Evolution of Intrusive Magmatism in West Sayan
S.N. Rudnev1, G.A. Babin2, D.V. Semenova1, A.V. Travin1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2A.P. Karpinsky Russian Geological Research Institute, St. Petersburg, Russia
Keywords: Evolution of granitoid and basic magmatism, geochronology, petrochemistry, Altai-Sayan folded region, West Sayan
Abstract
We summarize the results of geological, geochronological and petrochemical studies of the intrusive complexes of West Sayan, and on their basis analyze the scales, formation sequence, petrochemical characteristics and geodynamic environments of the formation of granitoid and gabbroid complexes. Geochronological data indicate that the formation of intrusive complexes (granitoids and gabbroids) of West Sayan ranged within 580-370 Ma at several age levels and in various geodynamic environments: island-arc - 580-570, 550-520 Ma, accretion-collision - 505-450 Ma, transform-shear of continental margins - 440-430 Ma, and active continental margin - 425-370 Ma. According to petrochemical characteristics, we distinguish the rocks of tholeiitic, calc-alkali and subalkaline series among the studied granitoid complexes. The study of xenogenic zircons from granitoid and gabbroid complexes indicate the age range of 650-440 Ma. Several age clusters are distinguished (~ 645, ~ 570, 555-520, 505-475, 455-440 Ma); this indicates heterogeneous composition of the West Sayan crust and participation of the Late Riphean, Vendian - Early Cambrian and Ordovician crust sources in granite formation.
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