Co-precipitation of gold and base metal sulfides during fluid boiling triggered by fault-valve processes in orogenic gold deposits

作者：Huajian Li, Qingfei Wang, Weijun Weng, Chaoyi Dong, Lin Yang, Xuan Wang, Jun Deng · 发表于：Ore Geology Reviews · 年份：2022 · DOI：10.1016/j.oregeorev.2022.105090 · 被引用次数：28 · 研究领域：Geochemistry and Geologic Mapping、Geological and Geochemical Analysis、earthquake and tectonic studies

The extreme fluctuations in pressure during earthquakes are widely regarded as responsible for gold mineralization in quartz-vein-hosted gold deposits. However, it is barely noticed that base metal sulfides can precipitate together with gold during these processes. Here we present the phenomenon and unravel the mechanism of the co-precipitation of Au and base metal sulfides during the fluid boiling via geological study and thermodynamic modeling, respectively. The Bangbu deposit, a lode-type orogenic gold deposit in Tibet shows two mineralization substages of pyrite. The pyrite formed in the later substage is hosted in the wall rock selvages of laminated crack-seal quartz veins formed by the fault-valve processes. The pyrite grains are characterized by anhedral small crystals with porous textures and abundant native gold, chalcopyrite, galena, and sphalerite inclusions. They also contain higher concentrations of Cu, Pb, Ag, Sb, and Au, and lower concentrations of Co and Ni, compared to the euhedral large-grained pyrite formed in the initial substage. The textural and trace element characteristics of the pyrite indicate that vigorous boiling occurred during fault-valve behavior, which decreased the solubilities of Au, Cu, Pb, and Zn in the ore fluid in Bangbu. The co-precipitation of Au and base metal sulfides triggered by fluid boiling has also been reported in other orogenic gold deposits worldwide. Thermodynamic models are designed to acquire the predominant species and sol...