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<p>Numerous Paleoproterozoic geological records, including 2.3–2.1 Ga magmatic rocks and 2.0–1.9 Ga high-grade metamorphic rocks, have been recently reported in the Yangtze Block and have been considered to record the orogenic event during the assembly of the Columbia (or Nuna) supercontinent. Late Paleoproterozoic (1.75–1.68 Ga) sedimentary-volcanic sequences, including the Dongchuan, Hekou, and Dahongshan groups, are widely developed in the southwestern margin of the Yangtze Block. They are considered to form within an intracontinental rift basin after assembly of the Columbia supercontinent and serve as key evidence for positioning the Yangtze Block in Columbia supercontinent. Dozens of iron-copper polymetallic deposits occur within these strata and are traditionally interpreted as marine volcanic-hosted iron (-copper) deposits. However, recent studies have indicated that the host rocks are predominantly intensely hydrothermally altered argillaceous siltstones and carbonates, interbedded with minor volcanic rocks. These deposits are primarily controlled by regional faults, and have stratabound orebodies exhibiting hydrothermal replacement characteristics. They display hydrothermal alteration phases typical of Iron Oxide-Copper-Gold (IOCG) deposit, and are closely associated with hydrothermal breccias as well as gabbro-diabase intrusions. The latest geochronological and geochemical evidence indicate that these IOCG deposits formed in the late Paleoproterozoic (1.7–1.66 Ga), contemporaneous with the emplacement of regional gabbroic dikes/sills exhibiting within-plate geochemical signatures. In addition, these IOCG deposits have been overprinted by later multiple magmatic events and/or metamorphism, resulting in a wide range of isotopic ages and leading to different interpretations. <i>In-situ</i> Nd isotope studies of apatite and allanite, along with <i>in-situ</i> B isotope studies of tourmaline, suggest that the ore metals and early-stage fluids were predominantly derived from mantle-related magmatic rocks, while significant involvement of basinal brines occurred during the late-stage Cu-sulfide precipitation process. These early Paleoproterozoic IOCG deposits in the southwestern margin of the Yangtze Block represent an IOCG metallogenic belt formed in an intracontinental rift basin. This belt is comparable to contemporaneous IOCG deposits in Australia and North America, and represents the products of the initial extensional breakup after the assembly of the Columbia supercontinent.</p>

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Iron Oxide-Copper-Gold (IOCG) deposits in the southwestern margin of the Yangtze Block and their relationship with the late Paleoproterozoic rift event

  • 期刊论文

  • 发表日期：

    2025年10月23日

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  • Xinfu Zhao,
  • Zhikun Su,
  • Xueqing Yin,
  • Jianwei Li,
  • Meifu Zhou

摘要

Numerous Paleoproterozoic geological records, including 2.3–2.1 Ga magmatic rocks and 2.0–1.9 Ga high-grade metamorphic rocks, have been recently reported in the Yangtze Block and have been considered to record the orogenic event during the assembly of the Columbia (or Nuna) supercontinent. Late Paleoproterozoic (1.75–1.68 Ga) sedimentary-volcanic sequences, including the Dongchuan, Hekou, and Dahongshan groups, are widely developed in the southwestern margin of the Yangtze Block. They are considered to form within an intracontinental rift basin after assembly of the Columbia supercontinent and serve as key evidence for positioning the Yangtze Block in Columbia supercontinent. Dozens of iron-copper polymetallic deposits occur within these strata and are traditionally interpreted as marine volcanic-hosted iron (-copper) deposits. However, recent studies have indicated that the host rocks are predominantly intensely hydrothermally altered argillaceous siltstones and carbonates, interbedded with minor volcanic rocks. These deposits are primarily controlled by regional faults, and have stratabound orebodies exhibiting hydrothermal replacement characteristics. They display hydrothermal alteration phases typical of Iron Oxide-Copper-Gold (IOCG) deposit, and are closely associated with hydrothermal breccias as well as gabbro-diabase intrusions. The latest geochronological and geochemical evidence indicate that these IOCG deposits formed in the late Paleoproterozoic (1.7–1.66 Ga), contemporaneous with the emplacement of regional gabbroic dikes/sills exhibiting within-plate geochemical signatures. In addition, these IOCG deposits have been overprinted by later multiple magmatic events and/or metamorphism, resulting in a wide range of isotopic ages and leading to different interpretations. In-situ Nd isotope studies of apatite and allanite, along with in-situ B isotope studies of tourmaline, suggest that the ore metals and early-stage fluids were predominantly derived from mantle-related magmatic rocks, while significant involvement of basinal brines occurred during the late-stage Cu-sulfide precipitation process. These early Paleoproterozoic IOCG deposits in the southwestern margin of the Yangtze Block represent an IOCG metallogenic belt formed in an intracontinental rift basin. This belt is comparable to contemporaneous IOCG deposits in Australia and North America, and represents the products of the initial extensional breakup after the assembly of the Columbia supercontinent.