Thinning of the cratonic lithosphere is common in nature, but its destruction is not. In either case, the mechanisms for both thinning and destruction are still widely under debate. In this study, we have made a revie...Thinning of the cratonic lithosphere is common in nature, but its destruction is not. In either case, the mechanisms for both thinning and destruction are still widely under debate. In this study, we have made a review on the processes and mechanisms of thinning and destruction of cratonic lithosphere according to previous studies of geological/geophysical observations and numerical simulations, with specific application to the North China Craton(NCC). Two main models are suggested for the thinning and destruction of the NCC, both of which are related to subduction of the oceanic lithosphere. One is the "bottom-up" model, in which the deeply subducting slab perturbs and induces upwelling from the hydrous mantle transition zone(MTZ). The upwelling produces mantle convection and erodes the bottom of the overriding lithosphere by the fluid-meltperidotite reaction. Mineral compositions and rheological properties of the overriding lithospheric mantle are changed, allowing downward dripping of lithospheric components into the asthenosphere. Consequently, lithospheric thinning or even destruction occurs. The other is the "top-down" model, characterized by the flat subduction of oceanic slab beneath the overriding cratonic lithosphere. Dehydration reactions from the subducting slab would significantly hydrate the lithospheric mantle and decrease its rheological strength. Then the subduction angle may be changed from shallow to steep, inducing lateral upwelling of the asthenosphere. This upwelling would heat and weaken the overriding lithospheric mantle, which led to the weakened lithospheric mantle dripping into the asthenosphere. These two models have some similarities, in that both take the subducting oceanic slab and relevant fluid migration as the major driving mechanism for thinning or destruction of the overriding cratonic lithosphere. The key difference between the two models is the effective depth of the subducting oceanic slab. One is stagnation and flattening in the MTZ, whereas the other is flat subduction at 展开更多
The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by sur-face wave velocity tomography and non-linear inve...The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by sur-face wave velocity tomography and non-linear inversion.Maps of the Moho depth, of the thickness of the lithos-phere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, iden-tified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the prmctpat recent votca-noes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria, a lithospheric dou-bling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenos-phere properties delineate a differentiation between the northern and the southern sectors of the Adriatic Sea,likely attesting the fragmentation of Adria.展开更多
A HACONS,mantle fluid, has been proposed in the light of current knowledge concerning Diwa,rift ,asthenosphere,anomalous and depleted mantle,plume, percolating magma fluid, degassing,inorganic origin of some oil and g...A HACONS,mantle fluid, has been proposed in the light of current knowledge concerning Diwa,rift ,asthenosphere,anomalous and depleted mantle,plume, percolating magma fluid, degassing,inorganic origin of some oil and gas,hypogeic salt deposits,alkali-metasomatism in hydrothermal depos-its and experimental studies of basalts.The HACONS fluid originated from the mantle and is composed of hydrogen and halogens(H), alkalis(A), carbon(C), oxygen(O),nitrogen(N) and sulfur(S) com-pound systems .Aluminosilicate magmas are expected when the HACONS fluid reacts with solid rocks.Many geological processes,including tectonism, magmatism,volcanism,metamorphism,hydrothermal activity,thermal sedimentation and related mineralizations are thought to be controlled to a certain extent by large -scale mouement of HACONS fluid in the earth's interior.The asthenosphere is essentially a layer with abundant HACONS fluid.展开更多
Based on the results of pure dispersions of Rayleigh wave tomography in the Qinghai-Tibet Plateau and its adjacent areas, taking S wave velocities from previous linear inversion as the initial model, us-ing the simula...Based on the results of pure dispersions of Rayleigh wave tomography in the Qinghai-Tibet Plateau and its adjacent areas, taking S wave velocities from previous linear inversion as the initial model, us-ing the simulated annealing algorithm, a nonlinear simultaneous inversion has been carried out for S wave velocity and thickness of different layers, including the crust, the lithosphere and the astheno-sphere. The results indicate: The crustal thickness shows strong correlation with geology structures sketched by the sutures and major faults. The crust is very thick in the Qinghai-Tibet Plateau, varying from 60 km to 80 km. The lithospheric thickness in the Qinghai-Tibet Plateau is thinner (130―160 km) than its adjacent areas. And two blocks can be recognized, divided by an NNE strike boundary running between 90°E―92°E inside the plateau. Its asthenosphere is relatively thick, varies from 150 km to 230 km, and the thickest area is located in the western Qiangtang. India has a thinner crust (32―38 km), a thicker lithosphere of 190 km and a rather thin asthenosphere of only 60 km. Sichuan and Tarim basins have the crust thickness less than 50 km. Their lithospheres are thicker than the Qinghai-Tibet Plateau, and their asthenospheres are thinner. A discussion has been made on the character and formation mechanism of the typical crust-mantle transition zone in the western Qiangtang block.展开更多
A recent study published in 20 March issue of the prestigious journal Nature by Dr. LIU Chuanzhou from the CAS Institute of Geology & Geophysics and his co-workers challenges the conventional wisdom that the Earth...A recent study published in 20 March issue of the prestigious journal Nature by Dr. LIU Chuanzhou from the CAS Institute of Geology & Geophysics and his co-workers challenges the conventional wisdom that the Earth's upper mantle is homogeneous. Teaming up with his colleagues from both Germany and US, Dr. Liu have conducted mineral, petrological and geochemical studies on abyssal peridotites selected from two dredge hauls in the ultraslow spreading Gakkel ridge, Arctic Ocean. Peridotite samples from one of these two dredge hauls are rarely fresh.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 41622404, 41688103)the Strategic Priority Research Program (B) of Chinese Academy of Sciences (Grant No. XDB18000000)the National Key Basic Research and Development Program of China (Grant No. 2015CB856106)
文摘Thinning of the cratonic lithosphere is common in nature, but its destruction is not. In either case, the mechanisms for both thinning and destruction are still widely under debate. In this study, we have made a review on the processes and mechanisms of thinning and destruction of cratonic lithosphere according to previous studies of geological/geophysical observations and numerical simulations, with specific application to the North China Craton(NCC). Two main models are suggested for the thinning and destruction of the NCC, both of which are related to subduction of the oceanic lithosphere. One is the "bottom-up" model, in which the deeply subducting slab perturbs and induces upwelling from the hydrous mantle transition zone(MTZ). The upwelling produces mantle convection and erodes the bottom of the overriding lithosphere by the fluid-meltperidotite reaction. Mineral compositions and rheological properties of the overriding lithospheric mantle are changed, allowing downward dripping of lithospheric components into the asthenosphere. Consequently, lithospheric thinning or even destruction occurs. The other is the "top-down" model, characterized by the flat subduction of oceanic slab beneath the overriding cratonic lithosphere. Dehydration reactions from the subducting slab would significantly hydrate the lithospheric mantle and decrease its rheological strength. Then the subduction angle may be changed from shallow to steep, inducing lateral upwelling of the asthenosphere. This upwelling would heat and weaken the overriding lithospheric mantle, which led to the weakened lithospheric mantle dripping into the asthenosphere. These two models have some similarities, in that both take the subducting oceanic slab and relevant fluid migration as the major driving mechanism for thinning or destruction of the overriding cratonic lithosphere. The key difference between the two models is the effective depth of the subducting oceanic slab. One is stagnation and flattening in the MTZ, whereas the other is flat subduction at
文摘The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by sur-face wave velocity tomography and non-linear inversion.Maps of the Moho depth, of the thickness of the lithos-phere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, iden-tified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the prmctpat recent votca-noes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria, a lithospheric dou-bling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenos-phere properties delineate a differentiation between the northern and the southern sectors of the Adriatic Sea,likely attesting the fragmentation of Adria.
文摘A HACONS,mantle fluid, has been proposed in the light of current knowledge concerning Diwa,rift ,asthenosphere,anomalous and depleted mantle,plume, percolating magma fluid, degassing,inorganic origin of some oil and gas,hypogeic salt deposits,alkali-metasomatism in hydrothermal depos-its and experimental studies of basalts.The HACONS fluid originated from the mantle and is composed of hydrogen and halogens(H), alkalis(A), carbon(C), oxygen(O),nitrogen(N) and sulfur(S) com-pound systems .Aluminosilicate magmas are expected when the HACONS fluid reacts with solid rocks.Many geological processes,including tectonism, magmatism,volcanism,metamorphism,hydrothermal activity,thermal sedimentation and related mineralizations are thought to be controlled to a certain extent by large -scale mouement of HACONS fluid in the earth's interior.The asthenosphere is essentially a layer with abundant HACONS fluid.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40274009 and 40434009)Open Fund of Geo-detection Laboratory, Ministry of Education of China, China University of Geosciences (Grant No. GDL0607)
文摘Based on the results of pure dispersions of Rayleigh wave tomography in the Qinghai-Tibet Plateau and its adjacent areas, taking S wave velocities from previous linear inversion as the initial model, us-ing the simulated annealing algorithm, a nonlinear simultaneous inversion has been carried out for S wave velocity and thickness of different layers, including the crust, the lithosphere and the astheno-sphere. The results indicate: The crustal thickness shows strong correlation with geology structures sketched by the sutures and major faults. The crust is very thick in the Qinghai-Tibet Plateau, varying from 60 km to 80 km. The lithospheric thickness in the Qinghai-Tibet Plateau is thinner (130―160 km) than its adjacent areas. And two blocks can be recognized, divided by an NNE strike boundary running between 90°E―92°E inside the plateau. Its asthenosphere is relatively thick, varies from 150 km to 230 km, and the thickest area is located in the western Qiangtang. India has a thinner crust (32―38 km), a thicker lithosphere of 190 km and a rather thin asthenosphere of only 60 km. Sichuan and Tarim basins have the crust thickness less than 50 km. Their lithospheres are thicker than the Qinghai-Tibet Plateau, and their asthenospheres are thinner. A discussion has been made on the character and formation mechanism of the typical crust-mantle transition zone in the western Qiangtang block.
文摘A recent study published in 20 March issue of the prestigious journal Nature by Dr. LIU Chuanzhou from the CAS Institute of Geology & Geophysics and his co-workers challenges the conventional wisdom that the Earth's upper mantle is homogeneous. Teaming up with his colleagues from both Germany and US, Dr. Liu have conducted mineral, petrological and geochemical studies on abyssal peridotites selected from two dredge hauls in the ultraslow spreading Gakkel ridge, Arctic Ocean. Peridotite samples from one of these two dredge hauls are rarely fresh.
