1. Fluid inclusion and H–O-S-Pb isotope constraints on the origin of carbonate-hosted Hg-Sb mineralization at Gongguan, central China.
- Author
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Zhao, Gang, Zhai, Degao, Liu, Jiajun, and Mathur, Ryan
- Subjects
GOLD ores ,FLUID inclusions ,SULFUR isotopes ,LEAD isotopes ,MINERALIZATION ,ISOTOPES ,ANTIMONY ,MERCURY - Abstract
The Gongguan deposit in southern Qinling district, central China, is characterized by a Hg and Sb metal association, with proven reserves of 7,543 t Hg and 17,100 t Sb. The Hg-Sb mineralized veins are primarily hosted by local Lower Devonian dolomite. Three primary paragenetic stages have been identified, including (I) pyrite-dolomite-quartz, (II) stibnite-cinnabar-quartz-calcite and (III) post-ore calcite. Dominant mercury and antimony mineralization occurred in stage II. Fluid inclusion microthermometry of quartz and calcite reveal that the Hg-Sb mineralization is associated with a low temperature (142° to 240 °C) and low salinity (< 8.6 wt% NaCl equivalent) fluid, belonging to a H
2 O-NaCl ± CO2 system. The H–O isotope compositions (δDH2O = −84 to −63‰, δ18 OH2O = 1.3 to 12.7‰) of the hydrothermal fluid suggest a mixture of metamorphic fluid and meteoric water. In situ sulfur isotope results of cinnabar (δ34 S = 3.4 to 14.5‰), stibnite (δ34 S = 4.9 to 10.5‰) and pyrite (δ34 S = 3.8 to 5.4‰) indicate sulfur sources from decomposition of diagenetic pyrite and/or the thermochemical sulfate reduction in local sedimentary rocks. In situ obtained206 Pb/204 Pb,207 Pb/204 Pb and208 Pb/204 Pb ratios (18.006 to 18.362, 15.445 to 15.610 and 37.871 to 38.288, respectively) of stibnite and pyrite substantially differ from those for the regional Carlin Au-Sb and SEDEX Pb–Zn ore deposits. The lead isotope results indicate that the underlying Paleozoic (Silurian to Cambrian) strata and Precambrian metamorphic basement supplied substantial metals for the studied Hg-Sb deposit, whereas the host Devonian carbonates did not contribute significant metals. In summary, we propose that fluid mixing between metamorphic fluid and meteoric water was the main cause for carbonate-hosted Hg-Sb deposition at Gongguan, which reduced the stibnite solubility, oxidized mercury (Hg0 to Hg2+ ), favoring the process of dedolomitization. [ABSTRACT FROM AUTHOR]- Published
- 2023
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