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Classification of Ordinary Chondrite NWA 6514 and Lead-Lead Chondrule Chronology

Posted on:2012-07-25Degree:M.A.ScType:Thesis
University:University of Toronto (Canada)Candidate:Koeoep, LevkeFull Text:PDF
GTID:2461390011963760Subject:Geology
Abstract/Summary:
This study presents a petrographic description and a classification of ordinary chondrite NWA 6514 and aims to establish the first high-precision Pb-Pb age of a single ordinary chondrite chondrule. Furthermore, the distribution of different isotopic Pb signatures among chondritic components will be investigated by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS).;This study shows that NWA 6514 can be classified as a highly unequilibrated (subtype 3.10) L or LL chondrite that has experienced moderate terrestrial weathering (W2) and a low degree of shock (S2). The LA-ICP-MS measurements suggest that radiogenic Pb signatures have been locally preserved in chondrules. However, the Pb isotopic compositions of leaches from a large chondrule obtained by thermal ionization mass spectrometry show an anomalous distribution that indicates the presence of an exotic Pb component. The best estimate for the chondrule formation age is a model age of the last leach (4566.8 +/- 2.6 Myr).
Keywords/Search Tags:Ordinary chondrite, NWA, Chondrule
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