Granite Characteristics And Tectonic Setting In Wulonggou Area,East Kunlun

Wulonggou,located in the middle of East Kunlun,the northern Tibetan Plateau,is a gold-based multi-metal mineralization concentrated area.This area appears intense magmatism and widespread granite,mainly formed in the late Proterozoic,Cambrian,Silurian and Devonian.The research work studies the geological characteristics,petrography,geochemical characteristics,and tectonic setting of the granite in the Danshuigou,Huanglonggou,Shihuigou,Shaqiugou,and Yanjingou in Wulonggou district.After 2 month of field work and a systematic study,the main conclusions and original aspects of the present dissertation are summarized as follows:?1?Mainly,diorite,granodiorite,monzonitic granite,and granite were outcropped in the study area.The rocks are mainly belong to sub-alkaline series,calc-alkaline of high-potassium calc-alkaline to alkaline rocks of shoshonitic series;and the rocks are alkali meta aluminous and weakly peraluminous granite.From neutral to acidic,compositions of intrusive rocks are gradually enriched in SiO₂,K₂O,and reduced in Na₂O,FeO,MgO,MnO,and CaO,which was negatively correlated to the content of SiO₂.While the contents of TiO₂ and AlO₃ are unchanged.From neutral to acidic,The differentiation index?DI?was gradually increased,the degree of differences becomes higher,and the evolution of magma tend to mature direction.?2?The granite REE patterns of the study area showed rightist type REE distribution patterns,with strong enrichment of LILE Rb,Th,U,K,Pb,moderate enrichment of HFSE Zr,Hf,and depletion of Nb,P,Ti,Which show "V" shaped valley.?3?The granite of the studied Huanglong Valley exhibits:high content of silicon high alkaline value of,high content of aluminum,high content of FeOt/MgO and 10⁴ Ga/Al value,enriched in light rare earth,apparent negative Eu anomalies,obvious enrichment of high field strength elements?Zr,Ga,Y,and Hf et.al.?and strong losses of Ba,Sr,P,and Ti et al.comparing with primitive mantle.These features are consistent with geochemical characteristics of A-type granitoids.By using zircon LA-ICP-MS zircon U-Pb method,a weighted average age of 416.9± 1.3 Ma?MSWD=3.6?was obtained,which indicates that the rock was the product of late Silurian magmatic activity.Combined with the whole rock analysis,geochemistry and experimental petrology,it can be concluded that the rocks are post-orogenic collision product in late orogenic cycle,late Silurian,Paleozoic,which signifying the East Kunlun orogenic cycle of early Paleozoic Late Silurian entered post-collision stage.?4?The late Paleozoic-early Mesozoic orogenic cycle is composed of four stages:the formation and spreading of oceanic basin?C₁-C₂?,the subduction?C₃-T₁?,the syn-collision?T₂,T₃?and post-collision?T₃-early period of J₁?.The zircon LA-ICP-MS zircon U-Pb age of the I-type granite rocks in the east of Yanjingou mine was 260.4±2.3 Ma and 258.9±2.1 Ma,and the tectonic setting discrimination belongs to subduction stage,which is the product of intense magmatism resulted by strong crust-mantle shearing between Southern District Bayan Har terrane and Central Queensland South Kunlun terrane,began with Late Permian.The zircon LA-ICP-MS zircon U-Pb age of the I-type granite rocks in the Shihuigou was 220.3± 1.3 Ma,and the tectonic setting discrimination belongs to syn-collision of the subduction stage,the formation of the I-type granite was the result of the syn-collision.