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| 1 | Redox processes in subduction zones:Progress and prospect显示文摘Oxygen fugacity(fO_(2))is an intensive variable that describes the redox state of a system.By controlling the valence state of multivalent elements,fO_(2)affects the stability of iron-bearing minerals,dominants the species of volatile elements(e.g.,carbon and sulfur),and controls the partitioning behaviors of multivalent elements(e.g.,iron,vanadium,cerium,europium).Thus,fO_(2)plays a key role in understanding the generation and differentiation of arc magmas,the formation of magmatic-hydrothermal deposits,and the nature of magmatic volatiles.Subduction zones are an important site for arc magmatism and fluid action,and the study of redox processes is indispensable in subduction zone geochemistry.In this paper,we first introduce the concept,expression,and estimation methods of fO_(2).Then we retrospect the history and progress about the oxidation state of the metasomatized mantle wedge,summarize the redox property of slab-derived fluids,and review the latest progress on redox evolution of arc magmas during magma generation and differentiation.The main conclusions include:(1)despite its wide variation range,fO_(2)of the mantle wedge is generally higher than that of the oceanic mantle;(2)the redox property of the subducting slab-derived fluids is still controversial and the mechanism for the oxidization of the mantle wedge remains unclear;(3)how the fO_(2)varies during the generation and differentiation of the arc magmas is debated.We propose that the crux in deciphering the oxidization mechanism of the mantle wedge is to determine the mobility of iron,carbon and sulfur in subducting slab-derived fluids(especially solute-rich fluid or supercritical fluid);the key in understanding the redox evolution during arc magma generation and differentiation is to determine the partition coefficients of Fe^(3+)and Fe^(2+)between ferromagnesian minerals and silicate melts. | Jintuan Wang Xiaolin Xiong Yixiang Chen Fangfang Huang | 2020 | Science China Earth Sciences2020，63，12： | 6 |
| 2 | The partitioning behavior of trace elements in subduction zones:Advances and prospects显示文摘The partitioning behavior of trace elements is of key importance for understanding the geochemical process and material cycle mechanism in subduction zones.This paper focuses on the advances and prospects on the studies of trace element partitioning in subduction zones from the following four aspects.(1)The properties of fluids derived from subducting slabs and their ability in element transport.How slab-derived solute-rich fluids and supercritical fluids are formed and what the roles and key control factors of these fluids are in transferring of elements(especially the high field strength elements)from slab to wedge are discussed.We point out that the detailed investigations of supercritical fluids may provide a new perspective for the element migration mechanism,material cycle process,arc magma genesis and so on.(2)The behavior of transition elements during mantle wedge melting.The behavior of the first row transition elements(Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn)in the mantle partial melting process is compatible or incompatible,depending on residual mineral assemblage and physicochemical conditions.The partitioning behavior of the elements such as Sc,Ti,Co,Ni and Zn whose valence states do not change in the melting process mainly depends on the residual mineral assemblage and temperature,whereas the partitioning behavior of the multivalent elements such as V and Fe is also the function of oxygen fugacity(fO_(2))in addition to mineral assemblage and temperature.Therefore,the partitioning behavior of transition elements has important applications in tracing lithologic inhomogeneity and fO_(2)of the mantle wedges.(3)The specificity of element partitioning behavior during arc magma evolution.Garnet has Dy/Yb partitioning behavior different from amphibole,and rutile has Nb/Ta partitioning behavior different from amphibole.Dy/Yb and Nb/Ta partitioning differences for these minerals enable to distinguish the specific evolution process of arc magmas.The Dy/Yb and Nb/Ta generally decrease with the increase of SiO_(2)in arc magmas,indicating that amphibole fractionation should be the most important during arc magma differentiation.(4)The behavior of sulfur and chalcophile elements and porphyry metallogeny.In subduction zones,the behavior of chalcophile elements such as Cu and Au is controlled by sulfide and fluid.Therefore,the stability of sulfide,the time at which the fluid exsolves from the melt relative to sulfide saturation,the fluid/sulfide mass ratio and fluid/melt Cu and Au partition coefficients in intermediate-felsic magma-H_(2)O systems are especially important in understanding Cu and Au enrichment in magma-hydrothermal processes.Intermediate-felsic magmas mainly originate from the differentiation of arc magmas at lower crustal reservoirs,and thus the fluid exsolution from the lower crustal reservoirs and the fluid/melt and fluid/sulfide partition coefficients of Cu and Au should be the keys to understanding quantitatively how Cu and Au are migrated from the deep crust to the shallow site of mineralization. | Xiaolin Xiong Xingcheng Liu Li Li Jintuan Wang Wei Chen Mengfei Ruan Ting Xu Zhongxing Sun Fangfang Huang Jianping Li&Lei Zhang | 2020 | Science China Earth Sciences2020，63，12： | 2 |
| 3 | Effect of Waste Marble Powder on Physical and Mechanical Properties of Concrete显示文摘The emission of greenhouse gases from cement production is an obstacle for sustainable development of construction industry.The use of waste materials in constructions instead of cement could be a feasible solution to green construction.Waste marble powder with good cementing property can be used in concrete partially replace cement.In this research,the effects of using waste marble powder on the physical and mechanical properties of concrete have been studied.Three groups of particle size and five levels of replacement ratio(5%,10%,15%,20%,25%)for each group have been designed.During the different stage of hydration process,the microstructure,phase composition and thermal properties of marble-cement paste have been investigated,the influence of particle size of marble powder on these properties has been discussed.The compressive strength and stressstrain relation were tested for different series prepared by partially replacing cement at proportions of 5%–25%separately.From the data analysis,it was observed that the using of waste marble powder would affect the hydration products and further affect the mechanical properties of concrete,the addition of marble powder that partially replace the cement at particular proportions in concrete is feasible. | Yumei Wang Jianzhuang Xiao Jintuan Zhang | 2022 | Journal of Renewable Materials2022，10，10： | 0 |
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