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<p>In this paper, we present a study of sulfide petrography, zircon and apatite geochemistry of various intrusions from the ~ 130&#xa0;Ma Diaoquan Ag-Cu-Au deposit (North China Craton) to reveal magmatic signatures related to Ag fertility. Zircons from the ore-related porphyries (~ 130&#xa0;Ma) have higher ΔFMQ (0.9–3.0), 10<sup>4</sup>×(Eu/Eu*)/Y ratios (&gt; 1), and lower Dy/Yb ratios (&lt; 0.3) than the barren intrusions (~ 140&#xa0;Ma), suggesting their formation from oxidized and hydrous magma. Apatite included in zircons from barren intrusions have large X<sub>Cl</sub>/X<sub>OH</sub> rations of 0.18–0.82 that are correlated positively with X<sub>F</sub>/X<sub>Cl</sub> (12.1–23.5) and negatively with X<sub>F</sub>/X<sub>OH</sub> (3.2–9.5). Compositional modeling indicates that these apatites crystallized from a volatile-undersaturated melt that subsequently became saturated. In contrast, apatite from the ore-related magmas has much lower X<sub>Cl</sub>/X<sub>OH</sub> (0.06–0.22) and higher X<sub>F</sub>/X<sub>Cl</sub> (16.8–97.6) variations, suggesting fluid exsolution during apatite crystallization. The low Cl and S contents in apatite from the ore-related porphyries are due to sulfide crystallization and subsequent fluid exsolution. Sulfide saturation would have led the residual magma to be depleted in Cu and Au, but enriched in Ag. This process may explain the metal association of the Diaoquan Ag-(Cu-Au) deposit. It is concluded that mineralization at Diaoquan was closely related to oxidized, hydrous magmas that have experienced significant sulfide separation and volatile evolution. These processes would have made the apatite be depleted in Cl and S, making it questionable as a fertility indicator. Additionally, based on Ag solubility data in melts, the Ag mineralization at Diaoquan is inferred to be related to a smaller, degassed magma chamber than similar-sized Ag deposits associated with reduced, less hydrous magmas.</p>

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Magmatic control on the formation of the Diaoquan Ag-(Cu-Au) skarn deposit in the eastern North China Craton as revealed by zircon, apatite and sulfides

  • 期刊论文

  • 发表日期：

    2025年10月31日

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  • Gao-Hua Fan,
  • Jian-Wei Li,
  • Paul T. Robinson,
  • Kai-Xuan Hui,
  • Xiao-Dong Deng,
  • Wen-Sheng Gao,
  • Jin-Hao Liu,
  • Hang-Jin Jiang

摘要

In this paper, we present a study of sulfide petrography, zircon and apatite geochemistry of various intrusions from the ~ 130 Ma Diaoquan Ag-Cu-Au deposit (North China Craton) to reveal magmatic signatures related to Ag fertility. Zircons from the ore-related porphyries (~ 130 Ma) have higher ΔFMQ (0.9–3.0), 104×(Eu/Eu*)/Y ratios (> 1), and lower Dy/Yb ratios (< 0.3) than the barren intrusions (~ 140 Ma), suggesting their formation from oxidized and hydrous magma. Apatite included in zircons from barren intrusions have large XCl/XOH rations of 0.18–0.82 that are correlated positively with XF/XCl (12.1–23.5) and negatively with XF/XOH (3.2–9.5). Compositional modeling indicates that these apatites crystallized from a volatile-undersaturated melt that subsequently became saturated. In contrast, apatite from the ore-related magmas has much lower XCl/XOH (0.06–0.22) and higher XF/XCl (16.8–97.6) variations, suggesting fluid exsolution during apatite crystallization. The low Cl and S contents in apatite from the ore-related porphyries are due to sulfide crystallization and subsequent fluid exsolution. Sulfide saturation would have led the residual magma to be depleted in Cu and Au, but enriched in Ag. This process may explain the metal association of the Diaoquan Ag-(Cu-Au) deposit. It is concluded that mineralization at Diaoquan was closely related to oxidized, hydrous magmas that have experienced significant sulfide separation and volatile evolution. These processes would have made the apatite be depleted in Cl and S, making it questionable as a fertility indicator. Additionally, based on Ag solubility data in melts, the Ag mineralization at Diaoquan is inferred to be related to a smaller, degassed magma chamber than similar-sized Ag deposits associated with reduced, less hydrous magmas.