Deformation events and the attributes of ore-controlling structures in the Yanlinsi gold field and its adjacent areas in eastern Hunan
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1.Geological Survey Institute of Hunan Province;2.Institute of Geomechanics,Chinese Academy of Geological Sciences

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    Abstract:

    The Yanlinsi gold field is located in the south of the northeastern Hunan gold mining area, where a large number of small and medium-sized gold deposits are developed. Predecessors have not explored and analyzed the kinematic characteristics, formation ages and mechanisms of various types of deformations including ore-controlling structures in the area, affecting a comprehensive understanding of the formation and preservation laws of ore deposits. In view of this, based on the regional structural characteristics and detailed analysis of a large number of surface outcrop structures, the authors determined the deformation sequences and their ages of the Yanlinsi gold field and its adjacent areas, and then combined with deposit geology and isotope dating, discussed the mineralization ages and attributes of ore-controlling structures. The main achievements are as follows: (1) The study area has experienced 9 tectonic events from early to late such as regional NW compression in the middle Neoproterozoic, NW compression in the early Silurian, active emplacement and compression of granite bodies in the late Silurian, NW compression in the late Middle Triassic, NNW to SN compression in the Late Triassic, NWW to EW compression in the late Middle Jurassic, NW-SE extension in the Cretaceous, NE to NNE compression in the middle-late Paleogene and NW compression during the late Paleogene to early Neogene, resulted in different trends and scales of structures such as folds, thrust faults, bedding shear zones, normal faults, dextral and sinistral strike-slip faults and shear fractures, faulted basins, cleavages and kinks, as well as late deflections of some structural trends. (2) There were two stages of gold mineralization in the area during the late Silurian and late Triassic, both of which are related to contemporaneous granitic magmatic activity. (3) The main ore-bearing structures in the Yanlinsi gold field include three types: pre Mesozoic bedding brittle-ductile shear zones and interlayer faults, NW- to NWW-trending dextral strike-slip faults and shear fractures formed during Middle to Late Triassic, and internal and external contact zones of granite branches. The ore-passing structures of the late Silurian gold deposits were pre NE-trending deep thrust faults, while those of the late Triassic gold deposits were NE-trending thrust faults in the late Middle Triassic, NEE- and EW-trending thrust faults in the early Late Triassic. For the two stages of gold deposits, different types of faults formed during each deformation events after mineralization may become ore-breaking structures.

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History
  • Received:March 26,2023
  • Revised:June 07,2023
  • Adopted:August 26,2023
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