A preliminary report on the achondrite meteorites in the 1979 U.S. Antarctic meteorite collection

概要

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The 1979 U.S. Antarctic meteorite collection comprises 73 meteorites, 7 of which are achondrites. The achondrite collection consists of one eucrite (390g), three polymict eucrites (86; 310; 451g), one howardite (716g), one shergottite (7.9kg), and one diogenite (2.8kg). Also present in the 1979 collection is a unique iron meteorite (10kg) with abundant silicate (orthopyroxene) inclusions. The most interesting meteorite is the shergottite in which two distinct lithologies are joined along what appears to be an undisturbed igneous contact. The fine grained lithology present at one end of the sample is texturally and mineralogically similar to Shergotty but is finer grained. The major portion of the meteorite consists of large complex zoned pyroxenes in a groundmass of pyroxene and maskelynite. The overall pyroxene to feldspar ratio is higher than in the Shergottylike portion and the pyroxenes are more Mg-rich and Ca-poor. Plagioclase has been converted to maskelynite in both lithologies and glass veinlets and pockets of black glass occur throughout the meteorite. Five of the seven achondrites were found in a new collection site, Elephant Moraine (EET). This site will be further investigated in the future.
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