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Russian Geology and Geophysics

2020 year, number 3

HIGH-PRESSURE PHASES IN THE DHOFAR 922 L6 CHONDRITE: СRYSTALLIZATION OF OLIVINE-RINGWOODITE AGGREGATES AND JADEITE FROM MELT

I.S. Bazhan1, K.D. Litasov2,3, D.D. Badyukov4
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Vereshchagin Institute for High Pressure Physics, Russian Academy of Sciences, Kaluzhskoe shosse 14, Troitsk, Moscow, 108840, Russia
3Fersman Mineralogical Museum, Russian Academy of Sciences, Leninsky pr. 18/2, Moscow, 119071, Russia
4Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991, Russia
Keywords: Meteorite, chondrite, ringwoodite, majorite, jadeite, maskelynite, shock metamorphism

Abstract

High-pressure phases (ringwoodite, maskelynite, and jadeite) present as coarse-grained fragments in the shock-melt vein of the Dhofar 922 L6 chondrite were studied by scanning electron microscopy and Raman spectroscopy. Ringwoodite and jadeite crystallized from melted plagioclase and olivine fragments, respectively, at the cooling-decompression stage. We assume that the high contents of Fe and Mg in maskelynite-jadeite aggregates are due to a miscibility gap in the hedenbergite-jadeite and diopside-jadeite joins at ~600 and ~700 °C, respectively. The P - T conditions of the formation of shock-melt veins are estimated at >19 GPa and >2150-2300 °C.

DOI: 10.15372/RGG2019072