Plate motion is one of the major dynamic sources for deformation in the crust and the mantle. Since the deformation in the crust can be observed by GPS and geological observation, the comparison between the deformatio...Plate motion is one of the major dynamic sources for deformation in the crust and the mantle. Since the deformation in the crust can be observed by GPS and geological observation, the comparison between the deformation of the crust and that of the mantle becomes one of the major methods available for studying the coupling between crust movement and mantle deformation. Regional crustal strain rate tensor values in China, inferred from Quaternary fault slip rates and earthquake deformation data within areas of approximately 200×200 km, are interpolated with smooth, continuous functions (spline) to determine a self-consistent model velocity gradient tensor field for the present-day Chinese continent. In the interpolation process, GPS velocity vectors are also matched, within a defined frame of reference, by the model velocity field. The directions of shear deformation calculated from the model velocity field are compared with the fast directions of shear-wave splitting inferred from SKS phases and Pn waves. The results might represent the shear deformation in mantle and the deep crust, respectively. There is a relatively large difference between the average direction of crustal shear and that of mantle shear in the area of active tectonics, which may indicate that in these active areas the crust and the mantle may be decoupled.展开更多
The greatest Phanerozoic mass extinction happened at the end-Permian to earliest Triassic. About 95% species, 82% genera, and more than half families became extinct, constituting the sole macro-mass extinction in geol...The greatest Phanerozoic mass extinction happened at the end-Permian to earliest Triassic. About 95% species, 82% genera, and more than half families became extinct, constituting the sole macro-mass extinction in geological history. This event not only caused the great extinction but also destroyed the 200 Myr-long Paleozoic marine ecosystem, prompted its transition to Mesozoic ecosystem, and induced coal gap on land as well as reef gap and chert gap in ocean. The biotic crisis during the Paleozoic-Mesozoic transition was a long process of co-evolution between geospheres and biosphere. The event sequence at the Permian-Triassic boundary （PTB） reveals two-episodic pattern of rapidly deteriorating global changes and biotic mass ex- tinction and the intimate relationship between them. The severe global changes coupling multiple geospheres may have affect- ed the Pangea integration on the Earth＇s surface spheres, which include： the Pangea integration→enhanced mountain height and basin depth, changes of wind and ocean current systems; enhanced ocean basin depth→the greatest Phanerozoic regression at PTB, disappearance of epeiric seas and subsequent rapid transgression; the Pangea integration→thermal isolation effect of continental lithosphere and decrease of mid-ocean ridges→development of continental volcanism; two-episode volcanism causing LIPs of the Emeishan Basalt and the Siberian Trap （25%251 Ma）→global warming and mass extinction; continental aridification and replacement of monsoon system by latitudinal wind system→destruction of vegetation; enhanced weathering and CH4 emission→negative excursion of δ^13C; mantle plume→crust doming→regression; possible relation between the Illawarra magnetic reversal and the PTB extinction, and so on. Mantle plume produced the Late Permian LIPs and mantle convection may have caused the process of the Pangea integration. Subduction, delamination, and accumulation of the earth＇s cool lithospheric material at the ＂D＂ layer of CMB started mantle plume by heat compensation and disturbed the outer core ther- too-convection, and the latter in turn would generate the mid-Permian geomagnetic reversal. These core and mantle perturbations may have caused the Pangea integration and two successive LIPs in the Permian, and probably finally the mass extinction at the PTB.展开更多
文摘Plate motion is one of the major dynamic sources for deformation in the crust and the mantle. Since the deformation in the crust can be observed by GPS and geological observation, the comparison between the deformation of the crust and that of the mantle becomes one of the major methods available for studying the coupling between crust movement and mantle deformation. Regional crustal strain rate tensor values in China, inferred from Quaternary fault slip rates and earthquake deformation data within areas of approximately 200×200 km, are interpolated with smooth, continuous functions (spline) to determine a self-consistent model velocity gradient tensor field for the present-day Chinese continent. In the interpolation process, GPS velocity vectors are also matched, within a defined frame of reference, by the model velocity field. The directions of shear deformation calculated from the model velocity field are compared with the fast directions of shear-wave splitting inferred from SKS phases and Pn waves. The results might represent the shear deformation in mantle and the deep crust, respectively. There is a relatively large difference between the average direction of crustal shear and that of mantle shear in the area of active tectonics, which may indicate that in these active areas the crust and the mantle may be decoupled.
基金supported by the National Basic Research Program of China(Grant No.2011CB808800)the 111 Project(Grant No.B08030)+1 种基金the National Natural Science Foundation of China(Grant Nos.40621002,40830212&40921062)the Fundamental Research Funds for the Central Universities(CUG130407)
文摘The greatest Phanerozoic mass extinction happened at the end-Permian to earliest Triassic. About 95% species, 82% genera, and more than half families became extinct, constituting the sole macro-mass extinction in geological history. This event not only caused the great extinction but also destroyed the 200 Myr-long Paleozoic marine ecosystem, prompted its transition to Mesozoic ecosystem, and induced coal gap on land as well as reef gap and chert gap in ocean. The biotic crisis during the Paleozoic-Mesozoic transition was a long process of co-evolution between geospheres and biosphere. The event sequence at the Permian-Triassic boundary （PTB） reveals two-episodic pattern of rapidly deteriorating global changes and biotic mass ex- tinction and the intimate relationship between them. The severe global changes coupling multiple geospheres may have affect- ed the Pangea integration on the Earth＇s surface spheres, which include： the Pangea integration→enhanced mountain height and basin depth, changes of wind and ocean current systems; enhanced ocean basin depth→the greatest Phanerozoic regression at PTB, disappearance of epeiric seas and subsequent rapid transgression; the Pangea integration→thermal isolation effect of continental lithosphere and decrease of mid-ocean ridges→development of continental volcanism; two-episode volcanism causing LIPs of the Emeishan Basalt and the Siberian Trap （25%251 Ma）→global warming and mass extinction; continental aridification and replacement of monsoon system by latitudinal wind system→destruction of vegetation; enhanced weathering and CH4 emission→negative excursion of δ^13C; mantle plume→crust doming→regression; possible relation between the Illawarra magnetic reversal and the PTB extinction, and so on. Mantle plume produced the Late Permian LIPs and mantle convection may have caused the process of the Pangea integration. Subduction, delamination, and accumulation of the earth＇s cool lithospheric material at the ＂D＂ layer of CMB started mantle plume by heat compensation and disturbed the outer core ther- too-convection, and the latter in turn would generate the mid-Permian geomagnetic reversal. These core and mantle perturbations may have caused the Pangea integration and two successive LIPs in the Permian, and probably finally the mass extinction at the PTB.
