Geological and geochemical characteristics of the Baogudi Carlintype gold district (Southwest Guizho

• 作者: Songtao Li Yong Xia Jianzhong Liu Zhuojun Xie Qinping Tan Yimeng Zhao Minghua Meng Lijin Tan Rong Nie Zepeng Wang Guanghong Zhou Haiyan Guo
• 来源期刊: 地球化学学报(英文）
• 关键词: Elemental geochemistry Fluid inclusions Stable isotopes Carlin-type gold deposits Baogudi gold district Southwestern Guizhou
• 年，卷（期）: 2019,（4）
• 页码范围: 587-609
• 页数: 22页
• 语种: 英文
• DOI: 10.1007/s11631-019-00355-9

摘要

The newly discovered Baogudi gold district is located in the southwestern Guizhou Province, China, where there are numerous Carlin-type gold deposits. To better understand the geological and geochemical characteristics of the Baogudi gold district, we carried out petrographic observations, elemental analyses, and fluid inclusion and isotopic composition studies. We also compared the results with those of typical Carlin-type gold deposits in southwestern Guizhou. Three mineralization stages, namely, the sedimentation diagenesis, hydrothermal (main-ore and late-ore substages), and supergene stages, were identified based on field and petrographic observations. The main-ore and late-ore stages correspond to Au and Sb mineralization, respectively, which are similar to typical Carlin-type mineralization. The mass transfer associated with alteration and mineralization shows that a significant amount of Au, As, Sb, Hg, Tl, Mo, and S were added to mineralized rocks during the main-ore stage. Remarkably, arsenic, Sb, and S were added to the mineralized rocks during the late-ore stage. Element migration indicates that the sulfidation process was responsible for ore formation. Four types of fluid inclusions were identified in ore-related quartz and fluorite. The main-ore stage fluids are characterized by an H2O–NaC1–CO2-–CH4 ± N2 system, with medium to low temperatures (180–260 ℃) and low salinity (0–9.08% NaCl equivalent). The late-ore stage fluids featured H2O-NaCl ± CO2 ± CH4, with low temperature (120-200 ℃) and low salinity (0–7.48% NaCl equivalent). The temperature, salinity, and CO2 and CH4 concentrations of ore-forming fluids decreased from the main-ore stage to the late-ore stage. The calculated δ13C, δD, and δ18O values of the ore-forming fluids range from -14.3 to - 7.0‰, -76 to –55.7‰, and 4.5–15.0‰,respectively. Late-ore-stage stibnite had δ34S values ranging from – 0.6 to 1.9‰. These stable isotopic compositions indicate that the ore-forming fluids originated mai