Characteristics Of Ore-forming Fluid And Ore Genesis Of The Tuwaishan Gold Deposit, Hainan Province

Located in the conjoint site of Eurasian plate, Pacific plate and Indian ocean plate, Gezhen shear zone is the most important Au metallogenic area in Hainan province. From NE to SW, there are five important gold deposits. In this paper, we choose the Tuwaishan gold deposit located in the most NE of Gezhen shear area as the target.Through systematical study in geology character, fluid inclusion geochemistry, stable isotope, and compare it with the other typical gold quartz vein in the Gezhen Au metallogenic area, we discussed the character and genesis of ore-forming fluid and the mineralization and precipitation process of the Tuwaishan gold deposit. The main result we got as follow:The main veins presents a paragenesis that can be divided into three stages:(a) an early quartz-pyrite stage;(b) quartz-polymetallic sulphides-gold stage, which is the main ore-forming stage; (c)quartz-calcite stage.The study of fluid inclusion indicates that the ore-forming fluid belongs to NaCl- H2O type characterized by low-moderate temperature (180℃～320℃) and low salinity (3%-10%). The homogenization temperature and salinity of the three mineralization stages have three distinct peak value, and they fall gradually from the first stage (240～320℃) to the third stage(180～240℃).The study of hydrogen and oxygen isotopic shows that ore-forming fluid of the Tuwaishan gold deposit were mainly derived from magmatic water mixed with meteoric water during the ore-process.According to the study of fluid inclusion and H, O isotopes, the ore-forming fluids were derived from magmatic water with a lot of volatilizable component, and gradually mixed with the meteoric water. Then gold was precipitated from H2O-NaCl fluids by cooling and by dilution caused by mixing with meteoric water.