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<p>Hydrothermal activity exerts dominant control on the spatial heterogeneity and quality of volcanic reservoirs. Permian volcaniclastic reservoirs distributed in the western Sichuan Basin, Southwestern China, which are closely associated with the Emeishan Large Igneous Province (ELIP), have undergone intensive superimposed alteration jointly induced by hydrothermal events and hydrocarbon emplacement. However, the timing, duration and formation mechanisms of this hydrothermal modification remain unclear. This study integrates petrology, geochemistry, geochronology and trace element analysis of hydrothermal zircon grains in eruptive-facies tuff breccia of the western Sichuan Basin, Southwestern China, aiming to constrain zircon formation ages and clarify their genetic mechanisms. Geochemical data indicate that the tuff breccia was derived from high-Ti alkaline basalt magmas with trace element signatures analogous to ocean island basalts (OIB), and was emplaced during the main eruptive phase of the ELIP (263–259&#xa0;Ma). Zircon geochronological results reveal two discrete episodes of hydrothermal fluid activity within the reservoir. The first episode (242.4 ± 3.6&#xa0;Ma and 238.1 ± 1.1&#xa0;Ma) is genetically linked to Indosinian orogeny-related magmatic-hydrothermal activity. During this stage, volatile-rich hydrothermal fluids triggered coupled dissolution-precipitation of primary zircon grains, resulting in radiogenic Pb loss and the formation of altered zircon domains. The second episode (159.0 ± 3.5&#xa0;Ma) corresponds to Yanshanian tectonically driven hydrothermal circulation, coinciding with the regional hydrocarbon charging peak. Early hydrothermal activity promoted the formation of devitrification-related pores in the tuff breccia. In contrast, late hydrothermal fluids facilitated mineral alteration and dissolution pore development, significantly enhancing secondary porosity. Hydrothermal zircon thus serves as reliable geochronological and geochemical tracers for recording multi-stage tectonic-magmatic-fluid interactions, which jointly dominate the diagenetic evolution and quality of Permian volcaniclastic reservoirs in the study area.</p>

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Hydrothermal zircon recording multi-stage tectonic reworking in Permian volcaniclastic rocks of the Emeishan Large Igneous Province, Southwest China

  • 期刊论文

  • 发表日期：

    2026年7月6日

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  • Junlang Chen,
  • Xiaohong Liu,
  • Tong Lin,
  • Mingyou Feng,
  • Hongming Tang,
  • Jie Tan,
  • Weiwei Wang,
  • Junxin Shang,
  • Tenglong Hu,
  • Yili Zhao

摘要

Hydrothermal activity exerts dominant control on the spatial heterogeneity and quality of volcanic reservoirs. Permian volcaniclastic reservoirs distributed in the western Sichuan Basin, Southwestern China, which are closely associated with the Emeishan Large Igneous Province (ELIP), have undergone intensive superimposed alteration jointly induced by hydrothermal events and hydrocarbon emplacement. However, the timing, duration and formation mechanisms of this hydrothermal modification remain unclear. This study integrates petrology, geochemistry, geochronology and trace element analysis of hydrothermal zircon grains in eruptive-facies tuff breccia of the western Sichuan Basin, Southwestern China, aiming to constrain zircon formation ages and clarify their genetic mechanisms. Geochemical data indicate that the tuff breccia was derived from high-Ti alkaline basalt magmas with trace element signatures analogous to ocean island basalts (OIB), and was emplaced during the main eruptive phase of the ELIP (263–259 Ma). Zircon geochronological results reveal two discrete episodes of hydrothermal fluid activity within the reservoir. The first episode (242.4 ± 3.6 Ma and 238.1 ± 1.1 Ma) is genetically linked to Indosinian orogeny-related magmatic-hydrothermal activity. During this stage, volatile-rich hydrothermal fluids triggered coupled dissolution-precipitation of primary zircon grains, resulting in radiogenic Pb loss and the formation of altered zircon domains. The second episode (159.0 ± 3.5 Ma) corresponds to Yanshanian tectonically driven hydrothermal circulation, coinciding with the regional hydrocarbon charging peak. Early hydrothermal activity promoted the formation of devitrification-related pores in the tuff breccia. In contrast, late hydrothermal fluids facilitated mineral alteration and dissolution pore development, significantly enhancing secondary porosity. Hydrothermal zircon thus serves as reliable geochronological and geochemical tracers for recording multi-stage tectonic-magmatic-fluid interactions, which jointly dominate the diagenetic evolution and quality of Permian volcaniclastic reservoirs in the study area.