Geochemical characteristics of fluid inclusions in Lijia copper mine, Zhangjiajie, Northwest Hunan

Northwest Hunan is a famous area producing lead-zinc ore and manganese ore. In order to improve the research on the metallogenic sequence in this area, the authors made some analyses on the intramineral quartz, calcite and barite in Lijia copper mine in Zhangjiajie, which include homogenization temperature, salinity, gas compositions, liquid compositions and oxygen and hydrogen isotope. The results show that the homogenization temperature of the inclusion is from 146 ℃ to 282 ℃, and the salinity of the ore-forming fluid is from 0.71% to 15.86% (NaCl). The gas components of the ore-forming fluid have a little CH₄ and H₂, and the ions in the inclusion liquid compositions are mainly Ca²⁺, Mg²⁺, Na⁺, K⁺, SO_4^2- and Cl^-. The oxygen isotope (δ¹⁸O_矿物) value is from 11.6‰ to 17‰, and the hydrogen isotope (δD) value is from -54.7‰ to -76.2‰. By calculation, the metallogenic pressure is from 1.02 MPa to 66.17 MPa, and the metallogenic depth is from 0.1 km to 6.57 km. It can be concluded that the metallogenic hydrothermal solution is a stratabound hot brine, and the metallogenic time is from Sinian Doushantuo period to Silurian Wenloch period.