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Dapeng Zhao - One of the best experts on this subject based on the ideXlab platform.

  • p wave tomography of northeast asia constraints on the western pacific plate subduction and Mantle Dynamics
    Physics of the Earth and Planetary Interiors, 2018
    Co-Authors: You Tian, Dapeng Zhao, Xuan Feng
    Abstract:

    Abstract A high-resolution model of 3-D P-wave velocity structure beneath Northeast Asia and adjacent regions is determined by using 244,180 arrival times of 14,163 local and regional earthquakes and 319,857 relative travel-time residuals of 9988 teleseismic events recorded at ∼2100 seismic stations in the study region. Our tomographic results reveal the subducting Pacific slab clearly as a prominent high-velocity anomaly from the Japan Trench to the North-South Gravity lineament (NSGL) in East China. The NSGL is roughly coincident with the western edge of the stagnant Pacific slab in the Mantle transition zone (MTZ). The subducting Pacific slab has partly sunk into the lower Mantle beneath Northeast China, but under the Sino-Korean Craton the slab lies horizontally in the MTZ. The NSGL, as an important tectonic line in Mainland China, is marked by sharp differences in the surface topography, gravity anomaly, crustal and lithospheric thickness and Mantle seismic velocity from the east to the west. These features of the NSGL and large-scale hot and wet upwelling in the big Mantle wedge (BMW) in the east of the NSGL are all related to the subduction processes of the Western Pacific plate. The Changbai intraplate volcanic group is underlain by a striking low-velocity anomaly from the upper MTZ and the BMW up to the surface, and deep earthquakes (410–650 km depths) occur actively in the subducting Pacific slab to the east of the Changbai volcano. We propose that the Changbai volcanic group is caused by upwelling of hot and wet asthenospheric materials and active convection in the BMW. The formation of other volcanic groups in the east of the NSGL is also associated with the subduction-driven corner flow in the BMW.

  • teleseismic p wave tomography and Mantle Dynamics beneath eastern tibet
    Geochemistry Geophysics Geosystems, 2016
    Co-Authors: Jianshe Lei, Dapeng Zhao
    Abstract:

    We determined a new 3-D P-wave velocity model of the upper Mantle beneath eastern Tibet using 112,613 high-quality arrival-time data collected from teleseismic seismograms recorded by a new portable seismic array in Yunnan and permanent networks in southwestern China. Our results provide new insights into the Mantle structure and Dynamics of eastern Tibet. High-velocity (high-V) anomalies are revealed down to 200 km depth under the Sichuan basin and the Ordos and Alashan blocks. Low-velocity (low-V) anomalies are imaged in the upper Mantle under the Kunlun-Qilian and Qinling fold zones, and the Songpan-Ganzi, Qiangtang, Lhasa and Chuan-Dian diamond blocks, suggesting that eastward moving low-V materials are extruded to eastern China after the obstruction by the Sichuan basin, and the Ordos and Alashan blocks. Furthermore, the extent and thickness of these low-V anomalies are correlated with the surface topography, suggesting that the uplift of eastern Tibet could be partially related to these low-V materials having a higher temperature and strong positive buoyancy. In the Mantle transition zone (MTZ), broad high-V anomalies are visible from the Burma arc northward to the Kunlun fault and eastward to the Xiaojiang fault, and they are connected upward with the Wadati-Benioff seismic zone. These results suggest that the subducted Indian slab has traveled horizontally for a long distance after it descended into the MTZ, and return corner flow and deep slab dehydration have contributed to forming the low-V anomalies in the big Mantle wedge. Our results shed new light on the Dynamics of the eastern Tibetan plateau.

  • Mantle Dynamics and cretaceous magmatism in east central china insight from teleseismic tomograms
    Tectonophysics, 2015
    Co-Authors: Guoming Jiang, Guibin Zhang, Dapeng Zhao
    Abstract:

    Abstract Both the rich mineralization in the Lower Yangtze Block (LYB) and the post-collisional mafic rocks in the Dabie Orogen (DBO) are closely related to the Cretaceous magmatism in east-central China. Various geodynamic models have been proposed for explaining the mechanism of the Cretaceous magmatism, but these models are controversial and even contradictory with each other, especially on the mechanism of adakites. A unified geodynamic model is required for explaining the magmatism in east-central China, in particular, the spatial and temporal correlations of magmatic activity in the DBO and that in the LYB. For this purpose, we apply teleseismic tomography to study P-wave velocity structure down to 800 km depth beneath east-central China. A modified multiple-channel cross-correlation method is used to collect 28,805 high-quality P-wave arrival-time data from seismograms of distant earthquakes recorded by permanent seismic stations and our temporary stations in the study region. To remove the influence of crustal heterogeneity on the Mantle tomography, we used the CRUST1.0 model to correct the teleseismic relative residuals. Our tomography revealed distinct high-velocity (high-V) anomalies beneath the DBO and two flanks of the LYB, and low-velocity (low-V) anomalies above the high-V zones. Combining our tomographic images with previous geological, geochemical and geophysical results, we infer that these high-V and low-V anomalies reflect the detached lithosphere and upwelling asthenospheric materials, respectively, which are associated with the Late Mesozoic dynamic process and the Cretaceous magmatism. We propose a double-slab subduction model that a ridge subduction yielded the adakitic rocks in the LYB during 150–135 Ma and the subsequent Pacific Plate subduction played a crucial role in not only the formation of igneous rocks in the LYB but also remelting of the subducted South China Block beneath the DBO during 135–101 Ma.

  • P wave tomography and anisotropy beneath Southeast Asia: Insight into Mantle Dynamics
    Journal of Geophysical Research: Solid Earth, 2015
    Co-Authors: Zhouchuan Huang, Dapeng Zhao, Liangshu Wang
    Abstract:

    Southeast Asia is surrounded by subduction zones resulting from the interactions of several lithospheric plates. Its evolution has been also influenced by active tectonics due to the Indo-Asian collision in the Cenozoic. In this study, we use a large number of arrival-time data of local and regional earthquakes to determine 3-D P wave tomography and azimuthal anisotropy in the Mantle beneath SE Asia. High-velocity (high-V) anomalies representing the subducting slabs are clearly visible in the upper Mantle and the Mantle transition zone (MTZ). Low-velocity (low-V) zones with trench-normal anisotropy are revealed in the uppermost Mantle, which indicate back-arc spreading or secondary Mantle-wedge flow induced by the slab subduction. In contrast, trench-parallel anisotropy dominates in the deep upper Mantle and reflects structures either in the subducting slab or in the upper Mantle surrounding the slab. The trench-parallel anisotropy is also significant in the lower MTZ, which may contribute to shear wave splitting observations. A low-V body extending down to the lower Mantle is visible under the Hainan volcano far away from the plate boundaries, suggesting that Hainan is a hot spot fed by a lower-Mantle plume. The low-V body under Hainan is connected with low-V zones in the upper Mantle under SE Tibet and Vietnam. Our P wave anisotropy results reflect significant Mantle flow existing in the asthenosphere from SE Tibet to Hainan and further southwestward to Vietnam. The present study, especially the 3-D P wave anisotropy results, provides important new insight into Mantle Dynamics in SE Asia.

  • east asia seismotectonics magmatism and Mantle Dynamics
    Journal of Asian Earth Sciences, 2011
    Co-Authors: Dapeng Zhao, Eiji Ohtani
    Abstract:

    Abstract In this article, we review the significant recent results of geophysical studies and discuss their implications on seismotectonics, magmatism, and Mantle Dynamics in East Asia. High-resolution geophysical imaging revealed structural heterogeneities in the source areas of large crustal earthquakes, which may reflect magma and fluids that affected the rupture nucleation of large earthquakes. In subduction zone regions, the crustal fluids originate from the dehydration of the subducting slab. Magmatism in arc and back-arc areas is caused by the corner flow in the Mantle wedge and dehydration of the subducting slab. The intraplate magmatism has different origins. The continental volcanoes in Northeast Asia (such as Changbai and Wudalianchi) seem to be caused by the corner flow in the big Mantle wedge (BMW) above the stagnant slab in the Mantle transition zone and the deep dehydration of the stagnant slab as well. The Tengchong volcano in Southwest China is possibly caused by a similar process in BMW above the subducting Burma microplate (or Indian plate). The Hainan volcano in southernmost China seems to be a hotspot fed by a lower-Mantle plume associated with the Pacific and Philippine Sea slabs’ deep subduction in the east and the Indian slab’s deep subduction in the west down to the lower Mantle. The occurrence of deep earthquakes under the Japan Sea and the East Asia margin may be related to a metastable olivine wedge in the subducting Pacific slab. The stagnant slab finally collapses down to the bottom of the Mantle, which may trigger upwelling of hot Mantle materials from the lower Mantle to the shallow Mantle beneath the subducting slabs and cause the slab–plume interactions. Some of these issues, such as the origin of intraplate magmatism, are still controversial, and so further detailed studies are needed from now.

Xinguo Wang - One of the best experts on this subject based on the ideXlab platform.

  • data for joint modeling of lithosphere and Mantle Dynamics sensitivity to viscosities within the lithosphere asthenosphere transition zone and d layers
    Data in Brief, 2020
    Co-Authors: Xinguo Wang, William E Holt, A Ghosh
    Abstract:

    Abstract The article presents the data calculated from four different viscosity structures V1, V2 [1], SH08 [2], and GHW13 [3], as well as two tomography models S40RTS [4] and SAW642AN [5], using the joint modeling of lithosphere and Mantle Dynamics technique [3, 6–9]. Besides, the data contain the information on the viscosity variations of the lithosphere, asthenosphere, transition zone, and D″ layer based on the viscosity structure SH08.

  • joint modeling of lithosphere and Mantle Dynamics sensitivity to viscosities within the lithosphere asthenosphere transition zone and d layers
    Physics of the Earth and Planetary Interiors, 2019
    Co-Authors: Xinguo Wang, William E Holt, A Ghosh
    Abstract:

    Abstract Although Mantle rheology is one of the most important properties of the Earth, how a radial Mantle viscosity structure affects lithosphere Dynamics is still poorly known, particularly the role of the lithosphere, asthenosphere, transition zone, and D" layer viscosities. Using constraints from the geoid, plate motions, and strain rates within plate boundary zones, we provide important new refinements to the radial viscosity profile within the key layers of the lithosphere, asthenosphere, transition zone, and D" layer. We follow the approach of the joint modeling of lithosphere and Mantle Dynamics (Ghosh and Holt, 2012; Ghosh et al., 2013b, 2019; Wang et al., 2015) to show how the viscosities within these key layers influence lithosphere Dynamics. We use the viscosity structure SH08 (Steinberger and Holme, 2008) as a starting model. The density variations within the Mantle are derived from the tomography models which, based on prior modeling, had provided a best fit to the surface observables (Wang et al., 2015). Our results show that narrow viscosity ranges of moderately strong lithosphere (2.6–5.6 × 1022 Pa-s) and moderately weak transition zone (5–9.3 × 1020 Pa-s), as well as slightly large ranges of moderately weak asthenosphere (5–34 × 1019 Pa-s) and D" layer (4.8–18 × 1020 Pa-s), are necessary to match all the surface observables. We also find that a very strong lithosphere (>8.6 × 1022 Pa-s) along with a weak asthenosphere (

  • Joint modeling of lithosphere and Mantle Dynamics: Evaluation of constraints from global tomography models
    Journal of Geophysical Research: Solid Earth, 2015
    Co-Authors: Xinguo Wang, William E Holt, A Ghosh
    Abstract:

    With the advances in technology, seismological theory, and data acquisition, a number of high-resolution seismic tomography models have been published. However, discrepancies between tomography models often arise from different theoretical treatments of seismic wave propagation, different inversion strategies, and different data sets. Using a fixed velocity-to-density scaling and a fixed radial viscosity profile, we compute global Mantle flow models associated with the different tomography models and test the impact of these for explaining surface geophysical observations (geoid, dynamic topography, stress, and strain rates). We use the joint modeling of lithosphere and Mantle Dynamics approach of Ghosh and Holt (2012) to compute the full lithosphere stresses, except that we use HC for the Mantle circulation model, which accounts for the primary flow-coupling features associated with density-driven Mantle flow. Our results show that the seismic tomography models of S40RTS and SAW642AN provide a better match with surface observables on a global scale than other models tested. Both of these tomography models have important similarities, including upwellings located in Pacific, Eastern Africa, Iceland, and mid-ocean ridges in the Atlantic and Indian Ocean and downwelling flows mainly located beneath the Andes, the Middle East, and central and Southeast Asia.

Thorsten W Becker - One of the best experts on this subject based on the ideXlab platform.

  • Topographic expressions of Mantle Dynamics in the Mediterranean
    Earth-Science Reviews, 2020
    Co-Authors: Claudio Faccenna, Thorsten W Becker
    Abstract:

    Abstract The surface of the Earth is the ever-changing expression of the dynamic processes occurring at depth and at or above its surface. However, our ability to “read” landscapes in terms of their underlying tectonic or climatic forcing remains rudimentary. During the last decade, particular attention has been drawn to the deep dynamic contributions to topography, related to the stresses that are produced at the base of the lithosphere by Mantle convection, and their relevance compared to the (iso)static component of topography. Here, we use examples from the Mediterranean and estimate residual and dynamic topography. We then compare those with surface uplift from geology for specific regions to disentangle the dynamic from the static components. Considering the different topographic signatures of tectonic processes (e.g. actual, residual, and dynamic topography as well as uplift rates) jointly provides a powerful way to distinguish between the contributions of Mantle, crustal, and surface processes. Such an approach might bring us closer to reading topographic expressions in terms of their geological cause.

  • Mantle Dynamics in the Mediterranean
    Reviews of Geophysics, 2014
    Co-Authors: Claudio Faccenna, Thorsten W Becker, Fabio A. Capitanio, Ludwig Auer, Andrea Billi, Lapo Boschi, Francesca Funiciello, Ferenc Horvàth, Laurent Jolivet, Claudia Piromallo
    Abstract:

    The Mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt. Lithospheric Dynamics are affected by slab rollback and collision of two large, slowly moving plates, forcing fragments of continental and oceanic lithosphere to interact. This paper reviews the rich and growing set of constraints from geological reconstructions, geodetic data, and crustal and upper Mantle heterogeneity imaged by structural seismology. We proceed to discuss a conceptual and quantitative framework for the causes of surface deformation. Exploring existing and newly developed tectonic and numerical geodynamic models, we illustrate the role of Mantle convection on surface geology. A coherent picture emerges which can be outlined by two, almost symmetric, upper Mantle convection cells. The downwellings are found in the center of the Mediterranean and are associated with the descent of the Tyrrhenian and the Hellenic slabs. During plate convergence, these slabs migrated backward with respect to the Eurasian upper plate, inducing a return flow of the asthenosphere from the backarc regions towards the subduction zones. This flow can be found at large distance from the subduction zones, and is at present expressed in two upwellings beneath Anatolia and eastern Iberia. This convection system provides an explanation for the general pattern of seismic anisotropy in the Mediterranean, first-order Anatolia and Adria microplate kinematics, and may contribute to the high elevation of scarcely deformed areas such as Anatolia and Eastern Iberia. More generally, the Mediterranean is an illustration of how upper Mantle, small-scale convection leads to intraplate deformation and complex plate boundary reconfiguration at the westernmost terminus of the Tethyan collision.

  • Mountain building and Mantle Dynamics
    Tectonics, 2013
    Co-Authors: Claudio Faccenna, Thorsten W Becker, Clinton P. Conrad, Laurent Husson
    Abstract:

    Mountain building at convergent margins requires tectonic forces that can overcome frictional resistance along large-scale thrust faults and support the gravitational potential energy stored within the thickened crust of the orogen. A general, dynamic model for this process is still lacking. Here we propose that mountain belts can be classified between two end-members. First, those of “slab pull” type, where subduction is mainly confined to the upper Mantle, and rollback trench motion lead to moderately thick crustal stacks, such as in the Mediterranean. Second, those of “slab suction” type, where whole-Mantle convection cells (“conveyor belts”) lead to the more extreme expressions of orogeny, such as the largely thickened crust and high plateaus of present-day Tibet and the Altiplano. For the slab suction type, deep Mantle convection produces the unique conditions to drag plates toward each other, irrespective of their nature and other boundary conditions. We support this hypothesis by analyzing the orogenic, volcanic, and convective history associated with the Tertiary formation of the Andes after ~40Ma and Himalayas after collision at ~55 Ma. Based on Mantle circulation modeling and tectonic reconstructions, we surmise that the forces necessary to sustain slab-suction mountain building in those orogens derive, after transient slab ponding, from the Mantle drag induced upon slab penetration into the lower Mantle, and from an associated surge of Mantle upwelling beneath Africa. This process started at ~65–55Ma for Tibet-Himalaya, when the Tethyan slab penetrated into the lower Mantle, and ~10 Myr later in the Andes, when the Nazca slab did. This surge of Mantle convection drags plates against each other, generating the necessary compressional forces to create and sustain these two orogenic belts. If our model is correct, the available geological records of orogeny can be used to decipher time-dependent Mantle convection, with implications for the supercontinental cycle.

  • Mantle Dynamics and seismic anisotropy
    Earth and Planetary Science Letters, 2010
    Co-Authors: Maureen D. Long, Thorsten W Becker
    Abstract:

    Abstract Observations of seismic anisotropy yield some of the most direct constraints available on both past and present-day deformation in the Earth's Mantle. Insight into the character of Mantle flow can also be gained from the geodynamical modeling of Mantle processes on both global and regional scales. We highlight recent progress toward understanding Mantle flow from both observations and modeling and discuss outstanding problems and avenues for progress, particularly in the integration of seismological and geodynamical constraints to understand seismic anisotropy and the deformation that produces it. To first order, the predictions of upper Mantle anisotropy made by global Mantle circulation models match seismological observations well beneath the ocean basins, but the fit is poorer in regions of greater tectonic complexity, such as beneath continental interiors and within subduction systems. In many regions of the upper Mantle, models of anisotropy derived from surface waves are seemingly inconsistent with shear wave splitting observations, which suggests that our understanding of complex anisotropic regions remains incomplete. Observations of anisotropy in the D" layer hold promise for improving our understanding of dynamic processes in the deep Earth but much progress remains to be made in characterizing anisotropic structure and relating it to the geometry of flow, geochemical heterogeneity, or phase transitions. Major outstanding problems related to understanding Mantle anisotropy remain, particularly regarding the deformation and evolution of continents, the nature of the asthenosphere, subduction zone geoDynamics, and the thermo-chemical state of the lowermost Mantle. However, we expect that new seismological deployments and closer integration of observations with geodynamical models will yield rapid progress in these areas.

Shigenori Maruyama - One of the best experts on this subject based on the ideXlab platform.

  • superplume supercontinent and post perovskite Mantle Dynamics and anti plate tectonics on the core Mantle boundary
    Gondwana Research, 2007
    Co-Authors: Shigenori Maruyama, Dapeng Zhao
    Abstract:

    Abstract The Western Pacific Triangular Zone (WPTZ) is the frontier of a future supercontinent to be formed at 250 Ma after present. The WPTZ is characterized by double-sided subduction zones to the east and south, and is a region dominated by extensive refrigeration and water supply into the Mantle wedge since at least 200 Ma. Long stagnant slabs extending over 1200 km are present in the mid-Mantle Boundary Layer (MBL, 410–660 km) under the WPTZ, whereas on the Core–Mantle Boundary (CMB, 2700–2900 km depth), there is a thick high-V anomaly, presumably representing a slab graveyard. To explain the D″ layer cold anomaly, catastrophic collapse of once stagnant slabs in MBL is necessary, which could have occurred at 30–20 Ma, acting as a trigger to open a series of back-arc basins, hot regions, small ocean basins, and presumably formation of a series of microplates in both ocean and continent. These events were the result of replacement of upper Mantle by hotter and more fertile materials from the lower Mantle. The thermal structure of the solid Earth was estimated by the phase diagrams of Mid Oceanic Ridge Basalt (MORB) and pyrolite combined with seismic discontinuity planes at 410–660 km, thickness of the D″ layers, and distribution of the ultra-low velocity zone (ULVZ). The result clearly shows the presence of two major superplumes and one downwelling. Thermal structure of the Earth seems to be controlled by the subduction history back to 180 Ma, except in the D″ layer. The thermal structure of the D″ layer seems to be controlled by older slab-graveyards, as expected by paleogeographic reconstructions for Laurasia, Gondwana and Rodinia back to 700 Ma. Comparison of Mantle tomography between the Pacific superplume and underneath the WPTZ suggests the transformation of a cold slab graveyard to a large-scale Mantle upwelling with time. The Pacific superplume was born from the coldest CMB underneath the 1.0–0.75 Ga supercontinent Rodinia where huge amounts of cold slabs had accumulated through collision-amalgamation of more than 12 continents. A high velocity P-wave anomaly on a whole-Mantle scale shows stagnant slabs restricted to the MBL of circum-Pacific and Tethyan regions. The high velocity zones can be clearly identified within the Pacific domain, suggesting the presence of slab graveyards formed at geological periods much older than the breakup of Rodinia. We speculate that the predominant subduction occurred through the formation period of Gondwana, presumably very active during 600 to 540 Ma period, and again from 400 to 300 Ma during the formation of the northern half of Pangea (Laurasia). We correlate the three dominant slab graveyards with three major orogenies in earth history, with the emerging picture suggesting that the present-day Pacific superplume is located at the center of the Rodinian slab graveyard. We speculate the mechanism of superplume formation through a comparison of the thermal structure of the Mantle combined with seismic tomography under the Western Pacific Triangular Zone (WPTZ), Laurasia (Asia), Gondwana (Africa), and Rodinia (Pacific). The coldest Mantle formed by extensive subduction to generate a supercontinent, changes with time of the order of several hundreds of million years to the hottest Mantle underneath the supercontinent. The Pacific superplume is tightly defined by a steep velocity gradient on the margin, particularly well documented by S-wave velocity. The outermost region of the superplume is characterized by the Rodinia slab graveyard forming a donut-shape. We develop a petrologic model for the Pacific superplume and show how larger plumes are generated at shallower depths in the Mantle. We link the mechanism of formation of the superplume to the presence of the mineral post-perovskite, the phase transformation of which to perovskite is exothermic, and thus aids in transporting core heat to Mantle, and finally to planetary space by plumes. We summarize the characteristics of tectonic processes operating at the CMB to propose the existence of an “anti-crust” generated through “anti-plate tectonics” at the bottom of the Mantle. The chemistry of the anti-crust markedly contrasts with that of the continental crust overlying the Mantle. Both the crust and the anti-crust must have increased in volume through geologic time, in close relation with the geochemical reservoirs of the Earth. The process of formation of a new superplume closely accompanies the process of development of anti-crust at the bottom of Mantle, through the production of dense melt from the partial melting of recycled MORB, observed now as the ULVZ. When CMB temperature is recovered to near 4000 K through phase transformation, the recycled MORB is partially melted imparting chemical buoyancy of the andesitic residual solid which rises up from CMB, leaving behind the dense melt to sink to CMB and thus increase the mass of anti-crust. These small-scale plumes develop to a large-scale superplume through collision and amalgamation with time. When all recycled MORBs are consumed, it is the time of demise of superplume. Immediately above the CMB, anti-plate tectonics operates to develop anti-crust through the horizontal movement of accumulated slab and their partial melting. Thus, we speculate that another continent, or even a supercontinent, has developed through geologic time at the bottom of the Mantle. We also evaluate the heating vs. cooling models in relation to Mantle Dynamics. Rising plumes control not only the rifting of supercontinents and continents, but also the Atlantic stage as seen by anchored ridge by hotspots in the last 200 Ma in the Atlantic. Therefore, we propose that the major driving force for the Mantle Dynamics is the heat supplied from the high-T core, and not the slab pull force by cooling. The best analogy for this is the atmospheric circulation driven by the energy from Sun.

  • Mantle Dynamics of Western Pacific and East Asia: Insight from seismic tomography and mineral physics
    Gondwana Research, 2006
    Co-Authors: Dapeng Zhao, Shigenori Maruyama, Soichi Omori
    Abstract:

    Abstract Recent results of high-resolution seismic tomography and mineral physics experiments are used to study Mantle Dynamics of Western Pacific and East Asia. The most important processes in subduction zones are the shallow and deep slab dehydration and the convective circulation (corner flow) processes in the Mantle wedge. The combination of the two processes may have caused the back-arc spreading in the Lau basin, affected the morphology of the subducting Philippine Sea slab and its seismicity under southwest Japan, and contributed to the formation of the continental rift system and intraplate volcanism in Northeast Asia, which are clearly visible in our tomographic images. Slow anomalies are also found in the Mantle under the subducting Pacific slab, which may represent (a) small Mantle plumes, (b) upwellings associated with the slab collapsing down to the lower Mantle, or (c) sub-slab dehydration associated with deep earthquakes caused by the reactivation of large faults preserved in the slab. Combining tomographic images and earthquake hypocenters with phase diagrams in the systems of peridotite + water, we proposed a petrologic model for arc volcanism. Arc magmas are caused by the dehydration reactions of hydrated slab peridotite that supply water-rich fluids to the Mantle wedge and cause partial melting of the convecting Mantle wedge. A large amount of fluids can be released from hydrated MORB at depths shallower than 55 km, which move upwards to hydrate the wedge corner under the fore-arc, and never drag down to the deeper Mantle along the slab surface. Slab dehydration reactions at 120 km depth are the antigorite-related 5 reactions which supply water-rich fluids for forming the volcanic front. Phase A and Mg-surssasite breakdown reactions at 200 and 300 km depths below 700 °C cause the second and third arcs, respectively. Moreover, the dehydration reactions of super-hydrous phase B, phases D and E at 500–660 km depths cause the fluid transportation to the Mantle boundary layer (MBL) (410–660 km depth). The stagnant slabs extend from Japan to Beijing, China for over 1000 km long, indicating that the arc–trench system covers the entire region from the Japan trench to East Asia. We propose a big Mantle wedge (BMW) model herein, where hydrous plumes originating from 410 km depth cause a series of intra-continental hot regions. Fluids derived from MBL accumulated by the double-sided subduction zones, rather than the India–Asia collision and the subsequent indentation into Asia, are the major cause for the active tectonics and Mantle Dynamics in this broad region.

A Ghosh - One of the best experts on this subject based on the ideXlab platform.

  • data for joint modeling of lithosphere and Mantle Dynamics sensitivity to viscosities within the lithosphere asthenosphere transition zone and d layers
    Data in Brief, 2020
    Co-Authors: Xinguo Wang, William E Holt, A Ghosh
    Abstract:

    Abstract The article presents the data calculated from four different viscosity structures V1, V2 [1], SH08 [2], and GHW13 [3], as well as two tomography models S40RTS [4] and SAW642AN [5], using the joint modeling of lithosphere and Mantle Dynamics technique [3, 6–9]. Besides, the data contain the information on the viscosity variations of the lithosphere, asthenosphere, transition zone, and D″ layer based on the viscosity structure SH08.

  • joint modeling of lithosphere and Mantle Dynamics sensitivity to viscosities within the lithosphere asthenosphere transition zone and d layers
    Physics of the Earth and Planetary Interiors, 2019
    Co-Authors: Xinguo Wang, William E Holt, A Ghosh
    Abstract:

    Abstract Although Mantle rheology is one of the most important properties of the Earth, how a radial Mantle viscosity structure affects lithosphere Dynamics is still poorly known, particularly the role of the lithosphere, asthenosphere, transition zone, and D" layer viscosities. Using constraints from the geoid, plate motions, and strain rates within plate boundary zones, we provide important new refinements to the radial viscosity profile within the key layers of the lithosphere, asthenosphere, transition zone, and D" layer. We follow the approach of the joint modeling of lithosphere and Mantle Dynamics (Ghosh and Holt, 2012; Ghosh et al., 2013b, 2019; Wang et al., 2015) to show how the viscosities within these key layers influence lithosphere Dynamics. We use the viscosity structure SH08 (Steinberger and Holme, 2008) as a starting model. The density variations within the Mantle are derived from the tomography models which, based on prior modeling, had provided a best fit to the surface observables (Wang et al., 2015). Our results show that narrow viscosity ranges of moderately strong lithosphere (2.6–5.6 × 1022 Pa-s) and moderately weak transition zone (5–9.3 × 1020 Pa-s), as well as slightly large ranges of moderately weak asthenosphere (5–34 × 1019 Pa-s) and D" layer (4.8–18 × 1020 Pa-s), are necessary to match all the surface observables. We also find that a very strong lithosphere (>8.6 × 1022 Pa-s) along with a weak asthenosphere (

  • Joint modeling of lithosphere and Mantle Dynamics: Evaluation of constraints from global tomography models
    Journal of Geophysical Research: Solid Earth, 2015
    Co-Authors: Xinguo Wang, William E Holt, A Ghosh
    Abstract:

    With the advances in technology, seismological theory, and data acquisition, a number of high-resolution seismic tomography models have been published. However, discrepancies between tomography models often arise from different theoretical treatments of seismic wave propagation, different inversion strategies, and different data sets. Using a fixed velocity-to-density scaling and a fixed radial viscosity profile, we compute global Mantle flow models associated with the different tomography models and test the impact of these for explaining surface geophysical observations (geoid, dynamic topography, stress, and strain rates). We use the joint modeling of lithosphere and Mantle Dynamics approach of Ghosh and Holt (2012) to compute the full lithosphere stresses, except that we use HC for the Mantle circulation model, which accounts for the primary flow-coupling features associated with density-driven Mantle flow. Our results show that the seismic tomography models of S40RTS and SAW642AN provide a better match with surface observables on a global scale than other models tested. Both of these tomography models have important similarities, including upwellings located in Pacific, Eastern Africa, Iceland, and mid-ocean ridges in the Atlantic and Indian Ocean and downwelling flows mainly located beneath the Andes, the Middle East, and central and Southeast Asia.

  • Predicting the lithospheric stress field and plate motions by joint modeling of lithosphere and Mantle Dynamics
    Journal of Geophysical Research: Solid Earth, 2013
    Co-Authors: A Ghosh, William E Holt, Lianxing Wen
    Abstract:

    The way in which basal tractions, associated with Mantle convection, couples with the lithosphere is a fundamental problem in geoDynamics. A successful lithosphere-Mantle coupling model for the Earth will satisfy observations of plate motions, intraplate stresses, and the plate boundary zone deformation. We solve the depth integrated three-dimensional force balance equations in a global finite element model that takes into account effects of both topography and shallow lithosphere structure as well as tractions originating from deeper Mantle convection. The contribution from topography and lithosphere structure is estimated by calculating gravitational potential energy differences. The basal tractions are derived from a fully dynamic flow model with both radial and lateral viscosity variations. We simultaneously fit stresses and plate motions in order to delineate a best-fit lithosphere-Mantle coupling model. We use both the World Stress Map and the Global Strain Rate Model to constrain the models. We find that a strongly coupled model with a stiff lithosphere and 3-4 orders of lateral viscosity variations in the lithosphere are best able to match the observational constraints. Our predicted deviatoric stresses, which are dominated by contribution from Mantle tractions, range between 20-70 MPa. The best-fitting coupled models predict strain rates that are consistent with observations. That is, the intraplate areas are nearly rigid whereas plate boundaries and some other continental deformation zones display high strain rates. Comparison of Mantle tractions and surface velocities indicate that in most areas tractions are driving, although in a few regions, including western North America, tractions are resistive. Citation: Ghosh, A., W. E. Holt, and L. M. Wen (2013), Predicting the lithospheric stress field and plate motions by joint modeling of lithosphere and Mantle Dynamics.