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We have determined [D.sub.Eu] between augite and melt in samples that crystallized from a highly spiked martian basalt composition at four [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] conditions. [D.sub.Eu] augite/melt shows a steady increase with [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] from 0.086 at IW-1 to 0.274 at IW + 3.5. This increase is because [Eu.sup.3+] is more compatible than [Eu.sup.2+] in the pyroxene structure; thus increasing [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] leads to greater [Eu.sup.3+]/[Eu.sup.2+] in the melt and more Eu (total) can partition into the crystallizing pyroxene. This interpretation is supported by direct determinations of Eu valence state by XANES, which show a steady increase of [Eu.sup.3+]/[Eu.sup.2+] with increasing [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] in both pyroxene (0.38 to 14.6) and glass (0.20 to 12.6) in the samples. Also, pyroxene [Eu.sup.3+]/[Eu.sup.2+] is higher than that of adjacent glass in all the samples, which verifies that [Eu.sup.3+] is more compatible than [Eu.sup.2+] in the pyroxene structure. Combining partitioning data with XANES data allows for the calculation of specific valence state D-values for augite/melt where [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] = 0.28 and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] = 0.07. Keywords: XANES, Eu partitioning, [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], augite DOI: 10.2138/am.2010.3394

[D.sub.Cr] augite/melt is approximately double that of [D.sub.Cr] pigeonite/melt in synthetic Martian basaltic samples equilibrated at the same [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. This increase is not related to changing [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and the valence of Cr, but rather to the increased availability of elements for coupled substitution with the [Cr.sup.3+] ion, namely Na and Al. The availability of Al and Na to partition into pyroxene is due to delayed nucleation of plagioclase for the QUE 94201 Martian basalt composition. Direct valence state determination by XANES shows that [Cr.sup.3+] is the dominant valence state in pyroxene at IW-1, IW, and IW+1. Trivalent Cr is apparently much more compatible in the pyroxene structure than divalent Cr, and thus an increasing [D.sub.Cr] for both augite/melt and pigeonite/melt with increasing [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is a function of the increased activity of [Cr.sup.3+] in the crystallizing melt. Keywords: Chromium, partitioning, multivalent elements, pyroxene, XANES, QUE 94201

The distribution of V in magmatic rocks is controlled primarily by spinel stability. Extensive previous experimental work at oxidized conditions on doped (V-rich) compositions has led to the recognition of the importance of temperature, oxygen fugacity, and spinel composition, but also left ambiguity with respect to the relative importance of these variables in controlling [D.sup.spinel/melt.sub.V]. One major uncertainty has been the valence of V in the spinel and glass. Spinel-melt pairs were equilibrated at low and variable oxygen fugacities, with a range of V and Ti contents. XANES spectra were measured on the spinel and glass products, and pre-edge peaks measured and calibrated against valence with the use of glass and oxide standards. The valence of V is always greater in the glass than in the spinels. In spinel, V is dominantly 3+ at oxygen fugacities near the FMQ (fayalite magnetite quartz) buffer, but we find evidence for mixed 3+, 4+, and 5+ at oxidized conditions (FMQ to air), and 2+ and 3+ at very reduced conditions [FMQ to IW-1 (1 log [fo.sub.2] unit below the iron wustite buffer)]. Increased V contents in spinels are correlated with increased [D.sup.spinel-melt.sub.V], at constant temperature and oxygen fugacity. However, increased Ti content causes only a slight decrease in [D.sup.spinel-melt.sub.V] and a shift to more reduced V (smaller pre-edge peak), which may be related to Fe-V exchange equilibria. Using the new partition coefficients, together with published results and valence information, expressions have been derived to predict [D.sup.spinel-melt.sub.V] for basaltic systems. Application of these expressions to natural suites illustrate their utility and also the great range of [D.sup.spinel-melt.sub.V] values relevant to natural systems. Calculation of V depletions in planetary mantles from basalt suites must take silicate, oxide, and metal fractionation into account, as is demonstrated using terrestrial, lunar, martian, and eucritic samples. Keywords: Vanadium, oxygen fugacity, basalt, spinel

The redox chemistry of soil Mn is important in Mn uptake by plants, the movement of trace elements absorbed on or occluded in Mn-oxides, and the etiology of some soil-borne plant fungal diseases. The objectives of this study were to develop calibration curves for determining Mn oxidation states in moist soil samples using micro-x-ray absorption near-edge structure spectroscopy and to test the method on selected soils. Oxidation-state standards were prepared by mixing dry powders of Mn[SO.sub.4].[H.sub.2]O ([Mn.sup.2+]) and a synthetic Na-birnessite, [Na.sub.4][Mn.sub.14][O.sub.27]-9[H.sub.2]O ([Mn.sup.4+]) to obtain various [Mn.sup.2+] mole fractions, f([Mn.sup.2+]), where f([Mn.sup.2+]) = [Mn.sup.2+]/([Mn.sup.2+] [Mn.sup.4+]). Corundum was used as a diluent to prepare mixtures containing 50, 1000, and 100 000 mg Mn [kg.sup.-1]. Quantitative analysis of Mn oxidation state is possible using either the energy of the pre-edge peak at 6540 eV or a ratio based on the intensity of the [Mn.sup.2+] white Une peak at 6552.6 eV divided by the intensity of the [Mn.sup.4+] white line peek at 6560.9 eV.. The white fine intensity ratio is more sensitive, with an estimated lower detection limit of 20 mg Mn [kg.sup.-1] using a 300 by 300 run spot, and predicts f([Mn.sup.2+]) with an accuracy of[+ or -] 0.1 mole fraction (95% confidence interval) through most of its range. The f([Mn.sup.2+]) for four air-dried Indiana surface soils ranged from 0.26 to 0.44 [+ or -] 0.1. Saturation and reduction for 5 d resulted in complete reduction of Mn in the soil matrix.

X-ray absorption near-edge structure (XANES) has been applied to the quantitative analysis of chromate (CrO42-) content in oxides, silicate glasses, and simulated cementitous waste forms. The method uses the normalized area of a pre-edge peak (bound-state transition) in XANES spectra acquired with the synchrotron X-ray microprobe on beam line X26A at the National Synchrotron Light Source. The estimated accuracy of the technique is + or - 5% in terms of Cr6+/total Cr. The minimum detection limit approaches 10 ppm Cr6+ using a 150-micrometer synchrotron X-ray beam. These results demonstrate the value of synchrotron-based microXANES for the nondestructive quantification of the first-row transition metal species present as tetrahedral oxyanions.

The grazing incidence x-ray fluorescence method has differentiated the terrestrial contamination from the low concentration implanted solar wind. The elemental depth distribution is obtained by using this method, which has resulted in the determination of absolute solar wind elemental abundance.

Laser heating plays an essential role for in-situ high pressure high temperature studies into the physical and chemical properties of materials in the diamond anvil cell (DAC) and minerals at conditions relevant to the Earth's deep interior. High temperature experiments in the multi-Mbar (over 100 GPa) pressure range require the use of very small samples and consequently the utmost stability and controllability of the laser heating is crucial. To accomplish this, we have modified the laser heating system at GSECARS employing newly developed beam shaping optics combined with two diode-pumped, single mode fiber lasers. Varying the settings of the laser heating system, we were able to shape the beam to almost any desired intensity profile and size on the surface of the sample in the DAC, including tight focus, flat top, trident and doughnut types. The advantages and excellent performance of the flat top laser heating (FTLH) technique were demonstrated in melting experiments on germanium in the DAC at pressures up to 40 GPa. [ABSTRACT FROM AUTHOR]