Study On The Fluid Characteristics And Ore-forming Material Sources Of The Peripheral Ore Bodies Of Pulang Porphyry Copper Deposit In Northwest Yunnan

The Pulang copper deposit is located in the southern section of the Sanjiangmetallogenic belt and the southern section of the Yidun-Zhongdian Island arc belt in the Ganzi-Litang combination zone.In this paper,the geological characteristics,alteration characteristics and mineralization characteristics of the ore body around the Pulang copper deposit were analyzed in detail.For the first time,the ore-formingstages of each ore body in the periphery of Prang have been divided in detail,and petrofacies of fluid inclusions,microthermometers,laser Raman spectral component analysis,and S and Pb isotopic tests have been performed.The fluid characteristics of each ore body have a certain understanding,and the fluid evolution process of each ore body and the source of ore-forming materials are analyzed.The followingpreliminary results have been achieved:(1)Metallogenic stage:The ore body porphyry in the first mining area is dominated by quartz diortho porphyry and quartz diorite.The early mineralization stage was a combination of quartz vein minerals of pyrite+molybdenite±chalcopyrite,The main mineralization period is a combination of quartz vein minerals of pyrite+chalcopyrite,The late mineralization is mainly quartz vein mineralcombination of pyrite+pyrrhotite+chalcopyrite;The ore-bearing porphyry in thenorthern ore body is dominated by quartz diorite.The early mineralization stage was a combination of quartz vein minerals of pyrite+pyrrhotite+chalcopyrite,The main mineralization period is the quartz vein mineral combination of pyrite+molybdenite and pyrrhotite+chalcopyrite,The late mineralization is a combination of pyrite+chalcopyrite+calcite+quartz;The ore-bearing porphyry in the south is dominated by quartz diorite,The early mineralization stage was a quartz vein mineral combination of pyrite+chalcopyrite,The main mineralization period is the combination of quartz vein minerals of pyrrhotite+pyrite+chalcopyrite,Late mineralization isunmineralized quartz veins;The ore-bearing porphyry in the eastern ore body is dominated by quartz diorite,In the early stage of mineralization,the quartz vein mineral combination of pyrrhotite+pyrite,The main mineralization stage is the quartz vein mineral combination of pyrite+pyrrhotite+chalcopyrite,The late metallogenic stage is a mineral combination of pyrrhotite+chalcopyrite±calcite+quartz.(2)Nature of the ore-forming fluids:There are L-type,V-type,S-type and C-type inclusions in the first mining area of the Pulang Copper Mine.The main ore-forming uniform temperature is mainly concentrated at 250～320℃,Salinity range is mainly concentrated in 16～20 wt%,Density range 0.8～0.92g/cm~3,Ore-formingfluids are generally characterized by medium-high temperature,medium-low salinity,and medium-low density;The northern ore body mainly develops L-shapedinclusions.The uniform temperature during the main ore-forming period is mainly concentrated at 220～270°C,the salinity range is mainly concentrated between 6～16 wt%,and the density range is 0.82～0.92g/cm~3.The ore-forming fluid Generally,it is characterized by medium-high temperature,medium-low salinity,and medium-low density;L-type inclusions are mainly developed in the southern ore body.Theuniform temperature in the main metallogenesis period is mainly 230～260℃,the salinity is mainly in the range of 2～10wt%,and the density range is 0.71～0.94g/cm~3.Characteristics of high temperature,medium and low salinity,and medium and low density;L-type,V-type,and S-type inclusions are mainly developed in the eastern ore body.The uniform temperature during the main metallogenesis period is mainly concentrated at 250～280℃,and the salinity is mainly concentrated at 4～16wt%and 34～36wt%,density range 0.77～1.11g/cm~3,the ore-forming fluids generallyshow the characteristics of medium-high temperature,medium-high salinity,and medium-low density.(3)Sources of ore-forming fluids and materials:The results of S isotope tests indicate that the source of S in the ore-forming fluid of the Pulang copper deposit and the surrounding deposits is relatively single,mainly from magma sources,but thepossibility of other end-element S mixing in is not ruled out.The H-O isotope results show that the fluid source in the early ore-forming stage is mainly magma-dissolving fluid,and the fluid in the late ore-forming stage tends to be miscible with the water.Pb test results show that the ore-forming magma and minerals of the Pulang copper deposit originate from the upper and lower crusts and belong to a mixed crust-mantle source.