矿床地球化学国家重点实验室知识库

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 flfluid 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 identifified based on fifield 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 signifificant 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 sulfifidation process was responsible for ore formation. Four types of flfluid inclusions were identifified in ore-related quartz and flfluorite. The main-ore stage flfluids are characterized by an H2O–NaCl–CO2–CH4 ± N2 system, with medium to low temperatures (180–260 C) and low salinity (0–9.08% NaCl equivalent). The late-ore stage flfluids featured H2O–NaCl ± CO2 ± CH4, with low temperature (120–200 C) and low salinity (0–7.48% NaCl equivalent). The temperature, salinity, and CO2 and CH4 concentrations of ore-forming flfluids decreased from the main-ore stage to the late-ore stage. The calculated d13C, dD, and d18O values of the ore-forming flfluids range from - 14.3 to - 7.0%, -76 to -55.7%, and 4.5–15.0%, respectively. Late-ore-stage stibnite had d34S values ranging from - 0.6 to 1.9%. These stable isotopic compositions indicate that the ore-forming flfluids originated mainly from deep magmatic hydrothermal flfluids, with minor contributions from strata. Collectively, the Baogudi metallogenic district has geological and geochemical characteristics that are typical of Carlin-type gold deposits in southwest Guizhou. It is likely that the Baogudi gold district, together with other Carlin-type gold deposits in southwestern Guizhou, was formed in response to a single widespread metallogenic event.