Deformation sequences and ore- controlling structuresof Au—Sb deposits in the Longshan area in central Hunan Province
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    Abstract:

    The Longshan Au—Sb mining area is located in the Longshan uplift of Xiangzhong basin. In the past, there were many views on the formation ages of the folds in the upper Paleozoic and on Longshan dome in central Hunan Province, and there is a lack of observation and understanding on the kinematic characteristics and ages of ore- bearing faults in Longshan Au—Sb mining area. Methods: In view of this, this study performed detailed structural observation and analysis of outcrops and in pits in the Longshan deposit and its surrounding areas, and then combined with the regional structural characteristics, Geological characteristics of the deposit and the previous research results of regional tectonics, distinguished the deformation sequences and the formation ages of the folds in the upper Paleozoic and of Longshan dome, and discussed the structural ore- controlling regularity and mechanism. Conclusions: The main achievements are as follows: ①The study area has experienced six main deformation events: Regional NW compression during late Ordovician to Silurian; Regional NW compression in the late Middle Triassic; Regional SN—NNE compression in the Late Triassic; Regional NWW compression in the late Middle Jurassic; Regional NW—SE extension in the Cretaceous; Regional NE compression in the middle—late Paleogene. ②The NE- trending folds in the upper Paleozoic were formed in the late Middle Triassic, the EW- trending folds were formed in the Late Triassic, and the NNE- trending folds were formed in the late Middle Jurassic; The Longshan dome was formed by the superposition of NE- trending anticlinorium of late Middle Triassic and EW- trending anticlinorium of Late Triassic. ③It was likely to form ore- guiding and ore- bearing faults in the core of the two stages of anticlinoriums due to stress concentration, in addition, the dome is accompanied by a hidden granite body, which resulted in the location of Longshan Au—Sb deposit in the middle of Longshan dome. The ore- guiding structures of Longshan Au—Sb deposit are NE- and EW- trending hidden thrust faults related to two- stages anticlinoriums; the ore- bearing structures are NWW- trending dextral strike- slip faults formed in late Middle Triassic, NNE- and NE- trending sinistral strike- slip faults and NW- trending dextral strike- slip faults formed in the Late Triassic. ④The high- angle plunging of the ore bodies in the area is related to the low- angle inclination of the movement direction of ore- bearing faults, and the latter is related to the inclination of the regional maximum principal compression caused by the unidirectional slip of the cover.

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BAI Daoyuan, LI Bin, JIN Hua, ZENG Guangqian.2023. Deformation sequences and ore- controlling structuresof Au—Sb deposits in the Longshan area in central Hunan Province[J]. Geological Review,69(1):88-112.

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History
  • Received:March 21,2022
  • Revised:July 18,2022
  • Adopted:
  • Online: January 20,2023
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