Copper is a moderately incompatible chalcophile element.Its behavior is strongly controlled by sulfides.The speciation of sulfur is controlled by oxygen fugacity.Therefore,porphyry Cu deposits are usually oxidized(wit...Copper is a moderately incompatible chalcophile element.Its behavior is strongly controlled by sulfides.The speciation of sulfur is controlled by oxygen fugacity.Therefore,porphyry Cu deposits are usually oxidized(with oxygen fugacities > AFMQ +2)(Mungall 2002;Sun et al.2015).The problem is that while most of the magmas at convergent margins are highly oxidized,porphyry Cu deposits are very rare,suggesting that high oxygen fugacity alone is not sufficient.Partial melting of mantle peridotite even at very high oxygen fugacities forms arc magmas with initial Cu contents too low to form porphyry Cu deposits directly(Lee et al.2012;Wilkinson 2013).Here we show that partial melting of subducted young oceanic slabs at high oxygen fugacity(>AFMQ +2) may form magmas with initial Cu contents up to >500 ppm,favorable for porphyry mineralization.Pre-enrichment of Cu through sulfide saturation and accumulation is not necessarily beneficial to porphyry Cu mineralization.In contrast,remelting of porphyritic hydrothermal sulfide associated with iron oxides may have major contributions to porphyry deposits.Thick overriding continental crust reduces the "leakage" of hydrothermal fluids,thereby promoting porphyry mineralization.Nevertheless,it is also more difficult for ore forming fluids to penetrate the thick continental crust to reach the depths of 2—4 km where porphyry deposits form.展开更多
Passivity degradation of Alloy 800 in simulated crevice chemistries was systematically investigated using cyclic polarization curve, electrochemical impedance spectroscopy(EIS), Mott-Schottky analysis, Auger electron ...Passivity degradation of Alloy 800 in simulated crevice chemistries was systematically investigated using cyclic polarization curve, electrochemical impedance spectroscopy(EIS), Mott-Schottky analysis, Auger electron spectroscopy(AES)and atomic absorption spectrometry(AAS). Cyclic polarization showed that the pitting potential in a thiosulfate solution was much lower than in either a chloride solution or a sulfate-chloride solution. Mott-Schottky results revealed that passive films showed n-type semiconductivity, and the presence of thiosulfate in chloride solution led to an increased donor density in the passive film. EIS spectra indicated that thiosulfate enhanced the film dissolution rate in chloride solutions. Moreover, thiosulfate enhanced the pitting propagation rate in chloride solution by stabilizing the metastable pits and forming sulfide within the pits.展开更多
With sulfide increasingly recognized as an important parameter to assess the oxidation-reduction level in aqueous enviromnent, research on its geochemical behavior is becoming important. Water samples collected in Boh...With sulfide increasingly recognized as an important parameter to assess the oxidation-reduction level in aqueous enviromnent, research on its geochemical behavior is becoming important. Water samples collected in Bohai Sea （1-19 August, 2010）, Yellow Sea （20-30 November, 2010） and East China Sea （3-17 June, 2010 and 1-10 November, 2010） were used to determine the occurrence and distribution of dissolved sulfide by methylene blue spectrophotometric method. Results show that： （1） horizontally, concentration of dissolved sulfide significantly varied from the coastal region to the open sea and profoundly influenced by physical processes. High values occurred in the river-sea boundary zone ＂marginal filter＂ due to rich riverine input, frequent upwelling and active exchange in shelf edge. Terrestrial input from adjacent rivers and the current cycling contributed to the high sulfide appeared in western Bohai Sea, eastern Shandong Peninsula, and northeast of Changjiang （Yangtze） River estuary. Especially, relative higher sulfide values occurred in Yellow Sea, which is consistent with the variation of salinity largely due to the hydrodynamic feature; （2） vertically, measurement of dissolved sulfide in bottom water was higher and more variable than that in surface water caused by the wind-induced resuspension and dissimilatory sulfate reduction. Moreover, nutrient-type profile clearly identified that oxidation plays a major role in the biogeochemistry cycle of sulfide in water; （3） seasonally, investigation for East China Sea in June and November reflected seasonal variation of Changjiang River Diluted Water, Kuroshio Current, and Taiwan Warm Current. Concentration in June was much higher than that sampled in November at most stations. Mean concentration of dissolved sulfide varied seasonally from 2.26 μg/L （June） to 1.16 μg/L （November） in surface and 3.00 μg/L （June） to 1.56 μg/L （November） in bottom. Progress in the field is slow and more effort is needed to ensure the accuracy and reliability of determination and estimate the natural or anthropogenic contribution of dissolved sulfide in ecosystems.展开更多
基金No.IS-2308 from GIGCAS,which is supported by the NSFC(No.91328204,41090374,41121002)the Chinese Academy of Sciences(KZCXl-YW-15)
文摘Copper is a moderately incompatible chalcophile element.Its behavior is strongly controlled by sulfides.The speciation of sulfur is controlled by oxygen fugacity.Therefore,porphyry Cu deposits are usually oxidized(with oxygen fugacities > AFMQ +2)(Mungall 2002;Sun et al.2015).The problem is that while most of the magmas at convergent margins are highly oxidized,porphyry Cu deposits are very rare,suggesting that high oxygen fugacity alone is not sufficient.Partial melting of mantle peridotite even at very high oxygen fugacities forms arc magmas with initial Cu contents too low to form porphyry Cu deposits directly(Lee et al.2012;Wilkinson 2013).Here we show that partial melting of subducted young oceanic slabs at high oxygen fugacity(>AFMQ +2) may form magmas with initial Cu contents up to >500 ppm,favorable for porphyry mineralization.Pre-enrichment of Cu through sulfide saturation and accumulation is not necessarily beneficial to porphyry Cu mineralization.In contrast,remelting of porphyritic hydrothermal sulfide associated with iron oxides may have major contributions to porphyry deposits.Thick overriding continental crust reduces the "leakage" of hydrothermal fluids,thereby promoting porphyry mineralization.Nevertheless,it is also more difficult for ore forming fluids to penetrate the thick continental crust to reach the depths of 2—4 km where porphyry deposits form.
基金Supported by the Atomic Energy of Canada Limited(AECL)and National Natural Science Foundation of China(No.51371124)
文摘Passivity degradation of Alloy 800 in simulated crevice chemistries was systematically investigated using cyclic polarization curve, electrochemical impedance spectroscopy(EIS), Mott-Schottky analysis, Auger electron spectroscopy(AES)and atomic absorption spectrometry(AAS). Cyclic polarization showed that the pitting potential in a thiosulfate solution was much lower than in either a chloride solution or a sulfate-chloride solution. Mott-Schottky results revealed that passive films showed n-type semiconductivity, and the presence of thiosulfate in chloride solution led to an increased donor density in the passive film. EIS spectra indicated that thiosulfate enhanced the film dissolution rate in chloride solutions. Moreover, thiosulfate enhanced the pitting propagation rate in chloride solution by stabilizing the metastable pits and forming sulfide within the pits.
基金Supported by the National Natural Science Foundation of China(Nos.41121064,41306055)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA05030402)the National Basic Research Program of China(973 Program)(No.2011CB403602)
文摘With sulfide increasingly recognized as an important parameter to assess the oxidation-reduction level in aqueous enviromnent, research on its geochemical behavior is becoming important. Water samples collected in Bohai Sea （1-19 August, 2010）, Yellow Sea （20-30 November, 2010） and East China Sea （3-17 June, 2010 and 1-10 November, 2010） were used to determine the occurrence and distribution of dissolved sulfide by methylene blue spectrophotometric method. Results show that： （1） horizontally, concentration of dissolved sulfide significantly varied from the coastal region to the open sea and profoundly influenced by physical processes. High values occurred in the river-sea boundary zone ＂marginal filter＂ due to rich riverine input, frequent upwelling and active exchange in shelf edge. Terrestrial input from adjacent rivers and the current cycling contributed to the high sulfide appeared in western Bohai Sea, eastern Shandong Peninsula, and northeast of Changjiang （Yangtze） River estuary. Especially, relative higher sulfide values occurred in Yellow Sea, which is consistent with the variation of salinity largely due to the hydrodynamic feature; （2） vertically, measurement of dissolved sulfide in bottom water was higher and more variable than that in surface water caused by the wind-induced resuspension and dissimilatory sulfate reduction. Moreover, nutrient-type profile clearly identified that oxidation plays a major role in the biogeochemistry cycle of sulfide in water; （3） seasonally, investigation for East China Sea in June and November reflected seasonal variation of Changjiang River Diluted Water, Kuroshio Current, and Taiwan Warm Current. Concentration in June was much higher than that sampled in November at most stations. Mean concentration of dissolved sulfide varied seasonally from 2.26 μg/L （June） to 1.16 μg/L （November） in surface and 3.00 μg/L （June） to 1.56 μg/L （November） in bottom. Progress in the field is slow and more effort is needed to ensure the accuracy and reliability of determination and estimate the natural or anthropogenic contribution of dissolved sulfide in ecosystems.
