THE MASLYANINO IRON METEORITE WITH SILICATE INCLUSIONS: MINERALOGICAL AND GEOCHEMICAL STUDY AND CLASSIFICATION SIGNATURES
D.S. Ponomarev1,2, K.D. Litasov1,2, A. Ishikawa3, I.S. Bazhan1, T. Hirata4, N.M. Podgornykh1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3Dept Earth Science and Astronomy, University of Tokyo, Komada, Meguro, Tokyo, 153-8902, Japan
4Geochemical Research Center, University of Tokyo, Hongo, Bunkyo, Tokyo, 113-8654, Japan
Keywords: Iron meteorite, kamacite, taenite, silicate inclusions, olivine, pyroxene, phosphates, crystallization, shock metamorphism, asteroids
Abstract
The minerals of the Maslyanino iron meteorite and their trace-element composition are described in detail for the first time, and the meteorite classification is substantiated. The meteorite is a fine-structural octahedrite. Its metallic matrix consists of kamacite, taenite, and schreibersite. Large troilite segregations are associated with silicate inclusions; in addition, rare minerals altaite and dobreelite are found. The silicate inclusions contain olivine, orthopyroxene, clinopyroxene, plagioclase, apatite, merrillite, chromite, and graphite. A detailed trace-element analysis of the metal matrix permits the Maslyanino meteorite to be assigned to the narrow Pitts subgroup of the IAB group. It is also similar to meteorites of the Udei Station subgroup. Both subgroups include meteorites with silicate inclusions and are intermediate between the sLL (low Au and Ni contents) and sLM (low Au and medium Ni contents) subgroups. According to the metallographic data, the cooling rate of the Maslyanino meteorite is 30-60 ºC/Myr. The data obtained are consistent with the formation of the meteoritic material under impact of a parent asteroid resulting in the removal of its outer chondrite-winonaite shell. Subsequent weaker impacts led to the formation of IAB group meteorites (including meteorites with silicate inclusions) and winonaites from the asteroid remnant.
DOI: 10.15372/RGG2019055
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