Petrography and classification of NWA 7402: A new sulfide-rich unequilibrated ordinary chondrite |
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| Institution: | 1. Department of Geology and Geophysics, University of Hawai‘i at Mānoa, 1680 East-West Road, POST 517A, Honolulu, HI 96822, USA;2. Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI, USA;3. Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble, France;4. The Meteorite Market, Port Townsend, WA, USA;1. Department of Statistical Science at the University of Bologna, Via delle Belle Arti, 41 - 40126 Bologna, Italy;2. Department of Statistical Science at Duke University, Box 90251, Durham NC 27708-0251, USA;1. Department of Mathematics, University Jaume I, Campus Riu Sec, E-12071 Castellón, Spain;2. Department of Economics and Statistics, University of Torino, Campus Luigi Einaudi, Torino, Italy;1. Department of Statistical Science, Southern Methodist University, P.O. Box 750332, Dallas, TX 75275-0332, USA;2. Department of Anthropology, Southern Methodist University, P.O. Box 750336, Dallas, TX 75275-0336, USA;1. University of Kaiserslautern, Mathematics Department, 67653 Kaiserslautern, Germany;2. Chalmers University of Technology and University of Gothenburg, Department of Mathematical Sciences, 412 96 Gothenburg, Sweden;3. Fraunhofer Institut für Techno- und Wirtschaftsmathematik, Fraunhofer-Platz 1, 67663 Kaiserslautern, Germany;1. State Key Laboratory of Geological Processes and Mineral Resources, Collaborative Innovation Center for Exploration of Strategic Mineral Resources, Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, PR China;2. State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, PR China |
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| Abstract: | We classify a new chondritic find Northwest Africa (NWA) 7402. This meteorite is highly unequilibrated, and is therefore potentially significant for the study of primitive Solar System materials. Mineralogy, mineral chemistry, and modal abundances of minerals indicate that NWA 7402 is most likely an L chondrite. However, the specimen contains a higher abundance of sulfide than commonly seen in ordinary chondrites. The structural order of organic matter in the matrix and the chromium content of Fe-rich olivine grains indicate a petrologic type of 3.1. NWA 7402 largely escaped thermal metamorphism, and secondary phases formed by aqueous alteration are rare to absent. Minor planar fractures and undulatory extinction of olivine grains suggest that NWA 7402 experienced shock up to stage 2 or 3. Terrestrial weathering is heterogeneous in the specimen; much of the stone's exterior shows substantial Fe oxidation (weathering grade 2), while some parts of the interior remain relatively fresh (weathering grade 1). NWA 7402 has some unusual features that should be investigated further. The sulfide abundance is higher than reported sulfide contents for other L chondrites, and the chromium content of the olivines does not fall on the trend established for unequilibrated ordinary chondrites by Grossman and Brearley (2005). |
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| Keywords: | Meteorite classification Unequilibrated ordinary chondrites Meteoritics Cosmochemistry Early solar system Petrography |
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