The Nature And Evolution Of Ore Fluids In Dabate Cu-Mo Deposit, Western Tianshan

The porphyry deposit is an important industrial type of Copper、Molybdenum、gold and any other minerals,but people is not very clear about the ore forming process of the porphyry deposit’s fluid in the Western Tianshan metallogenic belt. The Dabate porphyry Cu-Mo deposit is an important deposit in Western Tianshan of Xinjiang, the deposit reserves of copper 52,000 tons, molybdenum 5,600 tons.In the Dabate Cu-Mo deposit, four copper and one molybdenum ore body have been found, and the being mined ore body are No. Ⅲ copper ore body and molybdenum ore body. The No.Ⅲ-1 copper ore body is distribution within the contact zone of the rhyolite porphyry and tuff, like a nervation, it is mainly ore-bearing fluorite vein; The No.Ⅲ-2 copper ore body is developed in the rhyolite porphyry, showing the disseminated copper mineralization in the whole rock. Molybdenum ore body is a concealed deposite, is developed in the rhyolite porphyry, near the granite porphyry, is mainly molybdenite-bearing quartz vein.They are separated from each other in space.In the basis of a lot of field geological survey and comprehensive observation of petrography,we identified four types veins in molybdenum ore body of the Dabate deposit,they are the Ⅰ stage molybdenite-chalcopyrite-quartz vein,the Ⅱ stage barren quartz vein,the Ⅲ stage molybdenite-quartz vein and the Ⅳ stage calcite-quartz vein. The fluid inclusions of each stage veins record the ore forming process of the fluid,based on the microthermometry and the Raman spectroscopy,fluid inclusions of the veins are mainly vapour-rich fluid inclusions,liquid-rich fluid inclusions,Pure liquid fluid inclusions, Pure vapor fluid inclusions,moly-phase fluid inclusions with daughter minerals and two-phase fluid inclusions with molybdenite.The Ⅰ stage and Ⅲ stage both have the mineralization,and they both have the characteristic of fluid boiling,CO2 is found in vapor phase at Ⅰ stage and Ⅲ stage,this phenomenon can indicate that the fluid boiling can result in the precipitation of metal elements and CO2 has a significant effect on the metal-transport at these two stage.The liquid-rich fluid inclusions coexist with the two-phase fluid inclusions with molybdenite, this phenomenon can indicate that molybdenite can be transported by the fluid in the forms of grain. The ore-forming fluid from early stage to late stage,their temperature are gradually lower,their salinity are also gradually lower,their density are gradually higher. Through the analysis of previous H-O isotopic data, the ore-forming fluid of the molybdenum ore body is mainly magmatic water.At the same time, the No.Ⅲ-1 copper ore body(ore-bearing fluorite vein) which is located independently, The characteristics of the minor elements and the REE in the fluorite show that the fluorite is hydrothermal origin, and in the middle stage of the hydrothermal activity, the crystallized environment of the fluorite is the medium temperature, low fugacity of O2. Based on the microthermometry, the ore-forming fluid has the medium temperature, a low salinity, and contains CO2. The age of the copper ore body is 297.6±1.5Ma, the copper ore body should be the product of late metallogenic epoch.