Geochemical Characteristics and Tectonic Settings of Late Carboniferous Intrusive Rocks from North Tarshan Area in Junggar,Xinjiang

As an important part of the Central Asian Orogenic Belt,the North Tarshan area in Xinjiang provides an ideal place for studying the tectonic evolution of the Junggar region because of its distinctive location.The Late Carboniferous intrusive rocks in the area consist of a complex series of rock sequence showing distinctive features of crust-mantle hybrid,with the early stage rock body dominated by diorites and the late stage rock body predominated by granitoids.This set of rock sequence is produced by the evolution of primitive magma in different stages.All geochemical characteristics,along with Rittman index σ<3.3,A/CNK<1.1,P₂O₅<0.65%,Fe₂O₃/FeO>0.4,enrichment in LILE and depletion in HFSE,are typical of I-type granitoids.However,further studies show the late plutons characterized by the rich silicon and alkaline,high potassium,low CaO,FeO,MgO,are alkaline granites,indicating the area has finished environmental evolution from the extruding collision to the post-collisional setting at the end of late Carboniferous and should be formed in a period about or ahead of(290.4±3.2)Ma.The findings will supply crucial evidences to explore the tectonic setting cycle of the Junggar region and the Central Asian Orogenic Belt.