查看更多>>摘要：The Pulang giant porphyry Cu-Mo polymetal-lic deposit is located in the Zhongdian area in the center of the Sanjiang Tethys tectonic domain,which was formed by the westward subduction of the Garze-Litang oceanic slab beneath the Zhongza massif.Chalcopyrite-pyrrhotite-pyrite-molybdenite occurs as disseminations,veins,veinlets,and stockworks distributed in the K-silicate alteration zone in the monzonite porphyry,which is superimposed by propylitiza-tion.The chemical compositions of biotite and amphibole analyzed by electron probe microanalysis(EPMA)indicate that the ore-forming magma and exsolved fluids experienced a continuous decrease in the oxygen fugacity(fO2).Primary amphibolite and biotite(type Ⅰ)crystallized at relatively high temperatures(744-827 ℃)and low fO2(logfO2=-12.26 to-11.91)during the magmatic stage.Hydrothermal fluids exsolved from the magma have a relatively lower tempera-ture(621-711 ℃)and fO2(logfO2=-14.36 to-13.32)than the original magma.In addition,the presence of a high abundance of pyrrhotite and an insufficiency of pri-mary magnetite and sulfate in the ore(i.e.,anhydrite and gypsum)indicate that the deposit may be a reduced por-phyry deposit.Magma and fluid fO2 results,combined with previous research on magmatic fO2 at the Pulang deposit,indicate that the magma associated with the reduced Pulang ore assemblages was initially generated as a highly oxidized magma that was subsequently reduced by sedimentary rocks of the Tumugou Formation.
查看更多>>摘要：Fe(Ⅲ)has been proved to be a more effective oxidant than dissolved oxygen at ambient temperature,how-ever,the role of Fe(Ⅲ)in pyrite acidic pressure oxidation was rarely discussed so far.In this paper,in-situ electro-chemical investigation was performed using a flow-through autoclave system in acidic pressure oxidation environment.The results illustrated that increasing Fe(Ⅲ)concentra-tions led to raising in redox potential of the solution,and decreased passivation of pyrite caused by deposition of ele-mental sulfur.Reduction of Fe(Ⅲ)at pyrite surface was a fast reaction with low activation energy,it was only slightly promoted by rising temperatures.While,the oxidation rate of pyrite at all investigated Fe(Ⅲ)concentrations increased obviously with rising temperatures,the anodic reaction was the rate-limiting step in the overall reaction.Activation energy of pyrite oxidation decreased from 47.74 to 28.79 kJ/mol when Fe(Ⅲ)concentration was increased from 0.05 to 0.50 g/L,showing that the reaction kinetics were limited by the rate of electrochemical reaction at low Fe(Ⅲ)concentra-tions,while,it gradually turned to be diffusion control with increasing Fe(Ⅲ)concentrations.
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