Study On The Fluid Inclusions Of Gaerqiong-galale Copper-gold Ore Concentration Area,Tibet

The Gaerqiong-Galale copper-gold ore concentration area is located in thesouthern margin of the west of Bangong Lake-Nujiangmetallogenic belt, under thejurisdiction of Geji town in Geji count, Tibet. the ore concentration area has beenfound the copper-gold deposit of Gaerqiong and Galale. So far, the Gaerqiong-Galaleand Duolong copper-gold ore concentration area have the higher degree of work andresearch in the Bangong Lake-Nujiangmetallogenic belt.The strata of Gaerqiong-Galale copper-gold ore concentration area is CretaceousZenongqun Duoai formation(K1d), Langjiu formation(K1l) and Jiega formation(K1jg);The strata of Gaerqiong mining area is Cretaceous Zenongqun Duoai formation(K1d),the mainly lithology combination of Duoai formation is limestone，marble，volcanicbreccia，tuff and hornfels.The strata of Galale mining area is lower cretaceous Langjiuformation(K1l) and upper cretaceous Jiega formation （K1jg）. The lithologycombination of Langjiuformation(K1l) is ryolitic-dacite pyroclastic rocks andcoloradoite clip dacite pyroclastic lava. The lithology combination of Jiegaformation(K1jg) is dolomite、dolomitic marble、micrite、biological shell carbonateand sandy conglomerate.The mainly intrusive rock is quartz diorite，diorite-porphyrite，granodiorite，granodiorite-porphyry，granite porphyry of lateYanshanian.The gaerqiong deposit is mainly composed of I, II skarn type orebody andIII iron oxide-copper gold orebody.According to mineral assemblages, the ore-forming process and veins aredivided into early, middle and late stages, the main mineralization is middle stage.Fluid inclusions in quartzes of the early and middle stage are mainly aqueous and three-phase inclusions, together with CO2inclusions; whereas the late stages quartzesonly contain liquid-rich aqueous inclusions. Homogenization temperatures andsalinities of fluid inclusions in the early stage range from403℃to>540℃and15.2%to59.3%NaCleqv, respectively; while those of the middle stage range from205℃to398℃and1.9%to45.8%NaCleqv, respectively; the late stageliquid-rich aqueous inclusions yield homogenization temperatures of122℃~264℃and salinities of3%~16.4%NaCleqv. By microprobe Raman test resultsshow that the composition of gas phase in fluid inclusions are dominated by H2O,CO2, N2, and liquid phase composition are Na+, K+, Ca2+, Cu2+, Fe3+and Cl-, HCO3-,CO32-, and daughter minerals are dominated by halite, sylvite, chalcopyrite, calcite,hematite.The evolution of the ore-forming fluid in Gaerqiong-Galale copper-gold oreconcentration area from the early stage to the late stage is from the high temperatureand high salinities CO2-H2O-NaCl system to the middle-low temperature andmiddle-low salinities H2O-NaCl system. Different types and phase ratio inclusions inthe main mineralization stages have similar homogenization temperatures, the sametype inclusions have similar homogenization temperature, but differenthomogenization modes, which showed that the ore-forming fluid happenedimmiscibility or boiling action. Fluid immiscibility or boiling made CO2, H2S andother volatile gases escape, resulting in a large number of sulfides precipitation.Which cause the copper and gold of the Gaerqiong-Galale copper and gold OreConcentration Area enriched and mineralized.Combined with various ore controllingfactors of mineralization zone and the geochemical characteristics of rock, themetallogenic epoch and the ore-forming material sources, preliminarydiscussedore-forming process, established genetic model in this ore concentration area.