Thermodynamic analysis of ore-forming conditions and sulfur isotopic systematics of Dachang ore field |
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| Authors: | Zhang Zheru Bai Zhenghua Zhang Zhengen Yan Yunxiou |
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| Institution: | (1) Institute of Geochemistry, Academia Sinica, China;(2) Geological Team No. 215, Guangxi Non-ferrous Metal Company, China |
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| Abstract: | On the basis of ore-forming periods and stages of the Dachang ore field, the pH and
conditions and the S isotopic systematics during ore formation have been thcrmodynamically treated in this paper. Calculations
show a progressively decreased pH, an increased oxidation regime and an intensified activity of sulfur from the early to the
late stage. Owing to the unreliability of inferring the S source from δ34Smin,
has been calculated using the Ohmoto’s model. Results indicate that the δ34
min frequency distribution is more concentrated than that of δ34Smin and the peak value shifts to negative region by 2.5%. The sulfur in the whole ore field seems to be of multiple source, i.e.,
different deposits have their own S sources. But the S isotopic composition pertaining to each stage is nearly constant, suggesting
that the ore-forming system be open to sulfur and the supply of sulfur be sufficient. The conclusions deduced from calculations
are supported by many lines of geological evidence. |
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