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
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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