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<p>Porphyry copper systems hosted in mixed carbonate and silicate rocks may include porphyry, skarn, carbonate-replacement, and epithermal types of mineralization. The Bangpu deposit, located in the Gangdese metallogenic belt on the Tibet Plateau, China, represents such a system. It contains four ore types: (1) porphyry Mo‒Cu, (2) skarn Zn‒Pb‒Ag‒Cu, (3) breccia-type epithermal Ag‒Zn‒Pb, and (4) vein-type epithermal Ag‒Zn‒Pb. The porphyry Mo‒Cu ore is temporally and spatially associated with Miocene porphyry stocks. The skarn Zn‒Pb‒Ag‒Cu ore exhibits vertical metal zonation of shallower high-grade Zn + Pb (&gt; 15 wt%) and deeper Cu (&gt; 0.5 wt%). The breccia-type epithermal Ag‒Zn‒Pb ore is hosted in a breccia pipe within volcanic rocks, whereas the vein-type epithermal Ag‒Zn‒Pb ore is hosted along contacts between Paleogene volcanic rocks and Permian schists. Both epithermal Ag‒Zn‒Pb ores have high Ag/Au ratios (breccia-type: up to 605; vein-type: up to 475), low-Fe sphalerite (breccia-type: 7.81&#xa0;mol% FeS; vein-type: 5.15&#xa0;mol% FeS), and low estimated formation temperatures below 300&#xa0;°C, indicating an intermediate-sulfidation origin. In-situ Rb‒Sr isotopic dating of illite yielded dates of 12.7 ± 1.0&#xa0;Ma (2σ) for the skarn ore, and 12.3 ± 4.6&#xa0;Ma (2σ; breccia-type) and 14.3 ± 5.5&#xa0;Ma (2σ; vein-type) for the epithermal ores. <sup>40</sup>Ar‒<sup>39</sup>Ar dating of illite from the breccia-type epithermal ore yielded a date of 14.75 ± 0.10&#xa0;Ma (2σ). Zircon U‒Pb ages constrain the syn-mineralization brecciation to be 14.47 ± 0.09 to 14.33 ± 0.09&#xa0;Ma (2σ). Dates of the breccia-type and vein-type epithermal ore overlap with the previously reported molybdenite Re‒Os age of 14.11 ± 0.31&#xa0;Ma for the porphyry Mo‒Cu ore, whereas the skarn date is slightly younger. Geological and geochronological evidence supports a genetic link among the four ore types, indicating the formation of a Miocene intrusion-related polymetallic system with significant implications for mineral exploration in Tibet and beyond.</p>

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Geology and geochronology of the Bangpu porphyry‒skarn‒epithermal Mo‒Cu‒Zn‒Pb‒Ag deposit in the Gangdese metallogenic belt, Tibet

  • 期刊论文

  • 发表日期：

    2025年6月6日

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  • Junzeng Zuo,
  • Guiqing Xie,
  • Zhaoshan Chang,
  • Jingwen Mao,
  • Thomas R. Benson,
  • Nian Chen,
  • Shiqiang Huang,
  • Wenjun Huang

摘要

Porphyry copper systems hosted in mixed carbonate and silicate rocks may include porphyry, skarn, carbonate-replacement, and epithermal types of mineralization. The Bangpu deposit, located in the Gangdese metallogenic belt on the Tibet Plateau, China, represents such a system. It contains four ore types: (1) porphyry Mo‒Cu, (2) skarn Zn‒Pb‒Ag‒Cu, (3) breccia-type epithermal Ag‒Zn‒Pb, and (4) vein-type epithermal Ag‒Zn‒Pb. The porphyry Mo‒Cu ore is temporally and spatially associated with Miocene porphyry stocks. The skarn Zn‒Pb‒Ag‒Cu ore exhibits vertical metal zonation of shallower high-grade Zn + Pb (> 15 wt%) and deeper Cu (> 0.5 wt%). The breccia-type epithermal Ag‒Zn‒Pb ore is hosted in a breccia pipe within volcanic rocks, whereas the vein-type epithermal Ag‒Zn‒Pb ore is hosted along contacts between Paleogene volcanic rocks and Permian schists. Both epithermal Ag‒Zn‒Pb ores have high Ag/Au ratios (breccia-type: up to 605; vein-type: up to 475), low-Fe sphalerite (breccia-type: 7.81 mol% FeS; vein-type: 5.15 mol% FeS), and low estimated formation temperatures below 300 °C, indicating an intermediate-sulfidation origin. In-situ Rb‒Sr isotopic dating of illite yielded dates of 12.7 ± 1.0 Ma (2σ) for the skarn ore, and 12.3 ± 4.6 Ma (2σ; breccia-type) and 14.3 ± 5.5 Ma (2σ; vein-type) for the epithermal ores. 40Ar‒39Ar dating of illite from the breccia-type epithermal ore yielded a date of 14.75 ± 0.10 Ma (2σ). Zircon U‒Pb ages constrain the syn-mineralization brecciation to be 14.47 ± 0.09 to 14.33 ± 0.09 Ma (2σ). Dates of the breccia-type and vein-type epithermal ore overlap with the previously reported molybdenite Re‒Os age of 14.11 ± 0.31 Ma for the porphyry Mo‒Cu ore, whereas the skarn date is slightly younger. Geological and geochronological evidence supports a genetic link among the four ore types, indicating the formation of a Miocene intrusion-related polymetallic system with significant implications for mineral exploration in Tibet and beyond.