Ore-Forming And Exhumation Processes Of East Awulale Metallogenic Belt,Western Tianshan,Xinjiang

Rich mineral resource was hiding in the Awulale metallogenic belt and the exploration is closely associated with thermal evolution and the denudation process.Past researches always concentrated on regional geology,petro-geochemical,the genesis of ore and ore-forming process but neglect the history of uplift and exhumation after late Paleozoic.This dissertation based on pre-research results,conbined geochemical method and multi-method chronometric includes zircon U-Pb dating,potassium bearing minerals Ar/Ar dating and zircon/apatite(UTh)/He dating reveal the thermo-tectonic history of the East Awulale granitoids from emplacement to exhumation,geological setting of metallogeny in late Paleozoic and mineralization age of Zhibo/Beizhan iron ore.According to the geochemical chracters and different T-t tracks of the samples,this work find that the major intrusive rocks which finded in east Awulale emplaced during the subduction process of Tianshan ocean basin in Middle Devonian and collisional/post-collisional process in Carboniferous.Then all samples have a rapid cooling history until Late Permian as a result of heat exchange and orogenic movement.The major ores most formed when the tectonic framework transformed between Late Carboniferou and Early Permian in Late Paleozoic.The hydrothermal ore-forming age of Zhibo was-293Ma and the magmatic mineralization time of Beizhan was?300Ma.Although slower cooling rate during Mesozoic and Cenozoic mean that a relatively tectonic silent period was existed,rapid and drastic cooling/uplifting events still existed.Age-Elevation cross-section indicate that multiple rapid cooling events was happened during the intra-continental evolution process after post-collision and performed as obvious differential uplifting.The accretion of Qiangtang and Lasa block in the southern margin of Asian continent in Mesozoic and the collision of India-Asian in Cenozoic resulted in the reactive of faults in Tianshan.After the end of orogenic movement,Zhibo ore district keep slow uplift until Early Cretaceous.From Early Triassic to Early Jurassic,the cooling rate of Zhibo ore district was-0.96?/Ma,and the exhumation rate was-0.032km/Ma,the exhumation thickness was?3km.Affected by the extensive exhumation of Tianshan during Cretaceous,this district may have experienced bury history.Obvious differential uplifting was happened during Eocene between Zhibo and Beizhan ore district.During this period(?50Ma to?30Ma),the cooling rate of Zhibo was-4.25?/Ma,the exhumation rate was?0.14km/Ma and the exhumation thickness was?2.8km.Then the cooling rate of Beizhan from?50Ma to?30Ma was?2.1?/Ma,the exhumation rate was?0.07km/Ma and the exhumation thickness was?1.4km.Morever,the main ore body's cooling rate was 3.3?/Ma,the exhumation rate was 0.1km/Ma and the exhumation thickness was 2.3km from?55Ma to?34Ma.After Eocene,both Zhibo and Beizhan ore district turned into a quiet period of tectonic movement,and at this time the exhumation and buring keep an equal rate.