THE TRANSANGARA ALKALINE PLUTON, YENISEI RANGE: Rb-Sr AND Sm-Nd ISOTOPE AGES AND SOURCES OF FELDSPATHOID MAGMAS IN LATE PRECAMBRIAN

Abstract

According to the existing geodynamic models, the Precambrian fold-thrust belt of the Yenisei Range was formed by the successive accretion of several terranes to the western margin of the Siberian Craton in the Neoproterozoic. The main collisional events at 880–860 and 760–720 Ma B.P. were presumably accompanied by the emplacement of the Teisk, Tatar–Ayakhta, and Glushikha granitoid complexes located, respectively, in the central and western part of the Transangara region. This was followed by the amalgamation of an island-arc complex and obduction of the ophiolites of the Yenisei Range at the Riphean–Vendian boundary (700–630 B.P.). Noteworthy is the fact that this stage is close to the manifestation of small-scale spatially associated rift-type alkaline and carbonatite magmatism in the southern Yenisei Range (660–675 Ma B.P.).