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Guiting Hou – One of the best experts on this subject based on the ideXlab platform.

  • Mechanism of the Mesozoic African Rift System: Paleostress field modeling
    Journal of Geodynamics, 2019
    Co-Authors: Ge Min, Guiting Hou
    Abstract:

    Abstract The Mesozoic African Rift System is an important continental Rift System related to the Central African Shear Zone. While several geological models have been discussed, the mechanism of the Mesozoic African Rift System is still unclear. One model proposed that the mechanism of the Mesozoic African Rift System was inherited from the Benue Trough, which is a failed arm of the Guinea triple junction. Other models suggested that the mechanism of the Mesozoic African Rift System could be clarified by the spreading of the Atlantic and weak lithospheric zones, such as the Pan-African suture zone. In this research paper, we create a shell model that considers spherical curvature, the heterogeneous structure of the African basement framework, and a combination of the upwelling St. Helena plume and seafloor spreading. The calculation of the model is solved through the finite element software ANSYS, and the modeling results match the actual geological evidence. In this study, nine other models are created with altered rock parameters or boundary constraints and compared to the original model to examine the influence of these factors. Compared to the nine comparative models, the original model best reflects the calculated results, which indicates that the coupling of the St. Helena mantle plume and ocean-ridge spreading caused the initial lithospheric Rifting at ∼130 Ma and that the heterogeneities within Africa did not affect the extension direction of the Rift basin but did influence the location of the Rift basin.

  • geodynamics of the east African Rift System 30 ma ago a stress field model
    Journal of Geodynamics, 2018
    Co-Authors: Ge Min, Guiting Hou
    Abstract:

    Abstract The East African Rift System (EARS) is thought to be an intra-continental ridge that meets the Red Sea and the Gulf of Aden at the Ethiopian Afar as the failed arm of the Afar triple junction. The geodynamics of EARS is still unclear even though several models have been proposed. One model proposes that the EARS developed in a local tensile stress field derived from far-field loads because of the pushing of oceanic ridges. Alternatively, some scientists suggest that the formation of the EARS can be explained by upwelling mantle plumes beneath the lithospheric weak zone (e.g., the Pan-African suture zone). In our study, a shell model is established to consider the Earth’s spherical curvature, the lithospheric heterogeneity of the African continent, and the coupling between the mantle plumes and the mid-ocean ridge. The results are calculated via the finite element method using ANSYS software and fit the geological evidence well. To discuss the effects of the different rock mechanical parameters and the boundary conditions, four comparative models are established with different parameters or boundary conditions. Model I ignores the heterogeneity of the African continent, Model II ignores mid-ocean spreading, Model III ignores the upwelling mantle plumes, and Model IV ignores both the heterogeneity of the African continent and the upwelling mantle plumes. Compared to these models is the original model that shows the best-fit results; this model indicates that the coupling of the upwelling mantle plumes and the mid-ocean ridge spreading causes the initial lithospheric breakup in Afar and East Africa. The extension direction and the separation of the EARS around the Tanzanian craton are attributed to the heterogeneity of the East African basement.

  • Geodynamics of the East African Rift System ∼30 Ma ago: A stress field model
    Journal of Geodynamics, 2018
    Co-Authors: Ge Min, Guiting Hou
    Abstract:

    Abstract The East African Rift System (EARS) is thought to be an intra-continental ridge that meets the Red Sea and the Gulf of Aden at the Ethiopian Afar as the failed arm of the Afar triple junction. The geodynamics of EARS is still unclear even though several models have been proposed. One model proposes that the EARS developed in a local tensile stress field derived from far-field loads because of the pushing of oceanic ridges. Alternatively, some scientists suggest that the formation of the EARS can be explained by upwelling mantle plumes beneath the lithospheric weak zone (e.g., the Pan-African suture zone). In our study, a shell model is established to consider the Earth’s spherical curvature, the lithospheric heterogeneity of the African continent, and the coupling between the mantle plumes and the mid-ocean ridge. The results are calculated via the finite element method using ANSYS software and fit the geological evidence well. To discuss the effects of the different rock mechanical parameters and the boundary conditions, four comparative models are established with different parameters or boundary conditions. Model I ignores the heterogeneity of the African continent, Model II ignores mid-ocean spreading, Model III ignores the upwelling mantle plumes, and Model IV ignores both the heterogeneity of the African continent and the upwelling mantle plumes. Compared to these models is the original model that shows the best-fit results; this model indicates that the coupling of the upwelling mantle plumes and the mid-ocean ridge spreading causes the initial lithospheric breakup in Afar and East Africa. The extension direction and the separation of the EARS around the Tanzanian craton are attributed to the heterogeneity of the East African basement.

J. D. Fairhead – One of the best experts on this subject based on the ideXlab platform.

  • The role that plate tectonics, inferred stress changes and stratigraphic unconformities have on the evolution of the West and Central African Rift System and the Atlantic continental margins
    Tectonophysics, 2013
    Co-Authors: J. D. Fairhead, Chris Green, Sheona Masterton, R. Guiraud
    Abstract:

    The Muglad Rift basin of Sudan, is a good example of polyphase Rifting, with at least three major phases of basin development. Each phase has resulted in the generation of source rock, reservoir and seal geology with structural traps often closely linked to basement highs. In this paper we investigate on a regional scale the tectonic processes that have contributed to Rift basin development. On a regional scale, the evolution of the Africa-wide Mesozoic Rift System is intimately linked to relative movements of African sub-plates and to global plate tectonic processes and plate interactions. Changes in plate interactions are observed in the oceanic crust as azimuth changes of fracture zone geometries and by inference have caused significant modifications to both the orientation and magnitude of the motions of the African sub-plates. Such plate motion processes have controlled the polyphase development of the West and Central African Rift System. On the basinal scale, changes of sub-plate motions have resulted in changes in the stress field which have had a clear impact on the deformation and fault geometries of Rift basins and on the resulting stratigraphy. The construction of the first unified stratigraphic chart for the West and Central African Rift System shows a close correlation in the timing of the major unconformities with the timing of changes in relative plate motion as observed in the changes of the azimuthal geometry of the oceanic fracture zones in the Central Atlantic. Since similarly timed unconformities exist along the continental margins of Africa and South America, we propose that the causative mechanism is change in relative plate motion which leads to an increase or decrease in the tension on the plate and thus controls the strength or effective elastic thickness, Te, of the crust/plate beneath the margins. This results in a focused change in isostatic response of the margin during short-period changes in relative plate motion; i.e. more tension will mean that loads are not compensated locally resulting in local uplift of the margin.

  • Differential opening of the Central and South Atlantic Oceans and the opening of the West African Rift System
    Tectonophysics, 1991
    Co-Authors: J. D. Fairhead, R.m. Binks
    Abstract:

    Abstract Plate tectonic studies of the development of the Central and South Atlantic Oceans using Seasat and Geosat altimeter and magnetic anomaly isochron data now provide quantitative models of seafloor spreading through time. Such models enable an initial assessment of the differential opening between these two oceanic basins to be determined. The Equatorial Atlantic is an integral part of this oceanic Rifting process, allowing stresses arising from the differential opening to be dissipated into both the Caribbean and Africa along its northern and southern boundaries respectively. The tectonic model for the West African Rift System, based on geological and geophysical studies, shows a series of strike-slip fault zones diverging into Africa from the Gulf of Guinea and dissipating their shear movement into the development of extensional basins orientated perpendicular to these faults zones. The development of the West African Rift System was contemporaneous with the early opening of the South Atlantic, continued to develop well after the final breakup of South America from Africa and did not cease until the late Cretaceous when there was a major phase of basin inversion and deformation. Santonian ( ~ 80 Ma) deformation across the Benue Trough (Nigeria) is broadly contemporaneous with dextral shear reactivation of the central African fracture System which, in turn resulted in renewed extension in the Sudan basins during the late Cretaceous and early Tertiary. This paper illustrates the close linkage in both time and space between the history of the African Rift basins and the opening of the Atlantic. Both exhibit distinct phases of evolution with the Rift basins developing in direct response to the differential opening between the Central and South Atlantic in order to dissipate stresses generated by this opening. The Mesozoic tectonic model proposed is therefore one of an intimate interaction between oceanic and continental tectonics.

Ge Min – One of the best experts on this subject based on the ideXlab platform.

  • Mechanism of the Mesozoic African Rift System: Paleostress field modeling
    Journal of Geodynamics, 2019
    Co-Authors: Ge Min, Guiting Hou
    Abstract:

    Abstract The Mesozoic African Rift System is an important continental Rift System related to the Central African Shear Zone. While several geological models have been discussed, the mechanism of the Mesozoic African Rift System is still unclear. One model proposed that the mechanism of the Mesozoic African Rift System was inherited from the Benue Trough, which is a failed arm of the Guinea triple junction. Other models suggested that the mechanism of the Mesozoic African Rift System could be clarified by the spreading of the Atlantic and weak lithospheric zones, such as the Pan-African suture zone. In this research paper, we create a shell model that considers spherical curvature, the heterogeneous structure of the African basement framework, and a combination of the upwelling St. Helena plume and seafloor spreading. The calculation of the model is solved through the finite element software ANSYS, and the modeling results match the actual geological evidence. In this study, nine other models are created with altered rock parameters or boundary constraints and compared to the original model to examine the influence of these factors. Compared to the nine comparative models, the original model best reflects the calculated results, which indicates that the coupling of the St. Helena mantle plume and ocean-ridge spreading caused the initial lithospheric Rifting at ∼130 Ma and that the heterogeneities within Africa did not affect the extension direction of the Rift basin but did influence the location of the Rift basin.

  • geodynamics of the east African Rift System 30 ma ago a stress field model
    Journal of Geodynamics, 2018
    Co-Authors: Ge Min, Guiting Hou
    Abstract:

    Abstract The East African Rift System (EARS) is thought to be an intra-continental ridge that meets the Red Sea and the Gulf of Aden at the Ethiopian Afar as the failed arm of the Afar triple junction. The geodynamics of EARS is still unclear even though several models have been proposed. One model proposes that the EARS developed in a local tensile stress field derived from far-field loads because of the pushing of oceanic ridges. Alternatively, some scientists suggest that the formation of the EARS can be explained by upwelling mantle plumes beneath the lithospheric weak zone (e.g., the Pan-African suture zone). In our study, a shell model is established to consider the Earth’s spherical curvature, the lithospheric heterogeneity of the African continent, and the coupling between the mantle plumes and the mid-ocean ridge. The results are calculated via the finite element method using ANSYS software and fit the geological evidence well. To discuss the effects of the different rock mechanical parameters and the boundary conditions, four comparative models are established with different parameters or boundary conditions. Model I ignores the heterogeneity of the African continent, Model II ignores mid-ocean spreading, Model III ignores the upwelling mantle plumes, and Model IV ignores both the heterogeneity of the African continent and the upwelling mantle plumes. Compared to these models is the original model that shows the best-fit results; this model indicates that the coupling of the upwelling mantle plumes and the mid-ocean ridge spreading causes the initial lithospheric breakup in Afar and East Africa. The extension direction and the separation of the EARS around the Tanzanian craton are attributed to the heterogeneity of the East African basement.

  • Geodynamics of the East African Rift System ∼30 Ma ago: A stress field model
    Journal of Geodynamics, 2018
    Co-Authors: Ge Min, Guiting Hou
    Abstract:

    Abstract The East African Rift System (EARS) is thought to be an intra-continental ridge that meets the Red Sea and the Gulf of Aden at the Ethiopian Afar as the failed arm of the Afar triple junction. The geodynamics of EARS is still unclear even though several models have been proposed. One model proposes that the EARS developed in a local tensile stress field derived from far-field loads because of the pushing of oceanic ridges. Alternatively, some scientists suggest that the formation of the EARS can be explained by upwelling mantle plumes beneath the lithospheric weak zone (e.g., the Pan-African suture zone). In our study, a shell model is established to consider the Earth’s spherical curvature, the lithospheric heterogeneity of the African continent, and the coupling between the mantle plumes and the mid-ocean ridge. The results are calculated via the finite element method using ANSYS software and fit the geological evidence well. To discuss the effects of the different rock mechanical parameters and the boundary conditions, four comparative models are established with different parameters or boundary conditions. Model I ignores the heterogeneity of the African continent, Model II ignores mid-ocean spreading, Model III ignores the upwelling mantle plumes, and Model IV ignores both the heterogeneity of the African continent and the upwelling mantle plumes. Compared to these models is the original model that shows the best-fit results; this model indicates that the coupling of the upwelling mantle plumes and the mid-ocean ridge spreading causes the initial lithospheric breakup in Afar and East Africa. The extension direction and the separation of the EARS around the Tanzanian craton are attributed to the heterogeneity of the East African basement.

R.m. Binks – One of the best experts on this subject based on the ideXlab platform.

  • Differential opening of the Central and South Atlantic Oceans and the opening of the West African Rift System
    Tectonophysics, 1991
    Co-Authors: J. D. Fairhead, R.m. Binks
    Abstract:

    Abstract Plate tectonic studies of the development of the Central and South Atlantic Oceans using Seasat and Geosat altimeter and magnetic anomaly isochron data now provide quantitative models of seafloor spreading through time. Such models enable an initial assessment of the differential opening between these two oceanic basins to be determined. The Equatorial Atlantic is an integral part of this oceanic Rifting process, allowing stresses arising from the differential opening to be dissipated into both the Caribbean and Africa along its northern and southern boundaries respectively. The tectonic model for the West African Rift System, based on geological and geophysical studies, shows a series of strike-slip fault zones diverging into Africa from the Gulf of Guinea and dissipating their shear movement into the development of extensional basins orientated perpendicular to these faults zones. The development of the West African Rift System was contemporaneous with the early opening of the South Atlantic, continued to develop well after the final breakup of South America from Africa and did not cease until the late Cretaceous when there was a major phase of basin inversion and deformation. Santonian ( ~ 80 Ma) deformation across the Benue Trough (Nigeria) is broadly contemporaneous with dextral shear reactivation of the central African fracture System which, in turn resulted in renewed extension in the Sudan basins during the late Cretaceous and early Tertiary. This paper illustrates the close linkage in both time and space between the history of the African Rift basins and the opening of the Atlantic. Both exhibit distinct phases of evolution with the Rift basins developing in direct response to the differential opening between the Central and South Atlantic in order to dissipate stresses generated by this opening. The Mesozoic tectonic model proposed is therefore one of an intimate interaction between oceanic and continental tectonics.

Bernard Le Gall – One of the best experts on this subject based on the ideXlab platform.

  • Crustal rheology and depth distribution of earthquakes: Insights from the central and southern East African Rift System
    Tectonophysics, 2009
    Co-Authors: Julie Albaric, Julie Perrot, Jacques Deverchere, Carole Petit, Bernard Le Gall
    Abstract:

    International audienceThe seismicity depth distribution in the central and southern East African Rift System (EARS) is investigated using available catalogs from local, regional and global networks. We select well-determined events and make a re-assessment of these catalogs, including a relocation of 40 events and, where necessary, a declustering. About 560 events are finally used for determining foci depth distribution within 6 areas of the EARS. Assuming that short-term deformation expressed by seismicity reflects the long-term mechanical properties of the lithosphere, we build yield strength envelopes from seismicity depth distribution. Using brittle and ductile laws, we predict the strength percentage spaced every 5 km (or sometimes 2 km) in the crust, for a given composition and a specific geotherm, and constrain it with the relative abundance of seismicity. Results of this modeling indicate significant local and regional variations of the thermo-mechanical properties of the lithosphere which are broadly consistent with previous studies based on independent modelings. In order to explain relatively deep earthquakes, a highly resistant, mafic lower crust is generally required. We also find evidence for changes in the strength magnitude and in the depth of the brittle-ductile transitions which are clearly correlated to tectonic provinces, characterized by contrasted thermal gradients and basement types. A clear N-S increase and deepening of the peak strength level is evidenced along the eastern branch of the EARS, following a consistent southward migration of Rifting since ~ 8 Ma. We also detect the presence of a decoupling layer in the Kenya Rift, which suggests persisting influences of the deep crustal structures (Archaean and Proterozoic) on the behavior of the extending crust. More generally, our results suggest that seismicity peaks and cut-off depths may provide good proxies for bracketing the brittle-ductile transitions within the continental crust

  • Crustal rheology and depth distribution of earthquakes: Insights from the central and southern East African Rift System
    Tectonophysics, 2008
    Co-Authors: J Albaric, Julie Perrot, Jacques Deverchere, Carole Petit, Bernard Le Gall
    Abstract:

    Abstract The seismicity depth distribution in the central and southern East African Rift System (EARS) is investigated using available catalogs from local, regional and global networks. We select well-determined events and make a re-assessment of these catalogs, including a relocation of 40 events and, where necessary, a declustering. About 560 events are finally used for determining foci depth distribution within 6 areas of the EARS. Assuming that short-term deformation expressed by seismicity reflects the long-term mechanical properties of the lithosphere, we build yield strength envelopes from seismicity depth distribution. Using brittle and ductile laws, we predict the strength percentage spaced every 5 km (or sometimes 2 km) in the crust, for a given composition and a specific geotherm, and constrain it with the relative abundance of seismicity. Results of this modeling indicate significant local and regional variations of the thermo-mechanical properties of the lithosphere which are broadly consistent with previous studies based on independent modelings. In order to explain relatively deep earthquakes, a highly resistant, mafic lower crust is generally required. We also find evidence for changes in the strength magnitude and in the depth of the brittle–ductile transitions which are clearly correlated to tectonic provinces, characterized by contrasted thermal gradients and basement types. A clear N–S increase and deepening of the peak strength level is evidenced along the eastern branch of the EARS, following a consistent southward migration of Rifting since ~ 8 Ma. We also detect the presence of a decoupling layer in the Kenya Rift, which suggests persisting influences of the deep crustal structures (Archaean and Proterozoic) on the behavior of the extending crust. More generally, our results suggest that seismicity peaks and cut-off depths may provide good proxies for bracketing the brittle–ductile transitions within the continental crust.