LATE PALEOZOIC SUBALKALINE AND RARE-METAL GRANITOIDS IN THE SOUTHEASTERN EAST SAYANS: GEOCHEMICAL SIGNATURE AND Rb-Sr ISOTOPE SYSTEMATICS
S.V. Rasskazov, M.N. Maslovskaya, V.G. Skopintsev*, E.V. Saranina, A.M. Il'yasova, and Yu.I. Sizykh
Institute of the Earth's Crust, Siberian Branch of the RAS, 128 ul. Lermontova, Irkutsk, 664033, Russia
* Buryatgeocenter, 53 ul. Lenina, Ulan Ude, 670000, Russia
Keywords: Late Paleozoic, alkaline and subalkaline granites, amazonite granites, Rb-Sr isotope system, trace elements, Central Asia
Pages: 1093-1103
Subsection: PETROLOGY, GEOCHEMISTRY AND MINERALOGY
Abstract
Late Paleozoic granitoid magmatism in the southeastern East Sayans was focussed in the eastern Oka zone adjacent to the Sharyzhalgai basement uplift of the Siberian craton. The Rb-Sr systematics of the rocks and minerals indicates three magmatic episodes of 307-304 (1), 283-282 (2), and ca. 261 (3) Ma. The intrusion pulses of the Samsal subalkaline leucogranites and the Khon'chin rare-metal Li-F alkaline granites and syenites (episode 1) were followed by the formation of the Shagaite-Gol fluid-explosive rocks and amazonite-bearing pegmatite veins (episode 2) and then veins of fine-grained subalkaline leucogranites found within the Samsal intrusion (episode 3). The granitoids are mostly A-type. The Samsal pluton shows postcollisional trace element signature unlike the Khon'chin dikes and the Shagaite-Gol rocks with syncollisional and within-plate characteristics. The Late Carboniferous-Early Permian plutonism in the East Sayan region was roughly coeval with the intrusion of the Angara-Vitim batholith in western Transbaikalia (310 to 280 Ma) and Kalba intrusion in southwestern Altai (290-270 Ma).
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