The evolution of convergent plate margins includes a series of long-term and successive processes from subduction initiation(SI)through mature oceanic subduction to continental subduction and collision,leading to poss...The evolution of convergent plate margins includes a series of long-term and successive processes from subduction initiation(SI)through mature oceanic subduction to continental subduction and collision,leading to possible mountain building in different stages.This evolution pathway is one of the most important expressions of plate tectonics,which controls the mass and energy exchange between the Earth's surface and interior and produces the majority of volcanisms and great earthquakes.Based on extensive geological/geophysical observations and geodynamic simulations,we systematically summarize key tectonic and dynamic issues during SI,oceanic subduction,and continental collision and further propose several major unresolved scientific questions and future research directions.(1)For the SI,it generally requires the combination of multiple driving forces and,more importantly,lithospheric weakening.Thereby,it tends to occur at previous suture zones or weak belts.The geological records of SI include magmatic and metamorphic rocks formed in hot environments,as well as tectonic uplift/subsidence and accompanying sedimentary responses in cold environments.According to contrasting geological records,two different types of SI are defined:hot and cold.Hot SI prefers to be driven by a vertical force,whereas cold SI is dominated by horizontal force.(2)For mature oceanic subduction,two typical styles include flat slab subduction beneath an overriding lithosphere and slab stagnation in the mantle transition zone.The favorable conditions of flat subduction include young oceanic slabs,thick oceanic crust,and strong coupling between converging plates.On the other hand,slab stagnation is generally controlled by the resistance from the 660-km discontinuity and the trench retreat.The subducting slab is the major carrier of volatiles(e.g.,H2O and CO_(2))to the Earth's interior.The serpentinite layer beneath the oceanic crust plays a critical role in the transportation of water to the deep mantle,with the thickness and water content of serpentinite as controlling factors.The deep carbon cycling in subduction zone is controlled by multiple processes,including mechanical,metamorphic,dissolution,and partial melting-induced decarbonization.The flux of carbon cycling requires further systematic constraints.(3)For continental subduction,a deeply subducted lithosphere experiences metamorphic phase change and densification,which further results in considerable slab pull.Thereby,when the continental slab is dragged to great depths(e.g.,>300 km),continental subduction could be self-sustained.One of the most important continental collisional zones is that of the Himalayas and Tibetan Plateau.Its puzzling geodynamic issues include the mechanisms of multiple slab tearing of the underthrusting Indian plate,the deformation characteristics and material balance of the overriding plateau,and the collision-induced far-field intracontinental orogeny in central Asia.In addition,the coupling between these deep Earth tectonics and surficial processes(e.g.,erosion and sedimentation)plays a significant role in shaping the Earth as well as its environment and climate effects.In summary,the research on the dynamics of convergent plate margins requires effective integrations of multiple geological,geophysical,and geochemical observations as well as the coupled thermodynamic and thermomechanical numerical models.They may jointly contribute to the ultimate solution of relevant unresolved scientific issues.展开更多
Tethys tectonic system has experienced a long-term evolution history,including multiple Wilson cycles;thus,it is an ideal target for analyzing plate tectonics and geodynamics.Tethyan evolution is typically characteriz...Tethys tectonic system has experienced a long-term evolution history,including multiple Wilson cycles;thus,it is an ideal target for analyzing plate tectonics and geodynamics.Tethyan evolution is typically characterized by a series of continental blocks that separated from the Gondwana in the Southern Hemisphere,drifted northward,and collided and accreted with Laurasia in the Northern Hemisphere.During this process,the successive opening and closing of multistage Tethys oceans(e.g.,Proto-Tethys,Paleo-Tethys,and Neo-Tethys)are considered core parts of the Tethyan evolution.Herein,focusing on the life cycle of an oceanic plate,four key geodynamic processes during the Tethyan evolution,namely,continental margin breakup,subduction initiation(SI),Mid-Ocean Ridge(MOR)subduction,and continental collision,were highlighted and dynamically analyzed to gather the following insights.(1)Breakup of the narrow continental margin terranes from the northern Gondwana is probably controlled by plate subduction,particularly the subduction-induced far-field stretching.The breakup of the Indian continent and the subsequent spreading of the Indian Ocean can be attributed to the interactions between multiple mantle plumes and slab drag-induced far-field stretching.(2)Continental margin terrane collision-induced subduction transference/jump is a key factor in progressive Tethyan evolution,which is driven by the combined forces of collision-induced reverse push,far-field ridge push,and mantle flow traction.Moreover,lithospheric weakening plays an important role in the occurrence of SI.(3)MOR subduction is generally accompanied by slab break-off.In case of the considerably reduced or temporary absence of slab pull,mantle flow traction may contribute to the progression of plate subduction.MOR subduction can dynamically influence the overriding and downgoing plates by producing important and diagnostic geological records.(4)The large gravitational potential energy of the Tibetan Plateau indicates that the long-lasting India-Asia continental collision requires other driving forces beyond the far-field ridge push.Further,the mantle flow traction is a good candidate that may considerably contribute to the continuous collision.The possible future SI in the northern Indian Ocean will release the sustained convergent force and cause the collapse of the Tibetan Plateau.Based on the integration of these four geodynamic processes and their driving forces,a“multienginedriving”model is proposed for the dynamics of Tethyan evolution,indicating that the multiple stages of Tethys oceanic subduction provide the main driving force for the northward drifting of continental margin terranes.However,the subducting slab pull may be considerably reduced or even lost during tectonic transitional processes,such as terrane collision or MOR subduction.In such stages,the far-field ridge push and mantle flow traction will induce the initiation of new subduction zones,driving the continuous northward convergence of the Tethys tectonic system.展开更多
基金supported by the National Key R&D Program of China(Grant No.2022YFF0801001)the National Natural Science Foundation of China for Distinguished Young Scholars(Grant No.42225403)the Fundamental Research Funds for the Central Universities。
文摘The evolution of convergent plate margins includes a series of long-term and successive processes from subduction initiation(SI)through mature oceanic subduction to continental subduction and collision,leading to possible mountain building in different stages.This evolution pathway is one of the most important expressions of plate tectonics,which controls the mass and energy exchange between the Earth's surface and interior and produces the majority of volcanisms and great earthquakes.Based on extensive geological/geophysical observations and geodynamic simulations,we systematically summarize key tectonic and dynamic issues during SI,oceanic subduction,and continental collision and further propose several major unresolved scientific questions and future research directions.(1)For the SI,it generally requires the combination of multiple driving forces and,more importantly,lithospheric weakening.Thereby,it tends to occur at previous suture zones or weak belts.The geological records of SI include magmatic and metamorphic rocks formed in hot environments,as well as tectonic uplift/subsidence and accompanying sedimentary responses in cold environments.According to contrasting geological records,two different types of SI are defined:hot and cold.Hot SI prefers to be driven by a vertical force,whereas cold SI is dominated by horizontal force.(2)For mature oceanic subduction,two typical styles include flat slab subduction beneath an overriding lithosphere and slab stagnation in the mantle transition zone.The favorable conditions of flat subduction include young oceanic slabs,thick oceanic crust,and strong coupling between converging plates.On the other hand,slab stagnation is generally controlled by the resistance from the 660-km discontinuity and the trench retreat.The subducting slab is the major carrier of volatiles(e.g.,H2O and CO_(2))to the Earth's interior.The serpentinite layer beneath the oceanic crust plays a critical role in the transportation of water to the deep mantle,with the thickness and water content of serpentinite as controlling factors.The deep carbon cycling in subduction zone is controlled by multiple processes,including mechanical,metamorphic,dissolution,and partial melting-induced decarbonization.The flux of carbon cycling requires further systematic constraints.(3)For continental subduction,a deeply subducted lithosphere experiences metamorphic phase change and densification,which further results in considerable slab pull.Thereby,when the continental slab is dragged to great depths(e.g.,>300 km),continental subduction could be self-sustained.One of the most important continental collisional zones is that of the Himalayas and Tibetan Plateau.Its puzzling geodynamic issues include the mechanisms of multiple slab tearing of the underthrusting Indian plate,the deformation characteristics and material balance of the overriding plateau,and the collision-induced far-field intracontinental orogeny in central Asia.In addition,the coupling between these deep Earth tectonics and surficial processes(e.g.,erosion and sedimentation)plays a significant role in shaping the Earth as well as its environment and climate effects.In summary,the research on the dynamics of convergent plate margins requires effective integrations of multiple geological,geophysical,and geochemical observations as well as the coupled thermodynamic and thermomechanical numerical models.They may jointly contribute to the ultimate solution of relevant unresolved scientific issues.
基金a review of the geodynamic studies and extended thoughts during the past four years(2019–2022)in the platform of“Major Research Plan on Tethys Geodynamic System”funded by the National Natural Science Foundation of China(Grant No.91855208)supported by the National Natural Science Fundation of China for Distinguished Young Scholars(Grant No.42225403)。
文摘Tethys tectonic system has experienced a long-term evolution history,including multiple Wilson cycles;thus,it is an ideal target for analyzing plate tectonics and geodynamics.Tethyan evolution is typically characterized by a series of continental blocks that separated from the Gondwana in the Southern Hemisphere,drifted northward,and collided and accreted with Laurasia in the Northern Hemisphere.During this process,the successive opening and closing of multistage Tethys oceans(e.g.,Proto-Tethys,Paleo-Tethys,and Neo-Tethys)are considered core parts of the Tethyan evolution.Herein,focusing on the life cycle of an oceanic plate,four key geodynamic processes during the Tethyan evolution,namely,continental margin breakup,subduction initiation(SI),Mid-Ocean Ridge(MOR)subduction,and continental collision,were highlighted and dynamically analyzed to gather the following insights.(1)Breakup of the narrow continental margin terranes from the northern Gondwana is probably controlled by plate subduction,particularly the subduction-induced far-field stretching.The breakup of the Indian continent and the subsequent spreading of the Indian Ocean can be attributed to the interactions between multiple mantle plumes and slab drag-induced far-field stretching.(2)Continental margin terrane collision-induced subduction transference/jump is a key factor in progressive Tethyan evolution,which is driven by the combined forces of collision-induced reverse push,far-field ridge push,and mantle flow traction.Moreover,lithospheric weakening plays an important role in the occurrence of SI.(3)MOR subduction is generally accompanied by slab break-off.In case of the considerably reduced or temporary absence of slab pull,mantle flow traction may contribute to the progression of plate subduction.MOR subduction can dynamically influence the overriding and downgoing plates by producing important and diagnostic geological records.(4)The large gravitational potential energy of the Tibetan Plateau indicates that the long-lasting India-Asia continental collision requires other driving forces beyond the far-field ridge push.Further,the mantle flow traction is a good candidate that may considerably contribute to the continuous collision.The possible future SI in the northern Indian Ocean will release the sustained convergent force and cause the collapse of the Tibetan Plateau.Based on the integration of these four geodynamic processes and their driving forces,a“multienginedriving”model is proposed for the dynamics of Tethyan evolution,indicating that the multiple stages of Tethys oceanic subduction provide the main driving force for the northward drifting of continental margin terranes.However,the subducting slab pull may be considerably reduced or even lost during tectonic transitional processes,such as terrane collision or MOR subduction.In such stages,the far-field ridge push and mantle flow traction will induce the initiation of new subduction zones,driving the continuous northward convergence of the Tethys tectonic system.
