Composition and origin of peculiar pyropes from lherzolites: evidence for the evolution of the lithospheric mantle of the Siberian Platform
N.S. Tychkov, N.P. Pokhilenko, S.S. Kuligin, E.V. Malygina
Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Siberian Platform; kimberlites; LAC pyropes; lherzolites; pyroxenites; lithospheric mantle; structure
Pages: 225-239
Abstract
More than 1000 pyropes from the Muza (J3) and Ivushka (D-C) (northeastern Siberian Platform, and Khorkich (Mz) (southwestern part of the platform) kimberlite pipes, alluvial deposits of the Muna-Markha area, and granular peridotites of the Udachnaya pipe have been analyzed for major and some minor elements. As a result, a group of pyropes was distinguished whose composition is not typical of the lherzolite paragenesis (LAC pyropes). They are predominant in the Muza pipe and are widespread over the world. This group is described as a separate paragenetic type. In all known cases, LAC pyropes belong to granular clinopyroxene-bearing harzburgites, and in situ conditions for this suite are typically below 50 kbar and 1000
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