Strontium isotope geochemistry of the Lemachang independent silver ore deposit, northeastern Yunnan, China |
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Authors: | DENG Hailin LI Chaoyang TU Guangzhi ZHOU Yunman WANG Chongwu |
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Affiliation: | 1. The Open Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China 2. No. 1 Geological Party of the Yunnan Bureau of Geology and Mineral Resources, Xundian 655205, China |
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Abstract: | Sr isotope geochemical studies (the87Sr/86Sr and δ18O-87Sr/86Sr systems) on the wall rocks and ores from the Lemachang independent Ag deposit in northeastern Yunnan provide strong evidence that the ore-forming fluids had flown through radiogenetically Sr-enriched rocks or strata prior to their entry into the locus of ore precipitation, and water-rock interaction is the main mechanism of Ag ore precipitation. The radiogenetically Sr-enriched source region may be the Proterozoic basement (the Kunyang and Hekou groups). Moreover, the theoretical modeling of the Sr isotopic system indicates that the ore-forming fluids contain as much as 3×10-6 Sr with isotopic composition of Sr being 0.750 and that of oxygen 7.0‰ The ore-forming temperatures were estimated at 150–250°C for the carbonate rock-type ores and at 200–260°C for the clastic rock-type. |
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Keywords: | Lemachang northeastern Yunnan independent Ag deposit Sr isotope ore-forming fluid |
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