Precambrian geology of the Kazakh Uplands and Tien Shan: An overview

A comprehensive review of newdata on geology and geochronology of Precambrian terranes in the western Central Asian Orogenic Belt reveals new insights into its evolution. At the present surface, these terranes mostly consist of Meso-to Neoproterozoic sedimentary, magmatic and metamorphic assemblages, with insignificant Paleoproterozoic rocks. Archean material is represented exclusively by detrital and xenocrystic zircons in younger strata. Meso-to Neoproterozoic felsic magmatic rocks were mostly sourced from Neoarchean and Paleoproterozoic continental crust, indicating its reworking and potential wider presence at deeper crustal levels. Most Meso-to Neoproterozoic assemblages are of intraplate origin. The supra-subduction assemblages of Neoproterozoic and Mesoproterozoic ages are of limited extent. We propose to recognize the Issedonian and Ulutau-Moyunkum groups of terranes, separated by early Paleozoic Z-shaped ophiolitic suture, based on their different tectono-magmatic evolution in the Mesoproterozoic and Neoproterozoic. Distinctly different are the Mesoproterozoic and early Neoproterozoic assemblages, with lithological variations at the beginning of the late Neoproterozoic and practically no differences at the end of the Neoproterozoic. The Issedonian group of terranes could be part of a Mesoproterozoic (ca. 1100Ma) orogen between the Siberian, North China and Laurentian cratons. The pre-Mesoproterozoic crust of these terranes was completely reworked during the younger events. The Ulutau-Moyunkum group of terranes appear to be lithologically and geochronologically similar to the Tarim craton. Both the Issedonian and Ulutau-Moyunkum groups of terranes were metamorphosed during the Ulutau-Moyunkum event at 700 +/- 25 Ma. The breakup into currently mappable Precambrian terranes took place during end-Ediacaran to early Paleozoic times after opening of oceanic basins, whose relics are preserved in numerous Paleozoic ophiolitic sutures. (C) 2017 Published by Elsevier B.V. on behalf of International Association for Gondwana Research.