Recent seismic studies reveal a sharp velocity drop mostly at^70–100 km depth within the thick mantle keel beneath cratons, termed the mid-lithosphere discontinuity(MLD). The common presence of the MLD in cratonic re...Recent seismic studies reveal a sharp velocity drop mostly at^70–100 km depth within the thick mantle keel beneath cratons, termed the mid-lithosphere discontinuity(MLD). The common presence of the MLD in cratonic regions indicates structural and property layering of the subcontinental lithospheric mantle(SCLM). The nature and origin of the MLD, and many issues associated with the layering of the SCLM are essential to understand the formation and evolution of continents, and have become frontier subjects in the Earth sciences.展开更多
The present paper describes the characteristics of Cenozoic basalt in the Bohaiwan basin and its implication of the control of deep process over the basin evolution. The large scale Eogene basalts lying on the base... The present paper describes the characteristics of Cenozoic basalt in the Bohaiwan basin and its implication of the control of deep process over the basin evolution. The large scale Eogene basalts lying on the basement of the Bohaiwan basin belong to alkaline series and subalkaline series. The basalt magma originates at a depth of 48-76 km and a temperature of 1 300-1 400 ℃ with the mantle partial melting degree of 8%-14%. In Eogene period, the rising of the top of asthenosphere from 100-140 km to 50-70 km led to the strong extension and thinning of the overlying lithosphere, which was stretched at an average rate of 0.41 cm/a and the β value from 1.9 to 2.3. At the same time, it triggered the great scale rifting in the earth crust, forming large rift basins.展开更多
Tidal forces are generally neglected in the discussion about the mechanisms driving plate tectonics despite a worldwide geodynamic asymmetry also observed at subduction and rift zones.The tidal drag could theoreticall...Tidal forces are generally neglected in the discussion about the mechanisms driving plate tectonics despite a worldwide geodynamic asymmetry also observed at subduction and rift zones.The tidal drag could theoretically explain the westerly shift of the lithosphere relative to the underlying mantle.Notwithstanding,viscosity in the asthenosphere is apparently too high to allow mechanical decoupling produced by tidal forces.Here,we propose a model for global scale geodynamics accompanied by numerical simulations of the tidal interaction of the Earth with the Moon and the Sun.We provide for the first time a theoretical proof that the tidal drag can produce a westerly motion of the lithosphere,also compatible with the slowing of the Earth’s rotational spin.Our results suggest a westerly rotation of the lithosphere with a lower bound ofω≈(0.1-0.2)°/Myr in the presence of a basal effective shear viscosityη≈10^(16)Pa-s,but it may rise toω>1°/Myr with a viscosity ofη≈≤3×10^(14)Pa-s within the Low-Velocity Zone(LVZ)atop the asthenosphere.This faster velocity would be more compatible with the mainstream of plate motion and the global asymmetry at plate boundaries.Based on these computations,we suggest that the super-adiabatic asthenosphere,being vigorously convecting,may further reduce the viscous coupling within the LVZ Therefore,the combination of solid Earth tides,ultra-low viscosity LVZ and asthenospheric polarized small-scale convection may mechanically satisfy the large-scale decoupling of the lithosphere relative to the underlying mantle.Relative plate motions are explained because of lateral viscosity heterogeneities at the base of the lithosphere,which determine variable lithosphere-asthenosphere decoupling and plate interactions,hence plate tectonics.展开更多
Knowing Moho discontinuity undulation is fundamental to understanding mechanisms of lithosphereasthenosphere interaction, extensional tectonism and crustal deformation in volcanic passive margins such as the study are...Knowing Moho discontinuity undulation is fundamental to understanding mechanisms of lithosphereasthenosphere interaction, extensional tectonism and crustal deformation in volcanic passive margins such as the study area, which is located in the southwestern corner of the Arabian Peninsula bounded by the Red Sea and the Gulf of Aden. In this work, a 3D Moho depth model of the study area is constructed for the first time by inverting gravity data from the Earth Gravitational Model(EGM2008) using the ParkerOldenburg algorithm. This model indicates the shallow zone is situated at depths of 20 km to 24 km beneath coastal plains, whereas the deep zone is located below the plateau at depths of 30 km to 35 km and its deepest part coincides mainly with the Dhamar-Rada ’a Quaternary volcanic field. The results also indicate two channels of hot magmatic materials joining both the Sana’a-Amran Quaternary volcanic field and the Late Miocene Jabal An Nar volcanic area with the Dhamar-Rada’a volcanic field. This conclusion is supported by the widespread geothermal activity(of mantle origin) distributed along these channels,isotopic data, and the upper mantle low velocity zones indicated by earlier studies.展开更多
基金supported by the National Natural Science Foundation of China (41225016, 41688103, 91414301)Chinese Academy of Sciences
文摘Recent seismic studies reveal a sharp velocity drop mostly at^70–100 km depth within the thick mantle keel beneath cratons, termed the mid-lithosphere discontinuity(MLD). The common presence of the MLD in cratonic regions indicates structural and property layering of the subcontinental lithospheric mantle(SCLM). The nature and origin of the MLD, and many issues associated with the layering of the SCLM are essential to understand the formation and evolution of continents, and have become frontier subjects in the Earth sciences.
文摘 The present paper describes the characteristics of Cenozoic basalt in the Bohaiwan basin and its implication of the control of deep process over the basin evolution. The large scale Eogene basalts lying on the basement of the Bohaiwan basin belong to alkaline series and subalkaline series. The basalt magma originates at a depth of 48-76 km and a temperature of 1 300-1 400 ℃ with the mantle partial melting degree of 8%-14%. In Eogene period, the rising of the top of asthenosphere from 100-140 km to 50-70 km led to the strong extension and thinning of the overlying lithosphere, which was stretched at an average rate of 0.41 cm/a and the β value from 1.9 to 2.3. At the same time, it triggered the great scale rifting in the earth crust, forming large rift basins.
基金support from Progetto di Ricerca 2020,Progetto di Ricerca di Ateneo 2021,“Equazioni differenziali ellit-tiche e paraboliche non lineari”Sapienza n.RM120172B8F74615Oscar Bruno gratefully acknowledges support from NSF under con-tract DMS-2109831,from AFOSR under contract FA9550-21-1-0373+1 种基金from the NSSEFF Vannevar Bush Fellowship under ONR contract number N00014-16-1-2808The research was also sup-ported by ESA grant 4000133529/20/NL/GP(Doglioni).
文摘Tidal forces are generally neglected in the discussion about the mechanisms driving plate tectonics despite a worldwide geodynamic asymmetry also observed at subduction and rift zones.The tidal drag could theoretically explain the westerly shift of the lithosphere relative to the underlying mantle.Notwithstanding,viscosity in the asthenosphere is apparently too high to allow mechanical decoupling produced by tidal forces.Here,we propose a model for global scale geodynamics accompanied by numerical simulations of the tidal interaction of the Earth with the Moon and the Sun.We provide for the first time a theoretical proof that the tidal drag can produce a westerly motion of the lithosphere,also compatible with the slowing of the Earth’s rotational spin.Our results suggest a westerly rotation of the lithosphere with a lower bound ofω≈(0.1-0.2)°/Myr in the presence of a basal effective shear viscosityη≈10^(16)Pa-s,but it may rise toω>1°/Myr with a viscosity ofη≈≤3×10^(14)Pa-s within the Low-Velocity Zone(LVZ)atop the asthenosphere.This faster velocity would be more compatible with the mainstream of plate motion and the global asymmetry at plate boundaries.Based on these computations,we suggest that the super-adiabatic asthenosphere,being vigorously convecting,may further reduce the viscous coupling within the LVZ Therefore,the combination of solid Earth tides,ultra-low viscosity LVZ and asthenospheric polarized small-scale convection may mechanically satisfy the large-scale decoupling of the lithosphere relative to the underlying mantle.Relative plate motions are explained because of lateral viscosity heterogeneities at the base of the lithosphere,which determine variable lithosphere-asthenosphere decoupling and plate interactions,hence plate tectonics.
文摘Knowing Moho discontinuity undulation is fundamental to understanding mechanisms of lithosphereasthenosphere interaction, extensional tectonism and crustal deformation in volcanic passive margins such as the study area, which is located in the southwestern corner of the Arabian Peninsula bounded by the Red Sea and the Gulf of Aden. In this work, a 3D Moho depth model of the study area is constructed for the first time by inverting gravity data from the Earth Gravitational Model(EGM2008) using the ParkerOldenburg algorithm. This model indicates the shallow zone is situated at depths of 20 km to 24 km beneath coastal plains, whereas the deep zone is located below the plateau at depths of 30 km to 35 km and its deepest part coincides mainly with the Dhamar-Rada ’a Quaternary volcanic field. The results also indicate two channels of hot magmatic materials joining both the Sana’a-Amran Quaternary volcanic field and the Late Miocene Jabal An Nar volcanic area with the Dhamar-Rada’a volcanic field. This conclusion is supported by the widespread geothermal activity(of mantle origin) distributed along these channels,isotopic data, and the upper mantle low velocity zones indicated by earlier studies.
