Noble gases in the Xinjiang (Armanty) iron meteorite––A big object with a short cosmic‐ray exposure age |
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| Authors: | Katja AMMON Ingo LEYA Yangtin LIN |
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| Institution: | 1. Space Science and Planetology, University of Bern, Sidlerstrasse 5, CH‐3012 Bern, Switzerland;2. Key Laboratory of the Earth’s Deep Interior Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China |
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| Abstract: | Abstract– We measured the concentrations and isotopic ratios of the cosmogenic noble gases He, Ne, and Ar in the very large iron meteorite Xinjiang (IIIE). The 3He and 4He data indicate that a significant portion of the cosmogenic produced helium has been lost via diffusion or in a recent impact event. High 22Ne/21Ne ratios indicate that contributions to the cosmogenic 21Ne from sulfur and/or phosphorous are significant. By combining the measured nuclide concentrations with model calculations for iron meteorites we were able to determine the preatmospheric diameter of Xinjiang to 260–320 cm, which corresponds to a total mass of about 70–135 tons. The cosmic‐ray exposure age of Xinjiang is 62 ± 16 Ma, i.e., relatively short compared to most of the other iron meteorites. With the current database we cannot firmly determine whether Xinjiang experienced a complex irradiation history. The finding of 3He and 4He losses might argue for a recent impact event and therefore for a complex exposure. |
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