Gold mineralisation characteristics of the typical ore body and the potential for exploration in the Qiucun Au deposit, Dehua county, Fujian province, China

Le résumé fourni par la source

The Qiucun Au deposit is located in Dehua County, Fujian Province, within the Wuyi Mountain metallogenic belt. Gold mineralisation of the typical ore body exhibits distinct zoning characteristics between 940 m and 647 m, is structurally controlled by a volcanic conduit and its associated fracture zones, and is closely associated with quartz (chalcedony)-sericite-pyrite-calcite assemblages. To decipher the ore-forming processes of the Qiucun deposit, detailed geological investigations were carried out, along with sulfur isotope analysis of syn -ore pyrite, microthermometric analysis (homogenization temperature and salinity) of fluid inclusions in syn -ore quartz, and U-Pb dating of syn -ore calcite. The results show that in typical orebodies, gold grade increases and then decreases from shallow to deeper sections. Gold occurs mainly as fracture-fillings within pyrite, displaying diverse morphologies and colours that correlate with grade. Significant gold mineralisation is hosted within sericite alteration zones, whereas the presence of calcite is generally associated with lower gold grades. The δ 34 S values of gold-related pyrite range from –6.8‰ to + 1.6‰, suggesting a deep magmatic source for the ore-forming materials. Fluid inclusions in quartz are dominated by two-phase (liquid-rich) types with minor evidence of boiling assemblages, obtaining low-temperature (180–260 °C) and low-salinity (0.35–5.56 wt% NaCl equiv.). U-Pb dating of calcite yields an age of 152.0 ± 17 Ma. Integrated evidence indicates that the Qiucun low-sulfidation epithermal Au deposit is related to the subduction of the paleo-Pacific Plate. Fractured volcanic breccia zones served as the main pathways for hydrothermal fluid migration and ore precipitation. Pyrite, sericite, calcite, and other minerals at different elevations are the main indicators for further gold exploration in the Qiucun gold deposit and its adjacent areas.

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