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UDC 552.321.1:(549+550.42+550.93)(571.15-14) BURIED GRANITOIDS OF THE KALBA BELT IN THE RUSSIAN SOUTH-EASTERN ALTAI: MATERIAL CONSTITUTION, GEOCHEMISTRY, GEOCHRONOLOGY
Commercial deposits of Ta, Nb, Be, Li, Cs, Sn and W ores are associated with granites of the Kalba belt in the Eastern Kazakhstan. The continuation of the Kalba structures and magmatic formations is traced by drilling in the basement of the Kulunda depression in the Russian South-Western Altai. Based on petrographic, geochemical data and isotopic dating (7 datings using U-Pb method by zircon, SHRIMP II) three intrusive massives such as Semenovskiy, Meschanskiy and Borisovskiy are characterized. The massives’ structure includes peraluminous granitoids of three intrusive complexes: Kunushskiy (303±3 Ma), Early Kalbinskiy (283±2–271±3 Ma) and Late Kalbinskiy (258±2 Ma) ones. Geochemical rock features are similar to granites of volcanic arcs and post-collisional granitoids. There are adakite-like granitoids of collisional zones as a part of the Kunushskiy and Early Kalbinskiy complexes. Granitoid crystallization temperature was 740–830 °C according to the zirconium geothermometer. There are no any carboniferous granitoids to the north from the North-Eastern shear zone in the Gornyi Altai. Magmatism of the Kalba belt is interpreted as the consequence of post-collisional slab breakoff in the paleosubduction zone of south-western downwarping in present-day coordinates.
Key words: Kalba rare-metal belt, granites, adakite-like granitoids, U-Pb age by zircon, SHRIMP II.
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