Late Mesoproterozoic–early Neoproterozoic quartzite–schist sequences of the Aktau–Mointy terrane (Central Kazakhstan): Provenance, crustal evolution, and implications for paleotectonic reconstruction

Abstract

Metasedimentary complexes represented by quartzite–schist Kiik Group quartzite–schists play a significant role in the Aktau–Mointy terrane structure, which is one of the largest Precambrian blocks in the western Central Asian Orogenic Belt (CAOB). U-Pb LA-ICP-MS dating of detrital zircons from quartzites in different Kiik Group areas and related magmatic age data establish that accumulation occurred in the late Mesoproterozoic to early Neoproterozoic (from 1150 to 920 Ma). Concordant age estimates of detrital zircons from Kiik Group quartzites predominately fell within intervals of 1149–2105 and 2272–2850 Ma with the prominent peaks at 1217, 1332, 1466, 1582, 1621, 1748, 1849, 2517 and 2689 Ma, and minor peaks at 1992, 2282, 2791 and 2823 Ma. Hf-in-zircon and Nd whole rock data suggest that the primary stages of continental crustal growth in the Aktau–Mointy terrane were associated with the tectono-magmatic processes of the Neoarchean, Paleoproterozoic, and Mesoproterozoic. Juvenile continental crust production occurred during the Neoarchean and Paleoproterozoic, with older complex tectono-magmatic reworking, and juvenile crust production finally prevailed in the mid-Mesoproterozoic. Based on the age patterns and Hf isotopic compositions of detrital zircons from the Aktau–Mointy terrane and other terranes in the western CAOB, the crustal basement of the Aktau–Mointy terrane exhibits certain similarities with those of the Northern Kazakhstan and Issyk–Kul terranes. They all exhibit a close tectonic affinity with the Chinese Central Tian Shan terranes, Yili Block, North and China Craton, while differing from the Tarim Craton. In the Rodinia supercontinent structure, the Aktau–Mointy terrane was probably located near the Sveconorwegian Orogen in the western Baltica with other Kazakhstan and Northern Tian Shan Precambrian blocks.