Genesis of the giant Kangjiawan lead-zinc ore deposit in Hunan Province: Evidences from fluid inclusion, H-O and S isotope

Kangjiawan Pb-Zn deposit is located in the Shuikoushan Pb-Zn-Au ore field of Hunan Province. The orebodies were hosted in the interlayer silicified fracture zone of lower part of Permian Dangchong Formation mudstone, silicalite and Qixia Formation limestone. According to the mineral assemblage and interleaving relationship, the mineralization process of the Kangjiawan Pb-Zn deposit can be divided into three stages: early pyrite-quartz stage, sphalerite-galena (pyrite)-quartz stage and late calcite-sphaleritegalena stage. Microthermometric studies of fluid inclusions show that the fluid in the early pyrite-quartz stage of the Kangjiawan Pb-Zn deposit is mainly medium-high temperature (243 similar to 343 degrees C) and medium-high salinity (18.4% similar to 33.8% NaCleqv). The fluid of the sphalerite-galena (pyrite)-quartz stage is medium -low temperature (278 similar to 352 degrees C), medium-low salinity (1.1% similar to 20.7% NaCleqv) and has undergone boiling. The fluid in the late calcite-sphalerite-galena stage is low temperature (125 similar to 191 degrees C), low salinity (0. 2% similar to 6.7% NaCleqv) fliud. Laser Raman spectrum studies of fluid inclusions indicate that components of fluid inclusions in quartz and sphalerite during the mineralization period are mostly H2O. H-O and S isotope geochemistry shows that the ore-forming fluids of the Kangjiawan lead-zinc deposit were mainly derived from magmatic water, which is mixed with atmospheric water during the migration process. Combining the deposit geology, fluid inclusions, and hydrogen, oxygen, sulfur isotopic characteristics, the decrease of temperature, salinity and boiling may be important factors leading to the large-scale precipitation of ore-forming materials in the Kangjiawan Pb-Zn deposit.