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A spiked (with REE, V, Sc) martian basalt Yamato 980459 (Y98) composition was used to synthesize olivine, spinel, and pyroxene at 1200 °C at five oxygen fugacities: IW-1, IW, IW+1, IW+2, and QFM. These run products were analyzed by electron microprobe, ion microprobe, and X-ray absorption near-edge spectroscopy to establish four oxybarometers based on vanadium partitioning behavior between the following pairs of phases: V spinel-melt, V/(Cr+Al) spinel-melt, olivine-melt, and spinel-olivine. The results for the spinel-melt, olivine-melt, and V/(Cr+Al) spinel-melt are applicable for the entire oxygen fugacity range while the spinel-olivine oxybarometer is only applicable between IW-1 and IW+1. The oxybarometer based on V partitioning between spinel-olivine is restricted to basalts that crystallized under low oxygen fugacities, some martian, all lunar, as well as samples from 4 Vesta. The true potential and power of the new spinel-olivine oxybarometer is that it does not require samples representative of a melt composition or samples with some remnant of quenched melt present. It just requires that the spinel-olivine pairs were in equilibrium when the partitioning of V occurred. We have applied the V spinel-olivine oxybarometer to the Y98 meteorite as a test of the method. [ABSTRACT FROM AUTHOR]

DCr augite/melt is approximately double that of DCr pigeonite/melt in synthetic Martian basaltic samples equilibrated at the same fO2. This increase is not related to changing fO2 and the valence of Cr, but rather to the increased availability of elements for coupled substitution with the Cr3+ 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 Cr3+ 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 DCr for both augite/melt and pigeonite/melt with increasing fO2 is a function of the increased activity of Cr3+ in the crystallizing melt. [ABSTRACT FROM AUTHOR]

This is a comparative planetary mineralogy study emphasizing the valence-state partitioning of Cr, Fe, Ti, and V over crystallographic sites in olivine, pyroxene, and spinel from planetary basalts. The sites that accommodate these cations are the M2 site (6 to 8-coordinated) and M1 site (6-coordinated) in pyroxene, the M2 site (6- to 8-coordinated) and M1 (6-coordinated site) in olivine, and the tetrahedral and octahedral sites in spinel. The samples we studied are basalts from Earth, Moon, and Mars, and range in oxygen fugacity conditions from IW-2 (Moon) to IW+6 (Earth), with Mars somewhere in between (IW to IW+2). The significant elemental valence-states at these fo2 conditions are (from low to high fo2): Ti4+, V3+, Fe2+, Cr2+, Cr3+, V4+, and Fe3+.V2+ and Ti3+ play a minor role in the phases considered for the Moon, and are found in very low concentrations. V5+ plays a minor role in these phases in oxidized terrestrial basalts because it is probably lower in abundance than V4+, and has an ionic radius that is so small (0.054 nm, 6-coordinated), that it is almost at the lower limit for octahedral coordination, and can even be tetrahedrally coordinated. The role of Cr2+ in the Moon is significant, as Cr2+ predominates in basaltic melts at fo2 less than IW-1. Lunar olivine has been found to contain mostly Cr2+, whereas coexisting pyroxene contains mostly Cr3+. Fe3+ is very important in Earth, less so in Mars, and nonexistent in the Moon. The importance of the Fe2+ to Fe3+ transition cannot be overstated and, indeed, their crystal-chemical differences, in terms of behavior (based on size and charge), are similar to the differences between Mg and Al. We note that for pyroxene in six of the seven... [ABSTRACT FROM AUTHOR]

We have been developing oxygen barometers based largely on the behavior of V, which can occur in four valence states (V2+, V3+, V4+, and V5+), and record at least 8 orders of magnitude of fO2. Our first efforts in measuring these valence proportions were by XANES techniques in basaltic glasses from Earth, Moon, and Mars. We now address the behavior of V valence states in chromite in basalts from these bodies with a technique that uses the electron microprobe. Our first insights into this new technique resulted from running electron probe traverses across spinel grains from core to rim on grains that show zoning from chromite to ulvöspinel. The zoning profiles showed the normal trends of core to rim decreases of Cr, Al, and Mg, and increases of Fe, Ti, and Mn. However, the behavior of V was very different for Moon and Earth, with Mars in between. In terrestrial basalts V4+ > V3+, in lunar basalts V3+ > V4+, and in martian basalts V3+ and V4+ are both significant. The trends (core to rim) for the Moon show a strong positive correlation of V and Cr and negative correlation of V and Ti. For the Earth, the trends are just the opposite, with a strong negative correlation for V and Cr and a strong positive correlation of V and Ti. Chromite in martian basalts showed trends somewhere in between. We found that a convenient way to display these data for chromite is a plot showing the relative V/(Cr + Al) ratios. These ratios nicely reflect the oxygen fugacity ranges for Moon, Mars, and Earth. [ABSTRACT FROM AUTHOR]

Plagioclase grains from 15 basalt suites from the Earth, Moon, Mars, and 4 Vesta were studied by electron and ion microprobe techniques. The results demonstrate that chemical signatures in plagioclase record three planetary aspects that affect basaltic magmatism: (1) Volatile element depletions and enrichments in the planetary bodies are recorded by the systematics of Na and K in plagioclase. Terrestrial and Martian plagioclase are enriched in the volatile elements relative to plagioclase from the Moon and Vesta, a result that mimics the overall volatile budgets of these planets. Furthermore, the volatile-depleted nature of both the Moon and Vesta imply some similarities in planetary origin and/or evolution of these bodies. (2) The overall oxygen fugacity conditions on a planet may be realized by the Eu/Sm ratios of planetary plagioclase grains. Our data show that plagioclase from the Moon and 4 Vesta has higher Eu/Sm relative to plagioclase from the Earth and Mars. These data are consistent with low oxygen fugacity conditions on the Moon and Vesta, where divalent Eu is more compatible within the plagioclase structure than other trivalent REE elements. (3) The incompatible element systematics of K, REE, Ba, Y, and Sr in plagioclase-show that styles of igneous differentiation affect basaltic magmatism on planets and more specifically, within tectonic settings on each planet. Terrestrial plagioclase grains from continental flood, continental rift, and Hawaiian basalt suites are enriched in the incompatible elements K, Ce, Ba, and Sr compared with Ocean Floor and Island Arc suites. The enrichments in the former are caused by continental crust interaction with basaltic magmas, and/or derivation from undepleted (fertile) mantle sources. Lunar KREEP basalt plagioclase enrichment in incompatible elements reflect mare basalt assimilation of a KREEP component, or partial melting of a KREEP-rich source. The Martian incompatible element data show that ... [ABSTRACT FROM AUTHOR]

Presents a study which examined the chemical signatures that indicate planetary parentage and those that record igneous setting and process. Methods; Results; Discussion.