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Geoscience ›› 2021, Vol. 35 ›› Issue (06): 1551-1564.DOI: 10.19657/j.geoscience.1000-8527.2021.122

• Gold-polymetallic Mineralization in Qinling Orogens • Previous Articles     Next Articles

Fluid Inclusion and C-H-O-S Stable Isotopic Studies of Sanguanmiao Gold Deposit, Shangnan, Shaanxi Province

WANG Chao1,2,3(), WANG Ruiting1,3,4(), LIU Yunhua1, XUE Yushan2,3, HU Xishun2,3, NIU Liang2,3   

  1. 1. School of Earth Science and Resources, Chang'an University, Xi'an, Shaanxi 710054, China
    2. Xi'an Northwest Geology Research Institute of Nonferrous Metals Co., Ltd., Xi'an, Shaanxi 710054, China
    3. Shaanxi Engineering Technology Research Center of Comprehensive Utilization of Mineral Resources, Xi'an, Shaanxi 710054, China
    4. Northwest Nonferrous Geological and Mining Group Co., Ltd., Xi'an, Shaanxi 710054, China
  • Received:2021-06-21 Revised:2021-10-12 Online:2021-12-10 Published:2022-02-14
  • Contact: WANG Ruiting

Abstract:

The Sanguanmiao gold deposit is located in the thrust-nappe belt in the northern South Qinling Orogen. It is a fault-controlled magmatic-hydrothermal deposit. Gold mineralization at Sanguanmiao can be divided into pre-ore (S1), main-ore (S2) and post-ore (S3) stages. Massive sulfide and calcite-quartz veins with gold mineralization were formed in S2. The homogenization temperatures (Th) of S2 fluid inclusions are of 150-420 ℃, with salinities of 2.07%-24.15%NaCl, whereas the S3 ores are of 81-190 ℃ and 8.55%-22.17%NaCl. Fluid inclusion petrologic and microthermometric analyses show that the gold precipitation was resulted from fluid mixing and subsequent fluid boiling during the main ore stage. The δDV-SMOW values of the S2 ore-forming fluid range from -84.4‰ to -77.0‰, and the δ18${{\text{O}}_{{{\text{H}}_{2}}\text{O}}}$ values range from 5.0‰ to 5.7‰, indicating the mixing of magmatic water and meteoric fluids. The ore-fluid δ13CΣC values range from -13.5‰ to -5.2‰, indicating a magmatic carbon origin influenced by low-temperature alteration. The δ34SCDT values range from -2.73‰ to -1.31‰ for pyrite, and from -3.36‰ to 0.03‰ for arsenopyrite, suggesting a single magmatic sulfur source. Thus, we considered that the Sanguanmiao gold deposit is associated with magmatic-hydrothermal activity, and proposed a metallogenic model as follows: the gold-bearing hydrothermal fluids migrated along fault structures during the late Indosinian Orogeny. Fluid mixing and boiling then occurred in the interlayer fracture zone, which caused gold precipitation and eventually the Sanguanmiao gold mineralization.

Key words: fluid inclusion, C-H-O-S stable isotope, ore genesis, Sanguanmiao gold deposit, Shangnan,Shaanxi

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