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On the basis of ore-forming periods and stages of the Daehang ore field,the pH and f_o_2 conditions andthe S isotopic systematics during ore formation have been thermodynamically treated in thispaper.Calculations show a progressively decreased pH,an increased oxidation regime and an intensifiedactivity of sulfur from the early to the late stage.Owing to the unreliability of inferring the S source fromδ~(34)S_(min),δ~(34)S_Σ_s has been calculated using the Ohmoto’s model.Results indicate that the δ~(34)S_(min) frequencydistribution is more concentrated than that of δ~(34)S_(min) 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 Ssources.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 fromcalculations are supported by many lines of geological evidence.
On the basis of ore-forming periods and stages of the Daehang ore field, the pH and f_o_2 conditions and the S isotopic systematics during ore formation have been thermodynamically 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 δ ~ (34) S_ (min), δ ~ (34) S_Σ_s has been calculated using the Ohmoto’s model. Results indicate that the δ ~ (34) ) S_ (min) frequencydistribution is more concentrated than that of δ ~ (34) S_ (min) and the peak value shifts to negative region by 2.5%. The sulfur in the whole ore field seems to be multiple source, ie, different deposits have their own Ssources.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 concludes from ccalulations are supported by many lines of g eological evidence.