Chronology of Proterozoic schist at the core of Tugermin anticline in northern Tarim basin and its tectonic significance

Abstract：Basin basement is one of the key factors to control basin evolution and its structural deformation. The study of basement is an important way to analyze the basin’s tectonics and structures. The northern part of Tarim basin is in the negative magnetic anomaly,suggesting that the basement is composed of meta-sedimentary rocks. Utilizing the data of zircon U-Pb chronology and geochemistry of Proterozoic schist at the core of Tugerming anticline in Kuqa depression in the north of Tarim Basin, this paper conducted the studies. The results show that zircon 206Pb/238U dating ages are concentrated on 775.3± 5.8 Ma~787.1± 6.8 Ma,which demonstrates that the schist was formed in the early Neoproterozoic,and the basement of northern Tarim basin was formed during Jinning movement. SiO2 content of schist is more than 70%,with high felsic constituents and enriched Al2O3 and K2O；the average value of ΣREE is160 ppm. Chondrite-normalized REE patterns are rightly-oblique,the rocks possess weak Eu anomalies；primitive mantle standardized trace elements characterized by LILE（Rb, Ba etc.）are relatively enriched, while HFSE（Ta, Nb, Ti etc.）are depleted. Through the restoration of the proto-rock, it can be determined that the metamorphic rock is parametamorphic rock formed from a quartz sandstone,which is in good agreement with the negative aeromagnetic anomalies in the north of Tarim Basin. The basement had low rigidity, which resulted in large-scale tectonic subsidence and intense structural deformation in the subsequent evolution of the basin.