Trace element geochemistry of lunar meteorites Yamato-791197 and -82192

概要

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The lunar meteorites Yamato-791197 and -82192 have been analyzed for up to 36 minor and trace elements. Bulk compositional data are reported as well as data for grain size fractions and individual clasts separated from both meteorites. The data shows clearly that there are some significant chemical differences between Y-791197 and -82192,and also to ALHA81005. Y-82192 shows no sign of a KREEP component at all, and shows a slightly different REE (and incompatible element) pattern than the other two meteorites. Siderophile elements (Ir, Ni, Co, Au) and Se show an admixture of about 1.5% C1 component, but the patterns are quite different for all three lunar meteorites. Y-791197 shows an enrichment in some volatile elements (like Se and Au) already in the bulk composition. Both meteorites contain some volatile-rich clasts, but only Y-791197 has also a volatile rich bulk composition. This is in favor of an earlier suggestion of volcanic contaminations in the lunar source region for Y-791197. The trace element data seems to indicate that there have been at least three individual impacts responsible for the known lunar meteorites.
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