He-Ar Isotopic Systematics of Fluid Inclusions in Pyrites from PGEpolymetallic Deposits in Lower Cambrian Black Rock Series, South China |
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| Authors: | SUN Xiaoming WANG Min XUE Ting MA Mingyang and LI Yinhe |
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| Institution: | SUN Xiaoming,WANG Min,XUE Ting,MA Mingyang and LI YinheDepartment of Earth Sciences,Sun Yat-sen University,Guangzhou,Guangdong,State Key Laboratory for Mineral Deposits Research,Nanjing University,Nanjing,Jiangsu Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing |
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| Abstract: | Abstract He‐Ar isotopic compositions of fluid inclusions trapped in pyrites from some representative PGE‐polymetallic deposits in Lower Cambrian black rock series in South China were analyzed by using an inert gas isotopic mass spectrometer. The results show that the ore‐forming fluids possess a low 3He/4He ratio, varying from 0.43×10?8 to 26.39×10?8, with corresponding R/Ra value of 0.003‐0.189. The 40Ar/36Ar ratios are 258–287, close to those of air‐saturated water (ASW). He‐Ar isotopic indicator studies show that the ore‐forming fluids were mainly derived from the formation water or basinal hot brine and sea water, while the content of mantle‐derived fluid or deep‐derived magmatic water might be negligible. The PGE‐polymetallic mineralization might be related to the evolution of the Caledonian miogeosynclines distributed along the southern margin of the Yangtze Craton. During the Early Cambrian, the formation water or basinal hot brine trapped in Caledonian basins which accumulated giant thick sediments was expelled and migrated laterally along strata because of the pressure generated by overlying sediments. The basinal hot brine ascended along faults, mixed with sea water and finally deposited ore minerals. |
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| Keywords: | He-Ar isotopic systematics pyrite fluid inclusions PGE-polymetallic deposit basinal hot brine |
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