Iodine-xenon analysis of Chainpur (LL3.4) chondrules |
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| Authors: | G Holland JC Bridges A Busfield G Turner |
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| Institution: | 1 School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M13 9PL UK
2 Department of Mineralogy, Natural History Museum, London, SW7 5BD UK |
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| Abstract: | We present I-Xe analyses of ten chondrules from Chainpur LL3.4 by IR laser-stepped heating. Five chondrules provided isochrons of varying quality, giving a range of ages from 0.5 Ma before Shallowater to 17.8 after Shallowater. This confirms the extended range of Chainpur chondrule ages determined by previous data. We discuss evidence for fluid alteration, shock, and thermal events in explaining the chondrule ages and suggest that chondrule remelting events, presumably from bombardment of the parent body surface, are responsible for resetting the I-Xe chronometer. Previous data show a negative correlation between 132Xe/129Xe of the trapped Xe component and 127I/129I of an initial iodine component. This behaviour that requires the presence of a component with trapped 129Xe/132Xe lower than the planetary value has been cited as evidence for closed system evolution of the I-Xe system. We find no evidence of an unambiguous trapped component lower than planetary and no evidence of a negative correlation in our data. Therefore we suggest that open system behaviour more suitably explains the I-Xe systematics of Chainpur chondrules. |
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