Genesis of Chaoshan skarn Au deposit, Tongling, eastern China: Insights from mineral geochemistry

作者：Xie, Jiancheng^*; Zhang, Xin; Huang, Shan; Ge, Likai; Li, Quanzhong; Sun, Weidong

来源：Journal of Geochemical Exploration, 2022, 241: 107055.

DOI：10.1016/j.gexplo.2022.107055

• Skarn Au deposit
• Genesis
• Mineral geochemistry
• Chaoshan deposit
• Tongling region

Skarn Au deposits are particularly developed along Middle and Lower Yangtze River region, eastern China, but gold behavior and genesis of the skarn Au deposits remain unclear. Whole-rock geochemical, sulfur isotopic and in-situ mineralogical data from the mineralized alteration stages of Chaoshan skarn Au deposit in Tongling re-gion are systemically investigated to reveal Au distribution and precipitation, and useful information for ore -forming process. The altered rocks and ores in the Chaoshan deposit have total REE contents of 7.81-226 ppm and show LREE enrichment patterns with weak negative to positive Eu (delta Eu = 0.71-2.24) anomalies. Electron probe microanalysis results indicate that garnet and pyroxene of the Chaoshan deposit are grossular-andradite and diopside-hedenbergite series, respectively. In situ elemental compositions of the euhedral pyrite analyzed show that invisible Au is mainly of lattice-bound Au+ in As-bearing pyrite. The studied pyrite samples also have high Co/Ni (mainly >1) and Se/Tl (>10) ratios, highly variable Pb and As contents, low Se content (<5.00 ppm), low Tl/Pb and Sb/Pb ratios, and relatively consistent sulfur isotopic compositions (5.0-8.3 parts per thousand). The distinctly geochemical characteristics indicate that the Chaoshan skarn Au mineralization was likely derived from a magmatic-hydrothermal system. A comprehensive discriminant analysis shows that the Au precipitation and enrichment of the Chaoshan deposit are a result of boiling-induced trace element fractionation resulted from fluid boiling during the skarn formation process.

• 单位
  中国科学院研究生院