Exposure history, petrology, and shock-induced sulfidization reaction of Alatage Mountain 001 strewn field samples

1,2Shijie Li,3Ingo Leya,4Shijie Wang,3,4Thomas Smith,5,6Huiming Bao,1,7Yan Fan,1,2Bing Mo
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13710]
1Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081 China
2Chinese Academy of Sciences Center for Excellence in Comparative Planetology, Hefei, China
3Physikalisches Institut, Universität Bern, Bern, 3012 Switzerland
4State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029 China
5Department of Geology and Geophysics, E235 Howe-Russell Geoscience Complex, Louisiana State University, Baton Rouge, Louisiana, 70803 USA
6Center for Isotope Effects Research and School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023 China
7Department of Geology, Northwest University, Xi’an, 710069 China
Published by arrangement with John Wiley & Sons

Several hundred meteorites with a total mass of over 100 kg were collected as the Alatage Mountain (AM) strewn field located in the Kumtag desert, Xinjiang Province, China. Twelve AM meteorites were studied in this work. Petrography, mineralogy, bulk chemistry, bulk oxygen isotopic compositions, and light noble gas concentrations and isotopic compositions were determined for all or for a selection of the meteorites. The studied meteorites are L-chondrites that suffered a very strong impact; impact melt veins and melt pockets are widely distributed. More than 50% of the troilite exists in the form of blebs and veins in olivine and pyroxene. Some of these meteorites are impact melt recrystallized rocks (e.g., AM 037). The strong impact caused the decomposition of troilite, which led in AM 034 to the sulfidization reaction of olivine. The metal in most meteorites is almost completely altered, and the troilite has been significantly oxidized. Weathering resulted in the depletion of Mg, Fe, Co, and Ni, and the enrichment of Sr, Ba, Pb, and U in these meteorites. The cosmic ray exposure (CRE) ages measured for these specimens range between 6.2 ± 1.9 Ma and 9.0 ± 2.7 Ma, depending on the cosmogenic nuclide used. The average CRE age is 7.6 ± 1.3 Ma. Both 4He and 40Ar gas retention ages indicate that the strong impact which caused the shock effects occurred about 320 Ma ago.

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