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Russian Geology and Geophysics

2015 year, number 8

CONTINENTAL CRUST IN GORNY ALTAI: STAGES OF FORMATION AND EVOLUTION AND INDICATOR ROLE OF GRANITOIDS

N.N. Kruk1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Эволюция континентальной коры, гранитоиды, геохимия, изотопная геохимия, Горный Алтай, Evolution of continental crust, granitoids, geochemistry, isotope geochemistry, Gorny Altai

Abstract

The composition and mechanisms of formation of continental crust in Gorny Altai and the role of granitoid magmatism in its evolution are considered. Geochemical and isotope data for major types of rocks of primary crust and for Early-Middle Paleozoic granitoids of the region are presented. The role of granitoids as indicators of different stages of the continental-crust evolution is discussed. A review of the main models of continental-formation crust is made, and their applicability to the Gorny Altai segment of the Central Asian Fold Belt is shown. Based on the complex of geological, geochemical, isotope, and geochronological data, it has been established that the formation of continental crust in the Early and Late Caledonian terranes of Gorny Altai proceeded nearly synchronously (in the Middle-Late Devonian). In the Early Caledonian terranes, this process was the consequence of the multistage fractionation of primary juvenile crust of basic composition, and in the Late Caledonian ones it was the result of one-cycle intracrustal melting of hybrid andesitic crust rich in recycled material.