VENDIAN ISLAND ARC INTRUSIVE MAGMATISM OF THE LAKE ZONE OF WESTERN MONGOLIA (geological, geochronological, and petrochemical data)
S.N. Rudnev, A.S. Gibsher, D.V. Semenova
V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Vendian intrusive magmatism, geochronology, petrochemistry, Central Asia, Lake Zone of Western Mongolia
Abstract
Based on new geochronological data on gabbroid and plagiogranitoid associations (Tavan Hayrhan, East Bayan Tsagaan, Bayan Tsagaan Uul, Tungalag, Three Hills, and Shutkhuin massifs) located among the Vendian island-arc volcanic complexes of the Lake Zone of Western Mongolia, an independent stage of Vendian island-arc intrusive magmatism (560-542 Ma) is substantiated. Geochronological ages determined for xenogenic zircon from Vendian gabbroids and granitoids (716-559 Ma) indicate a wide time interval of their formation and different natures of the sources. Several types of such sources are assumed. The source of the first type is rocks of the late Riphean oceanic crust of the Paleoasian Ocean, on which the Vendian island arc of the Lake Zone formed later. This is evidenced by the presence of xenogenic zircon with ages of ~716, 658-642, and 613-611 Ma. The source of the second (probably main) type is rocks of the Vendian island arc crust of the Lake Zone. This is indicated by the presence of xenogenic zircon with ages of 583-559 Ma, observed in all studied Vendian intrusive associations.
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