Geochemical Characteristics of the Ore-forming Fluids of the Haigou Gold Deposit, Jilin

The quartz in the Haigou gold deposit contains a great abundance of three-phase CO2-NaCl-H2O and two-phase CO2-rich inclusions, which are associated with two-phase NaCl-H2O ones. The ore-forming fluids, which were rich in CO2, are classified into two types with two different sources: the high-salinity CO2-rich NaCl-H2O fluid derived from magmatic hydrothermal solution, and the low-salinity NaCl-H2O fluid from ancient meteoric water. The optimum conditions for gold mineralization are 220-300℃ for the temperature, 4-20 MPa for the fluid static pressure, 1-3 km for the mineralization depth, 2-7 w (NaCl)/10-2 for the fluid salinity, and 0.644 g/cm3 for the total density. The fluid was in a critical or supercritical state at the initial stage of mineralization, and it boiled and was unmixed with CO2 and NaCl-H2O in the climax of mineralization, leading to the decomposition of Au-chlorine complexes and the bulk precipitation of Au.The type, association, homogenization temperature and composition (CO2/H2O val

Geochemical Characteristics of the Ore-forming Fluids of the Haigou Gold Deposit, Jilin

Abstract The quartz in the Haigou gold deposit contains a great abundance of three-phase CO₂-NaCl-H₂O and two-phase CO₂-rich inclusions, which are associated with two-phase NaCl-H₂O ones. The ore-forming fluids, which were rich in CO₂, are classified into two types with two different sources: the high-salinity CO₂-rich NaCl-H₂O fluid derived from magmatic hydrothermal solution, and the low-salinity NaCl-H₂O fluid from ancient meteoric water. The optimum conditions for gold mineralization are 220-300°C for the temperature, 4-20 Mpa for the fluid static pressure, 1-3 km for the mineralization depth, 2-7 w (NaCl)/10^-2 for the fluid salinity, and 0.644 g/cm³ for the total density. The fluid was in a critical or supercritical state at the initial stage of mineralization, and it boiled and was unmixed with CO₂ and NaCl-H₂O in the climax of mineralization, leading to the decomposition of Au-chlorine complexes and the bulk precipitation of Au. The type, association, homogenization temperature and composition (CO₂/H₂O value etc.) are the microscopic criteria for distinguishing the auriferous quartz vein from the barren quartz vein.