Nephrites of East Siberia: geochemical features and problems of genesis |
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| Institution: | 1. Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sakh’yanovoi 6a, Ulan-Ude, 670047, Russia;2. Museum of the Buryatian Scientific Center, ul. Sakh’yanovoi 8, Ulan-Ude, 670047, Russia;1. Holcombe Department of Electrical and Computer Engineering, Clemson University, Clemson SC, 29634, United States;2. School of Computer Science, University of Oklahoma, Norman, OK 73019, United States;1. Tomsk State University, pr. Lenina 36, Tomsk, 634050, Russia;2. V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia;3. Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia;1. Laboratorio Nacional de Ciencias para la Investigación y Conservación del Patrimonio Cultural, Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica S/N, Ciudad Universitaria, Coyoacán, C.P. 04510 Ciudad de México, Mexico;2. CONACyT - Laboratorio Nacional de Ciencias para la Investigación y Conservación del Patrimonio Cultural, Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica S/N, Ciudad Universitaria, Coyoacán, C.P. 04510 Ciudad de México, Mexico;3. Laboratorio de Conservación, Diagnóstico y Caracterización Espectroscópica de Materiales (CODICE), Coordinación Nacional de Conservación del Patrimonio Cultural (CNCPC-INAH), General Anaya S/N, San Diego Churubusco, Coyoacan, C.P. 04120 Ciudad de México, Mexico |
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| Abstract: | The largest nephrite-bearing province of Russia is located on the southern folded periphery of the Siberian craton. Deposits of two formation types were established here: apoultrabasic (East Sayan and Dzhida areas, Parama massif) and apocarbonate (Vitim area). Nephrites compose schlieren and lenticular bodies usually in the zones of contact of serpentinous (lizardite–antogorite) dunite–harzburgite rocks and dolomitic marbles with aluminosilicate rocks of different compositions. Significant difference in composition has been established for nephrites of different formations. Apocarbonate nephrites are more magnesian and fluoric and less ferroan. The contents of Li, Be, Rb, and Cs in them are two orders of magnitude higher and the contents of Sc, Ti, and Mn are lower than those in apoultrabasic nephrites. The isotope data evidence that the fluid phase of apoultrabasic nephrites was released from serpentinites during metamorphism, whereas the fluid phase of apocarbonate nephrites is only meteoric water. Oxygen in minerals of metamorphosed carbonate rocks was borrowed from the matrix subjected to replacement, sometimes with the participation of formation waters. |
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