The first U–Pb geochronological and geochemical data on Late Vendian and Early Paleozoic acid volcanic rocks of the Mamyn Terrane (Central Asian Fold Belt)

Abstract

The first results of U–Pb geochronological studies of acid volcanic rocks from the Oktyabrsk Complex of the Mamyn Terrane, which had previously been conventionally attributed to the Late Proterozoic, are reported. It is established that rhyodacite of the Gar’–Dzheltulak volcanic field has Late Vendian age (546 ± 14 Ma) and trachyrhyodacite of the Kosmatinsk field has Late Cambrian age (490 ± 2 Ma). As a whole, the data obtained indicate two stages of acid volcanism on the Mamyn Terrane of the eastern part of the Central Asian Fold Belt covering the boundary between the Paleozoic and Neoproterozoic, as well as the Late Cambrian. Based on the geochemical peculiarities of rocks, it may be assumed that the early stage of volcanism was controlled by subduction, whereas the late stage was governed by riftogenic processes.