Mongol-Okhotsk Geosynclinal System

one of the folded systems that make up the Urals-Mongol folded geosynclinal belt; more than 2,000 km long, it stretches from northeastern Mongolia to the western coast of the Sea of Okhotsk. This territory was first identified as a geochemical zone in 1926 by A. E. Fersman, who called it the Mongol-Okhotsk belt. In the north the Mongol-Okhotsk geosynclinal system is bounded by the deep Mongol-Okhotsk faults; in the south its boundaries are the Bureia massif and the system of South Gobi faults. Riphean and Lower and Middle Paleozoic stages of geosynclinal development are present in the structure of the Mongol-Okhotsk geosynclinal system. During the Upper Paleozoic and Lower Triassic almost the entire territory was in an erogenic stage that was accompanied by the intrusion of enormous masses of granitoids. During the Permian the eugeosynclinal troughs were preserved only in the East, in the region where the MongolOkhotsk geosynclinal system is connected with the younger Sikhote-Alin’ geosynclinal system.

The Mesozoic structures of the Mongol-Okhotsk geosynclinal system (Upper Triassic-Upper Cretaceous) are considered by some researchers to be geosynclinal, while others believe they are structures of granitoid activation. These structures are characterized by marine and continental molassoid and carboniferous beds combined with extensive development of terrestrial volcanism (andesite formation) and the intrusion of comagmatic granitoids of abyssal volcanoplatonic formation. Deposits of lead and zinc ore, gold, tin, tungsten, fluorite, and other minerals are associated with Mesozoic magmatism.