Early Neoproterozoic Island-Arc Volcanogenic Sedimentary Complex of the Ulutau Terrane (Central Kazakhstan): Substantiation of Age and Conditions of Formation

Abstract An Early Neoproterozoic (Middle Tonian) complex of differentiated volcanics has been identified for the first time in the central part of the Karsakpai (eastern) zone of the Ulutau terrane. A U–Th–Pb (SIMS, LA-ICP-MS) geochronological study of acidic effusions and tuffs was performed, and the age of their formation was estimated in the range of 845–825 Ma. A characteristic feature of the effusions and tuffs is the presence of zircon crystals with ages ranging from the Neoarchean to the Late Paleoproterozoic. Petrogeochemical characteristics of the volcanics indicate the suprasubduction origin of their parental melts. There are known analogues of the studied volcanic complex within the Tarim and Yangtze cratons, suggesting the existence of an extended convergent margin, which had been evolving during the Tonian period of the Neoproterozoic.