PERMO-TRIASSIC STAGE OF ALKALINE MAGMATISM IN THE VITIM PLATEAU (western Transbaikalia)
A.G. Doroshkevich1,2, I.A. Izbrodin1, M.O. Rampilov1, G.S. Ripp1, E.I. Lastochkin1, V.B. Khubanov1
1Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sakh’yanovoi 6a, Ulan Ude, 670047, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Alkali and nepheline syenites, Permo-Triassic stage of magmatism, geochronological and isotope data, albitization, sources of material
Abstract
We present results of geochronological (40Ar-39Ar, U-Pb SHRIMP-II, and LA-ICP-MS) and geochemical studies of alkaline rocks of the Amalat, Sirikta, Tsipa, Pravyi Uligli, and Verkhnii Uligli massifs in the Vitim plateau (western Transbaikalia). The formation of the alkaline rocks and the accompanying albitization are dated at 261-242 Ma. The isotope inhomogeneity (εNd( T ) = +8.4 to -1.7) of the alkaline rocks indicates the heterogeneous composition of the source of their material having a depleted component, an enriched juvenile metasomatic fluid, and a crustal substrate.
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