Noble gas components in clasts and separates of the Abee meteorite |
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| Authors: | John F Wacker Kurt Marti |
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| Institution: | 1. Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721U.S.A.;2. Chemistry Department, University of California at San Diego, B-017, La Jolla, CA 92093U.S.A. |
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| Abstract: | The noble gas components and their distributions were studied in a variety of clasts and in separated phases of clast 2,2 using a detailed stepwise release program. The results show the presence of two distinct trapped components: one appears to be similar to Kenna-type gas 28], the other is characterized by element ratios36Ar/84Kr < 370 and36Ar/132Xe ≥ 900 and is termed Ar-rich component. Silicate phases are identified as carriers of both components; but since they are differentially released, the results imply that multiple carrier phases are required. Unlike results from other meteorites, HF attack removes all but 15% of the xenon. Substantial amounts of trapped and, in many cases, unfractionated air were observed, apparently in reaction products of reduced and easily oxidized minerals. The129Xer release systematics imply the presence of two distinct carriers of extinct129I and suggest lithophilic behavior of I in Abee. The U/Th-4He and K-40Ar data are consistent with a 4.5 Gy age. Amounts of spallogenic He, Ne and Ar yield a cosmic ray exposure age of 8 My. We compare the Ar-rich component to noble gas abundances in planetary atmospheres and we discuss a suggested model of origin. |
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