Characteristics and geological significance of fluid inclusions in the Yushui copper polymetallic deposit, Guangdong Province

The Yushui copper polymetallic deposit is located in the east zone of the South China MVT (Mississippi valley type zinclead deposits) metallogenic belt. The orebody mainly occurs between the littoral quartz sandstone of lower Carboniferous Zhongxin Group and littoral dolomite of upper Carboniferous Hutian Group, with a small number of mineral veins hosted in dolomite. The ore grade is so high that the processing grade was 15.5% in 2013. The ore is mainly in massive form while a small amount of ore being disseminated. The ore minerals include chalcopyrite, bornite, chalcocite, galena, sphalerite, pyrite, hematite and magnetite, and the main gangue minerals consist of dolomite, calcite and a small amount of quartz. The mineralization can be divided into hematitemagnetite stage characterized by existence of gel texture gangue and sulfide stage. By analyzing the temperature and salinity of fluid inclusions in sphalerite and quartz from the main metallogenic stage (sulfide stage) the authors found that the fluid inclusions from the Yushui copper polymetallic deposit mainly consist of gas-liquid two phase inclusions, with the gas-liquid ratio ranging from 5% to 20%, and the homogenization temperature ranging from 90℃ to 289℃. In addition, the homogenization temperature of fluid inclusions in sphalerite ranges from 90℃ to 289℃; the homogenization temperature of fluid inclusions in quartz ranges from 110℃ to 287℃; the homogenization temperature of fluid inclusions in calcite ranges from 125℃ to 210℃, the inclusion salinity range is concentrated on 8wt%-15wt%. The laser Raman microprobe test shows that the gas composition of the fluid inclusion is H₂O with minor CO₂. Fluid inclusion study combined with geological and geochemical studies of the deposit suggests that the Yushui copper polymetallic deposit is a stratabound and epithermal deposit.