Geochemistry and petrology of a suite of ten Yamato HED meteorites
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概要
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We have performed petrological characterization and geochemical studies by instrumental neutron activation analysis of a suite of ten Yamato HED samples : Y-74013,Y-74097 and Y-74136 (Type A diogenites); Y-75032 and Y-791199 (Type B diogenites); Y-791195 (cumulate eucrite); Y-793164 and Y-82066 (eucrites); and Y-791192 and Y-82049 (polymict eucrites). The Type A diogenites are essentially identical in composition except for slight differences in Cr, Co, Se and La, which are likely due to inhomogeneous distribution of the minor phases chromite, metal and troilite, and trapped interstitial melt, respectively. The petrology and REE patterns for Type B diogenites show that they are not adcumulate rocks, but rather, contain substantial, perhaps 15%, interstitial liquid trapped in the samples. Y-791195 is a cumulate eucrite intermediate in REE content between Serra de Mage and Moore County, but is more ferroan. Eucrite Y-82066 is similar in composition to trace element-poor main-group eucrites such as Sioux County, and may be a primitive partial melt of the HED parent body. Y-793164 is intermediate in composition between main-group eucrites and Nuevo Laredo in Fe, Cr, Sc and REE, and is an intermediate member of the Nuevo Laredo trend eucrites. Y-793164 is a residual liquid from perhaps 25-30% crystallization of a primitive main-group eucrite like Sioux County or Y-82066. Y-791192 and Y-82049 are classified as polymict eucrites, but major and trace element concentrations indicate that these meteorites contain about 36% and 48% diogenitic material, respectively. These samples are howardites based on our analyses. Y-82049 contains a wide range of pyroxene compositions, from magnesian orthopyroxene similar to Type A diogenite pyroxenes, to ferroan pigeonite similar to basaltic eucrite pyroxenes. Large pyroxene clasts in Y-791192 are dominantly similar to Type B diogenite pyroxenes.
- 国立極地研究所の論文
著者
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Lindstrom Marilyn
Sn2 Office Of The Curator Nasa Johnson Space Center
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Mittlefehldt David
C23, Lockheed Engineering & Sciences Co.
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Mittlefehldt David
C23 Lockheed Engineering & Sciences Co.