Abstract
CO2-rich fluid inclusions containing opaque mineral crystals were found in the Fenghuangshan skarn-porphyry Cu–Fe–Au deposit in Tongling, Anhui, China. These inclusions show variable CO2 contents and are accompanied by aqueous inclusions, both occurring as secondary inclusions in quartz and being locally associated with chalcopyrite mineralization. Laser Raman microspectroscopic analyses confirm the predominance of CO2 in the vapor and the presence of H2S as high as 8 mol%, and identify the opaque mineral with yellow reflectance color in the inclusions as chalcopyrite. More than half of the CO2-bearing inclusions contains chalcopyrite, whereas few of the associated aqueous inclusions do so. The chalcopyrite, occupying less than 1% (volume) of the inclusions, is interpreted to be a daughter mineral, and calculated Cu concentrations in the inclusions range from 0.1 to 3.4 wt%. Copper is inferred to have been transported in CO2-dominated fluids as HS− complexes. The occurrence of chalcopyrite daughter crystals in CO2-rich fluid inclusions indicates that CO2-rich vapor has the capacity of transporting large amounts of Cu, and possibly Au. This finding has significant implications for metal transport and mineralization in hydrothermal systems enriched in CO2, such as orogenic-type and granitic intrusion-related gold deposits.
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Acknowledgements
This study is supported by the tenth national “Five-year Project” of China (Project Nos. 2001BA609A-06 and 2004BA615A-02) and by the Chinese Scholarship Council (to Lai). Petrographic and microthermometric studies were carried out at the Geofluids Laboratory in the University of Regina with support from CFI and NSERC (to Chi). Laser Raman spectrum analyses were carried out by Therese Lhomme at CREGU-UMR G2R, Nancy, France. We would like to thank S. Peng, Y. Shao, B. Yang, Z. Cao, and S. Li for their help in the field work. Dr. Kalin Kouzmanov is thanked for his constructive review, which improved the quality of the paper.
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Lai, J., Chi, G. CO2-rich fluid inclusions with chalcopyrite daughter mineral from the Fenghuangshan Cu–Fe–Au deposit, China: implications for metal transport in vapor. Miner Deposita 42, 293–299 (2007). https://doi.org/10.1007/s00126-006-0109-z
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DOI: https://doi.org/10.1007/s00126-006-0109-z