1

GEOCHEMICAL AND PETROGRAPHIC ANALYSES OF THE BASALTS OF THE DARWIN PLATEAU, INYO COUNTY, CA; EVIDENCE FOR MULTI-DIMENSIONAL

VARIATION GOVERNING THE PRODUCTION OF VOLCANIC FIELDS IN THE OWENS VALLEY

By Matt Lusk

Geological Sciences Department California State Polytechnic University

Pomona, CA

Senior Thesis Submitted in partial fulfillment

of requirements for the B.S. Geology Degree

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Table of Contents

ABSTRACT ………………………………………………………………….1

INTRODUCTION ………………………………………………………….2

Generalized Geology of Southern Inyo Mountains ………………….3

Late Cenozoic Geology of Adjacent Fields ………………………….5

Tectonics ………………………………………………………….6

PETROLOGY ………………………………………………………….9

SAMPLE PREPARATION FOR XRF ………………………………….13

GEOCHEMISTRY ………………………………………………………….14

DISCUSSION ………………………………………………………….18

CONCLUSION ………………………………………………………….26

REFERENCES CITED ………………………………………………….28

APPENDIX A (Basalt Sample Correlation map and Figures) ………….31

APPENDIX B (Hand Sample Description) ………………………………….33

APPENDIX C (Table of Major Oxides) ………………………………….35

APPENDIX D (Table of Trace Elements) ………………………………….37

APPENDIX E (Table of Normative Mineralogy) ………………………….39

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ABSTRACT

The Darwin Plateau lies between the Inyo Mountains to the north, and the Coso Range to the

south. A series of basaltic flows and cones were emplaced on the plateau from 8 Ma to 4 Ma.

The Coso field (2 Ma-Pres.) lies 50 km to the southwest and the Ricardo volcanics (10-8 Ma)

100 km to the southwest. Sixty samples from basalt flows and cones of the Darwin Plateau

were analyzed for major, minor and trace elements. On a Le Bas diagram the basalts show a

considerable range in composition from basalt and basaltic andesite, to trachybasalt and basaltic

trachyandesite; straddling the alkaline-subalkaline boundary line. Major element and trace ele-

ment geochemistry are remarkably consistent within individual flows, but vary non-

systematically between adjacent flows.

When plotted on a basalt tetrahedron the Darwin basalts again show considerable variation in

composition, however the majority are olivine tholeiites. This is in marked contrast to the Ri-

cardo volcanics which are quartz-normative tholeiites and the Coso volcanics which are alkali

basalts. Petrographic examination of Darwin basalts reveals only small amounts of partially

altered olivine, unlike the complete olivine replacement by iddingsite in the Ricardo field and

large, unaltered phenocrysts of olivine in the Coso volcanics.

These differences may be related to evolutionary trends for the volcanic fields of the southern

Owens Valley. Older Ricardo volcanics are quartz normative, Darwin is neither quartz nor

nepheline normative, and Coso is distinctly nepheline normative. This can be attributed to

variation in the thermal regime represented by differing degrees of partial melt or depth of melt-

ing, and/or dissimilarity in water content and oxygen fugacity of the magma.

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INTRODUCTION

The Darwin volcanic field sits atop a horst known as the Darwin Plateau. It is located in

the southwest portion of the Great Basin within the Inyo Mountain Range (Fig. 1). The Darwin

Plateau sits approximately 1,670 meters above sea level. It displays a relatively moderate to-

pography when compared to the steep escarpments of the Panamint Valley to the east and

Owens Valley to the west. Local flora is characterized by sage brush, alkali grasses, and sev-

eral cacti species that are able to sustain existence in the high desert environment.

The Darwin Plateau basalt flows and cones were sampled in June and July of 2006.

Volcanic rocks of the Darwin Plateau and adjacent Pinto Peak (Nova basalts) have been ana-

lyzed by past researchers (Coleman and Walker, 1990; Schweig, 1989); however a comprehen-

sive study of Darwin Plateau has not been undertaken and detailed maps with ages of individual

cones and flows does not exist. The goal of this research was to generate a sample population

that could possibly delineate indi-

vidual flows (based on similar

bulk and trace element chemis-

try); provide an accurate basis for

overall composition of the Dar-

win volcanic field; and identify

any variation therein. Sample

data could then be compared to

other volcanic fields within and

near to the Owens Valley. Sam-

ple localities and a generalized

chemical composition map, cor-

relating flows, is presented in

Appendix A.

Figure 1. Location of Darwin Plateau as well as other volcanic fields of the Owens Valley.

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Generalized Geology of Southern Inyo Mountains

Devonian, Pennsylvanian, and Permian marine sedimentary and metasedimentary rocks

make up a large volume of the basement rocks within and adjacent to the study area (Fig. 2).

These rocks are intensely folded; the folds best exposed in the areas of Keeler and Rainbow

Canyon. The Paleozoic rocks have been intruded by post-kinematic Mesozoic granites (Taylor,

2002).

Devonian rocks consist of the Lost Burro formation which is comprised of light-gray

dolomite, (prominently striped with nearly black limestone and dolomite), interbedded light-and

dark-gray dolomite, quartzite, and sandy or cherty dolomite. The Stewart Valley Formation is

comprised of dark-gray limestone, cherty limestone, sandstone, quartzite, and conglomerate

(Death Valley Sheet, California Division of Mines and Geology, 1974).

Pennsylvanian units are exposed to the north and south of Darwin Plateau. These in-

clude the Bird Spring Formation, Keeler Canyon Formation, Lee Flat Limestone, and Rest

Spring Shale. The Bird Spring Formation consists of pebbly sandstone, coarsely bioclastic

limestone, sandy limestone, limestone, dolomite, and chert nodules. Keeler Canyon Formation

contains bluish-gray limestone, shaly limestone, black siliceous shale, pink fissile shale, and

limestone breccia. Lee Flat Limestone is comprised of white to light-gray marble, light-brown

dolomite marble, dark-gray limestone, and chert lenses. The Rest Spring Shale consists of

ovine-gray to olive-brown argillaceous shale and siltstone (Death Valley Sheet, California Divi-

sion of Mines and Geology, 1974).

Permian marine rocks contain sections of the Owens Valley Formation; gray, brown,

red, and yellow conglomerate, quartzite, sandstone, siltstone, shale, limestone, and limestone

breccia. Triassic marine sedimentary and metasedimentary rocks make up a small part of the

southern Inyo Mountains; they are comprised of limestone and shale (Death Valley Sheet, Cali-

fornia Division of Mines and Geology, 1974).

To the northwest of the Darwin Plateau, a section of the Inyo Mountains has been

deemed the Inyo Mountains Volcanic Arc Complex by Dunne and others (1998). These arc-

flank rocks consist of marine and non-marine units interspersed with periods of volcanism that

lie unconformable atop the Paleozoic metasedimentary strata. The complex was intruded by the

Jurassic French Springs Formation; U-Pb dating gives an age of 148 Ma for the French Springs

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Figure 2. Stratigraphic column of the Darwin Plateau geology.

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Granite (Dunne et. al, 1998). The Volcanic Complex is comprised mostly of epiclastic and py-

roclastic rocks; ranging from rhyolite tuff to basalt as well as sandstones, mudstones, conglom-

erates, and fluvial/debris flows.

The Paleozoic/Mesozoic basement rocks are overlain unconformably by the two domi-

nant rock types exposed on the plateau; Miocene-Pliocene volcanics (basaltic rocks age 4-8 Ma)

and alluvial/colluvium fanglomerates and stream deposits (Schweig, 1989; this study).

Late Cenozoic Geology of Adjacent Fields

The Coso volcanic field is located approximately 50 km south-southwest of the Darwin

Plateau. Two major periods of volcanism have occurred; the first approximately 4 to 2.5 Ma

and the second 1.1 to 0.04 Ma. Basalt, rhyodacite, dacite, andesite, and rhyolite were erupted

with rhyolite being the most voluminous rock type (Groves, 1996). Rhyolite flows and domes

are all high-silica rhyolite; xenocrysts of basalt and mafic inclusions are present however rare.

Slightly alkalic basalts were erupted during the same time as the rhyolite, however the basalts

were always derived from vents peripheral to the rhyolitic fields. Coso, today, continues to be

associated with a high heat flux and hydrothermal activity (Bacon, 1982; Groves, 1996).

Big Pine volcanic field lies approximately 80 km north-northwest of Darwin Plateau,

stretching from Independence to Big Pine, CA, a distance of about 20 km. The field lies along

the flank of a graben, proximal to oblique range-front faults. The field ranges in age from 1.2

Ma to 500 ka and shows a trend of decreasing age to the northwest (Bierman et al., 1991). The

rocks of the field vary from subalkaline basalt and basaltic andesite to alkaline basalts,

trachybasalts, and basaltic trachyandesite. One rhyolite dome/flow is present within the Big

Pine field (Varnell, 2006).

The Ricardo volcanics are located approximately 100 km south-southwest of the Darwin

Plateau. These are the oldest Cenozoic volcanics in the region at 10.1 to 8.2 Ma. They consist

of approximately twenty-three individual flows ranging from basalt to andesite as well as two

notable rhyolite flows. The volcanics are commonly interbedded with fluvial/lacustrine sedi-

ments. Basaltic rocks are dominantly tholeiitic and believed to be derived from a shallow,

lithospheric source (Anderson, 2005).

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The volcanic rocks of Pinto Peak (Nova basalts) are located on the eastern side of the

Panamint Valley, adjacent to the Panamint and Hunter Mountains. They are Miocene-Pliocene

in age, range from basalt to rhyolite and are characterized by high total alkalis. It has been

speculated, due to the similarity in age and chemistry of Pinto Peak and Darwin basalts, that

they are the from the same source, subsequently separated by extensional/transtensional faulting

(Coleman and Walker, 1990).

Tectonics

The White Mountains and the Inyo Mountains represent the western-most crustal block

of the Great Basin. To the west lies the Sierra Nevada Batholith and the San Joaquin Valley, to

the east, the Great Basin.

Thermochronological data reveals that an east-west extensional regime dominated the

White Mountains creating rapid uplift beginning at approximately 12 Ma. The range-front nor-

mal fault system along the west side of the White Mountains was then reactivated as dextral

strike slip faults, with motion occurring ~ 3 Ma. Some Post Miocene extension occurred along

with the younger regime of right lateral, transtensional deformation (Stockli, et. al 2003). The

reactivation of transtensional deformation seems to be concurrent with and related to increased

slip along the San Andreas Fault over approximately the past 4.5 Ma (Bierman, et. al 1991).

The San Andreas Fault Zone forms a major plate boundary between the North American

and Pacific plates. The fault experiences right lateral motion as the Pacific plate slides past the

North America plate at a rate of 39 + 2mm/yr. The San Andreas Fault does not, however, ac-

commodate all motion between the opposing plates. Geodetic studies show that the Sierra Ne-

vada block and portions of central California (Great Valley) behave as a microplate between the

North American and Pacific plates. This microplate experiences ~12 mm/yr of northern motion

relative to the North American plate, with as much as 11 mm/yr occurring in the area of Owens

Valley (Unruh, et. al 2003; Argus and Gordon, 1991; Wernicke and Snow, 1998). The motion

of the microplate accounts for approximately 25% of total movement between the North Ameri-

can and Pacific plates.

Accommodation of the motion between the North America and Pacific plates occurs

within a 50-100 km wide zone between the Basin and Range and microplate known as the

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Walker Lane Belt (WLB) and the

Eastern California Shear Zone

(ECSZ). Dextral shear results in a

series of major, sub-parallel,

oblique-right slip faults such as;

the Owens Valley Fault Zone, Fur-

nace Creek Fault Zone, Panamint

Valley Fault Zone, and Death Val-

ley Fault Zone (Fig. 3). It has also

produced a number of northeast

trending high angle normal faults

that created pull-apart basins

(Stockli, et. al 2003; Unruh, et. al

2003). These northeast trending

faults include the Towne Pass,

Eureka, and Deep Springs faults.

The Deep Springs pull-apart basin

separates the White Mountains

from the Inyo Mountains. The

White and Inyo Mountains are

bounded to the west by the high an-

gle, oblique, White Mountain and

Inyo Mountain faults, this fault zone

accommodates up to ~8 km of dip-

slip displacement (Stockli, et. al

2003).

Earthquake focal data suggests that local/small scale deformation in the eastern Sierras,

associated with the WLB and ECSZ, has generated a transtensional environment in the

Panamint Valley/Mountains (Darwin Plateau volcanic field) and in Owens Valley (Big Pine

volcanic field). Deformation in the Coso range however (Coso volcanic field), is extensional

due to a step over; transferring dextral shear between major fault zones (Unruh, et. al 2003).

Figure 3. ECSZ with the locations of basalt fields. Faults shown are DVFC-Death Valley-Furnace Creek; DSF-Deep Springs; FLV-Fish Lake Valley; HMF-Hunter Mountain; IF-Independence; INF-Inyo; OVF-Owens Valley: PVF-Panamint Valley; QVF-Queen Valley; TPEF-Towne Pass-Emigrant; WMF-White Mountain (after Taylor, 2002).

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Small scale faults of the Darwin Plateau display the same geometric patterns as the large

faults of the WLB and ECSZ (Fig. 4). The Darwin Plateau has two populations of faulting; one

north-northwest trending with steep dips of ~75° and striations that plunge at angles less than

30°, the other striking about N20°E and having dips of 65° to 70° to the east. The two popula-

tions seemingly display a time dependent relationship; with a strong east-west component of

extension predating the northwest-trending translational faults and the northeast tending normal

faults (Schweig, 1989).

Figure 4. Simplified geologic map of Darwin Plateau, showing some small scale faulting mimicking that of the ECSZ (after Schweig, 1989).

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PETROLOGY

The following observations were made during field sampling. Basalt flows were gener-

ally blocky; no flows exhibited columnar jointing such as that seen at Little Lake in the Coso

volcanic field. Field observation and Schweig (1989) showed that the basaltic dikes in the

Rainbow Canyon area had surface trends striking north-northwest. All flows had some form of

localized vesicular texture, either pervasive throughout the extent of the flow, or developed at

the top or along the outermost margins of the flow. Flows typically averaged 5 to 40 meters in

vertical thickness. Scoria cones are restricted to the peripherals of the plateau, with the highest

concentration being in the vicinity of Rainbow Canyon. This characteristic has been noted by

others (Coleman and Walker, 1990; Schweig, 1989).

Basalt outcrops were characterized by a distinctive desert varnish giving them a black to

shinny brown exterior. Fresh basalt samples, however, show a range in color from dark gray to

blue-gray to gray and red-purple. Samples with a fine groundmass were typically blue gray or

dark gray, while those with a coarser groundmass were typically red or purplish. Basalts col-

lected near Rainbow Canyon exhibited flow banding.

Olivine and plagioclase phenocrysts were present in some hand samples, the latter more

common. Plagioclase phenocrysts were typically 1.5 to 2.5 mm in the long dimension with

some upwards of 5 mm. The blockier olivine phenocrysts were typically 2 to 3 mm in diameter

with a few exceeding 6 mm. Both altered and unaltered olivine phenocrysts were noted.

Thin section analysis confirms the variation in groundmass grain size identified in hand-

sample. The coarser-grained basalts have an interlocking groundmass of euhedral plagioclase

averaging 0.25 mm in long dimension. The olivine and plagioclase crystals were occasionally

glomeroporphyritic. Much larger phenocrysts of plagioclase, olivine, and minor clinopyroxene

were present as well; with plagioclase the most common. The fine groundmass samples con-

sisted of euhedral plagioclase, olivine, glass, and pyroxene, with minor opaques (~3-4 % by

volume); olivine being the dominate phase. Trachytic texture was common in all samples,

however more pervasive in finer groundmass samples.

Two common olivine textures were observed in thin section. One shown in Figure 5

and Figure 6, depicts euhedral olivine mantled by a rim of iddingsite. A second olivine grain,

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also shown in Figure 5, is slightly smaller

in size, highly fractured and has no idding-

site rim. Larger olivine phenocrysts in the

coarser groundmass samples did not have

iddingsite rims, were typically highly frac-

tured, rounded and often embayed with

most subhedral to euhedral (Fig. 7). This is

similar to the Ricardo volcanics as noted

by Anderson (2005).

Furgal (2001) suggested the forma-

tion of iddingsite reaction rims occurs ei-

ther during or shortly after the magmatic

event; i.e., they do not represent a weather-

ing phenomenon. The presence of idding-

site in fine groundmass samples and its absence in coarser groundmass samples could signify

changes in oxygen fugacity and temperature within the magma chamber; the finer groundmass

magmas representing periods of higher

oxygen fugacity and significantly lower

temperatures (Baker and Haggerty, 1967).

This would be consistent with finer-grained

groundmass samples cooling more rapidly

in a near-surface, shallow crustal, oxygen-

rich environment.

Plagioclase phenocrysts also

showed two distinctly different characteris-

tics. Larger phenocrysts, 2.5 mm and up,

commonly displayed sieve texture in

coarse groundmass samples; while the

smaller phenocrysts 0.25 to 2.0 mm did

not. This texture was first observed in Dar-

win basalts by Colmeman and Walker

Figure 6. Embayed and fractured olivine with pyroxene re-action rims. Sample has a coarser groundmass and pervasive trachitic texture, crossed nicols.

Figure 5. Olivine with iddingsite coating in a finer ground-mass basalt sample, crossed nicols.

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(1990); they also observed that the smaller

plagioclase microlites did not display the

sieve texture and speculated they formed

due to a post mixing/heating event (Fig. 7).

The sieve texture can be explained by two

possible scenarios. One suggests mixing a

felsic plagioclase-rich magma with a mafic

magma. The second postulates a heating

event in which the temperature of the

magma was temporarily higher that the

solidus of the plagioclase (Takahashi and

Tsuchiyama, 1983).

Large unaltered augite phenocrysts

were present in some samples. The large

augite phenocrysts were approximately 2.5

to 5 mm in long dimension. Their presence was restricted to the coarse groundmass samples.

Pyroxenes were seen as microlites in the fine groundmass samples averaging about .05 to .10

mm; these crystals were euhedral and

slightly altered.

Opaques were present in all thin

sections. In coarse groundmass samples

opaques were larger, averaging .12 mm,

and more euhedral. In the fine groundmass

samples the opaques were approxi-

mately .05 mm and often rounded.

Opaques are thought to be primarily mag-

netite; however pyrite may be present as a

minor constituent.

Xenoliths of basalt were found in

coarse groundmass samples. Figure 8

shows a rounded xenolith consisting of Figure 8. Xenolith of fine groundmass basalt in a coarse groundmass sample, crossed nicols.

Figure 7. Sieve textured plagioclase and large embayed oli-vine; the embayed olivine together with the sieved plagio-clase suggests a mixing event.

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elongate plagioclase and very small,

rounded, olivine crystals. This texture sug-

gests magma mixing in which magma cool-

ing rapidly in a shallow crustal environment

produces the basalt xenoliths that are then

assimilated and almost fully enveloped by

the fresh pulse of magma.

Xenoliths of peridotite were also

found in one of the coarse-grained ground

mass samples. The rock fragment contained

euhedral plagioclase and olivine. The pla-

gioclase and olivine were blocky and eu-

hedral, averaging about 0.2 mm (Fig. 9). It

should be noted that this sample contained a

relatively high Cr value, 390 ppm.

Figure 9. Micro-peridotite fragment in basalt sample, crossed nicols.

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SAMPLE PREPARATION FOR XRF

Basalt samples were collected from flows using an eight pound sledge. All samples

were collected from outcrops, no float samples were taken. Upon collection, samples were

taken to the lab for chemical preparation and analysis. Weathering rinds were cut off with a

water saw; the samples then were passed through a chipmunk jaw crusher. Samples with obvi-

ous vesicle fillings were discarded, the remainder placed into a ball mill crusher for approxi-

mately 30 minutes. The resultant powder was then passed through a 60 micron sieve.

To make the pellet, 1.2 g of cellulose binder was combined with 6 g of basalt sample.

The powder mixture was placed into a ceramic mill for approximately one minute for mixing.

The mixture was funneled into an aluminum cup, placed into a die and pressed into a hardened

pellet ready for chemical analysis.

Sample pellets were analyzed using a Phillips x-ray spectrometer (XRF). The XRF ana-

lyzed each of the samples and printed out the results for the major and minor elements. The

major elements analyzed were; Si, Al, Ca, Mg, Fe, Mn, Na, K, P, and Ti. Results were reported

in weight percent oxide. The trace elements analyzed were; Ba, Ce, Cr, La, Nd, Rb, Sr, Sc, Y,

Zr, and Sm. The trace element program was developed by Dr. David Jessey at Cal Poly-

Pomona. Rock samples that reported greater than 55% SiO2 were not further studied as they

were outside the chemical range for a basalt.

The resultant data was entered into IgPet 2006 to make various petrographic diagrams.

While this program is capable of creating a wide variety of diagrams for volcanic rock classifi-

cation and genesis, only the diagrams that pertain to Darwin and the other volcanic fields of

Owens Valley were utilized for this research.

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GEOCHEMISTRY

The average Darwin ba-

salt is olivine normative. This is

similar to the basalts of the Big

Pine field (Varnell, 2006) and in

contrast to the nepheline norma-

tive Coso basalts (Groves, 1996)

and Ricardo basalts that are

quartz normative (Anderson,

2005).

A TAS (Le Bas) diagram,

plotting total alkalis (Na2O +

K2O) vs. silica, was used to clas-

sify the Darwin basalts (Fig. 10).

They range in composition from

basalt/trachybasalt to basaltic andesite/basaltic-trachyandesite. This broad compositional range

is similar to that for Big Pine. However, in general, the basalts are more alkaline than the Ri-

cardo volcanics and less alkaline than the Coso field. The latter two fields also have a more re-

stricted compositional

range.

Normative

mineralogy was ex-

amined with a basalt

tetrahedron (Fig. 11).

Again a wide varia-

tion in composition is

present for the Dar-

win and Big Pine ba-

salts; spanning

Figure 10. TAS diagram for fields of the Owens Valley, showing com-positional variation within and between fields (after Le Bas, 1986).

Figure 11. Basalt tetrahedron for Owens Valley (after Yoder and Tilley, 1962).

15

tholeiite, olivine tholeiite, to al-

kali basalt fields. Coso is domi-

nantly alkali while Ricardo is

dominantly tholeiitic.

A further anomaly for the

Darwin basalt field is shown in

Figure 12. This graph reveals

that approximately two-thirds of

the Darwin basalts would be con-

sidered alkaline, whereas the

other one-third would be sub-

alkaline. This could indicate two

distinct sources for the magmas. This is because evolutionary trends restrict the line of decent

for fractionating basaltic magma to either the alkaline or sub-alkaline portion of the diagram.

To generate both alkaline and sub-alkaline rocks requires differences in melting depth; the alka-

line rocks representing a deeper source (Winter, 2004), and/or changes in the oxygen fugacity

of the magma chamber.

Trace element data for Dar-

win, Coso, Ricardo, and Big Pine

were plotted utilizing a Rock/

MORB spider diagram (Fig. 13). In

general, Darwin most closely mim-

ics Big Pine in trace element distri-

bution. All basalt fields showed

enrichment in incompatible ele-

ments relative to a MORB standard

(as expected); a subtle Ba spike is

present for Darwin and more pro-

nounced for Big Pine. Darwin and

Big Pine also show higher Sr con-

centrations than that for Coso and Ricardo.

Figure 12. Alkaline/subalkaline diagram for the Darwin basalts (after De La Roche, 1980).

Figure 13. Spider Diagram for the Owens Valley basalts (after Pearce, 1984).

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Examination of trace ele-

ment data revealed a wide spread

in the chromium values for both

Darwin and Big Pine basalts.

Samples, in some cases, con-

tained concentrations that ex-

ceeded 500 ppm. This is in

marked contrast to the lower, less

varied chromium values for Coso

and Ricardo. A plot of Cr vs.

SiO2 showed a variable distribu-

tion of chromium for Darwin and

bimodal distribution for Big Pine

(Fig. 14). A table was created for Darwin and Big Pine samples to compare the two fields. The

table shows that samples containing > 400 ppm chromium also have high values for normative

olivine. This suggests that chromium occurs as a substituent in modal olivine or is present in

discrete spinel grains within peridotite xenoliths.

A graph of Cr vs. modal olivine was constructed to further examine their relationship

(Fig. 15). Darwin has a varied, yet seemingly linear distribution of values for chromium and

olivine. Again, it appears that Big

Pine has a bimodal distribution.

Coso and Ricardo have signifi-

cantly lower values for chromium

(Ricardo had few samples that

contain normative olivine). Fur-

thermore, the restricted values

deviate substantially from the best

fit applied for the Darwin sam-

ples. Darwin samples often show

an increase in chromium without

an increase in modal olivine, rein-

Figure 14. Graph of Cr vs. SiO2 concentrations; abnormally high values for the Darwin and Big Pine fields have been highlighted. The entire populations for Coso and Ricardo have been highlighted.

Figure 15. Graph of Cr vs. modal olivine. Darwin displays a linear rela-tionship; Big Pine shows a bimodal relationship as outlined in purple.

17

forcing the presence of discrete

spinel grains.

It has been observed

through melting experiments that

high-alumina basaltic liquids are

not a product of a low-pressure

fractionation (Ringwood, 1975).

A graph was constructed, plot-

ting Al2O3 vs. SiO2, using basal-

tic samples from Darwin, Coso,

Ricardo and Big Pine. Darwin

showed the greatest variation in

alumina and silica suggesting

variable depth (Fig. 16). Darwin was also higher in alumina than Ricardo. Note that Big Pine

and Coso also showed typically higher alumina values than those for the Ricardo field. This

indicates that liquid fractionation of the Ricardo basalts happened at lower pressures than that

of the other fields.

As stated previously, Darwin hand samples revealed several different textures. An at-

tempt was made to identify any commonality between texture and chemical composition. The

only difference noted is that coarse grain groundmass samples tended to be slightly depleted in

total alkalis and silica compared to fine groundmass and vesicular samples.

Megascopic examination also revealed a wide range of colors for the basalt samples.

However, no definitive pattern was observed between sample color and chemistry.

Figure. 16. Alumina vs. silica graph for the Owens Valley basalts.

18

DISCUSSION

Heterogeneous basaltic rocks can be generated from a homogeneous source by altering

several factors. The most obvious factor is a change in the source of the melt. The percentage

of partial melting can also have a strong influence on the chemical makeup of the fractionated

basaltic magma. A change in the tectonic regime that affects the depth of melting and frac-

tionation can cause variation in composition. Furthermore, variation in oxygen fugacity of the

magma chamber will create variable basalt chemistry. Magma mixing may also be a factor.

These factors are considered AND discussed and evidence for them examined to explain the

pattern of Neogene volcanism in the Owens Valley.

Examining differences in source; if the source varied substantially then the parental ba-

salt should reflect that variation as should the subsequent fractionated products. The alkaline/

subalkaline plot (Fig. 12) suggests that there are in two distinct sources since a thermal divide

exists between the two basalt subtypes. The continuous spectrum of basalt compositions, how-

ever (Figs. 10 & 11), argues that there is only a single source that has evolved over time.

However, if physical factors are altered, a continuous spectrum of basalt composition

can be generated without violation

of the alkaline/subalkaline thermal

divide. This will be discussed in

more detail below.

Trace element data better

displays source rock variation than

does bulk rock chemistry. Darwin

samples (Fig. 17) show little varia-

tion and relative consistency when

plotted on the Rock/MORB dia-

gram. Furthermore Darwin, Coso,

Ricardo, and Big Pine averages are

all similar (Fig. 13), suggesting that

there were no drastic differences in

Figure 17. Spider diagram for a selected population of Darwin sam-ples. While the graph is difficult to read, it shows that Darwin trace element concentrations show limited variation between suggesting a single source for all basalts (after Pearce, 1984).

19

source rock. So multiple sources seems rather improbable.

Magma composition can vary depending on variation of physical parameters (e.g., T

&P) as well as the length of residence time in the magma chamber. The reasons for this varia-

tion and types of change will be explored below.

It has been observed that Darwin basalts have a distinct calc-alkaline trend when plotted

on an AFM diagram. The calc-alkaline trend suggests that the oxygen fugacity of the magma

chamber was high, as low oxygen fugacity would produce a tholeiitic trend (Coleman and

Walker, 1990; Wang et. al, 2002). However, an AFM diagram constructed for Darwin samples

showed that a small percentage of samples fall on the tholeiitic line or within the tholeiitic field.

Irvine (1977) states that when low oxygen fugacity is imposed on a spinel species, the

Cr3+ that stabilizes spinel is reduced to Cr2+ which then dissolves and is absorbed into olivine

(Takahashi and Kushiro, 1983). Thus, low oxygen fugacity should result in a basalt that is both

tholeiitic and high in chromium.

AFM diagrams were constructed for the Darwin and Big Pine basalts (Fig. 18) to com-

pare Cr content (ppm) to wt.% SiO2 in order to test the above hypothesis. The results suggest

that the highest chromium concentrations for Darwin and Big Pine are indeed associated with

tholeiitic basalts (outline samples are the highest chromium concentrations from Fig. 14).

Therefore, it seems that when oxygen fugacity of the magma chamber is low high chromium,

Figure 18. AFM diagrams for both the Darwin and Big Pine fields showing the tholeiitic trend of high chromium basalts (after Irvine and Baragar, 1971).

20

tholeiitic basalt can be generated.

One reason that alkali basalts have a higher oxygen fugacity than tholeiites is because

Fe3+ behaves like an incompatible element. Its content in the magma increases as the extent of

the melt fraction decreases (Wang et. al, 2002). Hand samples from Darwin show a consider-

able variation in color from dark gray to red. In slates, red color can be attributed to higher Fe3+

values, whereas the green to gray slates are associated with reduced ferrous iron. Could the

same be possible for Darwin? Do alkali basalt samples from Darwin show a strong affinity for

a red color, and tholeiitic samples darker gray colors?

Unfortunately, this research revealed that color is not an important variable factor in the

formation of either alkali/tholeiitic basalts or alkaline/subalkaline basalts. Thus, color is not an

accurate indicator of chemistry. The range of colors is more likely attributed to weathering

phenomena.

It has also been suggested that basalts formed above subduction zones may also have

intrinsically higher oxygen fugacities (Wang, et. al 2002). However, Ricardo volcanics are

strictly tholeiites and were emplaced earlier than the other fields, when there was a stronger

component of subduction. If alkali basalts are generated due in a subduction environment then

the Ricardo basalts should have the strongest alkali trend should they not?. Furthermore, Dar-

win and Big Pine contain basaltic compositions range from alkali to tholeiitic. Does this imply

that there is a source related to subduction and one that seems to be ambiguous?

Little research has been done on the fugacity of the individual fields, and few actual

Fe2O3 / FeO ratios have been measured (Wang et. al, 2002). The ferrous/ferric iron ratio was

not measured for this study; therefore any speculation concerning fugacity of the magmas can

only be considered as a best guess. Based on the high chromium tholiitic basalts, it is possible

there was a time of lower fugacity for individual fields such as Darwin and Big Pine, perhaps

playing a minor role in the chemical variation. However, oxygen fugacity seems not to be the

major contributor to variation of basalt composition.

The percentage of melt is another factor that can strongly influence the chemical compo-

sition of basalts. The effect of this variable can generally by assessed by examining the parti-

tion of trace elements into crystallizing mineral phases; for example chromium into olivine.

First, the process that controls the concentration of chromium into olivine needs to be

discussed. The distribution coefficient (KD) determines the amount of a trace element incorpo-

21

rated into the melt or a crystallizing solid; it is derived from the equation:

KD = Cs / CL (1)

where Cs is the concentration of the trace element in the solid and CL is the concentration in the

liquid.

A KD < 1 indicates an incompatible element that will be concentrated in the melt phase,

not the solid. The distribution coefficient is slightly less than one for Cr in olivine, ~0.7. More

importantly, the concentration of the element (Cr) in the solid varies linearly. The graph of oli-

vine vs. chromium, for Darwin, shows a linear trend of increase in chromium concentration

with increasing normative olivine (Fig. 15).

Using a batch melt equation (2), it can be demonstrated that an increase in melt fraction

will systematically increase the concentration of a particular element in the liquid.

CL/Co = 1/Di(1-F) + F (2)

which is re-arranged to:

CL = Co/ Di(1-F) + F (3)

This equation shows that the concentration of any element in the melt (CL) will vary depending

on its concentration in the rock being melted (Co), the bulk distribution coefficient (Di), and the

melt fraction (F).

The bulk distribution coefficient is calculated from:

Di = ∑WADiA (4)

Where WA is the weight fraction of the mineral A in the rock, and DiA is the distribution coeffi-

cient for the element i in mineral A.

An increase in melt fraction will decrease the denominator of equation 3 and thus allow

for more chromium to be partitioned into the melt and ultimately into olivine. Furthermore, an

22

increase in the percentage of melt will create a tholeiitic basalt (Ringwood, 1976). This same

effect was observed experimentally by Takahashi and Kushiro, 1983 (Fig. 19). Thus simply

changing the percentage of partial melt could generate basalts of widely variable composition

without requiring differing source rocks.

Another factor that may have a significant impact on basalt composition is a variation in

depth/pressure. For a magma to melt it needs to be thermodynamically instable. Postulated

geothermal gradients suggest that mantle temperatures are hot enough to generate basaltic mag-

mas, but the elevated pressure of the mantle prevents this melting. However, if the mantle is

forced upward adiabatically, to depths of approximately 40 km it will melt (D. Mckenzie and

M.J. Bickle, 1988). Dehydration of micas could also create a higher heat flux further promoting

mantle melting. This melt rises to a depth at which it is in gravitationally stable, pools, and be-

gins to fractionate. The depth at which the melt is generated and fractionated has dramatic ef-

fect on the type of basalt produced.

Takahashi and Kushiro (1983) studied the melting of peridotite at various pressures

(Fig. 20). Their study showed that an increase in pressure changed the composition of the first

partial melt (eutectic) from a low pressure (below 0.5 GPa) quartz tholeiite, to a medium pres-

sure (1 GPa) olivine tholeiite, to a high pressure (1.5 to 2.5 GPa) nepheline normative alkali-

olivine basalt. These pressures correspond to depths of approximately 20 km for the low pres-

Figure 19. Petrogenetic table showing the compositional variation of basalts formed by melting a dry peridotite at different temperatures and pressures. Notice the trend of tholeiite to alkali with increase in pressure and from al-kali to tholeiite with an increase in melt/temperature (after Takahashi and Kushiro, 1983).

23

sure quartz tholeiite, to as deep

as 85 km for the nepheline nor-

mative alkali-olivine basalt.

Wang (2002) calculated

the melt columns for basalts of

the eastern Sierras and western

Great Basin based on primitive

FeO, MgO, and Na2O composi-

tions and the partitioning coeffi-

cients for Mg and Fe in olivine.

The results of the calculations

determined that relatively shal-

low, mantle lithosphere/crust

boundary melt columns gener-

ated the basalts for the eastern

Sierras. It was established that Big Pine basalts were produced from melting at ~2.0 to ~1.3

(approximately 70 to 40 km) GPa which generated ~8.8% partial melt (Wang, et. al 2002).

This is in general agreement with the 40 km thickness suggested for the crust in this part of the

eastern Sierra (Wernicke, 1992). This depth is shallower than the spinel-garnet transition.

This melt depth would explain the olivine tholeiites and nepheline normative alkali olivine ba-

salts that are common to both Darwin and Big Pine (Fig. 20). It would not, however, explain

the tholeiites found at Darwin and Big Pine. Furthermore, Darwin, Coso, and Big Pine lie

about the same distance to the east from the former subduction zone; yet Coso does not share

similar composition.

The melt column calculated by Wang indicates that mantle upwelling to depths of ~40

km could be the source of a parental magma giving rise the more alkaline basalts. This magma

would then pool at the crust/mantle boundary, or rise directly to the crust by deep penetrating

faults. The residence time in the crust will be a product of the tectonics of the area. For mag-

mas with extended residence times MASH (melting, assimilation, storage and homogenization)

should be expected to occur. The result would be a series of basaltic magmas of variable com-

position that would then rise through the crust to be extruded.

Figure 20. The effect of pressure on the position of the eutectic for the ternary system qtz-ol-neph. (after Takahashi and Kushiro, 1983).

24

The alumina vs. silica plot (Fig. 16) further supports the above conclusion. The varia-

tion in alumina content can be attributed to the depth of melting (Ringwood, 1976). Ricardo

having less alumina is from a shallower source while deeper sourced magmas are more alu-

mina-rich. It follows that chemical variation between flows in the Darwin field may be attrib-

uted to a change in the depth of melting for individual flows. The restricted data sets for both

Coso and Ricardo suggest a very consistent melting depth and percentage of melt/fractionation .

The variation that is seen in the Darwin and Big Pine basalts could be caused by and is there-

fore an indicator of a changing tectonic regime.

Ricardo (10 Ma) is the oldest basalt field. Its basalts are tholeiitic. These rocks were

emplaced during the waning phases of a Basin and Range extensional regime. Coso, the young-

est field (<2 Ma), is comprised of alkaline basalts emplaced during a tectonic episode domi-

nated by dextral shear. Darwin has both types of basalt. Structural mapping for the Darwin

Plateau suggests two distinct tectonic regimes; an older extensional regime and a younger pe-

riod of dextral shear.

Perhaps extension created more room for upwelling magma to melt/fractionate, generat-

ing a larger, tholeiitic melt. It could also be that the normal faults were not able to penetrate

into deep rooted magma chambers due to the limitations of lithostatic stress. Dextral shear does

not displace overlying rocks by uplift/downdrop like extensional faulting; therefore it may not

generate the same volume of melt. Furthermore, transverse faults associated with dextral shear

could penetrate deeper.

Big Pine, however, is not in a transitional tectonic environment (~2 Ma to present) yet

exhibits a similar varied geochemical signature to that of Darwin. It is speculated that a signifi-

cant thickening of continental crust northward in the Owens Valley may act as a retardant to the

ascending magmas. This would act as a damper on the timing of events. Thus, the similar

trends for the Big Pine basalts would simply reflect the longer time necessary for the magmas to

traverse the thickened crust. Sort of like the age progression from older to younger eastward

seen for Mesozoic intrusives of the western Cordillera. Indeed, evidence for extended residence

times in the crust for Big Pine magmas is present in the crustal contamination of these magmas

noted by Darrow (1971).

Some evidence for magma mixing is also present and cannot be ignored. This evidence

comes in the form of sieved plagioclase and the fine-grained groundmass xenoliths. Sieved pla-

25

gioclase has been noted in many basaltic rocks and has been reproduced in experiment

(Tsuchiyama and Takahashi, 1983). The sieve texture occurs when phenocrysts in low tem-

perature magma are partially melted as the temperature increases above their solidus, creating a

chaotic crystal structure. Sieve texture was formed in plagioclase by the reaction between al-

bite-rich plagioclase with an anorthite-rich melt. Both of these conditions require the presence

of two magma bodies; one hotter than the other, or one more mafic. If for some reason one

magma failed to breach the surface, it could remain pooled for some time. Another pulse of

chemically different magma may interacted with it and the “mixed” magma brought to the sur-

face.

26

CONCLUSIONS

The tectonic environment of the volcanic fields seems to have the greatest influence on

the basalt composition. The depth and percentage of partial melt generated are the factors con-

trolling the composition, which in turn are controlled by the tectonics. Magma mixing is evi-

dence of two magmas interacting in the substrate, suggesting variation in the depth of melting/

fractionation and some form of tectonic influence. Fugacity of the magma chamber can be an

important variable, however without more data it importance is only speculative.

The volcanism of Darwin spans a transitional tectonic setting. Geochronology confines

the age of the field to ~4 to 8 Ma. Structural and tectonic studies show that normal faults asso-

ciated with extension (~12 Ma) have been re-activated as dextral shear faults (~3 Ma). Pure

shear can be responsible for the tholeiitic basalts; the dextral shear responsible for the alkaline

basalts. Big Pine though is not completely consistent with this model but may be a product of a

thickened crust as explained above.

Darwin basalts therefore:

• Were derived from a mantle source based on Rock/MORB diagram and emplaced proximal

to faults, similar to Big Pine and Coso, with the faults serving as conduits for magma.

• Variations in basalt composition are a product of variable melting depths, the deeper mag-

mas being alkaline and the shallower being sub-alkaline. The tholeiites of the Ricardo field

reached the surface along normal faults, a consequence of extension. The alkaline magma

tapped deep-penetrating dextral faults. Subsidiary faults, perhaps normal faults associated

with pull-apart basins, created the second conduit for the magma tapping shallower fraction-

ated magma and generating some of the younger olivine tholeiites.

• Increasing the percentage of partial melt could create the tholeiites with high chromium val-

ues that are observed at Darwin.

• Changes in oxygen fugacity may be a factor in a compositional variation of individual

flows, but the extent of fugacity changes is difficult to determine.

• Magma mixing is also a possible explanation for variation in basalt composition for local-

ized tectonic settings.

27

• The melt column calculated by Wang explains olivine tholeiites and nepheline normative

alkaline olivine basalts based on the depth variation; it does not account for the tholeiites or

a change in melt volume.

The Big Pine field is similar to Darwin in many aspects except its age. It may be possi-

ble that volcanism has shifted from Darwin to Big Pine over time, due to the northward thicken-

ing of the crust. The Ricardo field appears to have been developed from a shallow partial melt

and a larger melt volume than any of the other fields. In contrast, Coso appears to be the prod-

uct of deeper fractionation and a smaller volume of melt.

Clearly the nature of basaltic volcanism in the Owens Valley has shifted over time. The

effect of multiple variables on the composition of Owens Valley basalts can be seen spatially in

adjacent fields, such as Big Pine and Coso; vertically as a change in the depth of magma gen-

eration between Big Pine and Coso; and chronologically as the changing in the tectonic regime

over time (Ricardo and Coso). Yet it is the change in the tectonic regime and subtle variations

in the fault geometries that has generated the most significant compositional variation in the

volcanic fields of the Owens Valley.

28

REFERENCES CITED

Anderson, Cami Jo, 2005, A Geochemical and Petrographic Analysis of the Basalts of the Ricardo Formation Southern El Paso Mountains, CA, unpublished Senior Thesis, Cal Poly Pomona, 37p.

Argus, D.F., and Gordon, R.G., 1991, Current Sierra Nevada-North America motion from very long baseline interferometry: Implications for the kinematics of the western United States: Geology, v. 19, p. 1085-1088.

Argus, D.F., and Gordon, R.G., 2001, Present tectonic motion across the Coast Ranges and San Andreas fault system in central California: Geological Society of America Bulletin, v.

113, p. 1580-1592.

Bacon, R., Charles, 1982, Time-predictable bimodal volcanism in the Coso Range, California United States Geological Survey Paper, Geology, v. 10. p. 65-69.

Baker, Ian and Haggerty E., Stephen, 1967, The Alteration of Olivine in Basaltic and Associ ated Lavas Part II: Intermediate and Low Temperature Alteration, Contr. Mineral. and Petrol. 16, p. 258-273. Bierman, Paul R.; Clark, Douglas: Gillespie, Alan; Hanan, Barry B., editor: Whipple, Kelin X. 1991, Quaternary geomorpholoty and geochronology of Owens Valley, California; Geo- logical Society of America field trip. Geological excursions in Southern California and Mexico, Walawender, Michael J., editor. San Diego, CA: San Diego State Univ., p. 199-223. Coleman, Drew, and Walker, J.D., 1990. Geochemistry of Mio-Pliocene volcanic rocks from

around Panamint Valley, Death Valley area, California, in Wernicke, B.P., ed., Basin and Range extensional tectonics near the latitude of Las Vegas, Nevada: Boulder Colorado, Geological Society of America Memoir, P. 391-411.

Darrow, Arthur, 1972, Origins of the basalts of the Big Pine volcanic field, California, unpublished Master’s Thesis, UCSB.

De la Roche, H., Leterrier, J., Grandclaude, P., Marchal, M., 1980, A classification of volcanic and plutonic rocks using R1R2-diagram and major-element analyses; its relationships with current nomenclature, Chemical Geology v.29, p. 183-210. Dunne, George C., Garvey, Timothy P., Oborne, Mark, Schneidereit, Daniel, Fritsche, Eugene

A., and Walker, Douglas J., 1998, Geology of the Inyo Mountains Volcanic Complex: Implications for Jurassic paleogeography of the Sierran magmatic arc in eastern California, GSA Bulletin, v. 110, p. 1376-1397.

Frugal, S. A., and McMillan, N. J., 2001, Magmatic Iddingsite: Changes in H2O in Magma Chambers Prior to Eruption, GSA Abstract.

29

Groves, Kristelle, 1996, Geochemical and isotope analysis of Pleistocene basalts from southern Coso volcanic field, California, unpublished Master’s Thesis, UNC-Chapel Hill, 84p. Irvine, T.N., 1977, Chromite crystallization in the join Mg2SiO4-CaMgSi2O6-CaAl2Si2O8-

MgCr2O4-SiO4, Carnegie Institution of Washington Year Book, v. 76, p. 465-472.

Irvine, T. N., and Baragar, W. R. A., 1971, A guide to the chemical classification of the com mon volcanic rocks, Canadian Journal of Earth Science, v. 8, p. 523-548 LeBas, M.J., LeMaitre, R. W., Streckeisen, A., and Zanettin, B., 1986, A chemical classifica tion of volcanic rocks based on the total alkali silica diagram, J. Petrol, v. 27, p. 745- 750. McKensie, D., and Bickle M.J., 1988, The Volume and Composition of Melt Generated by

Extension of the Lithoshere, Journal of Petrology, v. 29, p. 625-679. Pearce, J.A., Harris, B.W., and Tidle, A.G., 1984, Trace element discrimination diagrams for the tectonic interpretation of granitic rocks, J. Petrol, v. 25, p. 956-983. Ringwood, A. E., 1976, Composition and petrology of the Earth’s mantle, McGraw Hill Book Company, New York, NY, p. 618. Schweig, S., Eugene, 1989, Basin-range tectonics in the Darwin Plateau, southwestern Great

Basin, California: GSA Bulletin, v. 101, p. 652-662. Stinson, Melvin C., and Streitz, Robert, 1974, Geologic Map of California Death Valley

Sheet, Division of Mines and Geology, State of California. Stockli, Daniel F., Dumitru, Trevor A., McWilliams, Michael O., and Farley, Kenneth A., 2003 Cenozoic tectonic evolution of the White Mountains, California and Nevada, GSA

Bulletin, v. 115, p. 788-816. Takahashi, Eiichi, and Kushiro, Ikuo, 1983, Melting of a dry peridotite at high pressures and basalt magma genesis, American Mineralogist, v. 68, p. 859-879. Taylor, T.R., 2002, Origin and structure of the Poverty Hills, Owens Valley fault zone, Owens

Valley, California, unpublished Master’s Thesis, Miami University.

Tsuchiyama, Akira, and Takahashi, Eiichi, 1983, Melting Kinetics of a plagioclase feldspar, Contributions to Mineralogy and Petrology, v. 84, p. 345-354.

Unruh, Jeffrey; Humphrey, James and Barron, Andrew, 2003, Transtensional model for the

Sierra Nevada frontal fault system, eastern California: Geology, v. 31, p. 327-330.

Varnell, Ashley, 2006, Petrology and Geochemistry of the Big Pine Volcanic Field Inyo County, California, unpublished Senior Thesis, Cal Poly Pomona, 34p.

30

Wang, K., Plank, T., Walker, J.D., and Smith, E.I., 2002, A mantle melting profile across the Basin and Range, SW USA, pp ECV 5-1-19.

Wernicke, B., 1992, Cenozoic extensional tectonics of the U.S. Cordillera, The Geology of North America, vol G-3, The Cordillera Orogen: Conterminous U.S., p. 553-581. Wernicke, B., and Snow, J.K., 1998, Cenozoic extension in the central Basin and Range: Mo tion of the Sierran-Great Valley block: International Geological Review, v. 40, p. 403- 410. Winter, J. D., 2001, An Introduction to Igneous and Metamorphic Petrology, Prentice Hall, p.

669.

Yoder, H. S. Jr. and C. E. Tilley, 1962, Origin of basalt magmas: An experimental study of natural and synthetic rock systems, J. Petrol, v. 3, p. 342-532.

31

Appendix A

Basalt Sample Correlation Map and Figures

The Cr vs. normative olivine graph was used to further correlate some flows.

Samples from the basalt tetrahedron that show a similar or identical trend were grouped together, the group color corresponds to the color on the accompanying map.

32

33

Appendix B

Basalt Hand Sample Description

SAMPLE COLOR OLIVINE QUARTZ PLAGIOCLASE TEXTURE Sml < 1.5 mm Sample 1 dark gray yes/Lrg yes/Sml fine Lrg > 1.5 mm Sample 2 dark gray yes yes fine/vesicular alter = altered Sample 3 red scoria ves. = vesicular Sample 4 gray yes fine-porphyry Sample 5 purple gray yes/Lrg/alter. yes fine-porphyry Sample 6 red gray yes/Lrg/alter. coarse Sample 7 dark gray yes/Lrg/alter. yes fine-porphyry Sample 8 gray yes/Lrg yes coarse-porphyry Sample 9 gray yes coarse-laminated

Sample 10 gray yes/Lrg yes coarse Sample 11 gray yes/alter. coarse Sample 12 blue gray yes/Lrg/alter. coarse-laminated Sample 13 gray yes/alter. fine/vesicular Sample 15 red gray yes/alter. highly vesicular Sample 16 red gray yes/Lrg/alter. yes/Lrg coarse/vesicular Sample 17 dark gray yes/Lrg yes coarse Sample 18 dark gray yes/Lrg/alter. yes/Sml fine Sample 19 dark gray yes/Lrg/alter. porphyry Sample 20 blue gray yes no no fine/vesicular Sample 21 blue gray yes/Lrg/alter. fine/vesicular Sample 22 blue gray yes/Lrg/alter. fine/vesicular Sample 23 gray yes/Lrg fine/vesicular Sample 24 gray yes fine Sample 25 red gray yes/Lrg/alter. yes coarse Sample 26 purple gray yes yes coarse Sample 27 dark gray yes/Sml yes fine Sample 28 purple gray yes yes coarse Sample 29 dark gray yes yes yes coarse Sample 30 dark gray yes/alter. yes/Lrg coarse Sample 31 dark gray yes/Sml yes coarse Sample 32 red gray yes/alter. fine-laminated Sample 33 purple gray yes/Lrg/alter. coarse Sample 34 dark gray yes/alter. yes coarse/vesicular Sample 35 dark gray yes/Lrg yes coarse Sample 36 dark gray yes/Lrg/alter. yes porphyry Sample 37 gray yes yes/Sml fine Sample 38 dark gray yes/alter. yes/Sml coarse Sample 39 gray yes yes coarse Sample 40 red gray-banded yes fine Sample 41 red-scoria Sample 42 red gray-banded fine Sample 44 dark grey yes/alter. yes/Sml coarse Sample 45 red grey yes/Lrg yes coarse Sample 46 red gray-banded yes/Sml/alter. fine

34

SAMPLE COLOR OLIVINE QUARTZ PLAGIOCLASE TEXTURE Sample 47 red purple fine-scoria Sample 48 red gray yes/Lrg/alter. yes/Lrg coarse-porphyry Sample 49 red gray yes/Lrg/alter. yes coarse Sample 50 gray yes/Sml yes/Lrg fine/slightly ves. Sample 51 purple gray yes vesicular Sample 52 dark gray yes/alter. fine Sample 53 dark gray yes/Lrg/alter. yes/Lrg coarse Sample 54 gray yes/Lrg/alter. fine/vesicular Sample 55 dark gray yes/Lrg/alter. fine/vesicular Sample 56 dark gray yes/Lrg/alter. yes fine Sample 57 dark gray yes/Lrg/alter. yes/Sml fine/slightly ves. Sample 60 gray yes/alter. fine/vesicular Sample 62 gray yes yes/Lrg coarse-porphyry Sample 65 red gray yes/alter. fine/vesicular Sample 68 blue gray yes/Lrg yes coarse/vesicular Sample 69 gray yes/Lrg yes/Sml coarse

35

Sample Northing Easting SiO[2] TiO[2] Al[2]O[3] Fe[2]O[3] MnO MgO CaO Na[2]O K[2]O P[2]O[5] SP 1 427446 4029114 49.87 1.968 16.323 9.726 0.155 5.015 10.935 3.388 1.902 0.721 SP 2 427489 4029094 50.02 1.907 16.547 9.402 0.152 4.688 11.238 3.408 1.904 0.732 SP 3 427757 4027425 54.06 1.304 17.066 8.186 0.130 3.989 8.029 5.074 1.783 0.377 SP 4 427799 4027310 54.80 1.382 17.087 7.561 0.128 5.083 7.264 4.187 1.985 0.520 SP 5 427646 4027358 54.78 1.478 16.232 8.160 0.130 5.680 7.489 3.700 1.997 0.352 SP 6 427787 4027035 49.85 1.220 15.400 9.215 0.160 10.240 8.920 3.235 1.279 0.479 SP 7 427909 4026985 49.62 1.681 16.866 9.882 0.162 7.536 9.900 3.104 0.913 0.336 SP 8 444675 4015618 49.20 1.309 17.388 9.054 0.153 7.354 10.465 3.429 1.113 0.536 SP 9 444772 4015400 49.45 1.289 17.391 8.893 0.166 7.095 10.528 3.455 1.146 0.585

SP 10 444772 4016642 49.20 1.318 17.031 9.185 0.159 7.436 10.689 3.289 1.126 0.564 SP 11 445069 4017640 49.19 1.313 17.488 9.162 0.155 7.319 10.390 3.297 1.120 0.562

SP 12 445154 4017612 49.43 1.283 17.074 8.973 0.153 7.432 10.530 3.489 1.108 0.532 SP 13 445381 4017498 48.93 1.311 16.844 9.355 0.160 6.925 11.522 3.305 1.104 0.546 SP 15 449876 4022883 52.14 0.543 18.349 8.564 0.137 4.783 11.460 2.889 0.929 0.201 SP 16 449987 4022869 52.97 0.495 18.048 8.430 0.135 5.283 10.587 2.986 0.876 0.194 SP 17 451386 4023299 48.18 0.608 16.519 10.314 0.160 6.735 13.455 2.814 0.872 0.342 SP 18 456275 4022225 51.42 0.582 17.306 9.425 0.140 8.009 8.836 2.950 1.022 0.311 SP 19 454946 4022173 46.81 1.511 13.880 11.987 0.202 9.659 12.061 2.297 1.118 0.471 SP 20 423864 4027967 53.61 0.415 16.321 8.784 0.159 5.828 10.912 2.923 0.918 0.133 SP 21 424070 4027853 55.00 0.393 16.931 8.337 0.135 5.673 9.359 3.092 0.944 0.134 SP 22 424296 4027896 53.10 1.016 16.666 8.340 0.134 5.876 9.860 3.504 1.267 0.234 SP 23 424457 4028029 54.88 0.383 16.969 8.280 0.127 5.944 9.219 3.118 0.945 0.130 SP 24 436105 4022202 52.36 0.588 18.223 8.183 0.140 5.664 9.999 3.314 1.227 0.305 SP 25 438282 4023926 49.12 1.016 19.406 7.863 0.142 5.445 12.516 3.151 0.936 0.409 SP 26 438400 4024140 49.57 1.112 19.524 8.147 0.141 5.130 11.782 3.286 0.930 0.384 SP 27 438037 4024546 50.15 0.431 19.086 9.017 0.158 7.228 10.544 2.666 0.553 0.171 SP 28 438145 4024487 51.06 0.417 19.567 8.999 0.152 5.676 10.525 2.863 0.563 0.176 SP 29 437766 4024741 51.16 0.388 20.244 8.087 0.131 5.998 10.271 2.954 0.591 0.173 SP 30 438226 4025030 48.14 1.476 16.895 9.717 0.167 8.742 10.497 2.933 0.912 0.518 SP 31 438623 4025299 47.90 1.608 18.189 9.947 0.166 5.925 11.020 3.764 0.952 0.527 SP 32 438608 4025440 51.18 1.288 17.916 8.168 0.155 5.120 10.747 3.851 1.178 0.396 SP 33 443032 4031674 46.84 1.480 15.723 10.475 0.174 11.778 9.719 2.389 0.853 0.568 SP 34 443388 4031744 47.88 0.566 16.315 10.779 0.175 10.332 10.824 2.283 0.552 0.292 SP 35 439951 4027143 50.30 0.548 18.799 10.142 0.153 5.498 10.512 2.938 0.742 0.370 SP 36 439903 4027001 48.75 1.708 17.639 9.705 0.163 6.944 9.974 3.834 0.724 0.561 SP 37 439791 4026360 48.36 1.627 18.039 10.162 0.165 5.873 10.468 3.698 0.975 0.634 SP 38 439160 4025542 48.06 1.628 17.464 10.205 0.172 6.661 10.869 3.564 0.876 0.505 SP 39 451253 4022606 51.18 1.350 18.318 8.863 0.147 4.982 10.173 3.552 1.118 0.321 SP 40 452037 4022950 52.86 1.216 17.477 7.224 0.125 6.167 9.113 3.859 1.546 0.413 SP 41 452249 4023592 50.06 0.483 14.326 10.052 0.158 9.047 12.973 1.958 0.826 0.122 SP 42 452259 4023536 50.85 1.283 16.525 8.943 0.157 5.761 11.417 3.507 1.217 0.351 SP 44 456674 4022017 52.75 1.298 19.090 7.747 0.128 3.775 8.885 4.216 1.721 0.390 SP 45 454291 4021892 52.55 0.449 18.693 8.571 0.133 5.128 10.443 3.126 0.735 0.176 SP 46 452792 4022752 52.79 1.230 17.121 7.418 0.124 5.764 9.915 3.832 1.449 0.359

Appendix C

Major Element Table

36

Sample Northing Easting SiO[2] TiO[2] Al[2]O[3] Fe[2]O[3] MnO MgO CaO Na[2]O K[2]O P[2]O[5] SP 47 452474 4023666 50.13 0.525 16.552 9.218 0.152 6.044 13.443 2.914 0.816 0.210 SP 48 451555 4022498 51.11 1.233 18.775 8.199 0.139 4.953 10.280 3.741 1.197 0.374 SP 49 451692 4022124 52.10 1.187 18.357 8.212 0.138 4.706 9.871 3.773 1.252 0.399 SP 50 446754 4026081 49.77 1.339 17.392 8.558 0.152 5.156 12.163 3.399 1.530 0.547 SP 51 444321 4026199 55.95 1.188 16.111 7.939 0.136 4.335 8.090 3.962 1.936 0.352 SP 52 443681 4029006 50.75 1.312 16.804 8.830 0.158 7.328 9.465 3.538 1.255 0.565 SP 53 442861 4030620 47.54 1.522 17.493 9.895 0.166 8.249 10.488 3.120 1.018 0.508 SP 54 445054 4018653 49.43 1.311 17.062 9.122 0.154 7.298 10.436 3.464 1.170 0.550 SP 55 444249 4018300 50.02 0.502 16.669 9.696 0.154 7.563 11.672 2.646 0.797 0.284 SP 56 440484 4017303 49.70 1.420 16.564 9.343 0.159 9.231 9.073 3.291 0.807 0.412 SP 57 438995 4017245 49.71 1.438 16.702 9.391 0.154 8.739 9.231 3.394 0.846 0.398 SP 60 438252 4031900 49.51 1.859 18.135 9.353 0.154 5.262 9.110 4.689 1.301 0.627 SP 62 436541 4031038 54.39 1.142 15.617 8.277 0.131 7.331 7.425 3.494 1.835 0.358 SP 65 435076 4030439 51.28 1.357 15.921 9.050 0.163 7.465 10.111 2.962 1.220 0.475 SP 68 436564 4030926 47.11 1.555 18.280 9.971 0.169 6.662 11.252 3.530 0.918 0.553 SP 69 436934 4031146 49.22 1.673 17.847 9.282 0.157 5.830 10.017 4.032 1.364 0.580

DarwinAve 50.63 1.141 17.310 9.033 0.151 6.540 10.316 3.340 1.130 0.405

37

Appendix D

Trace Element Table

Sample Rb Ba Sr Cr Zr Sc La Ce Nd Sm Y SP 1 40.763 766.871 1424.315 42.755 354.817 6.035 27.217 62.298 29.232 4.638 35.488 SP 2 39.960 847.259 1430.528 47.082 346.700 2.510 31.300 62.942 32.876 5.002 34.991 SP 3 58.305 572.363 1300.554 25.534 275.091 1.861 7.659 52.194 11.981 3.607 43.330 SP 4 53.391 570.163 1161.149 199.279 293.313 14.581 14.269 51.993 12.051 3.086 44.570 SP 5 49.731 610.128 1454.413 217.695 311.181 17.502 17.924 53.581 26.247 4.180 44.398 SP 6 31.025 406.454 919.067 682.655 203.037 3.115 12.830 47.010 22.845 7.283 32.876 SP 7 26.657 284.635 986.132 266.909 251.526 27.499 16.874 43.973 21.631 7.325 36.065 SP 8 24.589 365.664 1062.284 386.401 210.976 3.051 4.820 46.417 22.151 4.159 30.697 SP 9 26.030 445.044 1055.051 351.675 209.124 18.196 6.648 47.244 19.270 3.534 32.111

SP 10 25.392 354.482 1055.400 383.132 209.632 14.842 10.342 46.931 20.485 3.336 31.510 SP 11 24.099 376.755 1059.343 389.903 207.942 19.710 7.309 46.981 16.737 2.982 31.197 SP 12 24.929 366.123 1041.998 371.942 207.953 4.782 9.292 45.581 17.604 5.440 31.586 SP 13 25.459 363.464 1063.859 385.974 207.960 6.188 9.992 45.289 15.001 4.502 30.770 SP 15 32.988 349.715 1115.401 47.907 212.467 3.223 10.536 44.487 15.140 2.117 35.412 SP 16 35.400 326.708 1060.592 60.773 210.884 10.515 4.937 44.086 14.203 4.836 37.108 SP 17 21.235 421.578 1102.645 210.408 235.516 14.950 17.885 47.541 26.698 3.242 29.541 SP 18 35.795 433.961 1194.255 121.202 248.951 18.088 17.341 49.984 28.642 5.742 35.864 SP 19 23.669 345.040 768.735 455.085 193.929 32.583 19.168 46.388 22.533 7.304 27.275 SP 20 32.326 443.944 929.425 167.314 199.323 9.866 3.965 167.314 13.023 2.784 33.366 SP 21 34.672 469.976 944.084 147.047 202.383 3.592 2.125 47.921 14.064 4.377 35.582 SP 22 32.952 467.501 929.713 160.397 198.601 5.170 3.304 48.497 8.510 4.513 33.507 SP 23 33.977 789.879 1007.674 150.435 206.640 7.162 5.014 56.977 15.834 4.950 34.481 SP 24 34.696 540.740 1505.203 1.710 313.917 2.078 20.296 52.052 24.511 1.451 42.223 SP 25 27.004 313.600 1129.716 72.101 189.842 1.925 3.731 42.173 7.226 1.420 33.972 SP 26 25.756 298.659 1119.299 69.056 195.097 4.304 1.946 43.660 6.879 3.003 33.651 SP 27 23.100 280.143 1017.987 20.695 187.394 31.285 11.430 44.224 20.485 1.451 32.676 SP 28 23.034 298.476 1051.012 31.113 187.735 12.246 15.397 44.395 18.854 0.680 32.134 SP 29 27.076 247.328 1073.719 89.038 192.696 8.352 15.474 42.227 16.285 1.018 34.332 SP 30 18.579 189.856 840.437 300.725 206.311 26.633 11.664 42.323 17.570 6.752 30.233 SP 31 14.935 253.836 847.383 202.410 209.003 8.352 10.497 43.476 13.752 3.836 29.065 SP 32 31.844 354.482 1124.374 6.890 258.999 5.494 8.786 45.623 6.046 2.097 40.265 SP 33 17.681 211.305 783.351 630.879 208.255 19.710 15.941 43.100 27.254 8.877 29.015 SP 34 15.690 174.640 851.240 414.154 215.174 30.095 30.600 42.144 30.204 3.326 29.059 SP 35 17.791 325.333 998.150 117.245 240.737 15.275 29.706 46.446 31.939 2.607 30.597 SP 36 11.871 202.505 809.924 172.067 225.958 21.441 16.446 43.330 23.678 7.398 30.758 SP 37 15.455 336.607 961.310 77.937 231.841 15.275 17.263 46.872 22.741 6.252 28.826 SP 38 14.453 190.131 829.158 268.247 203.931 10.624 12.986 42.499 19.548 5.273 28.532 SP 39 32.731 317.358 1081.400 79.815 215.132 2.790 6.842 44.692 8.823 4.544 35.717 SP 40 41.485 417.179 1239.257 40.962 278.753 5.711 6.920 47.248 4.588 1.867 40.628 SP 41 34.966 177.023 908.490 16.227 215.950 15.167 18.974 40.886 16.875 0.118 37.783 SP 42 31.310 267.494 999.543 15.970 225.202 1.708 4.665 43.042 6.983 2.617 35.277 SP 44 42.371 469.793 1177.611 34.069 255.132 13.607 5.442 48.439 12.190 1.940 39.520 SP 45 30.454 402.513 1113.209 49.017 212.703 4.025 14.502 46.780 10.211 0.643 35.410 SP 46 40.364 433.311 1237.996 58.040 276.796 2.357 7.970 47.031 7.191 2.857 40.777

38

Sample Rb Ba Sr Cr Zr Sc La Ce Nd Sm Y SP 47 29.320 122.575 952.829 6.402 217.829 1.429 15.397 41.363 7.886 10.839 35.613 SP 48 30.859 303.517 1094.238 37.774 212.412 0.951 2.176 44.604 6.705 1.482 35.607 SP 49 33.551 334.499 1078.514 55.564 214.176 8.136 6.142 44.792 14.272 3.086 37.082 SP 50 35.961 530.657 1311.990 92.510 260.899 9.217 9.136 50.586 11.044 1.555 35.264 SP 51 57.552 804.086 1018.364 172.636 253.211 12.850 12.130 58.234 13.335 2.763 43.428 SP 52 33.213 430.561 1167.359 228.711 244.808 15.491 11.858 48.309 22.255 5.596 34.635 SP 53 19.368 169.232 745.089 504.129 202.914 18.737 13.102 41.191 14.862 4.284 29.914 SP 54 24.943 403.979 1060.296 377.464 210.496 5.107 11.080 48.033 19.097 4.221 31.499 SP 55 25.721 318.183 1098.763 361.922 215.185 17.006 16.291 47.327 20.312 6.246 32.495 SP 56 20.668 130.183 746.666 309.833 179.328 14.626 14.619 39.704 19.895 5.679 31.291 SP 57 21.756 148.882 775.988 320.393 185.361 9.001 14.230 40.536 19.513 6.148 31.731 SP 60 26.064 357.323 1044.157 81.153 266.213 7.270 17.030 47.311 18.993 4.367 34.355 SP 62 50.602 504.533 832.061 393.916 233.804 2.033 11.392 50.435 17.917 4.138 37.400 SP 65 31.179 368.506 1241.403 190.512 226.621 7.486 5.442 46.108 14.966 4.513 34.956 SP 68 15.357 116.617 885.063 306.759 195.761 13.220 5.909 38.931 13.543 4.898 28.232 SP 69 26.231 277.118 977.927 194.440 253.469 4.304 18.585 44.867 15.869 4.784 33.658

DarwinAve 29.806 373.341 1046.618 194.567 228.617 10.839 12.212 48.677 17.184 4.059 34.322

39

Appendix E

Normative Mineralogy Table

Sample %AN Q or ab an ne di hy ol mt il ap SP 1 44.752 0.000 11.356 29.591 23.969 0.692 20.883 0.000 5.551 3.664 2.771 1.524 SP 2 45.486 0.000 11.366 29.348 24.487 0.944 21.621 0.000 4.403 3.599 2.684 1.547 SP 3 29.351 0.000 10.491 44.415 18.452 0.576 15.017 0.000 5.535 2.920 1.809 0.785 SP 4 36.884 1.826 11.699 37.504 21.917 0.000 8.519 12.524 0.000 3.006 1.921 1.085 SP 5 39.607 2.917 11.818 33.278 21.824 0.000 10.475 13.770 0.000 3.119 2.062 0.737 SP 6 44.958 0.000 7.476 28.740 23.475 0.000 13.776 3.978 17.068 2.814 1.682 0.991 SP 7 51.331 0.000 5.410 27.955 29.484 0.000 14.067 10.112 6.582 3.336 2.349 0.705 SP 8 49.601 0.000 6.554 29.140 28.678 0.930 15.672 0.000 13.164 2.927 1.818 1.117 SP 9 48.774 0.000 6.752 29.919 28.486 0.611 15.838 0.000 12.475 2.908 1.791 1.220

SP 10 49.540 0.000 6.642 28.868 28.341 0.370 16.746 0.000 13.082 2.941 1.833 1.177 SP 11 50.010 0.000 6.605 29.552 29.563 0.000 14.587 0.510 13.248 2.936 1.826 1.173 SP 12 48.447 0.000 6.521 29.319 27.552 1.133 16.825 0.000 12.863 2.898 1.780 1.108 SP 13 51.674 0.000 6.527 26.083 27.890 2.169 20.602 0.000 10.819 2.941 1.828 1.142 SP 15 56.982 1.302 5.533 26.150 34.638 0.000 17.087 11.951 0.000 2.153 0.763 0.424 SP 16 55.368 2.130 5.205 26.964 33.449 0.000 14.484 14.570 0.000 2.098 0.693 0.408 SP 17 62.583 0.000 5.183 17.968 30.053 4.471 27.892 0.000 10.645 2.217 0.852 0.719 SP 18 53.897 0.000 6.027 26.442 30.912 0.000 8.661 19.533 4.793 2.173 0.809 0.649 SP 19 58.131 0.000 6.659 17.618 24.461 1.904 26.213 0.000 16.856 3.173 2.122 0.993 SP 20 52.239 2.269 5.461 26.426 28.904 0.000 19.790 14.274 0.000 2.016 0.582 0.280 SP 21 51.546 4.446 5.604 27.900 29.681 0.000 12.885 16.662 0.000 1.989 0.550 0.282 SP 22 45.255 0.443 7.495 31.503 26.042 0.000 17.131 12.846 0.000 2.634 1.417 0.490 SP 23 51.324 3.975 5.602 28.090 29.618 0.000 12.341 17.591 0.000 1.975 0.535 0.273 SP 24 51.207 0.000 7.249 29.759 31.231 0.000 13.114 13.447 1.559 2.183 0.819 0.638 SP 25 58.580 0.000 5.530 25.489 36.050 1.683 18.706 0.000 7.642 2.630 1.415 0.855 SP 26 55.099 0.000 5.502 29.200 35.833 0.208 16.158 0.000 8.009 2.735 1.551 0.804 SP 27 61.651 0.000 3.267 23.936 38.481 0.000 10.172 15.523 5.644 2.019 0.600 0.358 SP 28 60.200 0.000 3.341 25.821 39.055 0.000 9.796 18.870 0.152 2.013 0.583 0.370 SP 29 60.271 0.000 3.488 26.496 40.196 0.000 7.667 18.048 1.233 1.972 0.540 0.361 SP 30 53.455 0.000 5.377 26.283 30.185 0.000 14.734 2.015 15.169 3.105 2.052 1.081 SP 31 53.432 0.000 5.634 26.130 29.982 4.637 17.077 0.000 9.936 3.255 2.244 1.104 SP 32 45.011 0.000 6.958 34.351 28.118 0.131 18.085 0.000 6.821 2.914 1.794 0.828 SP 33 58.034 0.000 5.006 21.309 29.468 0.000 11.801 5.542 20.551 3.095 2.048 1.180 SP 34 61.427 0.000 3.255 20.461 32.583 0.000 15.295 6.419 18.435 2.156 0.787 0.609 SP 35 57.657 0.000 4.421 26.609 36.232 0.000 11.151 14.059 3.817 2.160 0.770 0.780 SP 36 46.766 0.000 4.271 32.718 28.742 0.993 13.609 0.000 12.772 3.349 2.376 1.171 SP 37 49.954 0.000 5.782 29.918 29.862 2.049 14.497 0.000 11.004 3.282 2.275 1.331 SP 38 51.643 0.000 5.187 27.285 29.139 2.874 17.287 0.000 11.618 3.278 2.273 1.058 SP 39 49.080 0.000 6.635 32.037 30.879 0.000 14.173 8.387 2.333 2.993 1.889 0.674 SP 40 42.683 0.000 9.074 34.424 25.636 0.000 13.285 9.431 2.788 2.821 1.683 0.858 SP 41 61.315 0.000 4.908 17.684 28.029 0.000 28.732 9.747 7.882 2.085 0.677 0.257 SP 42 45.481 0.000 7.213 30.975 25.840 0.369 22.952 0.000 7.203 2.919 1.793 0.736 SP 44 42.592 0.000 10.163 37.841 28.075 0.000 10.757 5.330 2.288 2.924 1.807 0.815 SP 45 55.360 1.327 4.363 28.201 34.973 0.000 12.746 15.344 0.000 2.047 0.628 0.370 SP 46 42.315 0.000 8.528 34.278 25.145 0.000 17.224 7.073 2.454 2.843 1.707 0.748

40

Sample %AN Q or ab an ne di hy ol mt il ap SP 47 55.464 0.000 4.847 23.963 29.842 1.408 28.678 0.000 7.956 2.129 0.735 0.442 SP 48 47.919 0.000 7.073 33.597 30.913 0.000 14.128 3.232 5.698 2.858 1.718 0.782 SP 49 46.512 0.000 7.410 33.940 29.514 0.000 13.554 9.181 1.095 2.814 1.657 0.836 SP 50 52.266 0.000 9.073 25.379 27.789 3.153 23.362 0.000 5.244 2.979 1.872 1.148 SP 51 36.515 3.984 11.487 35.730 20.550 0.000 13.964 9.061 0.000 2.822 1.662 0.739 SP 52 45.261 0.000 7.390 31.665 26.182 0.000 13.559 6.432 8.842 2.930 1.822 1.178 SP 53 55.052 0.000 6.001 25.032 30.659 1.753 14.366 0.000 15.860 3.153 2.116 1.060 SP 54 48.180 0.000 6.894 29.557 27.481 0.878 16.462 0.000 12.829 2.931 1.821 1.147 SP 55 56.815 0.000 4.723 23.832 31.353 0.000 19.903 7.487 9.305 2.099 0.701 0.596 SP 56 48.694 0.000 4.736 29.352 27.857 0.000 11.349 9.021 11.833 3.032 1.965 0.856 SP 57 47.744 0.000 4.970 30.302 27.686 0.000 12.216 6.692 12.261 3.054 1.992 0.827 SP 60 42.183 0.000 7.660 33.598 24.513 5.016 13.162 0.000 8.664 3.500 2.581 1.307 SP 62 40.678 1.407 10.808 31.277 21.447 0.000 10.360 19.614 0.000 2.754 1.586 0.746 SP 65 49.954 0.000 7.227 26.669 26.620 0.000 16.459 16.170 0.967 2.995 1.896 0.996 SP 68 57.551 0.000 5.425 23.112 31.335 5.155 16.716 0.000 11.739 3.195 2.167 1.157 SP 69 46.970 0.000 8.048 29.966 26.542 3.716 15.452 0.000 9.425 3.313 2.328 1.211

DarwinAve 49.080 0.000 6.681 30.014 28.930 0.000 15.719 6.013 7.441 2.763 1.591 0.848