Magmatism And Mineralization Of Early Paleozoic Of Luliangshan Area, North Qaidam

North Qaidam experienced collisional orogenesis between the the Qaidam block with the Qilian block during Early Paleozoic, orogeny resulted in intense magmatism and mineralization. Based on Luliangshan area 1:50000 regional geological survey of the North Qaidam, zircon LA-ICP-MS U-Pb dating, chemical analysis of major and trace elements of rock and Hf isotope tracer was applyied to study the characteristics of orogenic magmatism, metamorphism and mineralization of various stages of early Paleozoic in Luliangshan area, and established the timing of the tectonic evolution of the region.The results show that, The process of orogeny magmatism of LuLiangshan has the following characteristics:(1) Luliangshan Tanjianshan volcanic give priority to basaltic andesite, zircon U-Pb dating acquired 432Ma magmatic crystallization age, rock geochemical analyzes revealed the basaltic andesite formed in back-arc basin environment, contrast, North Qaidam Tanjianshan dating results show that Tanjianshan formation lasted about 80Ma; (2) the Qaidamshan granite give priority to augen granite and granodiorite, zircon U-Pb dating give 436-446Ma of the magma crystallization age, TDM2=1.44-1.77Ga, studies show that the QaidamShan pluton original rock come from metamorphic basement of North Qaidam, Qaidamshan was the production of continent-continent collision; (3) Zircon U-Pb dating of TieShiguan granite give 422Ma magmatic crystallization age, rock chemical analysis results show that TieShiguan granite have adakites characteristics,implied TieShiguang granite resulted from re-melted thickened continental crust.Considering characteristics of every geological during orogenic process, tectonic evolution of Luliangshan can be divided into the following five stages:(1)Early stage of oceanic subduction (514-496Ma), in this stage ocean crust began to diving,and island arc volcanic began forming;(2) Middle stage of oceanic subduction (495-467Ma), in this stage ocean crust continue to dive, back-arc basin began forming and joined maturity; (3) Final stage of oceanic subduction (467-432Ma), in this stage northern Qaidam Basin margin integrate to island arc and Oulonguluke butt, back-arc basin gradually closed, and that a soft collision; (4) Stage of continental collision orogenic (432～423Ma), in this stage Qaidam Basin full-scale integrate to Oulongbuluke butt, producing S-type granites; (5) Continental post-collision orogenic stage (423～371 Ma), in this stage the subduction began exhumating, forming I-type granites and within the region forming a ductile shear area.Contrast tectonic evolution and mineralization, mineralization of early Paleozoic in Luliangshan can be roughly divided into the following phases:(1)Stage of magmatic differentiation mineralization (514Ma～496Ma), (2) Stage of VMS type mineralization (467Ma～432Ma) and (3) Stage of orogenic mineralization (423Ma～371Ma).