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Valence state partitioning of V between pyroxene‐melt: Effects of pyroxene and melt composition, and direct determination of V valence states by XANES. Application to Martian basalt QUE 94201 composition
Author(s) -
KARNER J. M.,
PAPIKE J. J.,
SUTTON S. R.,
SHEARER C. K.,
BURGER P.,
McKAY G.,
LE L.
Publication year - 2008
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/j.1945-5100.2008.tb00697.x
Subject(s) - pigeonite , augite , pyroxene , valence (chemistry) , basalt , geology , xanes , mineralogy , analytical chemistry (journal) , geochemistry , olivine , chemistry , spectroscopy , physics , plagioclase , paleontology , quartz , organic chemistry , quantum mechanics , chromatography
— Experiments on a Martian basalt composition show that D v augite/melt is greater than D v pigeonite/melt in samples equilibrated under the same f O 2 conditions. This increase is due to the increased availability of elements for coupled substitution with the V 3+ or V 4+ ions, namely A1 and Na. For this bulk composition, both A1 and Na are higher in concentration in augite compared with pigeonite; therefore more V can enter augite than pigeonite. Direct valence state determination by XANES shows that the V 3+ and V 4+ are the main V species in the melt at f O 2 conditions of IW‐1 to IW+3.5, whereas pyroxene grains at IW‐1, IW, and IW+1 contain mostly V 3+ . This confirms the idea that V 3+ is more compatible in pyroxene than V 4+ . The XANES data also indicates that a small percentage of V 2+ may exist in melt and pyroxene at IW‐1. The similar valence of V in glass and pyroxene at IW‐1 suggests that V 2+ and V 3+ may have similar compatibilities in pyroxene.