The dependence of the subduction regime on three-dimensional slab geometry poses a challenge for accurately estimating the evolving thermal structure of megathrusts globally. Although slab dips and ages have gained at...The dependence of the subduction regime on three-dimensional slab geometry poses a challenge for accurately estimating the evolving thermal structure of megathrusts globally. Although slab dips and ages have gained attention, the specific impacts of oblique subduction remain unmeasured. Here, we present an integrated thermal model that quantifies how slab morphology can shape the thermal state of megathrusts, such as those in the Makran Subduction Zone. The model considers both slab obliquity and depth variations along the trench. We find a considerable match between the slab petrological dehydration zone and the distribution of great crustal earthquakes. We suggest that the accumulation of fluids along megathrusts by slab metamorphism can foster more polarized conditions for decreasing plate coupling and increasing interplate ruptures. It is thus imperative to improve model representation and more realistically represent how drivers of slab geometry affect metamorphic transitions and the occurrence of earthquakes at megathrusts.展开更多
Water is essential for the formation of a magmatic arc by lowering the melting temperature of materials in the mantle wedge.As such,it is logical to attribute the absence of a magmatic arc to insufficient water releas...Water is essential for the formation of a magmatic arc by lowering the melting temperature of materials in the mantle wedge.As such,it is logical to attribute the absence of a magmatic arc to insufficient water released from the subducting plate,although a number of other factors may cause volcanic arc quiescence as well,such as a slab window or flat slab subduction.In this contribution,we present a possible but testable correlation between the occurrence of a magmatic arc and seamount subduction in light of bathymetric data obtained near trenches.This correlation,if it holds true,in turn means that a magmatic arc is unlikely to occur when the subducting slabs have not been severely fractured and that one of the main reasons for excluding effects such as the slab window or flat slab subduction may be that the plate is not accompanied by seamounts.Therefore,the role that seamount subduction plays in recycling water back into the mantle deserves more attention from the earth sciences community.展开更多
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 sp...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.展开更多
基金benefited from the financial support of the Chinese Academy of Sciences Pioneer Hundred Talents Programthe Second Tibetan Plateau Scientific Expedition and Research Program (Grant No. 2019QZKK0708)+2 种基金the MEXT KAKENHI grant (Grant No. 21H05203)the Kobe University Strategic International Collaborative Research Grant (Type B Fostering Joint Research)the “Science of Slowto-Fast Earthquakes” project。
文摘The dependence of the subduction regime on three-dimensional slab geometry poses a challenge for accurately estimating the evolving thermal structure of megathrusts globally. Although slab dips and ages have gained attention, the specific impacts of oblique subduction remain unmeasured. Here, we present an integrated thermal model that quantifies how slab morphology can shape the thermal state of megathrusts, such as those in the Makran Subduction Zone. The model considers both slab obliquity and depth variations along the trench. We find a considerable match between the slab petrological dehydration zone and the distribution of great crustal earthquakes. We suggest that the accumulation of fluids along megathrusts by slab metamorphism can foster more polarized conditions for decreasing plate coupling and increasing interplate ruptures. It is thus imperative to improve model representation and more realistically represent how drivers of slab geometry affect metamorphic transitions and the occurrence of earthquakes at megathrusts.
基金This work was funded by the National Natural Science Foundation of China(Grant Nos.91858205 and 91858212).
文摘Water is essential for the formation of a magmatic arc by lowering the melting temperature of materials in the mantle wedge.As such,it is logical to attribute the absence of a magmatic arc to insufficient water released from the subducting plate,although a number of other factors may cause volcanic arc quiescence as well,such as a slab window or flat slab subduction.In this contribution,we present a possible but testable correlation between the occurrence of a magmatic arc and seamount subduction in light of bathymetric data obtained near trenches.This correlation,if it holds true,in turn means that a magmatic arc is unlikely to occur when the subducting slabs have not been severely fractured and that one of the main reasons for excluding effects such as the slab window or flat slab subduction may be that the plate is not accompanied by seamounts.Therefore,the role that seamount subduction plays in recycling water back into the mantle deserves more attention from the earth sciences community.
基金the National Key Research and Development Program of China(Grant No.2018YFA0702704)the National Natural Science Foundation of China(Grant No.41921003)the Key Research Project of Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDJ-SSW-DQC012).
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.
