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<p>Numerous Mesozoic porphyry-skarn Cu-Au deposits occur in the Middle-Lower Yangtze River metallogenic belt (MLYRB), but their genetically related intermediate-sulfidation (IS) epithermal deposits are rarely reported. The recently discovered Paodaoling deposit (&gt; 35 t Au averaging 1.73&#xa0;g/t) offers an opportunity to address this gap. The IS epithermal mineralization, structurally controlled by NE-trending faults, is hosted in late Mesozoic granodiorite-quartz diorite porphyries and Silurian sedimentary rocks. There are four vein stages: Stage I quartz-carbonate-polymetallic sulfide veins with minor sulfosalts of Cu-rich phases; Stage II quartz-sphalerite-galena-pyrite ± barite veins featuring various Cu-poor Pb-sulfosalts; Stage III fine-grained pyrite-marcasite-quartz-barite ± realgar ± orpiment veins; and Stage IV barren carbonate-barite ± quartz veins. Gold is invisible in arsenian pyrite and arsenopyrite. Prevalent illite-quartz-pyrite ± carbonate alteration is closely associated with mineralization. The trend in illite crystallinity (0.8–3.5) predicts a hot center at depth around the Paodaoling South Zone. The <i>δ</i><sup>18</sup>O<sub>fluid</sub> values equilibrated with quartz indicate a predominantly magmatic fluid source for early stages (I-II: 4.5 to 12.7‰, V-SMOW) and gradual meteoric water involvement in late stages (III-IV: 0.5 to 6.1‰). In-situ Rb-Sr dating of hydrothermal white mica coexisting with auriferous pyrite yields ages of 134–132&#xa0;Ma, later than the host intrusions (148–141&#xa0;Ma; zircon U-Pb) and main porphyry-skarn mineralization (150–135&#xa0;Ma) in the MLYRB. The aforementioned lines of evidence support that mineralizing fluids were from a younger hidden intrusion. The preservation of Paodaoling implies potential to find other IS veins within or beneath the extensive early Cretaceous volcanic-sedimentary sequences in the MLYRB.</p>

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Geology and genesis of the Paodaoling intermediate-sulfidation epithermal gold deposit in the Chizhou district, Eastern China

  • 期刊论文

  • 发表日期：

    2025年10月24日

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  • Ke Huang,
  • Guiqing Xie,
  • Zhaoshan Chang,
  • Liuan Duan,
  • Shiqiang Huang,
  • Bin Fu

摘要

Numerous Mesozoic porphyry-skarn Cu-Au deposits occur in the Middle-Lower Yangtze River metallogenic belt (MLYRB), but their genetically related intermediate-sulfidation (IS) epithermal deposits are rarely reported. The recently discovered Paodaoling deposit (> 35 t Au averaging 1.73 g/t) offers an opportunity to address this gap. The IS epithermal mineralization, structurally controlled by NE-trending faults, is hosted in late Mesozoic granodiorite-quartz diorite porphyries and Silurian sedimentary rocks. There are four vein stages: Stage I quartz-carbonate-polymetallic sulfide veins with minor sulfosalts of Cu-rich phases; Stage II quartz-sphalerite-galena-pyrite ± barite veins featuring various Cu-poor Pb-sulfosalts; Stage III fine-grained pyrite-marcasite-quartz-barite ± realgar ± orpiment veins; and Stage IV barren carbonate-barite ± quartz veins. Gold is invisible in arsenian pyrite and arsenopyrite. Prevalent illite-quartz-pyrite ± carbonate alteration is closely associated with mineralization. The trend in illite crystallinity (0.8–3.5) predicts a hot center at depth around the Paodaoling South Zone. The δ18Ofluid values equilibrated with quartz indicate a predominantly magmatic fluid source for early stages (I-II: 4.5 to 12.7‰, V-SMOW) and gradual meteoric water involvement in late stages (III-IV: 0.5 to 6.1‰). In-situ Rb-Sr dating of hydrothermal white mica coexisting with auriferous pyrite yields ages of 134–132 Ma, later than the host intrusions (148–141 Ma; zircon U-Pb) and main porphyry-skarn mineralization (150–135 Ma) in the MLYRB. The aforementioned lines of evidence support that mineralizing fluids were from a younger hidden intrusion. The preservation of Paodaoling implies potential to find other IS veins within or beneath the extensive early Cretaceous volcanic-sedimentary sequences in the MLYRB.