Characteristics of polymetallic ore-forming fluid and metallogenesis of the Xiangshan ore?field in Jiangxi

Fluid inclusions of polymetallic mineralization in the Xiangshan uranium orefield were studied for the first time in this paper. A large number of polymetallic mineralizations were discovered recently with the deepening of geological exploration in the Xiangshan uranium orefield and the implementation of uranium scientific deep drilling. Based on studying petrography, microthermometry, pressure of ore-forming processes, composition and metallogenic depth of fluid inclusions as well as sulfur, carbon, oxygen isotopic composition, the authors hold that the lead and zinc ore-forming temperatures are mainly concentrated on 230~300℃, the metallogenic pressures are concentrated on 12~51MPa, and the salinities are concentrated on 4%~12% NaCleqv. The fluid inclusions are enriched in CO2 and to a lesser extent in CH4 and N2. The mineral assemblage is mainly sphalerite + gelenite + pyrite. The copper ore-forming temperatures are mainly concentrated on 320~380℃，metallogenic pressures on 33~95MPa , and salinities on 4%~12% NaCleqv. The fluid inclusions are enriched in CO2 and to a lesser extent in CH4 and N2. The mineral assemblage is mainly chalcopyrite + pyrrhotite + arsenikstein. All these data indicate that ore-forming fluids were characterized by medium-high temperature, high pressure, medium-high salinity, low oxygen fugacity and high content of CO2. The lead, zinc, copper and uranium ore-forming fluids were characterized by deep source, but there were obvious different in stage, space, alteration and fluid inclusion characteristics of lead, zinc, copper and uranium mineralization, so they were formed in different ore-forming stages and occurred in different separate hydrothermal mineralization processes in early-middle Cretaceous in South China.