The Rsearching Of Genetic Relationship Between Porphyry And Skarn Deposits Of Kelu-chongmuda Belt

There are a number of large, super-large, giant scale porphyry copper deposits discovered in the gandese,which formed in crust extension environment after continent-continent collision and controled by the large-scale strike-slip fault systems of NW in the eastern edge of the plateau.At the eastern segment of the Gandese is located in the Gangdese-magmatic arc of the southern margin of the east section of a secondary structure unite of Gangdese Nyainqentanglha plate,and is an important part of the Gangdese copperpolymetallic metallogenic belt,whichischaracterized by porphyry copperdeposits or skarn copper polymetallic deposits.The research work main focus on the mid-sub metallogenic belt with the porphyry Cu-Mo mineralization and the north sub metallogenic belt with Pb-Zn-Mo mineralization.However,the south sub metallogenic belt in gandese,the research is still very weak.The Kelu-Chongmuda belt belongs to the south sub belt of the the eastern segment of the Gangdese metallogenic belt,located in Zhang-Sangri county in the south of the Tibet,distributing the large Cu-Mo-W(±Au) deposit of the Nuri, Chengba, Kelu, Chongmuda and Panan. The Nuri and Chengba deposits are newly discoveredlarge skarn-porphyry deposits and porphyry deposits, the mineralization elements combination are Cu-Mo-W and Mo-Cu.The discovery of the porphyry copper deposits and skarn copperpolymetallic deposits have an extremely vital significance inexplorating and researching of the deposits in the Gangdese metallogenic belt.This paper relies on the project of China geological survey "The study of the mineralization geological background,metallogenic conditions and prospecting techniques in the southern area of Tibet"(12120113095700),On the basis of previous research work,with the results of other researchers, the typical deposits are analyzed, basing on the geological characteristics of rock mass, the geochemical characteristics, ore-forming material sources, the source of ore-forming fluid and the spatial and temporal distribution of deposits, themainresults achievedandunderstandingare as follows:(1)Through the study of the characteristics of geology and geochemistry indicates that porphyry deposits and skarn deposits of the Kelu-Chongmuda belt formed in the island arc environment or the same collision environment, with geochemical characteristics of adakite and adakite-like rocks.(2)Through S, Pb isotope of the pyrite, chalcopyrite and other sulfide shows that porphyry deposits and skarn deposits of the Kelu-Chongmuda belt had the similar minerogenic substances.Compared with the north sub and mid-sub, the north sub mainly came from crust source, the mid-sub and south sub mainly came from crust and mantle source, while the crust source in the south sub accounted for a larger proportion.(3)Through the petrography of the fluid inclusion, hydrogen and oxygen isotope and composition concludes that ore-forming fluid of the skarn deposits were mainly the magma water,atmospheric precipitation hybrid was secondary.Ore-forming fluid of the main metallogenic stage of the porphyry deposits was mainly magmatic water,but in the late mineralization stage had been mixed with a considerable amount of atmospheric precipitation.(4)The mineralization time ofthe porphyry deposits and skarn deposits in the Kelu-Chongmuda beltis of about the same age(30 ~ 23Ma).The skarn deposits generally distributed in the periphery of the porphyry copper deposit or independent deposits,so that top and superficial skarn type mineralization can be one of as a symbol of looking for porphyry deposits.Comprehensive the above research, the porphyry deposits and skarn deposits in the Kelu-Chongmuda belt were by a unified geodynamic background, caused by the magmatic hydrothermal of the unified porphyry skarn mineralization metallogenic system in the genesis.All was continuous convergence and extrusion background in the late stage of collision of Tibet Plateau,the intermediate-acid magmatic came from lower crust or upper mantle partial melting along tectonic fracture channel on the invasion,formed in the top of the granitic magma and its inner and outer contact zone of porphyry deposits, the ore fluid gas migrated from the magma activity center outward, formed skarn and its copper polymetallic deposits by the metasomatism in the outer contactzone of rock mass or away from the calcareous rock strata of rock mass.