The relationship between the Yanshanian Movement, destruction of the North China Craton(NCC), and subduction of the western Pacific plate is crucial to reconstructing the middle-late Mesozoic tectonic evolution of the...The relationship between the Yanshanian Movement, destruction of the North China Craton(NCC), and subduction of the western Pacific plate is crucial to reconstructing the middle-late Mesozoic tectonic evolution of the eastern Asian continent and margin. The Yanshanian Movement was a globally important change in crustal tectonics during the Middle-Late Jurassic.Previous research has systematically studied the formation and evolution of the Yanshanian Movement, focusing on the timing and location of tectonic movements, and the sedimentary and volcanic strata. However, the question of whether the tectonic activity occurred globally, and the characteristics of the Yanshanian Movement remain debated. The main argument is that if a tectonic movement can only be characterized by a regional or local disconformity, and if the tectonic movement occurred in an intracontinental setting, with extensive deformation but with no disconformity despite volcanic eruptions and magmatic intrusions, accompanied by changes in crustal structure and composition, should it be defined as a tectonic event or process? This question requires further analysis. The main aim of this study is to distinguish whether the Yanshanian Movement is a local feature of the eastern Asian continent, or a global tectonic event related to subduction of the Pacific Plate. In this paper, based on previous research, we discuss the spatial and temporal evolution of the Yanshanian Movement, the controlling tectonic mechanisms, and its relationship to the reactivation and destruction of the NCC and the subduction of the western Paleo-Pacific slab.We emphasize that the Yanshanian Movement in the Middle-Late Jurassic is distinct from the lithospheric thinning responsible for Early Cretaceous extension and magmatism related to the destruction of the NCC. The various tectonic stages were constrained by different dynamics and tectonic settings, or by different tectonic events and processes. Therefore, it is possible that the deformation and reactivation of the NCC contr展开更多
We applied the finite frequency tomography method to S wave data recorded by 350 broadband stations beneath the South China Block（SCB） and its surroundings from earthquakes occurring between July 2007 and July 2010,...We applied the finite frequency tomography method to S wave data recorded by 350 broadband stations beneath the South China Block（SCB） and its surroundings from earthquakes occurring between July 2007 and July 2010,to better understand upper mantle deformation.Differential travel-times in the pair of stations with appropriate weighting for each station are used in the inversion.Our results are consistent with previous tomography that show a high velocity anomaly beneath the Sichuan basin and a high velocity anomaly in the transition zone beneath the Yangtze Craton.However,the resolution of mantle heterogeneity provides new insight into the tectonic framework of subduction of Burmese lithosphere in the west part of the study region and subduction of oceanic lithosphere in the east.In the subduction realm,west of 107°E,a significant fast S-wave anomaly is located on the southeast of Sichuan Basin.East of 107°E,and two narrow and discontinuous fast S-wave anomalies occur at a depth of 400-600 km beneath the middle of the South China block overlain by the pronounced low S-wave anomalies at a depth of 100 and 400 km.If the fast anomalies located in the mantle transition zone represent stagnant slabs,their fragmented nature may suggest that they could be produced by different episodes of subduction beneath western Pacific island and the above slow velocity anomaly may associated with the back-arc regions of ongoing subduction.In addition,tomography also reveals an anomalously high S-wave velocity continental root extends eastward to a depth 400 km beneath the eastern Sichuan Basin.This anomaly may be related to eastern extrusion of Indian lithosphere associated with the collision of India and Eurasia.Moreover,our results also show large slow anomalies beneath the Red River fault region connected to deeper anomalies beneath the South China Fold Belt and South China Sea.AH these observations are consistent with the scenario that the South China block has been built by both of subduction of Paleopacific plate and ea展开更多
Late Mesozoic Nb-rich basaltic andesites and high-Mg adakitic volcanic rocks from the Hailar-Tamtsag Basin,northeast China,provide important insights into the recycling processes of crustal materials and their role in...Late Mesozoic Nb-rich basaltic andesites and high-Mg adakitic volcanic rocks from the Hailar-Tamtsag Basin,northeast China,provide important insights into the recycling processes of crustal materials and their role in late Mesozoic lithospheric thinning.The Late Jurassic Nb-rich basaltic andesites(154±4 Ma)are enriched in large-ion lithophile and light rare earth elements,slightly depleted in high-field-strength elements,and have high TiO_(2),P_(2)O_(5),and Nb contents,and(Nb/Th)PM and Nb/U ratios,which together with the relatively depleted Sr-Nd-Hf isotopic compositions indicate a derivation from a mantle wedge metasomatized by hydrous melts from subducted oceanic crust.The Early Cretaceous high-Mg adakitic volcanic rocks(129-117 Ma)are characterized by low Y and heavy rare earth element contents,and high Sr contents and Sr/Y ratios,similar to those of rocks derived from partial melting of an eclogitic source.They also have high Rb/Sr,K_(2)O/Na_(2)O,and Mg#values,and high MgO,Cr,and Ni contents.These geochemical features suggest that the adakitic lavas were derived from partial melting of delaminated lower continental crust,followed by interaction of the resulting melts with mantle material during their ascent.Our data,along with available geological,paleomagnetic,and geophysical evidence,lead us to propose that recycling of Paleo-Pacific oceanic crustal materials into the upper mantle due to flat-slab subduction and rollback of the Paleo-Pacific Plate during the late Mesozoic likely provided the precondition for lithospheric thinning in northeast China,with consequent lithospheric delamination causing recycling of continental crustal materials and further lithospheric thinning.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 90914004)
文摘The relationship between the Yanshanian Movement, destruction of the North China Craton(NCC), and subduction of the western Pacific plate is crucial to reconstructing the middle-late Mesozoic tectonic evolution of the eastern Asian continent and margin. The Yanshanian Movement was a globally important change in crustal tectonics during the Middle-Late Jurassic.Previous research has systematically studied the formation and evolution of the Yanshanian Movement, focusing on the timing and location of tectonic movements, and the sedimentary and volcanic strata. However, the question of whether the tectonic activity occurred globally, and the characteristics of the Yanshanian Movement remain debated. The main argument is that if a tectonic movement can only be characterized by a regional or local disconformity, and if the tectonic movement occurred in an intracontinental setting, with extensive deformation but with no disconformity despite volcanic eruptions and magmatic intrusions, accompanied by changes in crustal structure and composition, should it be defined as a tectonic event or process? This question requires further analysis. The main aim of this study is to distinguish whether the Yanshanian Movement is a local feature of the eastern Asian continent, or a global tectonic event related to subduction of the Pacific Plate. In this paper, based on previous research, we discuss the spatial and temporal evolution of the Yanshanian Movement, the controlling tectonic mechanisms, and its relationship to the reactivation and destruction of the NCC and the subduction of the western Paleo-Pacific slab.We emphasize that the Yanshanian Movement in the Middle-Late Jurassic is distinct from the lithospheric thinning responsible for Early Cretaceous extension and magmatism related to the destruction of the NCC. The various tectonic stages were constrained by different dynamics and tectonic settings, or by different tectonic events and processes. Therefore, it is possible that the deformation and reactivation of the NCC contr
基金supported by National Natural Science Foundation of China(Grand No.41404042,41504071,41274123)Postdoctoral Science Foundation of China(Grand Nos.2014M552147, 2015T80888)Innovation drive Foundation of Central South University(Grand No.2016CX005)
文摘We applied the finite frequency tomography method to S wave data recorded by 350 broadband stations beneath the South China Block（SCB） and its surroundings from earthquakes occurring between July 2007 and July 2010,to better understand upper mantle deformation.Differential travel-times in the pair of stations with appropriate weighting for each station are used in the inversion.Our results are consistent with previous tomography that show a high velocity anomaly beneath the Sichuan basin and a high velocity anomaly in the transition zone beneath the Yangtze Craton.However,the resolution of mantle heterogeneity provides new insight into the tectonic framework of subduction of Burmese lithosphere in the west part of the study region and subduction of oceanic lithosphere in the east.In the subduction realm,west of 107°E,a significant fast S-wave anomaly is located on the southeast of Sichuan Basin.East of 107°E,and two narrow and discontinuous fast S-wave anomalies occur at a depth of 400-600 km beneath the middle of the South China block overlain by the pronounced low S-wave anomalies at a depth of 100 and 400 km.If the fast anomalies located in the mantle transition zone represent stagnant slabs,their fragmented nature may suggest that they could be produced by different episodes of subduction beneath western Pacific island and the above slow velocity anomaly may associated with the back-arc regions of ongoing subduction.In addition,tomography also reveals an anomalously high S-wave velocity continental root extends eastward to a depth 400 km beneath the eastern Sichuan Basin.This anomaly may be related to eastern extrusion of Indian lithosphere associated with the collision of India and Eurasia.Moreover,our results also show large slow anomalies beneath the Red River fault region connected to deeper anomalies beneath the South China Fold Belt and South China Sea.AH these observations are consistent with the scenario that the South China block has been built by both of subduction of Paleopacific plate and ea
基金supported by the National Natural Science Foundation of China(Grants 41888101 and 92062216).
文摘Late Mesozoic Nb-rich basaltic andesites and high-Mg adakitic volcanic rocks from the Hailar-Tamtsag Basin,northeast China,provide important insights into the recycling processes of crustal materials and their role in late Mesozoic lithospheric thinning.The Late Jurassic Nb-rich basaltic andesites(154±4 Ma)are enriched in large-ion lithophile and light rare earth elements,slightly depleted in high-field-strength elements,and have high TiO_(2),P_(2)O_(5),and Nb contents,and(Nb/Th)PM and Nb/U ratios,which together with the relatively depleted Sr-Nd-Hf isotopic compositions indicate a derivation from a mantle wedge metasomatized by hydrous melts from subducted oceanic crust.The Early Cretaceous high-Mg adakitic volcanic rocks(129-117 Ma)are characterized by low Y and heavy rare earth element contents,and high Sr contents and Sr/Y ratios,similar to those of rocks derived from partial melting of an eclogitic source.They also have high Rb/Sr,K_(2)O/Na_(2)O,and Mg#values,and high MgO,Cr,and Ni contents.These geochemical features suggest that the adakitic lavas were derived from partial melting of delaminated lower continental crust,followed by interaction of the resulting melts with mantle material during their ascent.Our data,along with available geological,paleomagnetic,and geophysical evidence,lead us to propose that recycling of Paleo-Pacific oceanic crustal materials into the upper mantle due to flat-slab subduction and rollback of the Paleo-Pacific Plate during the late Mesozoic likely provided the precondition for lithospheric thinning in northeast China,with consequent lithospheric delamination causing recycling of continental crustal materials and further lithospheric thinning.
