TECTONO-MAGMATIC EVOLUTION OF THE RUSSIAN ALTAI, NORTHWESTERN CENTRAL ASIAN OROGENIC BELT
The Russian Altai is a key area in the northwestern Central Asian Orogenic Belt, comprising the northern segment of the Altai-Mongolian terrane in the south, the Gorny Altai terrane in the north and the Charysh-Terekta-Ulagan-Sayan suture zone between these two terranes. Our data suggest that the Altai-Mongolian terrane represents a huge subduction-accretion complex built upon the western Mongolia in the early Paleozoic. The Gorny Altai terrane was part of the Kuznetsk-Altai intra-oceanic arc system formed close to the southwestern margin of the Siberian continent, and underwent two contrasting magmatic stages in ca. 640-540 Ma and 540-470 Ma, respectively. These two subduction-accretion systems amalgamated prior to ca. 420 Ma, and then coherently underwent geological processes related to the subduction of the Ob-Zaisan Ocean (a branch of the Paleo-Asian Ocean) in the Devonian. This study provides important constrains on the tectono-mamgatic history of the Russian Altai, which in turn shed light on the accretionary orogenesis and crustal growth of the Central Asian Orogenic Belt.