Rb-Sr isochron age and isotopic compositions of H, O, S and Pb of the Gaozhuang gold deposit, Xixia County, Henan Province: Identification of intraplate orogenic metallogenesis in northern Qinling Mountain
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P597.3;P612

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    Abstract:

    The Gaozhuang gold deposit is one of the important Au deposits in Au polymetallic ore concentration area of northern Qinling Mountain, Henan Province. The Rb-Sr isochron age and H, O, S and Pb isotopes of ores from the Gaozhuang gold deposit were analyzed so as to constrain Au mineralization formation age and discuss the source of ore metals and the controlling factor of deep ore fluids discharge as well as the Au mineralization potential. The 87Rb/86Sr and 87Sr/86Sr ratios of pyrite and quartz from 7 ore samples are in the range of 0.0709-5.963 and 0.711139-0.721982, respectively. The initial 87Sr/86Sr ratios are in the range of 0.711025±0.000052 and the Rb-Sr isochron age is (129.8±1.4)Ma (MSWD=1.3), almost consistent with the age of the Yanzhen granitic intrusive and the Gaozhuang granitic aplite. It is suggested that they were nearly formed at the same time of -130Ma in early Cretaceous. The δ18OV-SMOW and δDV-SMOW values of 3 quartz samples are 11.6‰-12.1‰ and -60.9‰—-42.5‰, respectively. Their δ18OH2O values range from 2.16‰ to 2.66‰, suggesting that ore-forming fluids of the Gaozhuang gold deposit were a mixed source. The δ34SV-CTD values of 6 pyrite samples are from -2.8‰ to -1.6‰ with a tower shape in the δ34S histogram, which indicates a mantle source. The ratios of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb of 7 samples are 17.549-18.278, 15.461-15.619 and 37.593-38.428, respectively. Their μ, △α, Δβ and Δγ are 9.30-9.51, 59.52-75.10, 11.44-19.80 and 30.38-37.99. In 206Pb/204Pb-207Pb/204Pb and 206Pb/204Pb-208Pb/204Pb diagrams, sample points of the Gaozhuang gold deposit are close to the orogenic line. They fall into the crust-mantle subduction zone mixed lead source and the orogenic belt lead source in Δβγ of Pb isotopic diagram. It is suggested that metallogenic materials of the Gaozhuang gold deposit were derived from the lower crust and the upper mantle, with the addition of the upper crust materials in the ore-forming process. The formation of the Gaozhuang gold deposit was closely related to Yanshanian intraplate (intracontinental) orogenesis of northern Qinling Mountain. The Gaozhuang gold deposit, the Yanzhen granitic intrusive and the Gaozhuang granitic aplite are all products of regional lithosphere delamination. Deep fluids were rapidly discharged, and diverse sources of metallogenic materials at different depths were connected in the process of regional lithosphere delamination. The Gaozhuang gold deposit was formed when the mixed fluids stopped moving in shallow crust. It is suggested that the deep part beneath the Gaozhuang gold deposit and the Yanzhen area possessed endogenetic metallogenic potential with rapid discharging of deep fluids controlled by regional lithosphere delamination.

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LIANG Tao, LU Ren, YANG Nan, WANG Li, WEN Jingjing. Rb-Sr isochron age and isotopic compositions of H, O, S and Pb of the Gaozhuang gold deposit, Xixia County, Henan Province: Identification of intraplate orogenic metallogenesis in northern Qinling Mountain[J]. Geology in China, 2020, 47(2): 406-425(in Chinese with English abstract).

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History
  • Received:December 10,2018
  • Revised:April 09,2019
  • Adopted:
  • Online: April 22,2020
  • Published: