the behavior of li and b in lunar mare basalts during crystallization, shock, and thermal...

8/10/2019 The behavior of Li and B in lunar mare basalts during crystallization, shock, and thermal metamorphism: Implicati

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American Mineralogist, Volume 91, pages 15531564, 2006

0003-004X/06/00101553$05.00/DOI: 10.2138/am.2006.2088 1553

INTRODUCTION

The amount of water in martian magmas has significant

implications for the evolution of Mars through geologic time.

Volatile species in martian magmas could potentially influence

the planets atmosphere-hydrosphere cycle during volcanic

outgassing (McSween and Harvey 1993). The abundance of

volatile phases in extruded basalts affects the development of

acid-sulfate and neutral-chloride hydrothermal systems with

possibly significant consequences on prebiotic chemistry (Hu-

ber and Wchtershuser 1998). The abundance of magmatic

water affects physical properties of magmas, such as density

and viscosity, which in turn shape mantle dynamics and styles

of planetary volcanism (Mysen et al. 1998). Furthermore, the

extent of water in martian magmas can affect the compositionof the martian crust (Mysen et al. 1998). Basaltic magmas with

low water contents typically do not produce a broad spectrum of

diverse magmas through fractional crystallization; they instead

generate predominantly basaltic crustal compositions. Alterna-

tively, basaltic magmas with high water contents can evolve

to greater extents and produce rocks of greater compositional

variety, including more SiO2-rich, andesitic crust (Morse 1994;Hess 1989; Minitti and Rutherford 2000).

The amount and distribution of water in martian basalts is

a topic of debate among researchers (Dann et al. 2001; Foley

et al. 2003a, 2003b; Johnson et al. 1991; McSween et al. 2001,

2003; McSween and Harvey 1993; Mysen et al. 1998). Data from

orbital missions, such as Pathfinder and Global Surveyor, suggest

that andesites or basaltic andesites may exist on Mars, thereby

implying an important role for magmatic water (Minitti and Ruth-

erford 2000; Foley et al. 2003a, 2003b; McSween et al. 2003).

However, spectral signatures attributed to andesites or basaltic

andesites may instead reflect weathering of basalts (McSween et

al. 2003). Some martian basalts are characterized by melt inclu-

sions containing biotite, apatite, and amphibolephases typi-

cally associated with hydrous magmas on Earth (Johnson et al.

1991; Mysen et al. 1998; McSween and Harvey 1993). However,

the H contents of melt inclusions from these basalts are low, the

individual phases are generally anhydrous, and bulk rock water

contents are a meager 0.013 to 0.035 wt% in Shergotty (Dann

et al. 2001). Righter et al. (1997) determined that there was 0.1

wt% H2O in glass in the melt inclusions in Chassigny. Watson

et al. (1994) determined that there was approximately 0.5 wt%

H2O in biotite from melt inclusions in Chassigny. Nonetheless,

researchers note that low present-day water contents do not* Present address: 104-22 112thStreet Richmond Hill, New York11419, U.S.A. E-mail: [email protected]

The behavior of Li and B in lunar mare basalts during crystallization, shock, and thermal

metamorphism: Implications for volatile element contents of martian basalts

J. CHAKLADER,* C.K. SHEARER, ANDL.E. BORG

Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131-1126, U.S.A.

ABSTRACT

Late-stage rims of magmatic pyroxenes from some martian basalts show decreases in Li and B

contents relative to earlier-formed pyroxene cores. This behavior is different than expected from their

documented incompatible element behavior. Previous workers interpreted such depletions to reflect

the loss of several wt% magmatic water during basalt crystallization. This interpretation has profound

implications for the nature of the martian mantle and recent exchange of volatiles between the martian

mantle and atmosphere. To assess alternative mechanisms that may influence the behavior of Li and B

in the absence of aqueous fluid activity, the effects of changing pyroxene composition during crystal-

lization, shock pressure, and shock-associated thermal metamorphism were studied. Lithium and B

depletions are documented in late-stage rims of pyroxenes from anhydrous lunar basalts indicating that

mechanisms other than aqueous fluid activity must have influenced Li and B partitioning in these py-roxenes. Depletions of Li and B are most likely associated with changing pyroxene composition during

crystallization, and occur in lunar and martian pyroxenes with late-stage Fe-enrichment. It is interesting

that pyroxenes without late-stage Fe-enrichment show no concomitant Li and B increases. Lithium

loss may occur during breakdown of metastable pyroxferroite. Additionally, changes in Cr content

may influence the substitution mechanism involved for incorporating Li. Shock does not redistribute

Li or B but may facilitate subsequent thermally driven diffusion by the introduction of mechanical

defects in grains. Thermally metamorphosed pyroxenes exhibit higher Li and lower B contents rela-

tive to unheated pyroxenes. It is likely, therefore, that Li and B are redistributed through interactions

between pyroxenes and surrounding zones of mesostasis during thermal metamorphism.

Keywords: Lithium, boron, lunar mare basalts, martian basalts, shock pressure, thermal metamor-

phism, crystal chemistry, pyroxenes


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CHAKLADER ET AL.: THE BEHAVIOR OF Li AND B IN LUNAR MARE BASALTS1554

preclude a once hydrous past (McSween et al. 2001).

It is possible that pre-eruptive martian magmas contained

significant amounts of water, which were subsequently lost

through extensive volcanic outgassing (Dann et al. 2001; Johnson

et al. 1991; McSween and Harvey 1993). Geochemical evidence

of aqueous fluid loss from parent magmas may be preserved in

silicate minerals that crystallized from those magmas (McSween

et al. 2001; Lentz et al. 2001). Although volatile element behavior

under hydrous magmatic conditions is poorly constrained, work-

ers have suggested that Li and B depletions in pyroxene rims

of several martian basalts reflect removal of volatile elements

by escaping aqueous fluids from magmas during crystallization

(McSween et al. 2001; Lentz et al. 2001). Alternatively, given

that many martian basalts have experienced considerable shock

pressures (1545 GPa), it is possible that shock and subsequent

thermal metamorphism influenced the volatile element records of

these basalts (Fritz et al. 2003; Langenhorst et al. 1991; Stffler

et al. 1986). Previous experiments indicate that shock may affect

the extent of volatile-phase mobility and water loss from silicate

phases (Boslough et al. 1980; Minitti et al. 2003; Monkawa et al.

2003). Heating experiments on lunar basalts show that significant

redistribution and loss of volatile elements, such as Rb, occurs

from individual minerals (Nyquist et al. 1991a, 1991b). It has also

been demonstrated that pyroxene composition has a significant

effect on the partitioning behavior of elements (McKay et al.

1990; Shearer et al. 1989). Whether pyroxene composition has

an effect on Li and B behavior has not yet been documented.

To understand better the behavior of Li and B in pyroxenes

unaffected by aqueous fluid activity, this study was designed to

examine the effects of changing pyroxene composition, shock

pressure, and thermal metamorphism in anhydrous Apollo 17

and 11 lunar basalts.

SAMPLEDESCRIPTIONS

Apollo 17 Basalt 75035

Sample 75035 is a low-K, high-Ti basalt that was collected

from the Taurus-Littrow Valley along the eastern rim of the

Serenitatis impact basin at Station 5, near Camelot Crater (Fig.

1a). It is a medium-grained, subophitic basalt with subhedral

plagioclase laths (An8089, 0.10.3 mm 1 mm in size, 33%

in modal abundance) that occur in an interlocking network of

anhedral clinopyroxene (CPX) grains (continuously zoned from

early formed augitic to later-formed ferro-pigeonite composi-

tions, 0.250.5 mm in size, 44%) and irregular ilmenite laths

(0.53.0 mm in size, 15%). Anhedral to subhedral cristobalite

(5%), pyroxferroite (2%), and minor (


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CHAKLADER ET AL.: THE BEHAVIOR OF Li AND B IN LUNAR MARE BASALTS 1555

the 0.10200 g bulk sample. The test tube containing the sample was flame sealed

at ~104atm using an oxygen gas torch and a vacuum line equipped with a rotary

vein pump. Liquid nitrogen cooled the test tube during flame sealing to prevent

premature volatilization of the sample. The Apollo 11 basalt was heated for 168

hours at 1000 C, and prepared for imaging and microbeam analyses.

Pyroxenes in all samples initially were documented by back-scattered electron

(BSE) images and X-ray maps using a JEOL JSM-5800 LV scanning electron

microscope (SEM) at the Institute of Meteoritics. The BSE images and X-ray maps

of Si, Ti, Al, Mg, Fe, Mn, Ca, Na, and Cr were made with a 20 nA beam current,

20 kv accelerating potential, and


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by analyzing 9Be at a higher mass resolution (~600). The effect of matrix on Li

and B measurements is discussed in detail in previous works including Ottolini

et al. (1993), Hervig (1996), Herd et al. (2004a, 2005), and Grew et al. (1997).

Secondary ions were detected with an electron multiplier in pulse-counting mode.

All concentrations were calculated from empirical relationships between intensity

ratios against Si [(IX/ISi) SiO2, whereIXis intensity of the trace ion of interest and

ISiis the intensity of Si30]. Concentrations were obtained from well-documented

standards. Accuracy and precision are within approximately 15% for REE data

and within 5% for all other elements.

ANALYTICALRESULTS

Major- and minor-element characteristics of Apollo 17 and

11 pyroxenes

The major- and minor-element zoning characteristics of

pyroxenes from low-Ti basalts have been described exten-

sively elsewhere (Bence et al. 1970, 1971; Bence and Papike

1972). Zoning characteristics of pyroxenes in high-Ti basalts

have been discussed by Papike et al. (1976) and Longhi et al.

(1974). Representative EMP and SIMS analyses of unshocked

pyroxenes from Apollo 17 (75035) and 11 (10017) basalts areshown in Table 1.

The major- and minor-element distribution shows the follow-

ing characteristics. Pyroxenes in 75035 define a single crystalliza-

tion trend of Ca-depletion and Fe-enrichment (Fig. 3a). Samples

do not have hopper crystals, so we interpret crystal cores as early

and rims as relatively late. Most pyroxenes are zoned from augitic

(Wo43En42Fs15) cores to rims with composition of approximately

Wo9En4Fs87. Pyroxferroite is a late-stage mineral and plots at the

end of the pyroxene trajectory. In contrast, pyroxenes in 10017

show a more restricted Ca-depletion, Fe-enrichment trend (Fig.

3b). The very Fe-rich point in Figure 3b appears atypical. In

the present study, ~8.5 times as much major and minor element

data were collected for shocked 10017 pyroxenes relative to

unshocked or heated 10017 pyroxenes. The Fs content across

shocked, unshocked and heated samples is expected to be statis-

tically uniform if additional analyses of unshocked and heated

10017 samples are conducted. The 75035 data represent a more

equal distribution between shocked and unshocked samples and

are characterized by greater uniformity in Fs content. Early 10017

pyroxenes have augitic cores (Wo40En44Fs16) whereas late-stage

rims have a composition of approximately Wo11En21Fs68, and

pyroxferroite does not appear. These zoning trends contrast with

those observed within the low-Ti basalts. For example, pyroxenes

in the Apollo 12 and 15 pigeonite basaltsfirst exhibit an increase

in Ca (with limited Fe-enrichment) followed by an increase in

Fe (with limited variation) in Ca. In part, differences in zoning

between Apollo 12, 15, and 17 pyroxenes are a function of differ-

ences in crystallization sequence with plagioclase crystallization

occurring substantially after pyroxene in the Apollo 12 and 15pigeonite basalts.

Plots of Ti vs. Al + Cr provide insight on the role of octahe-

drally coordinated Cr substitution in addition to that of Ti and Al.

Cores of pyroxene crystals in 75035 have higher Ti and Al+Cr

abundances than their rims (Fig. 4a). No sharp compositional

discontinuities are observed in the trend of 75035 pyroxenes in

Figure 4a. The data define a slope of ~0.49 with a correlation

coefficient of ~0.96. The constant slope indicates early plagio-

clase saturation and concurrent crystallization in which Al must

enter plagioclase as well as pyroxene. Similarly, early pyroxene

FIGURE2.Chart summarizing variation in shock features as a function of pressure (GPa) in Apollo 17 and 11 basalts, based on the observations

of this study and a comprehensive review by Schaal and Hrz (1977).


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FIGURE3.Pyroxene quadrilaterals showing results for (a) unshocked 75035, (b) unshocked 10017, (c) shocked 75035, and (d) shocked and heated

10017 pyroxenes. Early refers to crystallographic cores, and late refers to crystallographic rims. Traverses are approximately 400 m in length.TABLE1A. Representative EMP analyses of unshocked pyroxenes from Apollo 17 and 11 basalts with listed oxide weight percents and cation

totals calculated per 6 O anions

Apollo 17 (75035)Unshocked Apollo 11 (10017)Unshocked

A17-01 A17-02 A17-03 A17-04 A17-05 A11-01 A11-02 A11-03 A11-04 A11-05

SiO2 51.48 51.31 50.19 48.41 45.84 51.32 49.49 51.27 50.28 50.61TiO2 1.59 1.30 1.06 0.82 0.65 1.98 1.87 1.20 1.01 0.67Al2O3 1.77 1.38 1.03 1.03 1.95 2.11 2.09 1.42 1.19 0.79MgO 15.70 15.36 10.90 5.76 3.39 17.03 14.25 13.90 13.01 12.99FeO 11.97 14.90 21.77 31.32 41.24 10.61 14.64 20.74 24.20 28.80MnO 0.25 0.32 0.40 0.53 0.68 0.21 0.25 0.37 0.38 0.47CaO 16.93 15.14 15.15 12.09 6.47 16.54 16.12 11.53 9.69 6.21Na2O 0.09 0.06 0.08 0.03 0.02 0.09 0.06 0.05 0.05 0.04Cr2O3 0.30 0.23 0.15 0.09 0.08 0.59 0.55 0.32 0.37 0.19 Total 100.08 99.99 100.73 100.09 100.32 100.49 99.31 100.80 100.18 100.76Si 1.92 1.93 1.94 1.96 1.92 1.90 1.89 1.95 1.95 1.97Ti 0.04 0.04 0.03 0.03 0.02 0.06 0.05 0.03 0.03 0.02Al 0.08 0.06 0.05 0.05 0.10 0.09 0.09 0.06 0.05 0.04Mg 0.87 0.86 0.63 0.35 0.21 0.94 0.81 0.79 0.75 0.75Fe 0.37 0.47 0.70 1.06 1.44 0.33 0.47 0.66 0.78 0.94Mn 0.01 0.01 0.01 0.02 0.02 0.01 0.01 0.01 0.01 0.02Ca 0.68 0.61 0.63 0.52 0.29 0.66 0.66 0.47 0.40 0.26Na 0.01 0.00 0.01 0.00 0.00 0.01 0.00 0.00 0.00 0.00Cr 0.01 0.01 0.00 0.00 0.00 0.02 0.02 0.01 0.01 0.01 Total 3.99 4.00 4 .00 3.99 4.01 4.00 4.00 3.98 3.99 3.99

TABLE1B.Distribution of cations across the Tetrahedral, M1, and M2 pyroxene sites for the same EMP analyses

Tetrahedral Site M1 Site M2 Site

Si Al Total Al Mg Cr Ti Mn Fe Total Fe Mn Mg Ca Na Total

A17-01 1.92 0.08 2.00 0.00 0.87 0.01 0.04 0.01 0.06 1.00 0.31 0.00 0.00 0.68 0.01 0.99A17-02 1.93 0.06 2.00 0.00 0.86 0.01 0.04 0.01 0.08 1.00 0.39 0.00 0.00 0.61 0.00 1.00A17-03 1.94 0.05 1.99 0.00 0.63 0.00 0.03 0.01 0.32 1.00 0.38 0.00 0.00 0.63 0.01 1.02A17-04 1.96 0.04 2.00 0.01 0.35 0.00 0.03 0.02 0.60 1.00 0.46 0.00 0.00 0.52 0.00 0.99A17-05 1.92 0.08 2.00 0.02 0.21 0.00 0.02 0.02 0.73 1.00 0.72 0.00 0.00 0.29 0.00 1.01A11-01 1.90 0.09 1.99 0.00 0.93 0.02 0.06 0.00 0.00 1.00 0.33 0.01 0.01 0.66 0.01 1.01A11-02 1.89 0.09 1.98 0.00 0.81 0.02 0.05 0.01 0.11 1.00 0.36 0.00 0.00 0.66 0.01 1.02

A11-03 1.95 0.05 2.00 0.01 0.79 0.01 0.03 0.01 0.15 1.00 0.51 0.00 0.00 0.47 0.00 0.98A11-04 1.95 0.05 2.00 0.00 0.75 0.01 0.03 0.01 0.20 1.00 0.59 0.00 0.00 0.40 0.00 0.99A11-05 1.97 0.03 2.00 0.00 0.75 0.01 0.02 0.02 0.20 1.00 0.73 0.00 0.00 0.26 0.00 0.99

TABLE1C.Representative SIMS analyses of unshocked pyroxenes from Apollo 17 and 11 basalts

Apollo 17 (75035)Unshocked Apollo 11 (10017)Unshocked

A17-01 A17-02 A17-03 A17-04 A17-05 A11-01 A11-02 A11-03 A11-04 A11-05

Li (ppm) 8.1 8.4 6.3 4.7 4.2 14.0 14.8 14.8 11.4 13.1B (ppm) 0.6 0.8 0.3 0.4 0.2 7.1 6.4 3.9 2.9 2.0Ce (ppm) 2.1 2.4 3.0 6.1 7.5 5.1 5.9 19.1 28.3 86.2Yb (ppm) 6.2 7.0 6.4 23.7 44.8 5.9 6.8 18.2 22.5 50.8Li/Yb 1.3 1.2 1.0 0.2 0.1 2.4 2.2 0.8 0.5 0.3B/Ce 0.3 0.3 0.1 0.1 0.0 1.4 1.1 0.2 0.1 0.0

Note:Trace elements were measured at the same spots as major and minor elements but with a larger beam diameter (10 m vs.


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in 10017 has higher Ti and Al+Cr values with respect to their rims

(Fig. 4b). Apollo 11 pyroxenes also show no sharp discontinuities

in their trend, and the constant slope of ~0.46 with a correlation

coefficient of ~0.89 also indicates early plagioclase saturation

and concurrent crystallization. Thus, Ti and Al behavior reflect

co-crystallization of plagioclase and pyroxene in both Apollo

17 and 11 basalts. This is not in agreement with the Apollo 11

crystallization sequence proposed by Bence and Papike (1972),

in which plagioclase crystallizes later. Additionally, the constant

slopes on plots of Ti vs. Al+Cr for pyroxenes from Apollo 17 and

11 high Ti basalts also contrast with slopes for analogous data

for pyroxenes from low-Ti basalts. For example, pyroxenes in

the Apollo 12 and 15 pigeonite basalts show a sharp change in

slope in Ti/Al from

0.25 to

0.5 (Bence and Papike 1972). Thisdiscontinuity reflects the onset of plagioclase crystallization and

is not seen in the high-Ti basalts where early plagioclase growth

was concurrent with that of pyroxene.

The trends on the pyroxene quadrilateral diagrams illustrate

that the properties of Wo-En-Fs components do not vary with

changes in shock pressure or thermal metamorphism for Apollo

17 and 11 pyroxenes (Figs. 3c and 3d). Given the significantly

greater number of analyses of shocked proxenes compared with

unshocked or heated proxenes, the apparent differences in Fs

content in 10017 pyroxenes are attributed to non-representative

sampling. Additionally, no significant change is seen in Ti or Al

+ Cr with changes in shock pressure or thermal metamorphism

(Fig. 4). However, heated pyroxenes have higher Na2O contents

(by ~15%) than unheated pyroxenes in the Apollo 11 basalt,

which likely reflects thermally driven Na redistribution between

pyroxenes and surrounding phases.

Trace-element characteristics of Apollo 17 and 11 pyroxenes

Within the Ca-depletion and Fe-enrichment trajectory for

pyroxenes in 75035, the concentrations of incompatible trace

elements, such as Ce, a light rare-earth element (REE), and Yb, a

heavy REE, increase from cores to rims. The partition coefficients

of REE in pyroxenes are dependent on Ca content, which expands

the distance between Si tetrahedra in pyroxenes and facilitates

partitioning of REE into the M2 site (Shearer et al. 1989). As Ca

contents decrease in pyroxenes, REE contents are expected to

decrease as well. The observation that Ca decreases with increas-

ing REE toward pyroxene rims implies that REE concentrations

in melt increased strongly enough to overcome the decrease

of REE partition coefficients. Increasing Ce and Yb contents

from pyroxene cores to rims is consistent with experimentally

determined partition coefficients for Ce and Yb between CPX

and basaltic melt of about 0.06 and 0.3, respectively (McKay

et al. 1990). Similar Ce and Yb increases are seen in the late-

stage rims of pyroxenes in 10017. These observations are also

consistent with late-stage Ce and Yb increases in pyroxenes from

the Apollo 12 and 15 low Ti basalts (Shearer et al. 1989). Both

Ce and Yb occur in greater abundance in Apollo 11 pyroxenes

compared to Apollo 17 pyroxenes. In part, this may reflect dif-

ferences in the overall Ce and Yb abundances in the bulk 75035

and 10017 basalts.

Although Li generally behaves as an incompatible element

in pyroxenes (with the exception of spodumene, LiAlSi2O6) and

has an average experimentally determined partition coeffi

cientof ~0.2, similar to that of Yb, Li distribution is unique in the

pyroxenes of this study (Brenan et al. 1998; Herd et al. 2002).

Lithium depletions are observed in late-stage, Yb-rich rims rela-

tive to early formed, Yb-poor cores of Apollo 17 pyroxenes (Fig.

5a). In contrast, Apollo 11 pyroxenes exhibit relatively constant

Li values from their cores to their rims (Fig. 5b).

Lithium distribution varies with compositional changes in

75035 pyroxenes. Low Li abundances correspond to regions of

high Fe, low Ca, and low octahedrally coordinated Cr3+in Apollo

17 pyroxenes (Fig. 6). In contrast, Apollo 11 pyroxenes show no

correlations between Li and Fe, Ca, or octahedrally coordinated

Cr3+. Boron depletions occur in rims relative to cores in both

75035 and 10017 pyroxenes (Fig. 7).

Trace-element behavior does not appear to be affected byshock pressure. However, experimentally heated pyroxenes

in 10017 are characterized by greater Li contents and lower B

contents than unheated pyroxenes. Boron contents in plagioclase

range from 0.4 to 0.7 ppm and are less than or equal to those of

pyroxene. Plagioclase that surrounds pyroxene has about 2 5

the Li content of pyroxenes, ranging from 18 to 20 ppm. In ad-

dition to pyroxferroite, plagioclase, and oxides, the mesostasis

of the lunar basalts contain basaltic glass and Si-rich glass, both

of which exhibit up to 50 the Li and B contents of pyroxenes,

ranging from 35 to 55 ppm Li and 25 to 60 ppm B.

y = x

y = 0.5x

y = 0.4916x

R2= 0.9579

0

0.05

0.1

0.15

0.2

0.25

0.3

0 0.05 0.1 0.15 0.2 0.25 0.3

[(Al+Cr)/Cation Sum]*4

[Ti/Catio

nSum]*4

y = x

y = 0.5x

y = 0.4572x

R2= 0.8941

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 0.1 0.2 0.3 0.4

[(Al+Cr)/Cation Sum]*4

(Ti/Catio

nSum)*4

(A)

(B)

Late

Early

Early

Late

75035 Pyroxenes

10017 Pyroxenes

y = 0.49xR

2= 0.96

y = 0.46xR

2= 0.89

FIGURE 4. Plots of Ti vs. (Al + Cr), normalized to cation sum

for (a) Apollo 17 pyroxenes and (b) Apollo 11 pyroxenes. Symbols

are identical to those used in Figure 3. Early to late distinctions are

based on the decreasing Ca and increasing Fe trends observed in the

pyroxene quadrilaterals of Figure 3. Traverses are approximately 400

m in length.


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DISCUSSION

Crystal chemistry of Li and B in pyroxene

The pyroxene structure has been described comprehensively

in previous works (Deer et al. 1992; Cameron and Papike 1981).

Cation partitioning into the tetrahedral, octahedral (M1), and

polyhedral (M2) sites of pyroxenes occurs through a balance

of charge and ionic radius (Fig. 8). Substitution of minor ele-

mentsincluding Ti, Cr, and Alinto the pyroxene structure

has been documented previously by Bence at al. (1970), Papike(1980), and Robinson (1980), whereas Shearer et al. (1989)

discussed potential substitution mechanisms for selected trace

elements.

The distribution of Ti, Cr, and Al in pyroxenes in 75035 and

10017 reflects magmatic changes during basalt crystallization

and has not been disturbed through shock or heating events (Fig.

4). Pyroxenes from both basalts have a slope of ~ on plots of

Ti vs. Al + Cr cations per six oxygen anions, thus [VI(Ti4+)+ 2

IV(Al3+)] [VI(R2+)+ IV2Si] was the dominant mechanism for

Al and Ti substitution. Negative deviations from the slope

FIGURE5.Plots ofLi (ppm) vs. Li/Yb for pyroxenes from (a) Apollo

17 and (b) Apollo 11 basalts. Symbols are identical to those used in

Figure 3. Early to late distinctions are based on the decreasing Ca and

increasing Fe trends observed in the pyroxene quadrilaterals of Figure3. Apollo 17 pyroxenes display greater extents of core-to-rim decreases

in Ca and increases in Fe, compared to Apollo 11 pyroxenes. Traverses

are approximately 400 m in length.

FIGURE6. Plot ofoctahedrally coordinated Cr3+vs. Li (ppm) for

pyroxenes from Apollo 17 basalt. Symbols are identical to those used

in Figure 3. Early to late distinctions are based on the decreasing Ca and

increasing Fe trends observed in the pyroxene quadrilaterals of Figures

3a and 3c. Traverses are approximately 400 m in length.

FIGURE7. Plots ofB (ppm) vs. B/Ce for pyroxenes from (a) Apollo 17

(75035) and (b) Apollo 11 (10017) basalts. Symbols are identical to those

used in Figure 3. Early to late distinctions are based on the decreasing

Ca and increasing Fe trends observed in the pyroxene quadrilaterals of

Figure 3. Traverses are approximately 400 m in length.


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imply incorporation of Cr through [VI(Cr3+)+ IV(Al3+)][VI(R2+)

+ IVSi] into pyroxenes. Alternatively, Al may have partitioned

into pyroxenes through [VI(Al3+)+ IV(Al3+)] [VI(R2+)+ IVSi].

Slopes of unity and represent 100% incorporation of Ti3+or

Ti4+, respectively in Figure 4. Positive deviations from a slope

of 1/2 have been interpreted as indicating the presence of a

minor Ti3+ component through [VI(Ti3+)+ IV(Al3+)] [VI(R2+)+IVSi] in Apollo 17 and 11 pyroxenes, which is consistent with

the low oxygen fugacity in which these basalts crystallized, as

well as the general lack of Fe3+in lunar minerals (Papike et al.

1998). Late-stage decreases in Ti content of pyroxenes may

reflect the appearance of ilmenite on the liquidus (Stimac and

Hickmott 1994).

As is the case for Ti, Cr, and Al, the partitioning behavior of

the REE and Li1+(0.076 nm ionic radius) into the M2-site and

B3+(0.011 nm ionic radius) into the tetrahedral site of pyroxenes

requires charge balancing and will be influenced by the avail-

ability of cations suitable for coupled substitutions (Fig. 8; Bloss

1994; Deer et al. 1992; Shearer et al. 1989). Trivalent REE, such

as Ce and Yb, occur in pyroxenes as M2(REE)3+M1R2+IV(Si,Al)O6,

where R2+is Fe or Mg (Shearer et al. 1989). Lithium (M2) may

couple with trivalent Al (M1) through [VI(Li1+)+ VI(Al3+)][2

VI(R2+)] or Cr (M1) through [VI(Li1+)+ VI(Cr3+)] [2VI(R2+)],

whereas B (tetrahedral) may couple with Al (M1) through [IV(B3+)

+ VI(Al3+)][VI(R2+)+ IVSi] during substitution.

Partitioning of Li is correlated with that of Cr in Apollo 17

pyroxenes (Fig. 6). Depletions in Li occur in late-stage rims,

which also exhibit depletions in Cr. These observations may

reflect the possibility that Li1+ (M2) and Cr3+ (M1) substitute

together into pyroxene through [VI(Li1+)+ VI(Cr3+)][VI2(R2+)].

With the appearance of spinel on the liquidus, partitioning of Cr3+

into the M1 site may be inhibited. Consequently, Li may lose

its coupled cation and may not be incorporated into late-stage

pyroxene rims as efficiently as in early cores.

Previous experimental work determined partition coefficients

(D-values) for the volatile elements, Li and B, between CPX and

basaltic melt (Brenan et al. 1998; Herd et al. 2002). D-values

average 0.2 and 0.02 for Li and B, respectively. As CPX crystals

grow in a closed basaltic system, concentrations of Li and B in

the melt increase. During final stages of pyroxene crystalliza-

tion, higher abundances of Li and B in the residual melt result in

higher concentrations of these elements in CPX. Thus, analyses

of pyroxene are expected to show increasing Li and B concentra-

tions from cores to rims (McSween et al. 2001). This behavior is

similar to that of other non-volatile, incompatible elements. The

D-value for Li closely matches that of Yb, whereas theD-value

for B is similar to that of Ce (McKay et al. 1990).

However, Li and B behavior does not resemble that of Yb

and Ce in pyroxenes of this study. Figure 5 compares Li (ppm)

against Li/Yb for pyroxenes from the Apollo 17 and 11 basalts.

Ytterbium behaves incompatibly, and its concentration increases

toward crystal rims. With increasing Yb contents, Li/Yb ratios

decrease such that rims are characterized by lower Li/Yb values

than cores. Figure 5a demonstrates that clear Li depletions (on

the order of ~10 ppm) exist in rims relative to cores in Apollo

17 pyroxenes. In comparison, B is lower in pyroxene rims rela-

tive to cores in both basalts by ~16 ppm, as shown in Figure 7,

which plots B (ppm) against B/Ce for pyroxenes from the Apollo

17 and 11 basalts. Cerium behaves incompatibly, increasing in

amount toward rims. Thus, Li and B do not correlate with REE

abundances, indicating that these elements are not behaving in

a manner predicted from measured Li, B, and REE partition

coefficients between CPX and basaltic melt.

Experimental studies on Li and B partitioning have yielded

FIGURE8. Plot of pyroxene crystallographic sites and associated cations (Shannon and Prewitt 1969). Despite the similarity in experimentally

determined partition coefficients between Li and Yb, mechanisms of Li incorporation into pyroxenes from basaltic melt are very different from

those of Yb, due largely to contrasts between ionic radii and valence. Ionic radii contrasts are particularly noteworthy for B and Ce, which also

have similar experimentally determinedD-values between pyroxene and basaltic melt.


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conflicting results. Herd et al. (2004b) suggested that the parti-

tion coefficients for Li and B between pyroxene and anhydrous

basaltic melt are not influenced by changing Ca (M2) or Al (tetra-

hedral, M1) contents of pyroxenes. However, Herd et al. (2004b)

did not study the effects of either Cr or Fe enrichment. Brenan et

al. (1998) examined the influence of changing CPX composition

on partitioning of Li and B between CPX and aqueousfluid. Their

results show that Li and B partitioning into aqueous fluid relative

to CPX decreases with decreasing Al/Si ratios in CPX (Brenan

et al. 1998). It is possible that D-values of trace elements vary

with the availability of coupled cations during substitution. For

the Apollo 17 basalt, Li couples with Cr during partitioning into

pyroxenes. During early stages of pyroxene growth, DLimay

approach unity with ready availability of Cr. Subsequently,DLi

decreases with decreasing magmatic Cr in 75035 pyroxenes.

The present study contends that coupled substitution can play a

significant role within the realm of Henrys law behavior.

Lithium-chromium coupling is seen in Apollo 17 pyroxenes

(Fig. 6), and Li partitioning into the M2-site of pyroxene is in-

fluenced by the availability of Cr, which enters the M1-site. The

REE partition into the M2-site coupled with divalent M1 cations,

typically Fe and Mg. Boron partitions into the tetrahedral site

with the octahedrally coordinated M1 cation, Al. However, such

coupled substitution was not observed and is not a satisfactory

explanation for late-stage B decreases in pyroxenes. Coupled sub-

stitution during early crystallization would have to increaseDB

between pyroxene and basaltic melt by two orders of magnitude

(from 0.02 to unity) for B to behave as a compatible element,

then decrease with diminishing Al availability during late-stages

of crystallization (Herd et al. 2004b). Such a dramatic increase

inDBwith Al has not been observed in previous experimental

studies (Herd et al. 2004b).

Abundances of incompatible element pairs with similar parti-

tion coeffi

cients in pyroxenes, such as Li-Yb and B-Ce, shouldincrease from cores to rims. However, contents of Li in the Apollo

17 basalt and B in both basalts decrease at rims of unshocked

pyroxenes. The depletion trends of Li and B in pyroxenes from

these lunar basalts are consistent with observations of McSween

et al. (2001) and Lentz et al. (2001) on pyroxenes from martian

basalts. Extrapolating the interpretations of McSween et al.

(2001) and Lentz et al. (2001), pyroxenes from high-Ti lunar

mare basalts would have had to exsolve greater than 4 wt%

magmatic water to achieve such Li and B depletions. However,

given the completely anhydrous nature of the lunar basalts,

alternative explanations are necessary.

Li and B partitioning into a volatile phase

As shown above, Li is infl

uenced more than B by changingpyroxene composition during crystallization of lunar basalts.

However, it is possible that partitioning into volatile phases also

may give rise to late-stage decreases. Analyses of pyroxenes from

several martian meteorites (QUE 94201, NWA 480, Shergotty,

Zagami) show that earlier-formed, augitic cores have higher Li

and B contents than later-formed rims of pigeonite composition

(McSween et al. 2001; Lentz et al. 2001, 2004; Beck et al. 2004).

This decrease in Li and B toward later-formed regions of py-

roxenes has been interpreted as indicating loss of several weight

percent magmatic water from mantle-derived, highly evolved

melt during crystallization (McSween et al. 2001; Lentz et al.

2001, 2004; Beck et al. 2004). Although lunar basalts have no

water, they do have vugs and vesicles, indicative of CO (Fogel

and Rutherford 1995; Weitz et al. 1999).

Recent analyses of Apollo 17 orange volcanic glasses suggest

that oxidation of C and reduction of multivalent cations, such as

Fe and Cr, likely formed CO that drove fire fountaining (Weitz et

al. 1999). Although experimental work on the partitioning of Li

and B between basalts and CO is lacking, observations of Li and

B volatility during gas-charged lunarfire-fountaining have been

discussed (Delano 1986; Meyer and Schonfeld 1977; Shearer et

al. 1994). Loss of volatile elements, such as S, during eruption has

been documented (e.g., Shearer et al. 1994). Delano (1986) and

Meyer and Schonfeld (1977) have suggested that B also may have

been lost during eruption. Alternatively, although S is depleted in

glasses relative to crystalline mare basalts, Li/Be and B/Be ratios

between the two are similar (Shearer et al. 1994). In fact, Li is

somewhat more enriched in some fire-fountain glasses relative

to crystalline mare basalts at the same Be content, whereas some

loss of B has been documented (Shearer et al. 1994). Significant

loss of Li to a volatile (gaseous) phase has not been inferred for

lunar fire-fountain glasses, and therefore may not have been an

important process in lunar basalt evolution. The observation from

the present study, that experimentally heated pyroxenes have

lower B contents than unheated pyroxenes, may lend support to

gas-phase losses of B during eruption. However, the extent of

such B loss has yet to be examined in detail.

Trace element behavior during shock

Shock effects in martian meteorites have been described in

detail by Stffler et al. (1986), and include complete transforma-

tion of plagioclase to diaplectic glass (maskelynite), formation

of planar deformation features, and mechanical twinning and

fi

ne-grained crystalline textures following localized melting atgrain boundaries.

The results of shock-recovery experiments on hydrous miner-

als suggest that variation in shock pressure influences the extent

of water mobility and dehydration (Boslough et al. 1980). Also,

recent work suggests that water-poor amphibole found in martian

meteorites did not crystallize at depth as a primary phase but

instead formed by impact at pressures ranging from 38 to 50 GPa

(Monkawa et al. 2003). Furthermore, during a series of heating

experiments on shocked lunar basalts, significant redistribution

and loss of volatile elements, such as Rb, was observed in pla-

gioclase and pyroxene mineral separates (Nyquist et al. 1991a).

Although workers have attributed volatile-element depletions in

pyroxene rims to outgassing-induced water loss on Mars, Li and

B rim depletions have been observed predominantly in basalticShergottites that show pervasive shock features in pyroxenes and

plagioclase (McSween et al. 2001; Lentz et al. 2001, 2004; Beck

et al. 2004). In contrast, the relatively unshocked Nakhlites do

not show extensive Li and B rim depletions.

The results of this study suggest that shock does not in-

duce loss and redistribution of volatile elements in pyroxenes,

plagioclase, or glass. As shown in Figure 3, pyroxene major-

element compositions are not affected by shock pressure. Also,

pyroxenes exhibit no loss or redistribution of Li or B. Sodium,

Li, and B contents in plagioclase remain the same in shocked


10/12


and unshocked basalts. Mesostasis, although remelted at high

pressure, does not appear to have lost Li and B. The textural and

petrographic observations of shocked samples in this study are

consistent with those from previous work and illustrate that shock

pressures generate mechanical defects, microfracturing, and

deformation in pyroxenes (Schaal and Hrz 1977; Kieffer et al.

1976). Such mechanical distortions of pyroxenes may facilitate

the redistribution of Li and B during subsequent shock-associated

thermal metamorphism.

Trace-element behavior during shock-associated thermal

metamorphism

Thorough discussions of diffusion mechanisms operational

during shock and thermal metamorphism are provided in Freer

(1981) and Manning (1974). Pyroxenes from all basalts that un-

derwent thermal metamorphism in the laboratory have increased

Li and Na contents relative to pyroxenes from unheated samples.

Plagioclase has 25the Li content and 100the Na concen-

tration of pyroxenes. Therefore, plagioclase may have been a

Li and Na contributor. Additionally, mesostasis surrounding

pyroxene has up to 50the Li content of pyroxenes. Mesostasis

may have re-melted during heating experiments and may be the

source for heightened Li contents in thermally metamorphosed

pyroxenes. The solidus temperature for high-Ti basalts exceeds

1100 C (Longhi 1992), whereas the heating experiments of this

study were conducted at 1000 C. The presence of even small

amounts of melt offers volatile elements like Li a free surface and

direction of rapid melt-mineral diffusion (Freer 1981). Recent

experimental work demonstrates that Li diffusivity in molten

silicates is extraordinarily high, with a diffusion coefficient (8

105cm2/s), similar to these of dissolved molecular water and

He at 7 105cm2/s and 5 105cm2/s, respectively (Richter

et al. 2003).

Experimentally heated pyroxenes show lower B contents thanunheated pyroxenes. Because mesostasis contains up to 50 the

B content of pyroxenes, it is not a likely sink for B lost from

heated pyroxenes. Plagioclase grains surrounding pyroxenes in

the heated sample show no increases in B content relative to

unheated samples and also are not viable sinks. It is possible that

B diffused into surrounding regions that were not analyzed. Con-

versely, efficient loss of B may suggest that the Apollo 11 basalt

behaved as an open system during heating. However, zones of

mesostasis do not show significant loss of B with heating. The re-

sults of this work demonstrate that the gradual diffusion effects of

thermal metamorphism are more significant than the immediate

effects of shock pressure in redistributing Li and B in anhydrous

basaltic pyroxenes. However, the textural variations caused by

shock likely facilitate the process of high-temperature Li and Bdiffusion between pyroxenes and surrounding phases.

Relevance to Li and B zoning in martian basalts

Analyses of pyroxenes from several martian meteorites

(QUE 94201, NWA 480, Shergotty, Zagami) show that Li and B

contents generally decrease from cores to rims (McSween et al.

2001; Lentz et al. 2001, 2004; Beck et al. 2004). The majority

of late-stage pigeonite rims of these pyroxenes exhibit extensive

Fe-enrichment (up to 30 wt% FeO) similar to those of pyroxenes

from lunar mare basalt 75035. Martian basalts with late-stage Li

and B decreases in pyroxene rims all contain pyroxferroite. Late-

stage Apollo 17 pyroxene also has significant Li and B decreases,

and pyroxferroite is present. The formation and breakdown of

pyroxferroite requires a net loss of Ca, during which Li loss also

may occur. Pyroxenes from the Apollo 11 basalt are more similar

to the majority of pyroxenes from Nakhla, in which late-stage Fe-

enrichments are not as extensive as those in 75035, QUE 94201,

NWA 480, Shergotty, and Zagami. No late-stage pyroxferroite or

Li decreases are observed in the Apollo 11 or Nakhla basalts. An

additional control on Li distribution could be Fe3+, which occurs

in martian pyroxenes. Karner et al. (2006) estimated that the

Fe3+/(Fe3++ Fe2+) in martian pyroxenes ranged up to 3%. Dyar

and Delaney (2000) estimated that this ratio could be as high as

20%. In either case, a coupled substitution involving trivalent

Fe and Li could be important. Until Fe3+variations in pyroxene

are systematically compared to those of Li, this relationship

cannot be confirmed.

CONCLUDINGREMARKS

McSween et al. (2001) and Lentz et al. (2001) suggested

that Li and B depletions in later-formed regions of pyroxenes

reflect the loss of several weight percent magmatic water during

crystallization and eruption of martian basalts. The results of the

present work show that clear Li and B depletions also occur in

later-formed regions of pyroxenes from anhydrous lunar mare

basalts. Thus, mechanisms other than fluid processes can give

rise to Li and B depletions in pyroxenes. Possible magmatic

processes that can cause Li and B decreases in the Apollo 17

and 11 pyroxenes of this study are mentioned below and sum-

marized in Figure 9. The availability of a cation-couple during

substitution can influence the compatibility of an element during

crystallization (e.g., octahedrally coordinated M2-Cr3+for M1-

Li in pyroxenes). Cation compatibility may also be influenced

by changes in mineral composition. Lithium concentrationsdecrease in pyroxenes with extreme Fe enrichment. Such high

Fe contents permit the formation of metastable pyroxferroite.

During pyroxferroite breakdown, a net loss of Ca is structurally

FIGURE9. Summary of magmatic processes that can give rise to

late-stage Li and B decreases in Apollo 17 and 11 pyroxene rim.


11/12


required and Li may be excluded in the process. Alternatively,

DLiduring pyroxene crystallization may exceedDLiduring py-

roxferroite crystallization. Volatile loss from lunar basalts into

CO during gas-charged fire-fountaining appears unlikely to in-

fluence Li but may affect B; pyroclastic glasses have somewhat

lower bulk B-contents than crystalline mare basalts (Shearer

et al. 1994). Additionally, experimentally heated pyroxenes in

this study exhibit lower B contents and higher Li contents than

unheated ones. Open-system loss and closed-system redistribu-

tion through interactions between pyroxenes and surrounding

zones of plagioclase and mesostasis have likely occurred during

heating in the laboratory. Although high shock pressures do not

redistribute Li or B in pyroxenes, shock likely facilitates later

thermal diffusion processes through the introduction of mechani-

cal defects in grains.

ACKNOWLEDGMENTSThanks go to Mike Spilde and Jana Berlin for assistance with EMP analyses,

to Dave Draper, Rhian Jones, Zachary Sharp, and Abdul-Mehdi Ali for assistancewith experimental set-up and sample preparation, and to Dave Vaniman, SteveSimon, and Kevin Righter for their diligent reviews. This research was partially

supported by the Institute of Meteoritics and NASA Mars Fundamental Researchgrant no. NAG5-12783 to C. K. Shearer. Lunar thin sections and bulk sampleswere provided by the NASA Johnson Space Center, where shock experimentswere carried out by Fred Hrz.

REFERENCESCITEDBeck, P., Barrat, J.-A., Chaussidon, M., Gillet, P. and Bohn, M. (2004) Li isotopic

composition of the NWA 480 Shergottite. Lunar and Planetary Science XXXV,Abstract no. 1509.

Bence, A.E. and Papike, J.J. (1972) Pyroxenes as recorders of lunar basalt petro-genesis: chemical trends due to crystal-liquid interaction. Proceedings of the3rdLunar Science Conference, Geochimica et Cosmochimica Acta, Supplement3, p. 431469. MIT Press, Cambridge, Massachusetts.

Bence, A.E., Papike, J.J., and Prewitt, C.T. (1970) Apollo 12 clinopyroxenes:chemical trends. Earth and Planetary Science Letters, 8, 393399.

Bence, A.E., Papike, J.J., and Lindsley, D.H. (1971) Crystallization histories ofclinopyroxenes in two porphyritic rocks from Oceanus Procellarum. Proceed-ings of the 2ndLunar Science Conference, Geochimica et Cosmochimica Acta,

Supplement 2, p. 559574. MIT Press, Cambridge, Massachusetts.Bloss, F.D. (1994) Crystallography and crystal chemistry, 545 p. Mineralogical

Society of America, Chantilly, Virginia.Boslough, M.B., Weldon, R.J., and Ahrens, T.J. (1980) Impact-induced water loss

from serpentine, nontronite and kernite. Proceedings of the 11 thLunar andPlanetary Science Conference, p. 21452158.

Brenan, J.M., Ryerson, F.J., and Shaw, H.F. (1998) The role of aqueous fluids in theslab-to-mantle transfer of boron, beryllium, and lithium during subduction: ex-periments and models. Geochimica et Cosmochimica Acta, 62, 33373347.

Cameron, M. and Papike, J. J. (1981) Structural and chemical variations in pyrox-enes. American Mineralogist, 66, 150.

Dann, J.C., Holzheid, A.H., Grove, T.L., and McSween, H.Y. (2001) Phase equi-libria of the Shergotty meteorite: constraints on pre-eruptive water contentsof martian magmas and fractional crystallization under hydrous conditions.Meteoritics and Planetary Science, 36, 793806.

Deer, W.A., Howie, R.A., and Zussman, J. (1992) An introduction to the rock form-ing minerals, 2ndedition, 696 p. Pearson Education Ltd., England.

Delano, J.W. (1986) Pristine lunar glasses; criteria, data, and implications. Journalof Geophysical Research B, 91, D201D213.

Dyar, M.D. and Delaney, J.S. (2000) Correction of the calibration of ferric/ferrousdeterminations in pyroxene from martian samples and achondritic meteoritesby synchrotron microXANES spectroscopy. Proceedings of the 31st AnnualLunar and Planetary Science Conference, abstract no. 1981.

Fogel, R.A. and Rutherford, M.J. (1995) Magmatic volatiles in primitive lunarglasses: I. FTIR and EPMA analyses of Apollo 15 green and yellow glassesand revision of the volatile-assisted fire-fountain theory. Geochimica et Cos-mochimica Acta, 59, 201.

Foley, C.N., Economou, T.E., and Clayton, R.N. (2003a) Final chemical results fromthe Mars Pathfinder alpha proton X-ray spectrometer. Journal of GeophysicalResearch, 108, 37-137-21.

Foley, C.N., Economou, T.E., Clayton, R.N., and Dietrich, W. (2003b) Calibrationof the Mars Pathfinder alpha proton X-ray spectrometer. Journal of GeophysicalResearch, 108, 36-136-22.

Freer, R. (1981) Diffusion in silicate minerals and glasses: a data digest and guideto the literature. Contributions to Mineralogy and Petrology, 76, 440454.

Fritz, J., Greshake, A., and Stffler, D. (2003) Launch conditions for Martianmeteorites: plagioclase as a shock pressure barometer. Lunar and PlanetaryScience XXXIV, abstract no. 1335.

Grew, E.S., McGee, J.J., Yates, M.G., Peacor, D.R., Rouse, R.C., Huijsmans,J.P.P., Shearer, C.K., Wiedenbeck, M., Thost, D.E., and Su, S.-C. (1997)Boralsilite: A new borosilicate mineral intermediate between sillimanite and

the alumino-borate Al4B2O9 and its paragenesis in pegmatites. AmericanMineralogist, 83, 638651.

Herd, C.D.K., Treiman, A.H., McKay, G.A., and Shearer, C.K. (2002) Implicationsof experimental lithium and boron partition coefficients for the petrogenesisof Martian basalts. 65thAnnual Meteoritical Society Meeting, Abstract no.5086.

Herd, C., Trieman, A., McKay, G., and Shearer, C.K. (2004a) Experimentalstudies of LLE partitioning in basaltic systems. American Mineralogist, 89,832840.

Herd, C.D.K, Treiman, A.H., McKay, G.A., and Shearer, C.K. (2004b) The behaviorof Li and B during planetary basalt crystallization. American Mineralogist,89, 832840.

Herd, C.D.K., Treiman, A.H., McKay, G.A. and Shearer, C.K. (2005). Light litho-phile elements in martian basalts: Evaluating the evidence for magmatic waterdegassing. Geochimica et Cosmochimica Acta, 69, 24312440.

Hervig, R.L. (1996) Analyses of geological materials for boron by secondary ionmass spectrometry. In L.M. Anovitz and E.S. Grew, Eds., Boron: Mineral-ogy, Petrology and Geochemistry, 33, p. 789802. Reviews in Mineralogy,Mineralogical Society of America, Chantilly, Virginia.

Hess, P. (1989) Origins of Igneous Rocks, 336 p. Harvard University Press,Cambridge, Massachusetts.

Huber, C. and Wchterschuser, G. (1998) Peptides by activation of amino acidswith CO on (Ni,Fe)S surfaces: implications for the origin of life. Science, NewSeries, 281(5377), p. 670672.

Johnson, M.C., Rutherford, M.J., and Hess, P.C. (1991) Chassigny petrogenesis:melt compositions, intensive parameters, and water contents of Martian (?)magmas. Geochimica et Cosmochimica Acta, 55, 349366.

Karner, J.M., Papike, J.J., and Shearer, C.K. (2006) Comparative planetarymineralogy: Pyroxene major- and minor-element chemistry and partition-ing of vanadium between pyroxene and melt in planetary basalts. AmericanMineralogist, 91, 15741582.

Kieffer, S.W., Schaal, R.B., Gibbons, R., Hrz, F., Milton, D.J., and Dube, A.(1976) Shocked basalt from Lonar Impact Crater, India, and experimentalanalogues. Proceedings of the 7thLunar and Planetary Science Conference,p. 13911412.

Langenhorst, F., Stffler, D., and Klein, D. (1991) Shock metamorphism of theZagami achondrite. Lunar and Planetary Science XXII, p. 779780.

Lentz, R.C.F., McSween, H.Y., Ryan, J.G. and Riciputi, L.R. (2001) Water in Mar-

tian magmas: clues from light lithophile elements in Shergottite and Nakhlitepyroxenes. Geochimica et Cosmochimica Acta, 65, 45514565.

Lentz, R.C.F., McSween, H.Y., and Fayek, M. (2004) Light lithophile abundancesand isotopic ratios in Shergottites. Lunar and Planetary Science XXXV, ab-stract no. 1633.

Longhi, J. (1992) Experimental petrology and petrogenesis of mare volcanics.Geochimica et Cosmochimica Acta, 56, 22352251.

Longhi, J., Walker, D., Grove, T.L., Stolper, E.M., and Hays, J.F. (1974) The petrol-ogy of the Apollo 17 mare basalts. Proceedings of the 5 thLunar and PlanetaryScience Conference, pp. 447469.

Manning, J.R. (1974) Diffusion kinetics and mechanisms in simple crystal s. Carn-egie Institution of Washington Publication, no. 634, Geochemical transportand kinetics, pp. 313.

McKay, G.A., Wagstaff, J., and Le, L. (1990) REE distribution coefficients forpigeonite; constraints on the origin of the mare basalt europium anomaly.Lunar and Planetary Science XXI, pp. 773774.

McSween, H.Y. and Harvey, R.P. (1993) Outgassed water on Mars: Constraintsfrom melt inclusions in SNC meteorites. Science, 259, 18901892.

McSween, H.Y., Grove, T.L., Lentz, R.C.F., Dann, J.C., Holzheid, A.H., Riciputi,

L.R., and Ryan, J.G. (2001) Geochemical evidence for magmatic water withinMars from pyroxenes in the Shergotty meteorite. Nature, 409, 487490.

McSween, H.Y., Grove, T.L., and Wyatt, M.B. (2003) Basalt versus andesite in theMartian crust: New geochemical perspectives. Lunar and Planetary ScienceXXXIV, abstract no. 1189.

Meyer, C., Jr. and Schonfeld, E. (1977) Ion microprobe study of glass particles fromlunar sample 15101. Lunar and Planetary Science VIII, pp. 661662.

Minitti, M.E. and Rutherford, M.J. (2000) Genesis of the Mars Pathfinder sulfur-free rock from SNC parental liquids. Geochimica et Cosmochimica Acta,64, 25352547.

Minitti, M.E., Leshin, L.A., Guan, Y., Luo, S., and Ahrens, T.J. (2003) The effectof impact shock on water and H isotopes in amphibole. Lunar and PlanetaryScience XXXIV, abstract no. 1524.

Monkawa, A., Mikouchi, T., Sekine, T., Koizumi, E., and Miyamoto, M. (2003)


12/12


Shock formation of Kaersutite in Martian meteorites: an experimental study.Lunar and Planetary Science XXXIV, abstract no. 1534.

Morse, S.A. (1994) Basalts and phase diagrams: an introduction to the quantita-tive use of phase diagrams in igneous petrology, 493 p. Krieger PublishingCompany, Malabar, Florida.

Mysen, B.O., Virgo, D., Popp, R.K., and Bertka, C.M. (1998) The role of H2O inMartian magmatic systems. American Mineralogist, 83, 942946.

Nyquist, L.E., Bogard, D.D., Garrison, D.H., Bansal, B.M., Weismann, H., and

Shih, C.-Y. (1991a) Thermal resetting of radiometric ages. I: experimentalinvestigation. Lunar and Planetary Science XXII, pp. 985986.

Nyquist, L.E., Bogard, D.D., Garrison, D.H., Bansal, B.M., Weismann, H., andShih, C.-Y. (1991b) thermal resetting of radiometric ages. II: modeling andapplications. Lunar and Planetary Science XXII, pp. 987988.

Ottolini, L., Bottazzi, P., and Vannucci, R. (1993) Quantification of lithium,beryllium, and boron in silicates by secondary ion mass spectrometry usingconventional energy filtering. Analytical Chemistry, 65, 19601968.

Papike, J.J. (1980) Pyroxene mineralogy of the moon and meteorites. In C.T.Prewitt, Ed., Pyroxenes, 7, p. 495525. Reviews in Mineralogy, MineralogicalSociety of America, Chantilly, Virginia.

Papike, J.J. and Hodges, F.N. (1975) Mare basalts, major element chemistry offeldspar, olivine, and pyroxene. LSI Contribution, 234, 120123.

Papike, J.J., Hodges, F.N., Bence, A.E., Cameron, M., and Rhodes, J.M. (1976)Mare basalts: crystal chemistry, mineralogy, and petrology. Reviews of Geo-physics and Space Physics, 14, p. 475540.

Papike, J.J., Ryder, G., and Shearer, C.K. (1998) Lunar Samples. In J.J. Papike, Ed.,Planetary Materials, 36, p. 5-15-234. Reviews in Mineralogy, MineralogicalSociety of America, Chantilly, Virginia.

Richter, F.M., Davis, A.M., DePaolo, D.J., and Watson, E.B. (2003) Isotope frac-tionation by chemical diffusion between molten basalt and rhyolite. Geochimicaet Cosmochimica Acta, 67, 39053923.

Righter, K., Hervig, R.L., and Kring, D.A. (1997) Ion microprobe analyses ofSNC meteorite melt inclusions. Lunar and Planetary Science XXVIII, pp.11811182.

Robinson, P. (1980) The composition space of terrestrial pyroxenesinternal andexternal limits. In C.T. Prewitt, Ed., Pyroxenes, 7, p. 419494. Reviews inMineralogy, Mineralogical Society of America, Chantilly, Virginia.

Schaal, R.B. and Hrz, F. (1977) Shock metamorphism of lunar and terrestrialbasalts. Proceedings of the 8thLunar and Planetary Science Conference, pp.16971729.

Schmitt, H.H., Lofgren, G., Swann, G.A., and Simmons, G. (1970) The Apollo 11Samples: introduction. Proceedings of the Apollo 11 Lunar Science Confer-ence, pp. 154.

Shannon, R.D. and Prewitt, C.T. (1969) Effective ionic radii in oxides and fluorides.Acta Crystallographica, B25, 925946.

Shearer, C.K., Papike, J.J., Simon, S.B., and Shimizu, N. (1989) An ion microprobestudy of the intra-crystalline behavior of REE and selected trace elements inpyroxene from mare basalts with different cooling and crystallization histories.Geochimica et Cosmochimica Acta, 53, 10411054.

Shearer, C.K., Layne, G.D., and Papike, J.J. (1994) The systematics of lightlithophile elements (Li, Be, and B) in lunar picritic glasses; implications forbasaltic magmatism on the Moon and the origin of the Moon. Geochimica etCosmochimica Acta, 58, 53495362.

Shimizu, N., Semet, M.P., Lorin, J.C., and Allegre, C.J. (1977) The energy filteringand geochemical applications of quantitative ion microprobe analysis. EOS,Transactions, American Geophysical Union, 58(6), 521.

Stimac, J. and Hickmott, D. (1994) Trace-element partition coefficients for ilmenite,orthopyroxene, and pyrrhotite in rhyolite determined by micro-pixe analysis.Chemical Geology, 117, 313330.

Stffler, D., Ostertag, R., Jammes, C., Pfannschmidt, G., Gupta, P.R., Simon,S.B., Papike, J.J., and Beauchamp, R.H. (1986) Shock metamorphism andpetrography of the Shergotty achondrite. Geochimica et Cosmochimica Acta,50, 889903.

Watson, L.L., Hutcheon, I.D., Epstein, S., and Stolper, E.M. (1994) Water on Mars:

Clues from D/H and water content of hydrous phases in SNC meteorites.Science, 265, 8690.

Weitz, C.M., Rutherford, M.J., Head, J.W., III, and McKay, D.S. (1999) Ascent anderuption of a lunar high-titanium magma as inferred from the petrology of the74001/2 drill core. Meteoritics and Planetary Science, 34, 527540.

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the behavior of li and b in lunar mare basalts during crystallization, shock, and thermal...

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