Age of granitoids from the conjunction zone of the Baikal-Muya foldbelt and the Kalar metamorphic terrane

Abstract

One of the key segments in the conjunction zone between the Baikal folded area of Baikalides, the Early Precambrian Aldan-Stanovoi shield, and the Barguzin-Vitim superterrane involving fragments of the Early Precambrian, Baikalian, and Paleozoic folded complexes is discussed. Within this segment, complicated tectonic contacts between the Late Riphean complexes of the Param-Shaman paleotrough zone in the Baikal-Muya foldbelt of Baikalides and Lower Precambrian complexes of the Kalar metamorphic terrane are mapped. The results of the U-Pb zircon isotopic dating (TIMS and SHRIMP-II) of gneisses-syenites from the Burgai Complex and gneissoid granites of the Drevnestanovoi Complex of the Early Precambrian age, as well as results of the Nd-isotope study of reference magmatic and stratified complexes of the region are presented. The ages of the oldest gneiss-syenites from the Burgai Complex and overlying plagiomigmatites in the conjunction zone have been established to differ by less than 1 Ma, making up 601 ± 5 Ma. Drevnestanovoi gneissoid granites in the conjunction zone are of the Late Paleozoic age (325–270 Ma). According to Nd isotopic data, the age of the source, from which Vendian gneisses-syenites and granites were melted, was established to be not older than the Riphean, and the material of the old continental crust to be the protolith of the upper Paleozoic granites. It has been inferred that the collision junction of Baikalian and Early Precambrian structures of the Baikal folded area and the Aldan-Stanovoi Shield into a single block took place 600 Ma ago.