139.001137.301133.60 1131.70 lgfO2 -8.96 -8.98 -9.00-9.02-9.04-9.09 -9.11 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 62.24 61.96 61.6861.3961.1060.52 60.21 CpxMG# 74.76 74.33 73.8973.4372.9671.97 71.45 OpxMG# 76.59 76.29 75.9975.6775.3574.68 74.33 MgtMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 Density 2.70 2.70 2.702.702.702.71 2.71 Ln 7.41 7.43 7.447.467.487.51 7.53 Melt% 63.84 62.84 61.8460.8359.8357.83 56.82 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 16.36 16.79 17.22 17.6518.0818.93 19.35 Cpx% 13.21 13.63 14.06 14.4914.9315.82 16.28 Opx% 5.77 5.92 6.066.216.346.61 6.73 Mgt% 0.00 0.00 0.000.000.000.00 0.00 inst F 0.98 0.98 0.980.980.980.98 0.98 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.44 0.43 0.430.430.430.42 0.42 Inst % cpx 0.41 0.42 0.430.430.440.45 0.46 Inst % opx 0.15 0.15 0.140.150.130.13 0.12 Inst % mgt 0.00 0.00 0.000.000.000.00 0.00 Ln = viscosity

PAGE 172

172 Table D-1: Continued. SiO2 51.54 51.53 51.5251.5151.5151.50 51.49 TiO2 2.73 2.77 2.812.852.902.94 3.03 Al2O3 12.68 12.65 12.6112.5812.5612.53 12.46 FeOT 13.48 13.60 13.7213.8413.9614.09 14.34 MnO 0.27 0.28 0.280.280.290.29 0.30 MgO 4.99 4.90 4.824.734.654.56 4.38 CaO 10.52 10.44 10.3710.2910.2010.11 9.92 Na2O 3.09 3.12 3.143.163.183.20 3.25 K2O 0.22 0.22 0.230.230.230.24 0.25 P2O5 0.26 0.26 0.270.270.280.29 0.30 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1129.80 1127.70 1125.601123.501121.301119.00 1114.20 lgfO2 -9.13 -9.16 -9.18-9.21-9.24-9.27 -9.33 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 59.91 59.60 59.2858.9658.6458.30 57.61 CpxMG# 70.91 70.35 69.7769.1868.5567.92 66.58 OpxMG# 73.97 73.61 73.2372.8472.4472.03 71.18 MgtMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 Density 2.71 2.71 2.712.712.712.71 2.71 Ln 6.91 6.93 6.966.987.017.04 7.09 Melt% 55.82 54.82 53.8152.8151.8150.81 48.81 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 19.77 20.18 20.60 21.0221.4321.84 22.65 Cpx% 16.75 17.22 17.70 18.1918.7019.20 20.22 Opx% 6.84 6.95 7.067.167.257.34 7.50 Mgt% 0.00 0.00 0.000.000.000.00 0.00 inst F 0.98 0.98 0.980.980.980.98 0.98 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.42 0.41 0.420.420.410.41 0.41 Inst % cpx 0.47 0.47 0.480.490.500.50 0.52 Inst % opx 0.11 0.11 0.110.100.090.09 0.07 Inst % mgt 0.00 0.00 0.000.000.000.00 0.00 Ln = viscosity

PAGE 173

173 Table D-1: Continued. SiO2 51.48 51.48 51.4751.4751.4651.46 51.45 TiO2 3.08 3.13 3.193.243.293.35 3.41 Al2O3 12.44 12.41 12.3812.3512.3112.29 12.25 FeOT 14.48 14.61 14.7514.8915.0315.18 15.33 MnO 0.30 0.30 0.300.310.310.31 0.32 MgO 4.29 4.20 4.104.013.923.82 3.72 CaO 9.81 9.71 9.599.479.359.22 9.08 Na2O 3.28 3.30 3.333.353.383.41 3.44 K2O 0.25 0.26 0.260.270.280.28 0.29 P2O5 0.30 0.31 0.320.320.330.34 0.35 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1111.70 1109.10 1106.501103.801101.001098.10 1095.10 lgfO2 -9.36 -9.39 -9.43-9.46-9.50-9.54 -9.57 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 57.26 56.90 56.5356.1455.7655.36 54.94 CpxMG# 65.87 65.15 64.4063.6362.8462.01 61.18 OpxMG# 70.74 70.29 69.8269.3568.8768.37 67.87 MgtMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 Density 2.71 2.71 2.712.712.712.71 2.71 Ln 7.12 7.15 7.197.227.257.29 7.32 Melt% 47.80 46.80 45.8044.8043.8042.80 41.79 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 23.06 23.46 23.87 24.2724.6725.07 25.48 Cpx% 20.76 21.29 21.84 22.3922.9623.53 24.11 Opx% 7.56 7.62 7.687.727.767.79 7.80 Mgt% 0.00 0.00 0.000.000.000.00 0.00 inst F 0.98 0.98 0.980.980.980.98 0.98 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.41 0.40 0.400.400.400.40 0.41 Inst % cpx 0.53 0.54 0.540.560.560.57 0.58 Inst % opx 0.06 0.06 0.060.040.040.03 0.01 Inst % mgt 0.00 0.00 0.000.000.000.00 0.00 Ln = viscosity

PAGE 174

174 Table D-1: Continued. SiO2 51.45 51.44 51.4451.4451.4451.44 51.72 TiO2 3.54 3.60 3.673.743.823.83 3.77 Al2O3 12.18 12.15 12.1212.0912.0612.05 12.11 FeOT 15.64 15.80 15.9516.1116.2716.29 16.11 MnO 0.32 0.33 0.330.330.340.34 0.34 MgO 3.53 3.43 3.333.223.113.10 3.01 CaO 8.78 8.63 8.478.308.138.11 8.03 Na2O 3.50 3.53 3.573.603.643.65 3.70 K2O 0.30 0.31 0.320.330.340.34 0.35 P2O5 0.36 0.37 0.380.390.410.41 0.42 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1088.90 1085.60 1082.201078.501074.601074.00 1072.50 lgfO2 -9.66 -9.70 -9.75-9.79-9.85-9.85 -9.88 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 54.07 53.62 53.1552.6852.2052.13 51.86 CpxMG# 59.43 58.51 57.5556.5455.4855.32 54.78 OpxMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 MgtMG# -1.00 -1.00 -1.00-1.00-1.009.65 9.39 Density 2.71 2.71 2.712.712.712.71 2.71 Ln 7.40 7.44 7.497.537.587.59 7.67 Melt% 39.79 38.78 37.7836.7835.7835.64 34.78 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 26.29 26.69 27.09 27.4927.8927.94 28.17 Cpx% 25.29 25.89 26.49 27.1027.7027.79 28.23 Opx% 7.82 7.82 7.827.827.827.82 7.82 Mgt% 0.00 0.00 0.000.000.000.00 0.19 inst F 0.98 0.97 0.970.970.971.00 0.98 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.41 0.40 0.400.400.400.36 0.27 Inst % cpx 0.59 0.60 0.600.600.600.64 0.51 Inst % opx 0.00 0.00 0.000.000.000.00 0.00 Inst % mgt 0.00 0.00 0.000.000.000.00 0.22 Ln = viscosity

PAGE 175

175 Table D-1: Continued. SiO2 52.07 52.82 53.2253.6454.0954.56 55.05 TiO2 3.70 3.54 3.453.353.253.13 3.01 Al2O3 12.18 12.35 12.4412.5312.6412.75 12.87 FeOT 15.88 15.41 15.1614.8914.6214.33 14.02 MnO 0.35 0.36 0.360.370.370.38 0.39 MgO 2.90 2.68 2.562.442.312.18 2.05 CaO 7.92 7.70 7.577.437.287.11 6.93 Na2O 3.76 3.90 3.974.054.134.22 4.32 K2O 0.36 0.38 0.390.410.420.44 0.45 P2O5 0.43 0.46 0.470.490.500.52 0.54 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1070.60 1066.50 1064.201061.901059.401056.70 1053.80 lgfO2 -9.90 -9.96 -9.99-10.02-10.05-10.09 -10.13 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 51.53 50.86 50.5050.1249.7349.32 48.90 CpxMG# 54.08 52.50 51.5950.5949.4948.27 46.91 OpxMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 MgtMG# 9.07 8.40 8.057.687.306.89 6.48 Density 2.70 2.69 2.682.672.672.66 2.65 Ln 7.78 8.01 8.138.268.408.54 8.70 Melt% 33.77 31.77 30.7729.7728.7727.77 26.77 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 28.44 28.97 29.24 29.5029.7730.03 30.29 Cpx% 28.75 29.81 30.34 30.8831.4331.98 32.54 Opx% 7.82 7.82 7.827.827.827.82 7.82 Mgt% 0.40 0.82 1.021.211.401.59 1.76 inst F 0.97 0.97 0.970.970.970.97 0.96 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.27 0.26 0.270.260.270.26 0.26 Inst % cpx 0.52 0.53 0.530.550.540.55 0.57 Inst % opx 0.00 0.00 0.000.000.000.00 0.00 Inst % mgt 0.21 0.21 0.200.190.190.19 0.17 Ln = viscosity

PAGE 176

176 Table D-1: Continued. SiO2 55.58 56.13 57.3458.0158.7159.46 60.27 TiO2 2.88 2.74 2.432.262.091.92 1.74 Al2O3 13.00 13.15 13.4713.6513.8414.05 14.28 FeOT 13.70 13.36 12.6112.1911.7411.24 10.69 MnO 0.39 0.40 0.410.420.430.44 0.44 MgO 1.91 1.76 1.461.301.150.99 0.83 CaO 6.73 6.52 6.025.735.425.07 4.69 Na2O 4.42 4.54 4.784.925.075.24 5.42 K2O 0.47 0.49 0.530.560.580.61 0.65 P2O5 0.56 0.59 0.640.670.700.74 0.77 Cr2O3 0.00 0.00 0.000.000.000.00 0.00 H2O 0.00 0.00 0.000.000.000.00 0.00 T(C) 1050.70 1047.40 1039.901035.601031.001025.90 1020.30 lgfO2 -10.17 -10.22 -10.33-10.39-10.45-10.53 -10.61 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 An 48.46 47.99 46.9646.4045.7945.14 44.42 CpxMG# 45.43 43.74 39.7937.4734.8731.99 28.79 OpxMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 -1.00 MgtMG# 6.05 5.60 4.674.193.703.20 2.71 Density 2.64 2.63 2.612.602.592.58 2.56 Ln 8.86 9.04 9.439.659.8810.13 10.40 Melt% 25.77 24.77 22.7621.7620.7619.76 18.76 Olv% 0.82 0.82 0.820.820.820.82 0.82 Plg% 30.55 30.81 31.34 31.6031.8732.13 32.40 Cpx% 33.11 33.69 34.87 35.4736.0936.72 37.36 Opx% 7.82 7.82 7.827.827.827.82 7.82 Mgt% 1.94 2.10 2.402.532.652.75 2.84 inst F 0.96 0.96 0.960.960.950.95 0.95 Inst % ol 0.00 0.00 0.000.000.000.00 0.00 Inst % plg 0.26 0.26 0.260.260.270.26 0.27 Inst % cpx 0.56 0.58 0.590.610.610.64 0.64 Inst % opx 0.00 0.00 0.000.000.000.00 0.00 Inst % mgt 0.18 0.16 0.150.130.120.10 0.09 Ln = viscosity

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177 Table D-1: Continued. SiO2 61.13 62.05 63.0665.8667.8170.15 TiO2 1.56 1.39 1.230.750.390.01 Al2O3 14.52 14.77 15.0416.1516.9617.75 FeOT 10.09 9.39 8.605.733.470.74 MnO 0.45 0.46 0.470.470.460.45 MgO 0.67 0.53 0.390.120.040.00 CaO 4.27 3.81 3.322.141.470.76 Na2O 5.61 5.83 6.076.787.287.86 K2O 0.68 0.72 0.770.880.951.03 P2O5 0.82 0.87 0.921.061.141.24 Cr2O3 0.00 0.00 0.000.000.000.00 H2O 0.00 0.00 0.000.000.000.00 T(C) 1014.20 1007.30 999.60969.70935.00812.20 lgfO2 -10.70 -10.80 -10.92-11.38-11.94-14.23 Fo -1.00 -1.00 -1.00-1.00-1.00-1.00 An 43.62 42.74 41.7340.10-1.00-1.00 CpxMG# 25.34 21.60 17.728.273.950.94 OpxMG# -1.00 -1.00 -1.00-1.00-1.00-1.00 MgtMG# 2.24 1.79 1.370.540.240.05 Density 2.55 2.53 2.512.462.422.39 Ln 10.69 11.00 11.3412.4413.3615.38 Melt% 17.76 16.76 15.7613.7612.7611.75 Olv% 0.82 0.82 0.820.820.820.82 Plg% 32.68 32.96 33.2633.5233.5233.52 Cpx% 38.01 38.67 39.3341.0141.9842.97 Opx% 7.82 7.82 7.827.827.827.82 Mgt% 2.92 2.98 3.023.083.103.12 inst F 0.95 0.94 0.940.930.930.92 Inst % ol 0.00 0.00 0.000.000.000.00 Inst % plg 0.28 0.28 0.300.000.000.00 Inst % cpx 0.64 0.66 0.660.970.980.98 Inst % opx 0.00 0.00 0.000.000.000.00 Inst % mgt 0.08 0.06 0.040.030.020.02 Ln = viscosity

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178 LIST OF REFERENCES Agee, C.B., 1990, A new look at differentiation of the Earth from melting experiments on the Allende Meteorite, Nature vol. 346(6287), pp. 834-837. Anderson, R.N., et al.., 1982, DSDP Hole 504B, th e first reference sect ion over 1 km through Layer 2 of the oceanic crust, Nature v. 300, pp. 589-594. Barbarin, B., 1990, Plagioclase xeno crysts and mafic magmatic encl aves in some granitoids of the Sierra Nevada batholith, California, Journal of Geophysical Research vol. 95, pp. 17,747-17,756. Beard, J.S. and Lofgren, G.E., 1991, Dehydration me lting and water-saturated melting of basaltic and andesitic greenstones and amphibolites at 1, 3, and 6.9 kb, Journal of Petrology vol. 32, pp. 365-401. Beard, J.S., 1998, Polygenetic tonalite-trondhjem ite-granodiorite (TTG) magmatism in the Smartville Complex, northern California with a note on LILE depletion in plagiogranites, Mineralogy and Petrology vol. 64, pp. 15. Bbien, J., 1991, Enclaves in plagiogranites of the Guevgueli ophioli tic complex, Macedonia, Greece, In: Didier J, Barbarin B (eds) Enclaves and granite petrology, developments in petrology vol 13. Elsevier, Amsterdam, pp. 205. Berndt, J., 2002, Differentiation of MOR Basalt at 200 MPa: Experiment al techniques and influence of H2O and fO2 on phase relations and liquid line of descent, PhD Thesis, Universitaet Hannover, p. 118. Berndt, J., Koepke, J. and Holtz, F., 2005, An expe rimental Investigation of the Influence of Water and Oxygen Fugacity on Differentiation of MORB at 200 MPa, Journal of Petrology v. 46, no. 1, pp. 135-167. Bindeman, I.N., Davis, A.M. and Drake, M.J., 1 998, Ion microprobe study of plagioclase-basalt partition experiments at natural concen tration levels of trace elements, Geochimica et Cosmochimica Acta vol. 62, no. 7, pp. 1,175-1,193. Bohrson, W.A. and Reid, M.R., 1998, Genesis of evolved ocean island magmas by deepand shallow-level basement recycling, Socorro Isla nd, Mexico: Constraints from Th and other isotope signatures, Journal of Petrology v. 39, no. 5, pp. 995-1,008. Bougault, H. and Hekinian, R., 1974, Rift Va lley in the Atlantic Ocean near 36 50 N: petrology and geochemistry of basaltic rocks, Earth and Planetary Science Letters vol. 24, p. 249.

PAGE 179

179 Canales, J.P., Singh, S.C., Detrick, R.S., Carbotte S.M., Harding, A., Kent, G.M., Diebold, J.B., Babcock, J. and Nedimovic, M.R., 2006, Seismic evidence for variations in axial magma chamber properties along the Juan de Fuca Ridge, Earth and Planetary Science Letters vol. 246, pp. 353-366. Carpenter, M.A., 1980, Composition and cation order variations in a sector-zoned blueschist pyroxene, American Mineralogist v. 65, pp. 313-320 Castillo, P. R., Hawkins, J. W., Lonsdale, P. F., Hilton, D.R., Shaw, A.M. and Glascock, M.D., 2002, Petrology of Alarcon Rise lavas, Gulf of California: Nascent intracontinental ocean crust, Journal of Geophysical Research vol. 107, no. B10, p. 2222. Chadwick, J., Perfit, M.R., Ridley, W.I., J onasson, I., Kamenov, G., Chadwick, W.W., Embley, R., le Roux, P. and Smith, M., 2005, Magmatic effects of the Cobb hot spot on the Juan de Fuca Ridge, Journal of Geophysical Research v. 110, no.B3, pp. 12,713-12,733. Chadwick, W.W., Embley, R.W. and Sha nk, T.M., 1998, The 1996 Gorda Ridge eruption: geologic mapping, sidescan sonar, and SeaBeam comparison results, Deep-Sea Research II vol. 45, pp. 2,547-2,569. Chadwick, W.W. and Embley, R.W., 1994, Lava flows from a mid-1980s submarine eruption on the Cleft segment, Juan de Fuca Ridge, Journal of Geophysical Research v. 99, no. B3, pp. 4,761-4,776. Christie, D.M. and Sinton, J.M., 1981, Evolution of abyssal lavas along propagating segments of the Galapagos spreading center, Earth and Planetary Science Letters v. 56, pp. 321-335. Colson, R.O., Mckay, G.A. and Taylor, L.A., 1988, Temperature and Composition Dependencies of Trace-Element Partitioning Olivine Melt and Low-Ca Pyroxene Melt, Geochimica et Cosmochimica Acta vol. 52(2), pp. 539-553. Coogan, L.A., Jenkin, G.R.T. and Wilson, R.N., 2002, Constraining the cooling rate of the lower oceanic crust: a new approach applied to the Oman ophiolite, Earth and Planetary Science Letters v. 199, pp. 127-146. Coogan, L. A., Mitchell, N. C. and O'Hara, M. J., 2003, Roof assimilation at fast spreading ridges: An investigation combining geophys ical, geochemical, and field evidence, Journal of Geophysical Research vol. 108, no. B1, pp. 1-12. Crisp, J.A., 1984, Rates of magma emplacement and volcanic output, Journal of Volcanological and Geothermal Research v. 20, pp. 177-211. Danyushevsky, L.V., 2001, The effect of small am ounts of H2O on crystallisation of mid-ocean ridge and backarc basin magmas, Journal of Volcanology and Geothermal Research 110, pp. 265. Dixon-Spulber, S. and Rutherford, M.J., 1983, Th e origin of rhyolite and plagiogranite in oceanic crust: an experimental study, Journal of Petrology vol. 24, no. 1, pp. 1.

PAGE 180

180 Duke, J.M., 1976, Distribution of the period four transition elements among olivine, calcic clinopyroxene and mafic silicate liquid; experimental results, Journal of Petrology vol. 17, no.4, pp. 499-521. Embley, R.W., Chadwick, W.W., Perfit, M.R. and Baker, E.T., 1991, Geology of the northern Cleft segment, Juan de Fuca Ridge: Recent lava flows, sea-floor spreading, and the formation of megaplumes, Geology v. 19, pp. 771-775. Embley, R.W. and Chadwick, W.W., 1994, Volcanic and hydrothermal processes associated with a recent phase of seafloor spreading at the northern Cleft segment: Juan de Fuca Ridge, Journal of Geophysical Research v. 99, no. B3, pp. 4,741-4,760. Embley R.W., Jonasson I.R., Perfit M.R., Frank lin J.M., Tivey M.A., Malahoff A., Smith M.F. and Francis T.J.G., 1988, Submersible investigat ions of an extinct hydrothermal system on the Galapagos Ridge: Sulfide mound, stoc kwork zone, and differentiated lavas, Canadian Mineralogy, vol. 26, pp. 517. Embley, R.W., Chadwick, W.W., Perfit, M.R ., Smith, M.C. and Delaney, J.R., 2000, Recent eruptions on the CoAxial segment of the Juan de Fuca Ridge: Implications for mid-ocean ridge accretion processes, Journal of Geophysical Research vol. 105, no. B7, pp. 16,501 16,525. Falloon, T.J., Malahoff, A., Zonenshai n, L.P. and Bogdanov, Y., 1992, Petrology and geochemistry of back-arc basin basalts from Lau Basin spreading ridges at 15 degree, 18 degree and 19 degree S., Mineralogy and Petrology vol. 47, pp. 1. Fornari, D.J., Perfit, M.R., Malahoff, A. a nd Embley, R.U., 1983, Geochemical studies of abyssal lavas recovered by DSRV Alvin from the Eastern Gala pagos Rift, Inca Transform, and Ecuador Rift. 1. Major element variations in natural glasses and sp atial distri bution of lavas, Journal of Geophysical Research vol. 88, pp. 10,159-10,529. Flagler, P.A., Spray, J.G., 1991, Generation of plagiogranite by amphibolite anatexis in oceanic shear zones, Geology vol. 19, pp. 70. Flanagan, F.J., 1976, Descriptions and Analysis of Eight New USGS Rock Standards U.S. Geological Survey Prof essional Paper 840, p. 192. Furman, T., Frey, F. and Park, K., 1995, The scal e of source heterogeneity beneath the Eastern neovolcanic zone, Iceland, Journal of the Geological Society v. 152, no. 6, pp. 997-1,002. Garcia, M.O., Ito, E., Eiler, J.M. and Pietrusz ka, A.J., 1998, Crustal Contamination of Kilauea Volcano Magmas Revealed by Oxygen Isotope Analyses of Glass and Olivine from Puu Oo Eruption Lavas, Journal of Petrology v.39, no. 5, pp. 803-817. Gee, M.A.M., Thirlwall, M.F., Taylor, R. N., Lowry, D. and Murton, B.J., 1998, Crustal Processes: Major Controls on Reykjanes Peninsula Lava Chemistry, SW Iceland, Journal of Petrology v. 39, no. 5, pp. 819-839.

PAGE 181

181 Geist, D., Naumann, T. and Larson, P., 1998, E volution of Galapagos Magmas: Mantle and Crustal Fractionation without Assimilation, Journal of Petrology v.39, no. 5, pp. 953-971. Goldstein, S.J., Perfit, M.R., Batiza, R., Fo rnari, D.J. and Murrel, M.T., 1994, Off-axis volcanism at the East Pacific Rise detect ed by uranium-series dating of basalts, Nature v. 367 p. 157. Graham, D.W., Castillo, P.R., Lupton, J.E. and Batiza, R., 1996, Correlated He and Sr isotope ratios in South Atlantic n ear-ridge seamounts and impli cations for mantle dynamics, Earth Planetary Science Letters 144 pp. 491-503. Haase, K.M., Stroncik, N.A, Hkinian, R. And St offers, P., 2005, Nb-depleted andesites from the Pacific-Antarctic Rise as analogs for early continential crust, Geology v. 33, no. 12, pp. 921-924. Hart, S.R. and Dunn, T., 1993, Experimental cpx/melt partitioning of 24 trace elements. Contributions to Mineralogy and Petrology vol. 113, pp. 1-8. Hauri, E.H., Wagner, T.P. and Grove, T.L., 1994, Experimental and natural partitioning of Th, U, Pb and other trace elements between garnet, clinopyroxene and basaltic melts, Chemical Geology vol. 117, pp. 149-166. Hekinian, R., Stoffers, P., Devey, C.W., Ackerma n, D. Hemond, C. OConner, J., Bihard, N. and Maia M., 1997, Intraplate ve rsus ridge volcanism on the P acific Antarctic Ridge near 37S-111W, Journal of Geophysical Research v. 102, pp. 12,265-12,286. Hekinian, R., Stoffers, P., Ackermand, D., Revillon, S., Maia, M. and Bohn, 1999, Marcel Ridge-hotspot interaction; the Pacific-An tarctic Ridge and the Foundation seamounts, Marine Geology v. 160 pp.199-223 Helz, R.T., 1973, Phase relations of basalt in their melting ranges at P H2O=5 kb. Part II: melt compositions, Journal of Petrology vol. 14, pp. 249-302. Herzberg, C., 2004, Partial Crystallization of MidOcean Ridge Basalts in the Crust and Mantle, Journal of Petrology Advance Access published on August 5, 2004. Higgins, M.D., 1998, Origin of Anorthosite by Text ural Coarsening: Quantitative Measurements of a Natural Sequence of Textural Development, Journal of Petrology v. 39, no. 7. pp. 1,307-1,323. Hoernle, K., 1998, Geochemistry of Jurassic Oceanic Crust beneath Gran Canaria (Canary Islands): Implications for Crustal Recycling and Assimilation, Journal of Petrology v. 39, no. 5, pp. 859-880. Holloway, J.R. and Burnham, C.R., 1972, Melting relations of basalt with equilibrium water pressure less then total pressure, Journal of Petrology vol. 13, pp. 1-29.

PAGE 182

182 Jambon, A., and J. L. Zimmerman, 1990, Water in oceanic basalts: Evidence for dehydration of recycled crust, Earth and Planetary Science Letters vol. 101, pp. 323. Johnson, H.P., and Holmes, M.L., 1989, Chapter 5: Evolution in plate tectonics; The Juan de Fuca Ridge, in The Eastern Pacific Ocean and Hawaii pp. 73-91, Winterer, E.L., Hussong, D.M., and Decker, R.W., eds., Geologi cal Society of America, Boulder, CO, pp. 73-91. Johnson, K.T.M., Graham, D.W., Rubin, K.H., Nico laysen, K., Scheirer, D.S., Forsyth, D.W., Baker, E.T. and Douglas-Priebe, L.M., 2000, Boomerang Seamount; the active expression of the Amsterdam-St. Paul Ho tspot, Southeast Indian Ridge, Earth and Planetary Science Letters v. 183, pp. 245-259. Juster, T.C., Grove, T.L. and Perfit, M.R., 1989, Experimental Constraints on the Generation of FeTi Basalts, Andesites, and Rhyodacites at the Galapogos Spreading Center, 85W, and 95W, Journal of Geophysical Research v. 94, pp. 9,251-9,274. Juteau, T., Bideau, D., Dauteuil, O., Manach, G. Naidoo, D.D., Nehlig, P., Ondreas, H., Tivey, M.A., Whipple, K.X. and Delaney, J.R., 1995, A submersible study in the western Blanco Fracture Zone, N.E. Pacific: Structur e and evolution duri ng the last 1.6 Ma, Marine Geophysical Researches v. 17, i. 5, pp. 399-430. Karson, J.A., Tivey, M.A. and Delaney, J.R., 2002, In ternal structure of uppermost oceanic crust along the Western Blanco Transform Scarp: Implications for subaxial accretion and deformation at the Juan de Fuca Ridge, Journal of Geophysical Research v. 107, pp. 1-24. Kawamoto, T., 1996, Experimental cons traints on differentiation and H2O abundance of calcalkaline magmas, Earth and Planetary Science Letters vol. 144, pp. 577-589. Keleman, P.B. and Dunn, J.T., 1992, Depletion of Nb relative to other highly incompatible elements by melt/rock reaction in the upper mantle. EOS vol. 73, pp. 656-657. Kerr, A.C., Tarney, J., Marriner, G.F., Klaver, G.T., Saunders, A.D. and Thirlwall, M.F., 1996, The geochemistry and petrogenesis of the late -Cretaceous picrites and basalts of Curacao, Netherlands Antilles: a remnant of an oceanic plateau, Contributions to Mineralogy and Petrology v. 124, pp. 29-43. Klingelhofer, F., Minshull, T.A., Blackman, D.K., Harben, P. and Childers V., 2001, Crustal structure of Ascension Island fr om wide-angle seismic data: implications for the formation of near-ridge volcanic islands, Earth and Planetary Science Letters v. 190, pp. 41-56. Kloeck, W. and Palme, H., 1988, Partitioning of siderophile and chalcophile elements between sulfide, olivine, and glass in a naturally reduced basalt from Disko Island, Greenland. In: Proceedings of the Lunar and Planetary Science Conference vol.18. Ryder, G. (Editors), Pergamon, New York. 18, pp. 471-483. Koepke, J., 1986, Die Ophiolithe de r su da ga ischen Inselbru cke, PhD Thesis, Technische Universitaet Braunschweig, p. 204.

PAGE 183

183 Koepke, J., Seidel, E. and Kruzer, H., 2002, Ophi oliteson the southern Ae gean islands, Crete, Karpathos and Rhodes: composition, geochronol ogy and position within the ophiolite belts of the Eastern Mediterranean, Lithosphere vol. 65, pp. 183-203. Koepke, J., Berndt, J. and Bussy, F., 2003, An experimental study on the shallow-level migmatization of ferrogabbros from the Fu erteventura Basal complex, Canary Islands, Lithosphere vol. 69, pp. 105-125. Koepke, J., Feig, S.T., Snow, J. And Freise, M ., 2004, Petrogenesis of oceanic plagiogranites by partial melting of gabbros: an experimental study, Contributions to Mineralogy and Petrology vol. 146, pp. 414-432. Kravuchuk, I.K., Chernysheva, I. and Urosov, S., 1981, Element distribution between plagioclase and groundmass as an indicator for crystallization condition s of the basalts in the southern vent of Tolbachik, Geochemistry International, vol 17, pp. 18-24 Langmuir, C.H., Vocke Jr, R.D. and Hans on, G.N., 1978, A general mixing equation with applications to Icelandic basalts, Earth and Planetary Science Letters vol. 37, pp. 380392. Le Roux, P.J., Shirey, S.B., Hauri, E.H., Perfit, M.R. and Bender, J.F., 2006, The effects of variable sources, processes and contaminan ts on the composition of northern EPR MORB (8N and 12N): Evidence from volatiles (H 2O, CO2, S) and halogens (F, Cl), Earth and Planetary Science Letters vol. 251, pp. 209-231. Malpas, J., 1979, Two contrasti ng trondhjemite associations from transported ophiolites in Western Newfoundland: Initial report, In: Barker F (ed) Trondhjemites, dacites, and related rocks, Elsevier, Amsterdam, pp. 465. Marsh, B. D., 2000, Magma Chambers, Encyclopedia of Volcanoes Academic Press, pp. 191206. Matsui, Y., Onuma, N., Nagasawa, H., Higuc hi, H. and Banno, S., 1977, Crystal structure control in trace element partition between crystal and magma, Tectonics vol. 100, pp. 315324. McDonald, M.A., Webb, S.C., Hildebrand, J.A. a nd Cornuelle, B.D., 1994, Seismic structure and anisotropy of the Juan de Fuca Ridge at 45N, Journal of Geophysical Research v. 99, no. B3, pp. 4857-4873. McGarvie, D., 1984, Torfajkull: A volcano dominated by magma mixing, Geology v. 12, pp.685-688. McGarvie, D.W., MacDonald, R., Pinkerton H. a nd Smith, R.L., 1990, Petrogenetic evolution of the Torfajkull Volcanic Complex, I celand II, the role of magma mixing, Journal of Petrology v. 31, no. 2, pp. 461-481.

PAGE 184

184 McKenzie, D. and ONions, R.K., 1991, Partial melt distributions fr om inversion of rare Earth element concentrations, Journal of Petrology vol. 32, pp. 1,021-1,091. Mvel, C., 1988, Metamorphism in ocean layer 3, Gorringe Bank, Eastern Atlantic, Contributions to Mineralogy and Petrology vol. 100, pp. 496-509. Michael, P. J., and J.G. Schilling, 1989, Chlori ne in mid-ocean ridge magmas: Evidence for assimilation of seawater-influenced components, Geochim. Cosmochim. Acta vol. 53, pp. 3,131,143. Michael, P. J., and W. C. Cornell, 1998, In fluence of spreading ra te and magma supply on crystallisation and assimilation beneath midocean ridges: Evidence from chlorine and major element chemistry of mid-ocean ridge basalts, Journal of Geophysical Research vol. 103, no. 18, pp. 18,325,356. Mysen, B, 1978, Experimental determination of ni ckel partition coeffi cients between liquid, pargasite and garnet peridotite minerals and co ncentration limits of behavior according to Henry's Law at high pressure and temperature, American Journal of Science, vol. 278, pp. 217-243. Nakada, S., Maillet, P., Monjaret, M.C., Fujinaw a, A. and Urabe, T., 1994, High-Na dacite from the Jean Charcot Trough (Vanuatu), Southwest Pacific, Marine Geology vol. 116, pp. 197. Nicholson, H., Condomines, M ., Fitton, J.G., Fallick, A.E., Grnvold, K. and Rogers, G., 1991, Geochemical and isotopic evidence for crus tal assimilation beneath Krafla, Iceland, Journal of Petrology v. 32, pp. 1005-1020. Nielsen, R.L., and Delong, S.E., 1992, A numerical approach to boundary layer fractionation: Application to differentiation in natural magma systems, Contributions to Mineralogy and Petrology v. 110, p. 355-369. Nikogosian, I.K. and Sobolev, A.V., 1997, Ion-microprobe analysis of melt Inclusions in olivine: experience in estimating the olivine-melt pa rtition coefficients of trace elements, Geochemistry International vol. 35, pp. 119-126. OHara, M.J., 1998, Volcanic plumbing and the space problem-thermal and geochemical consequences of large-scale assim ilation in ocean island development, Journal of Petrology v. 39, no. 5, pp. 1,077-1,089. Pedersen, R.B., Malpas, J., 1984, The origin of oceanic plagiogranites from the Karmoy ophiolite, Western Norway, Contributions to Mi neralogy and Petrology vol. 88, pp. 36 52. Perfit, M.R. and Fornari, D.J., 1983, Geochemical studies of abyssal lava s recovered by DSRV Alvin rrom Eastern Galapagos Rift, Inca Transf orm, and Ecuador Rift 2. Phase chemistry and crystallization history, Journal of Geophysical Research v. 88, pp. 10,530-10,550.

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185 Perfit, M.R. and Fornari, D.J., 1983, Geochemical Studies of abyssal la vas recovered by DSRV Alvin from Eastern Galapagos Rift, Inca Tran sform, and Ecuador Rift 3. Trace element abundances and petrogenesis, Journal of Geophysical Research v. 88, pp. 10,551-10,572. Perfit, M.R., Fornari, D.J., Smith M.C., Bende r, J.F., Langmuir, C.H. and Haymon, R.M., 1994, Small-scale spatial and temporal variations in mid-ocean ridge crest magmatic processes, Geology v. 22, pp. 375-379. Perfit, M.R. and Chadwick, W.W., 1998, Magma tism at mid-ocean ridges: Constraints from volcanological and geochemical iiinvestigations, Faulting and Magmatism at Mid-Ocean Ridges Geophysical Monograph 106 pp. 59-115. Perfit, M.R., Ridley, W.I. and Jonasson, I.R. m 1999, Geologic, petrologic, and geochemical relationships between magmatism and massive sulfide mineralizati on along the Eastern Galapagos Spreading Center, in Barrie, C.T. and Hannington, M.D.., eds., Volcanicassociated massive sulfide deposits: Proce sses and examples in modern and ancient settings: Society of Economic Geologi sts Reviews Economic Geology, vol. 10, pp. 75-100. Perfit, M.R., 2001, Mid-Ocean Ridge Geochemistry and Petrology, in J. Steel, S. Thorpe and K. Turekian, eds., Encyclopedia of Ocean Sciences Academic Press, San Diego, CA, pp. 1,778-1,788. Phelps, D. and Ave Lallemant, H.G., 1980, The Sparta ophiolite comple x, northeast Oregon: a plutonic equivalent to low K2O island-arc volcanism, American Journal of Science vol. 280-A, pp. 345. Raff, A.D. and Mason, R.G., 1961, Magnetics survey off the west coast of North America, 40N latitude to 52N latitude, Geological Society of America Bulletin v. 72, pp. 1,267-1,270. Ratajeski, K., Glazner, A.F. and Miller, B.V., 2001, Geology and geochemistry of mafic to felsic plutonic rocks in the Cretaceous intrusiv e suite of Yosemite Valley, California, GSA Bulletin v. 113, pp. 1,486-1,502. Reid, J.B., Evans, O.C. and Fates, D.G., 1982, Ma gma mixing in granitic rocks of the central Sierra Nevada, California, Earth and Planetary Science Letters v. 66, pp. 243-261. Riehle, J.R., Meyer, C.E., and Miyaoka, R.T ., 1999, Data on holocene tephra (Volcanic Ash) deposits in the Alaska Peninsula and lower Cook Inlet Region of the Aleutian Volcanic Arc, Alaska, USGS Open-File Report pp. 99-135 Saunders, A.D., Tarney, J., Stern, C.R. and Dalz iel, I.W.D., 1979, Geochemistry of mesozoic marginal basin floor igneous rocks from southern Chile, Geological Society of America Bulletin Part I 90, pp. 237. Shelley, David, 1993, Igneous and Metamorphic Rocks Under the Microscope Chapman and Hall, London, UK.

PAGE 186

186 Shimizu, N. and Kushiro, I., 1975, The partitioning of rare earth elements between garnet and liquid at high pressures: Preliminary experiments, Geophysical Research Letters vol. 2, issue 10, pp. 413-416. Sigurdsson, H. and Sparks, R.S.J., 1981, Petrolo gy of Rhyolitic and Mixed Magma Ejecta from the 1875 Eruption of Askja, Iceland, Journal of Petrology v. 22, no. 1, pp. 41-84. Smith, M.C., 1993, Petrologic and geochemical investigations of basalts from the southern Juan de Fuca Ridge masters thesis, University of Florida, pp. 193. Smith, M.C., Perfit, M.R. and Jonasson, I.R., 1994, Petrology and geochemistry of basalts from the Southern Juan de Fuca Ridge: Controls on the spatial and temporal evolution of midocean ridge basalt, Journal of Geophysical Research v. 99, pp. 4,787-4,812. Stakes, D. S., W. W. Chadwic k, Jr., N. Maher, and D. S. Sc heirer, Results of nested high resolution mapping of the southern Cl eft segment, Juan de Fuca Ridge, Eos Transactions American Geophysical Union 79 45, Fall Meeting Supplement, F810, 1998. Stakes, D.S., Perfit, M.R., Tivey, M.A., Caress, D., Ramirez, T.M. and Maher, N., 2006, The Cleft Revealed: Geologic, magnetic and mor phologic evidence for construction of upper oceanic crust along the sout hern Juan de Fuca Ridge, Geochemistry Geophysics Geosystems vol. 7. Stoffers, P., Worthington, T., Hekinian, R., Peterson, S., Hannington, M., Trkay, M., and the SO 157 Shipboard Scientific Party, 2002, S ilicic volcanism and hydrothermal activity documented at the Pacific-Antarctic Ridge, EOS v. 83, no. 28, p. 301, 304. Sun, S.S. and McDonough, W.F., 1989, Chemical and isotopic systematics of oceanic basalts; implications for mantle composition and processes, Magmatism in the ocean basins Saunders, A.D. and Norry, M.J. (Editors), Geological Society of London, London, pp. 313345. Tierney, S. E., 2003, Distribution and compositi on of lavas from the sout hern Cleft segment of the Juan de Fuca Ridge: Tectonomagnetic evolu tion of a ridge-transform intersection masters thesis, University of Florida, pp. 195. Tsikouras, B., Hatzipanagiotou, K., 1998, Plagiogr anite and leucogranite relationships in an ophiolite on the Thethys Ocean (S amothraki, N. Aegean, Greece), Neues Jahrb Miner Monatsh vol. 1, pp. 13. Villemant, B., Jaffrezic, H., Joron, J.L. and Tr euil, M.,1981, Distribution Coefficients of Major and Trace-Elements Fractional Crystallization in the Alkali Basalt Series of Chaine-DesPuys (Massif Central, France), Geochimica et Co smochimica Acta, vol. 45(11), pp. 1,9972,016.

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187 Weis, D., Frey, F.A., Giret, A. and Cantagrel, J.-M., 1998, Geochemical characteristics of the youngest volcano (Mount Ross) in the Kerguele n Archipelago: Inferences for magma flux, lithosphere assimilation and compos ition of the Kerguelen Plume, Journal of Petrology v. 39, no. 5, pp. 973-994. Wilson, M., 1989, Igneous Petrogenesis: A Gl obal Tectonic Approach Kluwer Academic Publishers, Dordrecht/Boston/London. Zou, H., Zindler, A. and Niu, y., 2002, Constraints on melt movement beneath the East Pacific Rise from 230Th-238U Disequilibrium, Science, vol. 295, p. 107

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188 BIOGRAPHICAL SKETCH Laurie A. Cotsonika attended the University of Michigan from the fall of 1998 through the spring of 2002, at which time she earned a Bachelor of Science in oceanography. She then began graduate study at the University of Florida in the fall of 2003, and earned her Masters of Science in December of 2006.