I-Xe age and trapped Xe components of the Murray (C-2) chondrite |
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| Authors: | S Niemeyer A Zaikowski |
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| Institution: | Department of Physics, University of California, Berkeley, CA 94720 U.S.A. |
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| Abstract: | A neutron-irradiated bulk sample of the Murray (C-2) carbonaceous chondrite was etched with H2O2 and then divided into colloidal and non-colloidal fractions. The H2O2 treatment removed ～80% of the trapped Xe and greatly increased variations in the129Xe/132Xe ratio measured in stepwise heating. The colloid showed very little excess129Xe, but the anti-colloid gave a fairly good I-Xe correlation corresponding to formation 3.7 ± 2.1 m.y. after Bjurböle.Variations in the trapped Xe component were also observed; most notably the 550°C anti-colloid fraction has large deficiencies relative to AVCC at the heavy isotopes. A tentative decomposition suggests U-Xe, a “primitive” trapped component, as the dominant component with minor contributions from H-Xe, L-Xe, and S-Xe (s-process nucleosynthesis). The identification of U-Xe rests primarily on the agreement of themeasured134Xe/136Xe ratio with U-Xe. This observation lends support to proposals for such a “primitive” trapped Xe component and demonstrates that at least some carbonaceous chondrite phases sampled a xenon reservoir nearly devoid of H-Xe. |
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