Objective The North China Craton （NCC） is one of the oldest cratons in the world. The accretionary belt at its northern margin has been the focus of scholars both at home and abroad （Zhu Junbing and Ren Jishun, 2...Objective The North China Craton （NCC） is one of the oldest cratons in the world. The accretionary belt at its northern margin has been the focus of scholars both at home and abroad （Zhu Junbing and Ren Jishun, 2017）. In recent years, a series of Late Paleozoic-Mesozoic intrusions trending E-W have been discovered within the northern margin of the NCC, forming a magmatic belt. The study on the origin and tectonic setting of this magmatic belt not only has important significance for understanding the Late Paleozoic-Mesozoic tectonic evolution history of the northern margin of the NCC, but also can provide key constraints on the evolution of its surrounding Xing＇an- Mongolia orogenic belt and the Paleo-Asian Ocean. At present, no Devonian to early stage of Early Carboniferous intrusion has been reported within the northern margin of the NCC.展开更多
Five tectonic modes of mantle convection are obtained and analyzed with three-dimensional numerical models in a spherical shell domain.The five tectonic convective modes are non-plate mobile-lid,plate-like mobile-lid,...Five tectonic modes of mantle convection are obtained and analyzed with three-dimensional numerical models in a spherical shell domain.The five tectonic convective modes are non-plate mobile-lid,plate-like mobile-lid,episodic plate-like mobile-lid,episodic stagnant-lid,and stagnant-lid convective modes,respectively.The typical characteristics of these five tectonic modes and their numerical classification criteria based on plateness,mobility,and their standard deviations are presented and discussed.The results show that the yield stress of the lithosphere has profound effects on the tectonic convective modes.With the gradual increase of yield stress,the tectonic mode of mantle convection changes from one to another sequentially through the aforementioned five modes.Additionally,as the Rayleigh number increases,the range of yield stress for the platelike mobile-lid convective mode decreases,and the dimensionless transition stress between different tectonic modes increases.Specifically,the dimensional transition stress between the non-plate mobile-lid convective mode and plate-like mobile-lid convective mode increases with the increase of Rayleigh number,but decreases between other tectonic modes.Furthermore,we find that the transition stress between different tectonic modes is inversely proportional to the internal heating rate,with the transition stress decreasing as the internal heating rate increases.The fitting analysis of the transition stress between tectonic modes shows that Earth's current plate tectonics correspond to a lithospheric yield stress of 150–250 MPa,which aligns with the strength of serpentinized mantle rock determined by experimental petrography.If the Archean mantle was 300℃warmer than it is today,then the Earth was in an episodic stagnant-lid convective mode.The tectonic evolution of the Earth's surface is closely related to the lithospheric strength and the process of thermal evolution.If the lithospheric strength was only 150 MPa,plate tectonics in the early mantle rapid cooling model would have begun before 3.8 Ga,and plate tectonics in the late mantle rapid cooling model would have begun at approximately 1.5 Ga.However,at a lithospheric strength of 200 MPa,plate tectonics in the late mantle rapid cooling model would have begun later than 0.95 Ga,and plate tectonics in the early mantle rapid cooling model would have begun at approximately 2 Ga.The early Earth was in the episodic stagnant-lid convective mode,which means that subduction might still have occurred at that time.The presence of the episodic plate-like mobile-lid convective mode in Earth's later history indicates that there might also have been intermittent surface stagnation during plate tectonics,which may provide an explanation for the quiet period of tectonic activity at approximately 1.0 Ga on Earth.This indicates that tectonic inactivity during a geological period is not an indicator that plate tectonics did not begin.展开更多
基金financially supported by the China Geological Survey(grants No.DD20160048-05,12120113053400 and 12120114055501)
文摘Objective The North China Craton （NCC） is one of the oldest cratons in the world. The accretionary belt at its northern margin has been the focus of scholars both at home and abroad （Zhu Junbing and Ren Jishun, 2017）. In recent years, a series of Late Paleozoic-Mesozoic intrusions trending E-W have been discovered within the northern margin of the NCC, forming a magmatic belt. The study on the origin and tectonic setting of this magmatic belt not only has important significance for understanding the Late Paleozoic-Mesozoic tectonic evolution history of the northern margin of the NCC, but also can provide key constraints on the evolution of its surrounding Xing＇an- Mongolia orogenic belt and the Paleo-Asian Ocean. At present, no Devonian to early stage of Early Carboniferous intrusion has been reported within the northern margin of the NCC.
基金supported by the National Natural Science Foundation of China(Grant Nos.42074105 and 92155204)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB 41000000)。
文摘Five tectonic modes of mantle convection are obtained and analyzed with three-dimensional numerical models in a spherical shell domain.The five tectonic convective modes are non-plate mobile-lid,plate-like mobile-lid,episodic plate-like mobile-lid,episodic stagnant-lid,and stagnant-lid convective modes,respectively.The typical characteristics of these five tectonic modes and their numerical classification criteria based on plateness,mobility,and their standard deviations are presented and discussed.The results show that the yield stress of the lithosphere has profound effects on the tectonic convective modes.With the gradual increase of yield stress,the tectonic mode of mantle convection changes from one to another sequentially through the aforementioned five modes.Additionally,as the Rayleigh number increases,the range of yield stress for the platelike mobile-lid convective mode decreases,and the dimensionless transition stress between different tectonic modes increases.Specifically,the dimensional transition stress between the non-plate mobile-lid convective mode and plate-like mobile-lid convective mode increases with the increase of Rayleigh number,but decreases between other tectonic modes.Furthermore,we find that the transition stress between different tectonic modes is inversely proportional to the internal heating rate,with the transition stress decreasing as the internal heating rate increases.The fitting analysis of the transition stress between tectonic modes shows that Earth's current plate tectonics correspond to a lithospheric yield stress of 150–250 MPa,which aligns with the strength of serpentinized mantle rock determined by experimental petrography.If the Archean mantle was 300℃warmer than it is today,then the Earth was in an episodic stagnant-lid convective mode.The tectonic evolution of the Earth's surface is closely related to the lithospheric strength and the process of thermal evolution.If the lithospheric strength was only 150 MPa,plate tectonics in the early mantle rapid cooling model would have begun before 3.8 Ga,and plate tectonics in the late mantle rapid cooling model would have begun at approximately 1.5 Ga.However,at a lithospheric strength of 200 MPa,plate tectonics in the late mantle rapid cooling model would have begun later than 0.95 Ga,and plate tectonics in the early mantle rapid cooling model would have begun at approximately 2 Ga.The early Earth was in the episodic stagnant-lid convective mode,which means that subduction might still have occurred at that time.The presence of the episodic plate-like mobile-lid convective mode in Earth's later history indicates that there might also have been intermittent surface stagnation during plate tectonics,which may provide an explanation for the quiet period of tectonic activity at approximately 1.0 Ga on Earth.This indicates that tectonic inactivity during a geological period is not an indicator that plate tectonics did not begin.
