The Occurrence and Chemical Composition of Bismuth-Bearing Minerals in the Niuxingba-Liumukeng Ag-Pb-Zn Deposit, Jiangxi Province, South China

The Niuxingba-Liumukeng deposit, located in the Yinkeng ore field (Jiangxi province, South China), is a typical Ag-Pb-Zn deposit hosted in the Yudu-Ganxian metallogenic belt. Based on the field investigation and mineralogical studies, the mineralization of this deposit can be divided into three stages: quartz-pyrite-arsenopyrite stage (I), quartz-galena-sphalerite-sulfosalt stage (II), and quartz-carbonate stage (III), with stage II being the main Ag mineralization stage. In this contribution, we reported the occurrence of bismuth-bearing minerals in this hydrothermal deposit and its implications for ore formation. Based on the results of electron microprobe analyses, we infer that the dominant occurrence of bismuth at Niuxingba-Liumukeng is primarily marked by solid solutions within the crystal lattice of galena and as visible independent bismuth-bearing minerals. The independent bismuth minerals consist of berryite [Pb3(Ag,Cu)5Bi7S16], emplectite (CuBiS2), and aikinite (PbCuBiS3). Most bismuth minerals replace chalcopyrite or fill in the cracks of pyrite and chalcopyrite. Meanwhile, we found a large number of Bi-bearing minerals closely coexisting with Ag-bearing minerals, indicating that bismuth may have played a crucial role in silver deposition from hydrothermal fluids. We considered that the existence of bismuth-rich melts associated with the ore-forming hydrothermal systems could help to promote the enrichment and precipitation of silver to form economic ores.