Ni isotopic compositions in Allende and other meteorites |
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| Authors: | T Shimamura GW Lugmair |
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| Institution: | Chemistry Department, B-017, University of California at San Diego, La Jolla, CA 92093 U.S.A. |
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| Abstract: | A new technique for high-precision isotopic analyses of Ni was developed and applied to terrestrial samples, Allende inclusions and materials from other meteorites. Most of the Allende inclusions analysed here were previously reported to contain isotopically anomalous Ti. In contrast, the Ni isotopic abundances are indistinguishable from normal within presently obtainable precision with only one possible exception. The latter inclusion was shown by others to contain a significantly fractionated magnesium isotopic pattern of 9‰/amu. A normal Ni isotopic pattern has also been observed for the chromite/carbon fraction of an Allende acid residue which is known to contain heavy noble gases of highly anomalous isotopic composition. All other meteoritic samples analysed (Khohar matrix and chondrules, Murray matrix, a Tieschitz chondrule and an Orgueil magnetic fraction) also show normal isotopic compositions of Ni; no evidence for effects from now extinct60Fe could be detected. In spite of ubiquitous isotopic anomalies in Ti from normal Allende inclusions, there is no signature of isotopic variations in Ni from the same samples. Possible constraints for the nucleosynthesis of iron peak elements and for astrophysical and cosmochemical conditions during formation of the solar system are discussed. |
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