Article

Mantle Flow and Deforming Continents: From India-Asia Convergence to Pacific Subduction

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Abstract

The formation of mountain belts or rift zones is commonly attributed to interactions between plates along their boundaries, but the widely distributed deformation of Asia from Himalaya to the Japan Sea and other back-arc basins is difficult to reconcile with this notion. Through comparison of the tectonic and kinematic records of the last 50 Ma with seismic tomography and anisotropy models, we show that the closure of the former Tethys Ocean and the extensional deformation of East Asia can be best explained if the asthenospheric mantle transporting India northward, forming the Himalaya and the Tibetan Plateau, reaches East Asia where it overrides the westward flowing Pacific mantle and contributes to subduction dynamics, distributing extensional deformation over a 3,000-km wide region. This deep asthenospheric flow partly controls the compressional stresses transmitted through the continent-continent collision, driving crustal thickening below the Himalayas and Tibet and the propagation of strike-slip faults across Asian lithosphere further north and east, as well as with the lithospheric and crustal flow powered by slab retreat east of the collision zone below East and SE Asia. The main shortening direction in the deforming continent between the collision zone and the Pacific subduction zones may in this case be a proxy for the direction of flow in the asthenosphere underneath, which may become a useful tool for studying mantle flow in the distant past. Our model of the India-Asia collision emphasizes the role of asthenospheric flow underneath continents and may offer alternative ways of understanding tectonic processes.

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... Jolivet et al., (2018) [79] synthesize the tectonic studies of Indian plate colliding into Eurasia and its geodynamic consequences such as the formation of intercontinental fault zones, from the Himalayas to the Asian plate margins where the back-arc basin, for example, the Sea of Japan, formed just above the subduction zones of the Pacific and Indian Oceans. However, these authors argue that the role of extrusion and subduction in controlling destruction within the Asian plate at such a long distance (from the impact zone) has not been fully explained. ...
... The mantle flow then intrudes Asia as far as oceanic trenches in the east and southeast, leading to subducted slab roll-back, forming the shape and dynamics of regional faults and back-arcs. The authors suggested that the continental deformation by the asthenospheric flows provided a different view on the process of continental destruction and arose a new research direction on the mantle dynamics below the continent in the past [79]. ...
... The work of Jolivet et al., (2018) [79] has several conclusions about the deformation of Asia from the time India began to collide and extrude Asia about 50 million years ago as follows: The Asian deformation is driven by (1) asthenosphere flow originating from anomalous low-velocity regions below the south and west Africa and the southwest Indian Ocean reaching as far as back-arc regions in the Western Pacific, (2) the compression initiated from the continent-continent collision zones in the lithosphere, and by (3) the plate roll-back to the east and southeast from the collision zone. ...
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The spreading of the East Vietnam Sea (EVS, also known as Bien Dong, or the South China Sea), leading to the occurrence of syn-spreading (33-16 Ma) and post-spreading (< 16 to present) volcanism. Syn-spreading magma making up thick layers of tholeiitic basalt with a geochemical composition close to the refractory and depleted mid-ocean ridge basalt (MORB) is mainly distributed inside the EVS basin. The post-spreading magma is widely distributed inside the basin and extended to South and SE China, Hainan island, Southern Laos (Bolaven), Khorat Plateau (Thailand), and Vietnam, showing the typical intraplate geochemistry. Basaltic samples were collected at many places in Indochina countries, Vietnam’s coastal and continental shelf areas, to analyze for eruption age, petrographical, geochemical, and isotopic composition to understand the similarities and differences in the mantle sources between regions. The results reveal that basalts from some areas show geochemical features suggesting they were derived subsequently by spinel peridotite and garnet peridotite melting, forming high-Si, low-Mg, and low-Ti tholeiitic basalt to low-Si, high-Mg, and high-Ti alkaline basalt with the trace element enrichment increasing over time. Other basalts have geochemical and isotopic characteristics unchanged over a long period. The post-spreading basalt’s radiogenic Sr-Nd-Hf-Pb isotopic compositions show different regional basalts distribute in the various fields regardless of eruption age, suggesting that their mantle source feature is space-dependent. The post-EVS spreading basalts expose the regional heterogeneity, reflecting the mixture of at least three components, including a depleted mantle (DM) represented by the syn-EVS spreading source, similar to the DUPAL-bearing Indian MORB source; an enriched mantle type 1 (EM1), and type 2 (EM2). The DM may interact and acquire either EM1 or EM2 in the sub-continental lithospheric mantle; as a result, different eruption at different area acquires distinct isotopic signature, reflecting the heterogeneous nature of the subcontinental lithospheric mantle. The study proposes a suitable mantle dynamic model that explains the EVS spreading kinematics and induced volcanism following the India - Eurasian collision from the Eocene based on the research outcomes.
... Within eastern Eurasia, the Cenozoic tectonic events were conducted by the Pacific plate motion relative to the Eurasian plate since 25 Ma (Hall 2002). This motion was favored by mantle flows (Jolivet et al. 2018). The asthenospheric flow causes the northward migration of the Indian plate, which enter into a collision with the Eurasia plate; this flow is relayed by the westward flow of the Pacific mantle in eastern Asia leading to the Pacific subduction beneath Eurasia Fig. 11 Possible scenario of tectonic stress field evolution in the region during the late Cenozoic times based on our findings from the Taiyuan basin and consequently to the extensional deformation recorded in this area (Jolivet et al. 2018). ...
... This motion was favored by mantle flows (Jolivet et al. 2018). The asthenospheric flow causes the northward migration of the Indian plate, which enter into a collision with the Eurasia plate; this flow is relayed by the westward flow of the Pacific mantle in eastern Asia leading to the Pacific subduction beneath Eurasia Fig. 11 Possible scenario of tectonic stress field evolution in the region during the late Cenozoic times based on our findings from the Taiyuan basin and consequently to the extensional deformation recorded in this area (Jolivet et al. 2018). The deep asthenospheric flow partly accommodates the compressional stresses communicated via the Indo-Eurasia collision (Jolivet et al. 2018). ...
... The asthenospheric flow causes the northward migration of the Indian plate, which enter into a collision with the Eurasia plate; this flow is relayed by the westward flow of the Pacific mantle in eastern Asia leading to the Pacific subduction beneath Eurasia Fig. 11 Possible scenario of tectonic stress field evolution in the region during the late Cenozoic times based on our findings from the Taiyuan basin and consequently to the extensional deformation recorded in this area (Jolivet et al. 2018). The deep asthenospheric flow partly accommodates the compressional stresses communicated via the Indo-Eurasia collision (Jolivet et al. 2018). Wang et al. (2001), based on GPS data, pointing out that the convergence between India and Eurasia essentially accommodated the crustal shortening in China. ...
Article
The Taiyuan basin, initiated during the late Cenozoic, is part of the left-stepping en-echelon graben systems of Shanxi. The state of stress in this area and its evolution over time is a significant concern given the existence of high shear strain and seismic risk along the basin boundary faults. In the present study, the inversion of fault-slip data through the right dihedron and the rotational optimization methods led us to identify 21 significant paleostress tensors. The maximum principal stress orientation shows two modes trending NE–SW and ENE–WSW with most of stress tensors having stress ratio values within a wrench regime. The extensional sites reveal NW–SE and NE–SW directions. Three tectonic stages with different kinematics were successfully identified since the late Cenozoic. The oldest event has been identified in our analysis since the late Miocene to late Pliocene and belongs to NW–SE extension/strike-slip stress regime. The next was generated in the early Pleistocene under the NE–SW extension stress regime, and the youngest activity recorded belongs to the NNW–SSE extension/strike-slip regime developed since the late Pleistocene. These events were dynamically driven by the northeastward extrusion of the Tibetan Plateau in response to the plate boundary motion involving the Indian and Eurasian plates and lesser by the NW subduction of the Pacific plate. The present-day stress state is characterized by ENE–WSW compression and NNW–SSE extension derived from earthquake focal mechanisms.
... The mantle potential temperatures for modeling is constrained by the result of thermobarometry (Tp= 1450°C, Figure 5.7). The average lithosphere thickness beneath Vietnam is from seismic studies (60 km, C. A. Dalton et al., 2017;Jolivet et al., 2018;H.-H. Wu et al., 2004). ...
... For DMM melt, non-modal batch melting is applied for garnet peridotite at 3GPa correspond to ~90km depth. Considering the thickness of lithosphere about 60 km in this area (Ball et al., 2021;Jolivet et al., 2018;H.-H. Wu et al., 2004), and assuming deep melting of peridotite with mineral mode (ol:opx:cpx:grt=55:25:12:0.08) ...
... The intraplate volcanic rocks in Vietnam generated through a thick lithosphere (Jolivet et al., 2018) with this range of Tp = 1398-1490°C is slightly higher than EVS-165 MORB basalts (Tp = 1380-1450°C; Yu & Liu, 2020), but not extremely as high as a mantle plume like Hawaiian OIB lavas (Tp = ~1550-1600°C; Herzberg, 2006;Herzberg & Gazel, 2009;Sobolev et al., 2005). This range of Tp = 1450 ± 50°C does not necessarily require a mantle plume rooted from the core-mantle boundary (Hole, 2015). ...
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Intraplate basaltic volcanism has been active in the Indochina Peninsula of SE Asia during the Cenozoic, and attributed to mantle upwelling to the base of lithosphere. Two contrasting scenarios have been proposed for a cause of mantle upwelling; one proposed that mantle upwelling has been induced by the collision of the Indian and Eurasian continents (Scenario 1), and the other proposed that mantle upwelling has been driven by thermal or compositional buoyancy within the asthenosphere (Scenario 2). In Scenario 1, the upwelling mantle flow is confined to the shallow asthenospheric region, while in Scenario 2, mantle upwelling is rooted from the deep region within or below the asthenosphere. Key to solve these contrasting ideas is geochemical signatures of basaltic magmas, which suggest the involvement of non-peridotitic, mafic-crustal lithology in production of basalts in this region. These two scenarios may ascribe the involvements of mafic-crustal lithology by different ways. In Scenario 1, the shallow origin of crustal lithology is inferred, and it is most likely preserved within the continental lithosphere. In Scenario 2, crustal lithology is considered to have been delivered with the ambient mantle from the deep asthenosphere. Thus, solving these contrasting ideas is crucial to decipher the evolution of magmatism in the Indochina Peninsula. In this study, I have carried out detailed investigation of geology, geochronology, and geochemistry of intraplate basalts in Vietnam, the most volcanically active region in the Indochina Peninsula during the Cenozoic. I found geochemical evidence of the mantle-transition-zone (MTZ) origin for the source of intraplate basalts in Vietnam and the nearby offshore regions, having erupted during the last 15 Myrs. Results of geochemical analyses reveal that basalts in Vietnam have considerable isotopic variation, which can be accounted for by mixing of melts derived from materials so far identified as DMM, FOZO, EM1 and EM2 components. Among these components, EM1 and EM2 components are considered to represent mafic crustal lithologies based on major- and trace-element characteristics. I also confirmed widespread occurrences of Cenozoic intraplate basalts with EM1 or EM2 signature in the other volcanic fields in Indochina Peninsula (e.g., Thailand, Cambodia, Laos) by literature survey. High-precision Pb and Sr-Nd isotopes and trace element data reveal that Vietnamese basalts consists of isotopically different subpopulations distributed separately in Central and Southern Vietnam. I also found that key trace-element signatures show significant correlations with isotope features; EM1 basalts exhibit enrichments of Sr and Eu, while EM2 basalts show enrichments of Pb and Th. These features imply that EM1 and EM2 components are originated from different crustal materials from deep asthenosphere; the formers represent subducted gabbros, and the latter represents subducted sediments. Transportation of such crustal materials should have been associated with subduction of oceanic lithosphere. Given that distributions of basalts with contributions of different crustal lithologies are clearly different, mantle beneath SE Asia has two chemically distinct domains, likely formed by convection induced by subduction of oceanic lithosphere. Numerical experimental studies demonstrated that subduction of dense oceanic lithosphere can induce a convection cell in the upper mantle. In addition, bi-vergent subduction could cause two convection cells with vigorous upwelling at their interface. I infer that the chemically different basalts from the Central and South of Vietnam represent the surface expression of melting in different convecting cells, one is driven by subduction of the Pacific plate and the other by subduction of the Indo-Australian plate. South-central Vietnam, where the most voluminous basaltic eruption in Southeast Asia is recorded, is the center of mantle upwelling that transports fusible, recycled materials to sub-lithospheric melting regions and triggers intensive surface volcanism.
... These deformation were generally considered to be the impact of the Pacific Plate subduction (Li, Ma, Robinson, Zhou, & Liu, 2015;Niu, 2013;Xu, Zhang, Qiu, Ge, & Wu, 2012). However, more and more geophysical, petrological, and numerical simulation studies suggest that the India-Eurasia collision has a tremendous or decisive effect on the tectonic evolution of South F I G U R E 1 Cenozoic tectonic map in Asia, distribution of Mesozoic granite in South China, and main rift basin in East China (modified from Suo, Li, Dai, Liu, & Zhou, 2012;Suo et al., 2014;Wang, Fan, Zhang, & Zhang, 2013;Wu et al., 2018;Yin, 2010;Yin & Harrison, 2000;Zhou, Sun, Shen, Shu, & Niu, 2006) China and even East Asia (Flower, Russo, Tamaki, & Hoang, 2001;Gong & John Chen, 2014;Huang et al., 2015c;Jolivet et al., 2018;Liu, Cui, & Liu, 2004;Wu et al., 2018;Yu & Chen, 2016). Similarly, the collision between the Philippine Sea Plate and East Asia has a tremendous impact on tectonic deformation in South China, for example, formation or resurrection of large-scale strike-slip fault (Suo et al., 2014), crust uplift (Ge et al., 2010). ...
... (b) The onset of the India-Eurasia collision caused the Eurasian continent in a state of intense shear stress, leading the Eurasian lithosphere to creep to the SE and the formation of large-scale strike-slip shear faults in the plate boundary and intraplate (Bendick, Bilham, Freymueller, Larson, & Yin, 2000;Jolivet et al., 2018;Larson, Bürgmann, Bilham, & Freymueller, 1999;Peltzer & Tapponnier, 1988;Tapponnier, Peltzer, Le Dain, Armijo, & Cobbold, 1982). ...
... For the opening of the back-arc basins of the West Pacific, a mantle extrusion flow in response to the closure of the Tethys ocean slabs was considered to be an incentive (Flower et al., 2001;Harris, 2003). Similarly, the initiation of the South China Sea and Japan Sea was regarded as a result of the mantle conveyor belt effect between southern India and the West Pacific (Jolivet et al., 2018). Importantly, the change of Pacific Plate motion may be likely caused by the resistance of collision-induced eastward mantle flow (Flower et al., 2001;Jolivet et al., 2018). ...
Article
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The Cenozoic tectonic dynamic process controlled by the Pacific subduction and Tethyan subduction/collision in South China are still controversial and lacks geological evidence of intracontinental deformation to define. Here, we focused on the Huangshadong‐Shiba area (HSA) in the south‐eastern coastal area of China. This study aims to obtain multi‐stage geological events by an integrated multidisciplinary investigation to decipher the multiple tectonic deformation in Cenozoic South China. We found that the Jurassic and Cretaceous granite not only dominates in surface magmatic rocks but also integrates into a whole with buried depth more than 2 km. This plate‐like granite (it means the occurrence of granite is like a tremendous plate) with thickness more than 3 km is sliced by Heyuan Fault, Renzishi Fault, and Zijin‐Boluo Fault. The basalts in the Shiba Basin have an Ocean Island Basalt‐like property, and the Heyuan Fault controlled the distribution of basalt. Our results, merged with a review of the Cenozoic tectonic evolution in South China, emphasise the decisive role of the India–Eurasia collision on the tectonics of South China in the Palaeogene and suggest the continuous northward drift of the Philippine Sea Plate and Australian Plate had a substantial effect on South China in the Neogene. This study also proposes a two‐stage tectonic activity model to visualise the Cenozoic tectonic activity acting on the HSA or South China.
... The basement is dominated by epimetamorphic detrital rocks, and the cover sequence consists of folded Paleozoic and Lower Triassic shallow-marine strata and Middle Triassic to Cretaceous terrigenous clastic rocks (e.g., Qiu et al., 2014Qiu et al., , 2016Qiu et al., , 2020. The retreat of the West-Pacific trench system causes~2,000 km extended East Asia and back-arc basin with oceanic crust (e.g., Japan Sea, South China Sea; Yin, 2010;Jolivet et al., 2018). The Cenozoic tectonic evolution of the SCB is dominated by eastward expansion of the Himalayan-Tibetan Orogeny or the back-arc extension of the West-Pacific trench system (e.g., Qiu et al., 2020;Yin, 2010). ...
... The Cenozoic tectonic evolution of SE Asia is well known for the subduction, rifting, collision, and strike-slip faulting in a complex spatiotemporal relation (e.g., Cullen et al., 2010;Jolivet et al., 2018;Qiu et al., 2020;Yin, 2010). Two compelling end-member models, that is, SE-ward extrusion of the Tibetan Plateau and retreat of a Pacific trench system, have been proposed to address the thousand kilometres of extension on the eastern Asian margin (e.g., Jolivet et al., 2018;Royden, Burchfiel, & van der Hilst, 2008;Yin, 2010). ...
... The Cenozoic tectonic evolution of SE Asia is well known for the subduction, rifting, collision, and strike-slip faulting in a complex spatiotemporal relation (e.g., Cullen et al., 2010;Jolivet et al., 2018;Qiu et al., 2020;Yin, 2010). Two compelling end-member models, that is, SE-ward extrusion of the Tibetan Plateau and retreat of a Pacific trench system, have been proposed to address the thousand kilometres of extension on the eastern Asian margin (e.g., Jolivet et al., 2018;Royden, Burchfiel, & van der Hilst, 2008;Yin, 2010). ...
Article
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The Cenozoic evolution of SE Asia is marked by thousands of kilometres extension on the continental margin, including normal faults, half‐grabens, and volcanic rocks, but dating of brittle faults in the shallow crust is difficult because of a lack of synkinematic minerals. The Cenozoic extension in the Youjiang fold‐thrust belt in southwest China is marked by brittle normal faults and half‐grabens filled with Paleogene sediments in the region. Here, we identified a strongly weathered mafic sill that was truncated by normal faults in the fold‐thrust belt and present the age and chemistry of zircons from a weathered sill. The zircons from the sill yielded a mean age of ~35 Ma. Integrating cross‐cutting relationship and zircon U–Pb dating suggest that the Cenozoic extension was initiated later than ~35 Ma in Youjiang fold‐thrust belt in southwest China. Combined with structural analysis and previous fission track data in the region, we suggest that the normal faults in this study provide evidence of surface fault activity of Cenozoic extension in SE Asia caused by retreat of a trench system. Furthermore, this study provides a case study to discuss how to decipher brittle normal faulting using zircon geochronology and structural and textural analysis from the mesoscale to the microscale.
... This phase of possible craton reworking was accompanied by crustal stretching, resulting in the formation of rifting basins around the Ordos block, for example, the Shanxi rift to the east, the Weihe rift to the southeast, and the Yinchuan-Hetao rifts to the northwest of the Ordos block. Cenozoic modification of the Ordos block has been attributed to lithospheric basal erosion triggered by small-scale convection, deep upwelling from the mantle transition zone or lower mantle, or lateral mantle flow associated with Pacific Plate subduction/retreat and Tibetan Plateau expansion (Chen, 2010;Jolivet et al., 2018;Schellart & Lister, 2005). Nevertheless, the actual mechanisms and processes responsible for the modification of the Ordos block's lithospheric keel continue to be debated. ...
... The APM-parallel anisotropy in these continental regions appears to reflect the development of LPO due to simple shear strain caused by relative deformation between the lithosphere and asthenosphere (Conrad et al., 2007;Ismail & Mainprice, 1998;Marone & Romanowicz, 2007;Refayee et al., 2014). Moreover, it is likely that both slab suction due to the retreat of the Pacific Plate to the east and eastward expansion of the Tibetan Plateau in response to the Indian-Eurasian convergence to the west of the study area (Jolivet et al., 2018;Schellart et al., 2019;Schellart & Lister, 2005), respectively, could further enhance the APM-parallel flow and induce significant anisotropy with associated large delay times that can reach >1.2 s. ...
Article
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We use 123 temporary seismic stations to determine shear wave splitting patterns beneath the northern Ordos block and its surrounding areas. The mapped pattern of anisotropy shows a dramatic arc‐shaped anisotropy contrast beneath the northeastern Ordos block that closely follows the lateral fast/slow‐velocity interface seen in a recent surface tomographic model at ~140 km depth. Both seismic anisotropy and velocity appear to demarcate the current boundary of cratonic lithosphere in the upper mantle at this depth, located >150 km south of the geological surface boundary of cratonic crust. We suggest that the craton's keel in the northeastern corner of Ordos block has already been eroded and replaced by warmer asthenospheric mantle, while the cratonic crust above this “missing” keel has yet to be destroyed by deformation and/or crustal metamorphism, thus creating the keel divot at the northeastern corner of the Ordos block. The fast polarization direction of anisotropy tends to wrap around the northeastern margin of the Ordos block, changing from predominantly NW‐SE beneath the western part of the margin to nearly E‐W beneath the east. We suggest this pattern reflects that plate motion‐related asthenosphere flow is being deflected by the cratonic keel of the Ordos block. Such keel‐deflected asthenospheric flow could enhance the erosion of the craton's keel, leading to the observed lithospheric reworking beneath this region.
... Local factors, such as the pre-existing continental-scale weak zones, can explain the Paleogene differential evolution of various depressions in the BBB, but they cannot explain the regional extension, strike-slip faulting, inversion and weak reactivation there in the Cenozoic. Those regional events are viewed as the tectonic responses of coeval plate interactions around the Eurasian Plate, such as the Pacific Plate subduction and India-Eurasia collision, and/or their resulting crust-mantle processes (e.g., Yin, 2010;Li et al., 2010;Hinsbergen et al., 2012;Jolivet et al., 2018). There is no doubt that those plate-related events have play important roles in the formation and evolution of Cenozoic basins, such as the BBB, along the East Asian continental margin, considering that the Pacific Plate subduction and the India-Eurasia collision initiated as "ridge subduction" and "soft collision", respectively, at 60-50 Ma (e.g., Lee and Lawver, 1995;Torsvik et al., 2008;Seton et al., 2015;Wu and Wu, 2019;Kimura et al., 2019), and now the former is subducting under the Eurasia Plate with the leading edge of its stagnant slab right under the BBB (Fig. 11a), while the latter is still pushing blocks in China towards the Pacific Plate (Fig. 11f). ...
... Yang et al., 2018), when the leading edge of the subducted Pacific slab still did not reach the BBB (Figs. 11d-e and 12d; Liu et al., 2017). As to the eastward lateral mantle flow triggered by the India-Eurasia collision (e.g., Liu et al., 2004;Li et al., 2010;Suo et al., 2014;Jolivet et al., 2018), numerical modelling result indicates that it would take about 30-50 Myr for that lateral flow to result in the mantle upwelling beneath the East Asia , thus it would mainly influence the Neogene-Quaternary extension and magmatic activity in East Asia and cannot lead to the Paleogene extension in the BBB. Therefore, there must be other factors triggering the mantle upwelling beneath the BBB and resulting in its Paleogene extension. ...
Article
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The Bohai Bay Basin (BBB) is a Meso–Cenozoic intracontinental petroliferous basin, where four pre-existing continental-scale fault zones intersect, in East China. The BBB has experienced complex deformational and evolutionary history that records significant information about how the lithosphere there has responded to the coeval plate interactions around the Eurasian Plate and/or their resulting deep crust-mantle processes in the Cenozoic. Now both deep and shallow deformational and evolutionary processes of the BBB have been well-studied, but many geodynamic mechanisms previously proposed for those processes are too general to explain them well. Based on various data and principles, we first summarized both deep and shallow responses and processes of the BBB in the Cenozoic and then matched reasonable geodynamic mechanisms for each of them. The results show as follows: the Cenozoic differential reactivation of pre-existing continental-scale weak zones controlled the coeval deep-shallow differential coupling evolution of the BBB. The Paleogene extension in the BBB was mainly caused by crust-mantle processes triggered by the stagnant Izanagi slab. The Cenozoic strike-slip faulting was influenced by various plate interactions, in which the oblique subduction and anticlockwise rotation of young Pacific Plate resulted in the complex pre-Oligocene strike-slip history of the Tan–Lu Fault Zone to the south of the Zhang–Peng Fault Zone, while the India-Eurasia collision has caused the intense and synchronous strike-slip faulting of various faults there since ~35 Ma, which was then weakened by the oblique subduction and clockwise rotation of young Philippine Sea Plate in the Neogene. The compression resulting from both the India-Eurasia collision and the Philippine Sea Plate's subduction contributed to the latest Paleogene tectonic inversion in the BBB. The arrival of mantle flow triggered by both the India-Eurasia collision and the stagnant slab of the Pacific Plate resulted in the tectonic reactivation there in the late Neogene.
... Subduction of the Indian plate beneath the Eurasian plate has governed the horizontal shortening and growth of the Tibetan Plateau (e.g., Yin & Harrison, 2000; Figure 1), and asthenospheric mantle flow in general responds to the India-Asia convergence (e.g., Jolivet et al., 2018). As a result of this convergence, Asian continental lithosphere has subducted southward beneath northern Tibet in the areas of the eastern Kunlun Fault (e.g., Zhao et al., 2011). ...
... The northeastward motion of the Indian plate with respect to the Eurasian plate (e.g., Replumaz et al., 2010;Zhang et al., 2004) and the steeply dipping lithospheric barriers in the mantle may have induced southeastward flow the upwelling mantle zones (Lei & Zhao, 2016). The geometries of slabs subducting into the mantle beneath Asia, including intracontinental subduction in northern Tibet , and the continued northward migration of India into Asia are responsible for the flow of sub-Tibetan asthenosphere toward the Burmese microplate (e.g., Jolivet et al., 2018). This mantle flow model is supported by the results of azimuthal anisotropy inferred from SKS splitting results (Figure 1; Liu et al., 2019;Wang et al., 2008). ...
Article
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Magmatic processes that occur during the transition from oceanic to continental subduction and collision in orogens are critical and still poorly resolved. Oceanic slab detachment in particular is hypothesized to mark a fundamental change in magmatism and deformation within an orogen. Here, we report on two Quaternary volcanic centers of Myanmar that may help us better understand the process of slab detachment. The Monywa volcanic rocks are composed of low-K tholeiitic, medium-K calk-alkaline, and high-K to shoshonitic basalts with arc signatures, while the Singu volcanic rocks show geochemical characteristics similar to asthenosphere-derived magmas. These volcanic rocks have low Os concentrations but extremely high Os-187/Os-186(i) ratios (0.1498 to 0.3824) due to minor (<4%) crustal contamination. The Monywa arc-like rocks were generated by small degrees of partial melting of subduction-modified asthenospheric mantle at variable depths from the spinel to garnet stability fields. Distinct from the Monywa arc-like rocks (Sr-87/Sr-86(i) = 0.7043 to 0.7047; epsilon Nd-i = +2.3 to +4.7), the Singu OIB-like rocks exhibit higher Sr-87/Sr-86(i) (0.7056 to 0.7064) and lower epsilon Nd-i (+0.8 to +1.6) values. These isotopic characteristics indicate a large contribution of an isotopically enriched asthenosphere layer beneath the Burmese microplate, which possibly flowed from SE Tibet. We interpret that this short-lived, small-scale, and low-degree melting Quaternary volcanism in Myanmar was triggered by its position above a slab window resulting from the tearing of the oceanic lithosphere from buoyant continental lithosphere of the Indian plate.
... On the other hand, intracontinental asthenospheric plumes are not necessarily associated with major extensional faulting (e.g., Burke and Whiteman, 1973;Le Bas, 1987;Wilson and Guiraud, 1998), suggesting that mantle flow alone cannot lead to rifting. Extension and rupturing of the continental lithosphere likely result by a combination of divergent plate-boundary forces and viscous coupling between the lithosphere and the convecting mantle (e.g., Forsyth and Uyeda, 1975;Ziegler and Cloetingh, 2004;Buiter and Torsvik, 2014;Jolivet et al., 2018;Jolivet et al., 2018b). It should also be noted that asthenospheric plumes may be long-or short-lived, and impingement of plumes on zones of lithospheric extension can thus affect various stages of continental rifting (e.g., Ziegler et al., 2001;Nikishin et al., 2002;Ziegler and Cloetingh, 2004). ...
... It should also be noted that asthenospheric plumes may be long-or short-lived, and impingement of plumes on zones of lithospheric extension can thus affect various stages of continental rifting (e.g., Ziegler et al., 2001;Nikishin et al., 2002;Ziegler and Cloetingh, 2004). During these stages, mantle drag forces are strong enough to drive plate motion and the modes of continental lithospheric stretching across extensional settings (e.g., Houseman and England, 1986;White and McKenzie, 1989;Wilson and Guiraud, 1998;Doglioni et al., 2003;Sternai et al., 2014;Jolivet et al., 2018;Jolivet et al., 2018b). ...
Article
Asthenosphere-lithosphere interactions modulated by surface processes generate outstanding topographies and sedimentary basins, but the nature of these interactions and the mechanisms through which they control the evolution of extensional tectonic settings are elusive. Basal lithospheric shearing due to plume-related mantle flow leads to extensional lithospheric rupturing and associated magmatism, rock exhumation, and topographic uplift away from the plume axis by a distance inversely correlated to the lithospheric elastic thickness. When moisturized air encounters a topographic barrier, it rises, decompresses, and saturates, leading to enhanced erosion on the windward side of the uplifted terrain. Orographic precipitation and asymmetric erosional unloading facilitate strain localization and lithospheric rupturing on the wetter and more eroded side of an extensional system. This simple analytical model is validated against thermo-mechanical numerical experiments where a rheologically stratified lithosphere above an asthenospheric plume is subject to fluvial erosion proportional to stream power during extension. Our modeling results are consistent with Paleogene mantle upwelling and flood basalts in Ethiopia synchronous to distal initiation of lithospheric stretching/rupturing in the Gulf of Aden, which progressively propagates into the Red Sea. The present-day asymmetric topography and extensional structures in the Main Ethiopian Rift may also be an effect of a Neogene-to-present orographic erosional gradient. Although inherently related to the lithosphere rheology, the evolution of continental rifts appears even more conditioned by the mantle and surface dynamics than previously thought.
... Wang et al. [7] suggested that slab break-off triggered lithosphere-asthenosphere interaction at the convergent margin. Jolivet et al. [8] showed that The growth of Himalayan orogen was reconstructed using a paleoaltimeter based on paleoenthalpy contained in fossil leaves from two newly reported assemblages in southern Tibet (Liuqu and Qiabulin) and four previously known floras from the Himalaya foreland basin, using climate leaf analysis, multivariate program analysis, and isotopic data [4]. Zircon U-Pb dating has constrained the Liuqu flora to the latest Paleocene (ca. ...
... Wang et al. [7] suggested that slab break-off triggered lithosphere-asthenosphere interaction at the convergent margin. Jolivet et al. [8] showed that the closure of the former Tethys Ocean can best be explained by asthenospheric mantle flow transporting India northward, forming the Himalayas and the Tibetan Plateau, by comparing the tectonic and kinematic records from last 50 Ma with seismic tomography and anisotropy models. ...
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Himalayan orogenesis remains enigmatic in terms of Tibetan Plateau geodynamics originating from the Cenozoic India–Eurasian continental collision. India underthrusts below Tibet to the Yarlung–Tsangpo suture, which has been identified as the northernmost boundary for underplating. However, the way in which the historical evolution of continental subduction induces plateau uplift and the way it controls the variation in uplift between outboard and inboard areas is still unclear. To interpret the evolutionary mechanisms involved in the Himalayan growth history, we constructed different 3-D dynamic models at important stages to address these questions related to the formation of the Himalayas on the basis of paleoenthalpy evidence encoded in fossil leaves from recently documented assemblages in southern Tibet. The results show that (1) the effect of crustal thickening was the predominant factor in the early evolution from the Paleocene to the early Eocene, which resulted in a moderate growth rate. (2) The consecutive slab break-off eastward from the western syntaxis and the associated slab rebound significantly accelerated orogenesis from the late Eocene to the Oligocene. The upwelling asthenospheric flow was a key control of increasing crustal buoyancy, which resulted in the fastest growth of the Himalayas during the early Miocene. (3) Thereafter, the gradually enhanced monsoon and surface erosion during accompanying the increasing mountain height resulted in a slowdown of the orogenic rate, which counterbalanced the buoyant force produced by asthenospheric flow driving continuous Himalayan growth.
... Along the Tethyan collisional belt, the subduction and Cenozoic closure of the Neo-Tethys ocean and subsequent collisions of the Indian, Arabian plates and the micro continental ribbon of Africa with Eurasia have led to not only the formation of the strongly deformed thrust belts of the Alps-Zagros-Himalayan orogens at the collisional front but also severe reactivation of pre-existing weaknesses and diffuse deformation within the continental interior in south to central Eurasia (Figure 17), accompanying widespread syn-and post-collisional igneous activities (Faccenna et al., 2014;Müller et al., 2019;Yin, 2010). Specifically, the India-Eurasia collision processes have given rise to the development of the giant Tibetan plateau in south Asia featured by the highest topography (∼5 km) and thickest continental crust (∼60-80 km) over the world ZHU ET AL. ( Figure 18), which has exerted profound impacts on the tectonic framework, climate and life on Earth (e.g., Guo et al., 2002;Jolivet et al., 2018;Molnar et al., 1993). ...
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The continental crust is unique to the Earth in the solar system, and controversies remain regarding its origin, accretion and reworking of continents. The plate tectonics theory has been significantly challenged in explaining the origin of Archean (especially pre-3.0 Ga) continents as they rarely preserve hallmarks of plate tectonics. In contrast, growing evidence emerges to support oceanic plateau models that better explain characteristics of Archean continents, including the bimodal volcanics and nearly coeval emplacement of tonalite-trondjhemite-granodiorite (TTG) rocks, presence of ∼1600°C komatiites and dominant dome structures, and lack of ultra-high-pressure rocks, paired metamorphic belts and ophiolites. On the other hand, the theory of plate tectonics has been successfully applied to interpret the accretion of continents along subduction zones since the late Archean (3.0–2.5 Ga). During subduction processes, the new mafic crust is generated at the base of continents through partial melting of mantle wedge with the addition of H2O-dominant fluids from subducted oceanic slabs and partial melting of the juvenile mafic crust results in the generation of new felsic crusts. This eventually leads to the outgrowth of continents. Subduction processes also cause softening, thinning, and recycling of continental lithosphere due to the vigorous infiltration of volatile-rich fluids and melts, especially along weak belts/layers, leading to widespread continental reworking and even craton destruction. Reworking of continents also occurs in continental interiors due to either plate boundary processes or plume-lithosphere interactions. The effects of plumes have proven to be less significant and cause lower degrees of lithospheric modification than subduction-induced craton destruction.
... Under such a scenario, the spreading ridge between the Izanagi and Pacific plates would have been located far east of the continent. Jolivet et al. (2018) conclude that the mid-ocean ridge between the plates was parallel to the continental margin and did not enter the trench until ca. 50 Ma. ...
Article
Yanshanian (ca. 200–100 Ma) metallogeny of eastern Asia was dominantly controlled by oblique subduction and rollback of the Izanagi plate, and also, more locally in the north, by closure of the Mudanjiang Ocean basin and accretion of the Bureya-Jiamusi-Khanka block and the Sikhote-Alin terranes. Although exact distances are difficult to estimate due to Early Cretaceous crustal extension, ores related to Yanshanian subduction certainly developed for more than 1500 km landward from the active trench, such as exemplified by those deposits overprinting the Paleoproterozoic Trans-North China orogen. In the northern part of the Yanshanian orogen, and thus hosted within the eastern edge of the Central Asian orogenic belt, Endako-type porphyry Mo deposits related to subduction of the Mudanjiang slab formed throughout northeast China from 200 to 135 Ma. Extensional magmatism related to rollback of the slab led to widespread Au-Ag epithermal vein development and a scattering of small Cu-Au porphyry occurrences across the same area from 125 to 100 Ma. Sinistral strike-slip motion along the continental margin in adjacent Russia, caused by the NNW motion of the Izanagi plate, led to formation of 115–95 Ma post-collisional Cu-Au porphyries, Sn-W ores associated with reduced intrusions, and orogenic gold deposits in the central Sikhote-Alin region. In the North China block, whereas early Yanshanian ore formation was relatively limited, 130–120 Ma extension-related basement uplifts were associated with formation of two of China’s most important orogenic gold provinces on the Jiaodong Peninsula and in the East Qinling; in the latter, the entire period of late Yanshanian extension may be defined by widespread 148–107 Ma Mo-rich porphyry and skarn deposit formation. To the south along the Asian margin, the oblique NW-directed subduction of the Izanagi slab was responsible for the adakitic porphyry Cu deposit formation on the eastern side of the South China block at 175–155 Ma, which continued inland for as much as 500 km to the Cathaysia-Yangtze suture. The transition at 160–150 Ma to development of the Nanling W-Sn belt in the interior of Cathaysia roughly overlaps the time of tectonic switch to slab retreat, which gradually led to seaward migration of the extension-related magmatism forming the 145–133 Ma Sn ores and 110–100 Ma high to low sulfidation epithermal deposits along the Southeast Coast belt. A period of sinistral strike-slip along the southern end of the Tan-Lu fault system was possibly responsible for a tear in the Izanagi plate and consequential S-type magmatism forming W porphyry-skarn ores of the Jiangnan belt at 145–133 Ma and I-type magmatism leading to Fe-Cu-Au skarns at the northern edge of the Yangtze block. In summary, the early Yanshanian of eastern Asia was dominated by widespread subduction-related porphyry Mo formation in the north and localized porphyry Cu formation to the south, followed by late Yanshanian development of world-class Au, Mo, Sn, and W resources during subsequent slab retreat, continental-scale extension, and strike-slip events along continental margin transform faults.
... Previous studies have investigated the causes of continental rifting through analyzing geological records, geophysical data, and modeling results (e.g., Bercovici, 2003;Buck, 1991;Coltice et al., 2019;Mohn et al., 2012;Nirrengarten et al., 2018;Péron-Pinvidic & Manatschal, 2009;Turcotte et al., 1983). Some of their end-members emphasized the role of plume-lithospheric interaction (e.g., Behn et al., 2004;Cande & Stegman, 2011;Husson, 2012;Jolivet et al., 2018;Koptev et al., 2015Koptev et al., , 2019Mondy et al., 2018;Phillips & Bunge, 2005;Yamato et al., 2013;Yoshida & Hamano, 2015), while others related the continental rifting to the tensional stresses generated at the plate boundary (e.g., Choi et al., 2013;Huismans & Beaumont, 2003;Le Pourhiet et al., 2018;Liao et al., 2013;Marotta et al., 2009;Naliboff et al., 2017;Pérez-Gussinyé et al., 2006). A series of numerical modeling studies further showed that, in both (Li, Sun, & Yang, 2018). ...
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The dynamics of continental breakup at convergent margins have been described as the results of back-arc opening caused by slab rollback or drag force induced by subduction direction reversal. Although the rollback hypothesis has been intensively studied, our understanding of the consequence of subduction direction reversal remains limited. Using thermo-mechanical modeling based on constraints from the South China Sea (SCS) region, we investigate how subduction direction reversal controls the breakup of convergent margins. The numerical results show that two distinct breakup modes, namely continental interior and edge breakup (“edge” refer to continent above the plate boundary interface), may develop depending on the “maturity” of the convergent margin and the age of the oceanic lithosphere. For a slab age of ~15-~45 Ma, increasing the duration of subduction promotes the continental interior breakup mode, where a large block of the continental material is separated from the overriding plate. In contrast, the continental edge breakup mode develops when the subduction is a short‐duration event, and in this mode a wide zone of less continuous continental fragments and tearing of the subducted slab occur. These two modes are consistent with the interior (relic late Mesozoic arc) and edge (relic fore-arc) rifting characteristics in the western and eastern SCS margin, suggesting that variation in the northwest-directed subduction duration of the Proto-SCS might be a reason for the differential breakup locus along the strike of the SCS margin. Besides, a two-segment trench associated with the northwest-directed subduction is implied in the present-day SCS region.
... Eastward retreat of the Ryukyu Trench has been responsible for back-arc extension in the Okinawa Trough ( Fig. 1; Faccenna et al., 2018;Sibuet et al., 1998). The Philippine Sea plate is made up of numerous Paleogene to present back-arc basins, including the West Philippine and Shikoku-Parece Vela basins ( Fig. 1; Chamot-Rooke et al., 1987;Hall, 2002;Hickey-Vargas, 2005;Hilde and Chao-Shing, 1984;Jolivet et al., 2018;Lallemand, 2016;Okino et al., 1998). The Philippine Sea plate also contains arc fragments, including the Cretaceous Amami Plateau, Oki-Daito Ridge and Daito Ridge, and the Eocene Kyushu-Palau Ridge ( Fig. 1; Hickey -Vargas, 2005;Yamazaki et al., 2010). ...
Article
A number of Holocene volcanoes in East Asia — Jeju, Ulleungdo, Tianchi, Longgang, Jingbohu, Erkeshan and Wudalianchi — are located far (600–1500 km) from the nearest subduction zone. The origin of these intraplate volcanoes remains unclear, and mechanisms proposed to explain their origin include plume activity and subduction processes with or without slab fluid involvement. Here we evaluate the feasibility of these mechanisms. We present an analysis of available geophysical data, including slab geometry models and the full-waveform FWEA18 tomography model, as well as statistical tests on a compilation of geochemical data. High-resolution tomography data provide no evidence for a deep-seated mantle plume. Instead, the tomography shows that Tianchi, Longgang, Jingbohu, Erkeshan and Wudalianchi are located above edges of the Pacific slab, which is stagnant near the 660 km discontinuity under East Asia. The tomography also shows that Jeju is situated above a section of the Philippine Sea slab that has subducted to the 410 km discontinuity. While the intraplate volcanoes are underlain by subducted slabs, their geochemical signatures do not support melting via slab metasomatism typical of subduction zones. Instead, the Holocene intraplate volcanoes are alkaline and have trace element compositions comparable to those of ocean island basalts. Given the absence of geophysical or geochemical evidence for plume activity or slab metasomatism, we propose that volcanism has been generated by decompression melting associated with convective upwellings at the edges of the Pacific and Philippine Sea slabs. Tectonic reconstructions suggest that the Pacific slab may have been stagnant in the mantle transition zone for millions of years, so we speculate that localised convection at Pacific slab edges was triggered by changes in Western Pacific subduction dynamics during late Neogene–Quaternary time. The geophysical and geochemical data also suggest that Quaternary rollback of the Philippine slab might be responsible for volcanism at Jeju, which is located at the leading edge of the Philippine Sea slab.
... Indian Plate began colliding with Eurasian Plate over 40-50 million years ago. Since then, the Asian lithosphere has been deforming across a wide region, and crustal shortening in the vicinity of the collision zone formed the Himalaya and the Tibetan Plateau (Jolivet et al., 2018). The induced tectonic movement of Eurasian Plate still keeps a horizontal crustal deformation rate of about 20 mm/yr to the north-east direction. ...
Article
Pore pressures in the Xujiahe gas-bearing formations are highly overpressured in the western Sichuan basin. The abnormally high overpressure and strong tectonic stress cause very high horizontal stresses. The high in-situ stresses, tectonic stress regimes, and tight formations severely impact development and production of the Xujiahe tight sandstone reservoirs. Overpressure generation mechanisms are analyzed based on measured data in several dozen wells in the studied gas fields. It is found that the sonic or seismic transit time can be used to predict pore pressure. Two major reservoirs (Xu2 and Xu4) belong to different fluid compartments with distinct pore pressure gradients. The Xu4 has a much higher pore pressure gradient (20 MPa/km) than the Xu2 (15.6 MPa/km). Measured data from hydraulic fracturing tests and borehole image logs in vertical wells are analyzed. The results show that the minimum horizontal stress gradient in the Xu4 reservoir reaches as high as 24 MPa/km, close to the overburden gradient. The Xu2 reservoir has a slightly lower minimum horizontal stress gradient. The high minimum horizontal stress and high rock strength cause abnormally high formation breakdown pressure gradient (24.8–34 MPa/km). The high breakdown pressure, high propagation pressure, and unfavorable stress regime result in a great difficulty for the reservoir stimulation. One of the major impacts is that hydraulic fracturing operations can only create very short hydraulic fractures, which markedly limits reservoir productivity. Based on field measurements, in-situ stress determination and assessment are given, and a new method for horizontal stress estimation is proposed. Accordingly, reliable prediction of formation breakdown and propagation pressures are proposed, which are more suitable for the tight reservoirs. Recommendations are given for effective development of the tight reservoirs with impacts of high in-situ stresses.
... En las grandes cadenas de montañas actuales, por ejemplo, en el Mediterráneo (Faccenna et al., 2014) o en Asia (Jolivet et al., 2018), las colisiones no suelen ser únicas ni ocurren simultáneamente a lo largo de los límites de placa, por lo que diferentes sectores de la cordillera se encuentran en diferentes episodios evolutivos en un momento determinado. En el registro geológico de la cordillera Varisca en el noroeste peninsular se observa este diacronismo en la edad de las estructuras y rocas y por tanto en los procesos geológicos (Dallmeyer et al., 1997;Dias et al., 2016). ...
... However, the interaction between the India-Eurasia Plate collision and the subduction of the western Pacific Plate should not be ignored. Jolivet et al. (2018) hypothesized that the extension in north China was dominated by asthenospheric flow that carried the J o u r n a l P r e -p r o o f Journal Pre-proof Indian slab northward by ~3000 km, reach far beyond the collision zone, accommodated the retreat of the Pacific margin of Asia and led associated extensional deformation in eastern Asia. To test these models, more geophysical and geological work is required to find out the records of mechanic processes of the broad region. ...
Article
The basin history of the northeastern Tibetan Plateau provides an ideal record for understanding the tectonic evolution of the plateau. We present high-resolution magnetostratigraphy and cosmogenic ¹⁰Be/²⁶Al burial chronology from the Tongxin Basin in the Arcuate Ranges area in the northeastern Tibetan Plateau and reconstruct a long depositional history ranging from >21.7 to 4.6 Ma. Our new chronologic data suggest that a broad N-S-trending elongated basin existed during the Late Oligocene-Early Miocene (>21.7–16.5 Ma). WNW-trending faulting initiated at ca. 16.5 Ma and resulted in the formation of some fault-bounded basins outward from the western margin of the broad basin, but did not strongly affect the deposition within the basin region. Subsequently, intense northeastward compression elevated both WNW- and NWN-trending mountain ranges at ca. 7.6 Ma. Thrust-induced surface uplift elevated basin sediments and formed piggy-back basins in the hanging-wall blocks, reflecting the northeastward expansion of the northeastern Tibetan Plateau.
... Traditional tectonic regimes of mantle upwelling, such as regional extension, do not adequately explain the observed abundance (70,000 km 2 ) of volcanism . Previous studies have proposed a role for extrusion tectonics, positing that the adjacent Himalayan collision extruded Southeast Asia eastward and caused mantle upwelling beneath Indochina ( Fig. 1) (Hoang et al., 1996;2013;Flower et al., 1998;Hoang and Flower, 1998;Jolivet et al., 2018). However, the origin and character of the mantle upwelling has not been well explained. ...
Article
Extrusion tectonics has been invoked to explain the extensive basaltic magmatism that has erupted over Indochina within the last 17 Ma. The basalts display two-stage eruptive cycles consisting of tholeiites followed by alkaline basalts. Lithospheric mantle xenoliths recently sampled from the alkaline basalts of two volcanic centers, Pleiku and Xuan Loc, primarily consist of fertile spinel lherzolites, and Xuan Loc also contains refractory spinel harzburgites. We measured major elements in xenolith mineral separates, trace elements in clinopyroxenes and orthopyroxenes, and Pb-Sr-Nd isotopic compositions in clinopyroxenes to determine the origin and history of the subcontinental lithospheric mantle (SCLM) beneath Vietnam. Most peridotites from Pleiku and Xuan Loc exhibit fertile major element compositions, “depleted” and “spoon-shaped” rare earth element (REE) patterns, and isotopic signatures ranging from typical depleted MORB mantle to an even more depleted source (87Sr/86Sr = 0.702381 - 0.703365 and εNd = +8.84 - +30.28). A smaller group of peridotites from Xuan Loc show distinct refractory major element compositions, “enriched” REE patterns, and more incompatible element enriched isotopic signatures (87Sr/86Sr = 0.704050 and εNd = +3.16 in one sample) than the fertile peridotites. Based on their major and trace element compositions, Pleiku and Xuan Loc xenoliths have calculated equilibrium temperatures of 807-1052 ÅãC which indicate extraction depths of 30 to 45 km. We interpret the fertile peridotites from Pleiku and Xuan Loc to sample recently emplaced lithospheric mantle from the convecting asthenosphere, whereas the refractory peridotites from Xuan Loc may represent partial melting residues derived from older SCLM. We conclude that the extrusion of Indochina initiated regional asthenospheric upwelling, resulting in the partial removal and replacement of the lithospheric mantle. Advisor: Lynne J. Elkins
... Rifting and strike-slip faulting occurred in the Liaodong Bay Depression in the Cenozoic. It is controlled and influenced by the subduction of the Izanagi-Pacific plate, continental collision between the Indian plate and the Eurasian plate, and deep lithosphere-mantle processes (Yin, 2010;Li et al., 2010;Hinsbergen et al., 2012;Jolivet et al., 2018). ...
Article
The Liaodong Bay Depression was shaped by the Bohai Bay rift basin (BBRB) and the Tan-Lu strike-slip fault system (TSFS) in the Cenozoic and has undergone a tectonic transition from rifting to strike-slip. Therefore, it is an ideal region to study the transition from rifting to strike-slip. Based on new 3D serial seismic data interpretation, we investigated the types and formation times of the main faults in the Liaodong Bay Depression and restored them within the palaeogeography of each evolution stage. Our results show that the Liaodong Bay Depression underwent a tectonic transition from rifting to strike-slip: (1) The mantle material upsurge caused by the Izanagi plate trapped in the mantle transition zone led to rifting of the Liaodong Bay Depression from the Palaeocene to the Eocene. (2) In the middle Eocene, the change in the subduction direction of the Pacific plate led to dextral strike-slip movement along the Tan-Lu fault zone. (3) The rifting and strike-slip in the Liaodong Bay depression are related, and the transition from rifting to strike-slip occurred from the middle Eocene to the early Oligocene. The strike-slip faults developed when rifting was weak in the Oligocene. The transition from rifting to strike-slip faulting formed oil-gas accumulation zones along the strike-slip fault zone and thus resulted in the good oil and gas exploration prospects of this area.
... They might also act as barriers to the eastward asthenospheric flow. However, the impact of the asthenospheric flow from the Tibetan Plateau is claimed to be not only restricted to its margins but may also affect far to the east (Jolivet et al., 2018;Liu et al., 2004;Y.-J. Tang et al., 2006). ...
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The collision between India and Eurasia forming the Tibetan Plateau since the early Cenozoic had led to the crustal and upper-mantle (asthenospheric) extrusion from the plateau to the east. However, the Ordos and Yangtze cratonic keels next to the northeastern and eastern Tibetan Plateau obstruct this eastward asthenospheric extrusion. With a dense seismic array, for the first time, we imaged a narrow low P-wave and S-wave velocity anomaly characterized with higher Vp/Vs between these two Archean cratons at depths ranging from 150 to 300 km using finite-frequency tomography. We interpret this low-velocity anomaly as a channel of the eastward asthenospheric flow from the Tibetan Plateau. We provide solid seismic observations for a pathway of the Tibetan asthenospheric extrusion due to the ongoing collision of the Indian and Eurasian continents. This asthenospheric extrusion from the Tibetan Plateau could influence the lithospheric reworking in the central and eastern North China Craton.
... An exciting avenue of future research, afforded by geologically consistent numerical geodynamic simulations and seismic images of subducted and/or sunken lithosphere, is exploring how large continental collisions both influence and are influenced by tectonism along adjacent plate boundaries 201,202 and by global-scale mantle convection 203 . ...
Article
The timing of the initial India–Asia collision and the mechanisms that led to the eventual formation of the high (>5 km) Tibetan Plateau remain enigmatic. In this Review, we describe the spatio-temporal distribution and geodynamic mechanisms of surface uplift in the Tibetan Plateau, based on geologic and palaeo-altimetric constraints. Localized mountain building was initiated during a Cretaceous microcontinent collision event in central Tibet and ocean–continent convergence in southern Tibet. Geological data indicate that India began colliding with Asian-affinity rocks 65–60 million years ago (Ma). High-elevation (>4 km) east–west mountain belts were established in southern and central Tibet by ~55 Ma and ~45 Ma, respectively. These mountain belts were separated by ≤2 km elevation basins centred on the microcontinent suture in central Tibet, until the basins were uplifted further between ~38 and 29 Ma. Basin uplift to ≥4 km elevation was delayed along the India–Asia suture zone until ~20 Ma, along with that in northern Tibet. Delamination and break-off of the subducted Indian and Asian lithosphere were the dominant mechanisms of surface uplift, with spatial variations controlled by inherited lithospheric heterogeneities. Future research should explore why surface uplift along suture zones — the loci of the initial collision — was substantially delayed compared with the time of initial collision. The geodynamic mechanisms and timing of Tibetan Plateau formation are debated, but are critical to understanding tectonic–climatic links. This Review discusses the stages of Tibetan Plateau evolution, and highlights that inherited weaknesses from pre-Cenozoic tectonic events influenced its variable surface uplift history. The Tibetan Plateau did not get uplifted as a large entity or grow systematically outward from the India–Asia suture (IAS), because lithospheric heterogeneities in Asia imparted by pre-Cenozoic tectonic events created relatively weak and strong zones that deformed differently during collision.Cretaceous tectonic events built embryonic mountains belts and weakened the lithosphere in southern and central Tibet.Continental Asian detritus appeared in Indian continental margin sedimentary rocks by 65–60 million years ago (Ma). The most conservative interpretation based on available geologic constraints is that these sediments mark the initiation of India–Asia collision.The quest to further quantify the history of surface elevation change across Tibet spurred the field of quantitative palaeo-altimetry, such as measurement of oxygen and hydrogen isotopes in palaeo-water proxies, carbonate clumped isotope thermometry and fossil leaf physiognomy.Quantitative palaeo-altimetry suggests that high (≥4 km) elevations were obtained in southern Tibet by ~55 Ma and in central Tibet by ~45 Ma, whereas an intervening valley remained at <2 km elevation until between ~38 and 29 Ma. The IAS zone and Himalaya Mountains were rapidly uplifted from <3 km to near-modern elevations at ~20 Ma.Subcrustal processes such as subduction, delamination and break-off of Indian and Asian continental lithosphere were important tectonic events during the formation of the Tibetan Plateau. The Tibetan Plateau did not get uplifted as a large entity or grow systematically outward from the India–Asia suture (IAS), because lithospheric heterogeneities in Asia imparted by pre-Cenozoic tectonic events created relatively weak and strong zones that deformed differently during collision. Cretaceous tectonic events built embryonic mountains belts and weakened the lithosphere in southern and central Tibet. Continental Asian detritus appeared in Indian continental margin sedimentary rocks by 65–60 million years ago (Ma). The most conservative interpretation based on available geologic constraints is that these sediments mark the initiation of India–Asia collision. The quest to further quantify the history of surface elevation change across Tibet spurred the field of quantitative palaeo-altimetry, such as measurement of oxygen and hydrogen isotopes in palaeo-water proxies, carbonate clumped isotope thermometry and fossil leaf physiognomy. Quantitative palaeo-altimetry suggests that high (≥4 km) elevations were obtained in southern Tibet by ~55 Ma and in central Tibet by ~45 Ma, whereas an intervening valley remained at <2 km elevation until between ~38 and 29 Ma. The IAS zone and Himalaya Mountains were rapidly uplifted from <3 km to near-modern elevations at ~20 Ma. Subcrustal processes such as subduction, delamination and break-off of Indian and Asian continental lithosphere were important tectonic events during the formation of the Tibetan Plateau.
... Gibraltar and Palau were part of a much wider subduction at the time of their initiation. Back to the first observation that a majority of SI occurred in the Western Pacific during the Cenozoic, one may suspect a large contribution of far-field tectonic forces resulting from the India-Eurasia collision (Jolivet et al., 2018) with strain localization where the largest density contrasts prevailed. The same happened when the Australia plate accelerated its northward motion and collisions occurred between its northern margin and eastern Sundaland in the Early Miocene (Hall, 2002;Zahirovic et al., 2016). ...
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... This is not substantially worse than larger-scale models with a fixed extreme of zero velocity in a distal location (maybe in Gobi Alxa, North of Tibet) and the other as a moving extreme (maybe in Himalayas), where the asthenospheric velocities will also obey some form of intermediate values along the model-transect axis, and where our 600 km-long model would be a small subset. From an observational perspective, the study of Jolivet et al. (2018) finds that seismic-anisotropy (SL2013sv) axes at about ∼200 km-depths throughout Eastern Asia are roughly aligned with the India-Eurasia convergence direction, suggesting an asthenosphere that locally follows the moving Indian lithosphere and Tibetan SW-NE contraction, being congruent with a largescale upper mantle motion, likely with a good degree of viscous coupling with the moving plates. Regarding timing, our assumed velocities at model boundaries are invariant in time. ...
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Present‐day seismic imaging, reveals crustal thickness varying from about 70 km under SongPan‐Ganzi (SG) to about 50 km under Qaidam basin (QB) terranes in NE Tibet. This vertical Moho offset occurs over horizontal spans of less than 20 km, and is somehow confirmed by gravimetric and electromagnetic observations. Paleotectonic and litho‐stratigraphic reconstructions suggest that the region amalgamates at least three microcontinents, but current geophysical observations reveal basically two distinct microplates (SG and QB). We conduct 2D Stokes' flow numerical simulations to understand the mechanical evolution of the SG‐QB contact, focusing our attention on Moho‐offset kinematics. We find that in the absence of tectonic horizontal motions, generic systems with a Moho offset of the sort, are unstable in timescales of about ∼3 Ma, solely due to the effect of vertical driving‐forces (gravity‐driven relaxation given topographic‐ or Moho‐gradients). Then, an observation‐controlled parameter setting (seismically derived densities, locally accepted viscosities and layer thicknesses, and considering a potentially likely QB litho‐mantle weakening by SG‐derived melts) suggests that added tectonic horizontal convergence (GPS constraints on Tibetan deformations) to the previous scenario, tends to dominate the internal velocity field and deformation. Topography‐driven SG‐lower‐crustal flow may inject a small amount of mass into QB. The Moho‐offset changes significantly in timescales of about ∼5–10 Ma; an initially vertical Moho‐offset, aside from a reference‐frame‐dependent translation, differentially deforms (stretches) and rotates (becoming oblique), smoothing‐out the terranes' crustal‐thickness transition. Through time, accumulated Moho‐offset rotation and smoothing are somewhat smaller when there is tectonic horizontal shortening. The left‐lateral Kunlun‐suture motion might rejuvenate the Moho‐offset through time.
... However, the spatial distribution and depth extent of asthenospheric flow is still a subject of debate. Furthermore, the role of the asthenospheric flow in influencing the widespread continental deformation of eastern Eurasia remains unclear (Flower et al., 1998;Jolivet et al., 2018;Liu et al., 2004;Schellart et al., 2019;Schellart & Lister, 2005). ...
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During the last 50 Ma, the eastern Eurasian continent has experienced widespread crustal and lithospheric deformation. However, mechanisms in creating such widespread intra‐continental deformation are still not well understood. Here, we present a 3‐D S‐wave velocity model of the northeastern Tibetan Plateau and adjacent regions by jointly inverting teleseismic body and surface waves. The resulting model clearly suggests that lateral extrusion of asthenosphere from northern Tibet is being blocked by the thick cratonic keels of Ordos and Sichuan, and therefore the asthenosphere is channeled into a strong eastward flow beneath the northern Qinglin between these two cratonic keels. Our results also demonstrate that continental deformation in eastern Eurasia is likely influenced by the small‐scale convection when the lateral asthenospheric flow from NE Tibet encounters preexisting continental lithospheric steps to the east of Ordos.
... Along the Tethyan collisional belt, the subduction and Cenozoic closure of the Neo-Tethys ocean and subsequent collisions of the Indian, Arabian plates and the micro continental ribbon of Africa with Eurasia have led to not only the formation of the strongly deformed thrust belts of the Alps-Zagros-Himalayan orogens at the collisional front but also severe reactivation of pre-existing weaknesses and diffuse deformation within the continental interior in south to central Eurasia (Figure 17), accompanying widespread syn-and post-collisional igneous activities (Faccenna et al., 2014;Müller et al., 2019;Yin, 2010). Specifically, the India-Eurasia collision processes have given rise to the development of the giant Tibetan plateau in south Asia featured by the highest topography (∼5 km) and thickest continental crust (∼60-80 km) over the world ZHU ET AL. ( Figure 18), which has exerted profound impacts on the tectonic framework, climate and life on Earth (e.g., Guo et al., 2002;Jolivet et al., 2018;Molnar et al., 1993). ...
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There are various explanations for how the Earth’s continents form, develop, and change but challenges remain in fully understanding the driving forces behind plate tectonics on our planet.
... ;Guyonnet-Benaize et al. 2010;Handy et al. 2010 ;Jolivet et al. 2016). This contractional event causes moderate inversion of the Jurassic and Lower Cretaceous normal faults, folding of these thick series and strong salt diapirisme along the pre-existing network of faults.During Albian to Cenomanian time, the compressive regime is intimately related to the drift of Africa with respect to Europe and to the opening of Atlantic Ocean.Dercourt et al. (1986),Dewey et al. (1989),Mazzoli and Helman (1994), Ziegler (1994),Carminati et al. (1998); Jolivet and Faccena (2000), Rosembaum et al. (2002), Handy et al. (2010), Barrier et al. (2018), Jolivet et al. (2008), Sibuet et al. 2012, Berra and Angiolini (2014) Menant et al. (2016), and Ye et al. (2017) Guerrera et al. (2019) have proven that the motion of Africa with respect to Europe during this period is characterised by left-lateral strike-slip motion. ...
Article
The Zebbag and Fahdene Formations outcrop on-shore Tunisia and provide an excellent opportunity to test models for the tecton-sedimentary evolution of this region during the Albian-Cenomanian. In this contribution, a NW-SE compressive stress regime resulted in shortening of the Tunisian margin and this compressional tectonism defines the Austrian phase described in the surrounding margins. This event is not widely documented but evidence provided by NE-SW thrusting and folding, that resulted in an angular unconformity, active halokinetic diapirs and transpressional NW-SE pull apart basins confirm our findings, suggesting regionally extensive tectonism. The observed compressional deformation can be considered as a precursor to the Alpine Orogeny causing an important and general inversion of the paleoblocks inherited from the Tethyan Jurassic and Lower Cretaceous rifting. A late Albian-Cenomanian onset of compressional deformation along the Tunisian margin may be intimately related to the drift of Africa with respect to Europe and to the opening of Atlantic Ocean.
... Along the Tethyan collisional belt, the subduction and Cenozoic closure of the Neo-Tethys ocean and subsequent collisions of the Indian, Arabian plates and the micro continental ribbon of Africa with Eurasia have led to not only the formation of the strongly deformed thrust belts of the Alps-Zagros-Himalayan orogens at the collisional front but also severe reactivation of pre-existing weaknesses and diffuse deformation within the continental interior in south to central Eurasia (Figure 17), accompanying widespread syn-and post-collisional igneous activities (Faccenna et al., 2014;Müller et al., 2019;Yin, 2010). Specifically, the India-Eurasia collision processes have given rise to the development of the giant Tibetan plateau in south Asia featured by the highest topography (∼5 km) and thickest continental crust (∼60-80 km) over the world ZHU ET AL. ( Figure 18), which has exerted profound impacts on the tectonic framework, climate and life on Earth (e.g., Guo et al., 2002;Jolivet et al., 2018;Molnar et al., 1993). ...
... The debate between different developmental patterns is mainly about the spreading mechanisms and the initial opening time. There are several mainstream views: (a) extrusion mode (Leloup et al., 2001;Tapponnier et al., 1990), with a late Eocene initial opening time; (b) slab-pull mode (Hall, 2002;Morley, 2002;Taylor & Hayes, 1983), with a Late Eocene initial opening time; (c) backarc extension mode (Taylor & Hayes, 1983;Yin, 2010), with a Late Cretaceous initial opening time; (d) mantle plume model (Yan, Shi, & Castillo, 2014;Yu et al., 2018;Zhang et al., 2018), with a Late Eocene initial opening time; and (e) mantle convection mode (Jolivet et al., 2018), with an Early Cenozoic initial opening time. However, no model above can fully explain the opening process of the SCS, and certain contradictions persist between these models and the tectonic features of the SCS. ...
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We systematically expound the processes of Cenozoic sedimentary evolution in the South China Sea (SCS) regions by synthesizing relevant previous research and our own long‐term sedimentological work. The process of changes in Cenozoic sedimentary environments and palaeogeography can be divided into three stages corresponding to the tectonic evolution of the SCS. Stage I, the formation and development of the Proto‐South China Sea (Proto‐SCS) from the Late Mesozoic to Early Cenozoic; the SCS was a vast erosion zone, and terrestrial lacustrine deposits were only distributed sporadically. Stage II, the subduction of the Proto‐SCS and the opening of the SCS since the Late Eocene. The northern basins of the SCS gradually changed from terrestrial to marine environments. Southern basins were affected by the disappearance of the Proto‐SCS in the early stage. The distribution of marine environments shrank in the Late Eocene–Early Oligocene, but as the SCS expanded, these marine environments gradually recovered. Stage III, the stagnation and atrophy of SCS expansion from the Late Miocene to the present. The sedimentary environment of the SCS is basically stable in this stage. The most prominent feature of sedimentary evolution is the development and destruction of carbonate platforms.
... The tectonic evolution of Northeast Asia included an accretionary orogeny during the closure of the paleo-Asian Ocean in the Paleozoic (Xiao et al., 2003Jian et al., 2010), Mongolian-Okhotsk Ocean subduction and a collisional orogeny during the Permian-Cretaceous (Donskaya et al., 2013;Wang et al., 2015), paleo -Pacific to Pacific subduction during the Late Mesozoic-Cenozoic (Wilde, 2015;Liu et al., 2017), and even the far-field effects of the Cenozoic India-Eurasia collision (Molnar and Tapponnier, 1975;Jolivet et al., 2018). These previous studies have shown that the tectonic framework of Northeast Asia is the result of multi-stage, multi-tectonic domain superposition. ...
Article
Early Cretaceous rift basins in Northeast Asia typically experienced varying degrees of post-rifting thermal subsidence and compressional deformation. However, previous workers believed that only a thin post-rifting sequence was developed in basins west of the Great Xing'an Range, making a proper understanding of the post-rift tectonic history in this part of Northeast Asia difficult. In this study, newly acquired shallow seismic reflection data were utilized to unravel the shallow deformation of the Erlian Basin, which to the west of the Great Xing'an Range contains a thin post-rifting sequence. Furthermore, we used apatite fission-track thermochronology to analyze the post-rifting deposition and uplift processes in the Erlian Basin, for which there are limited stratigraphic records. Our results show that the Erlian Basin experienced a typical post-rifting stage whose sequence from the Albian to the Campanian was not controlled by normal faults. The corresponding sedimentary thickness was up to 2 km, which contradicts the previously reported little or no post-rifting thermal subsidence. The current thin post-rifting sequence is the remaining stratum after 1.4–1.8 km of denudation at the end of the Erlian period. In addition, by further comparing the sedimentary thickness and time-lag in the onset of post-rifting to those of other basins in Northeast Asia, we found two driving mechanisms of rifting in Northeast Asia, which occurred simultaneously: the gravitational collapse and back-arc extension. Moreover, the basins in Northeast Asia experienced a gradual weakening in the compressional deformation from east to west during the Cenomanian to the Coniacian, and an intense compressional deformation in the east of Northeast Asia and large-scale vertical uplift in the west during the Late Cretaceous Campanian to the Eocene.
... It has been proposed that the Cenozoic intracontinental deformation in East Asia is closely associated with the Indian-Eurasian continental collision since ∼55 Ma to the west and the on-going subduction of the Pacific plate to the east (Shi et al., 2020;Yin, 2010). The collision-and subduction-induced mantle flow under continents is considered to play a significant role in the intracontinental deformation (Jolivet et al., 2018;Schellart et al., 2019) and the lithospheric destruction of eastern NCC (He, 2014;Zhu et al., 2012). However, the actual role of mantle flow and its impact on the Cenozoic lithospheric modification in and around the Ordos block remain poorly understood. ...
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Plain Language Summary It is generally accepted that the thick mantle lithosphere of eastern North China Craton (NCC) was largely destroyed during the late Mesozoic, however, the Ordos block in the western NCC had preserved a relatively intact cratonic keel. In this study, we image the crustal and lithospheric structures across the Ordos block and its margins using P and S receiver functions. Our observations with a better resolution of lateral variations than seismic tomography results show distinct structural heterogeneities across the Ordos block, suggesting the lithospheric reworking could have already taken place at its boundaries. Local mantle upwelling at the northern boundary has significantly thinned the lithosphere, leading to a south‐dipping lithosphere‐asthenosphere boundary (LAB). However, the eastward asthenospheric flow at the southern boundary has little effect on the Ordos lithosphere, left with a sharp LAB there.
... Several Meso-Cenozoic subduction systems are distributed surrounding the Pacific Ocean, e.g., Kuril, Japan, Izu-Bonin-Mariana, Cascades, Central and South America subduction systems (Stern and Bloomer, 1992;Nokleberg et al., 1998;Yakubchuk, 2009;Yin, 2010;Faccenna et al., 2018). Subduction of the Pacific plate beneath the Eurasian (west-dipping), and of the Farallon/Juan De Fuca, the Cocos and the Nazca plates beneath the North and South American plates (eastdipping) gave rise to the Cenozoic circum-Pacific earthquake-volcanic belt that shows spectacular physiographical, geological and geophysical features along both convergent margins (Fig. 1, Hilde et al., 1977; Engebretson et al., 1985Yin, 2010;Wang et al., 2013;Jolivet et al., 2018;Ruiz and Madariaga, 2018;Boschman et al., 2019;Fernández Paz et al., 2019;Li et al., 2019). The trench-arc-basin system along the western coast and the trench-arc system along the eastern coast of the Pacific, respectively, form the particular examples of the tectonic interactions between the oceanic and continental plates. ...
Article
How deep mantle processes affected plate interactions and the dynamics of deformation on both sides of the PaleoPacific has been a first order scientific challenge. The ubiquitous Early Cretaceous multiphase tectonic extensional structures in eastern Eurasia (EE) show marked contrasts to the episodic compressional structures in western North America (WNA), which provides convincing arguments linking deep and shallow tectonic processes. Recent studies on Early Cretaceous tectonics in EE have shown that the continent is characterized by multiple phase of tectonic extension and weak compression, forming extensional structures in several major provinces in a vast area of ca. 3000 km × 3000 km. Temporally, the peak tectonic extension occurred at 135–120 Ma, in addition to extensional episodes at pre- (160–145 Ma) and post-peak (120 Ma-) stages. Kinematic analysis reveals an identical NW-SE-oriented tectonic extension field for their formation. In addition, synextensional magmatism sourced from ancient and juvenile crust or lithospheric mantle was episodically active and peaked at ca. 160, 125 and 100–80 Ma. Particularly, a magmatic flare-up of extensional origin occurred at 125 ± 5 Ma in eastern China. In contrast, the WNA Cordillera displays a prolonged and episodic tectonic compression beginning ~170 Ma (Jurassic). Tectonic deformation involved the Nevadan, Sevier and Laramide orogenies from ca. 175 Ma, 125 Ma and 80 Ma, respectively, to form the Cordillera orogenic system. During the Nevadan orogeny strong compression between 154 and 150 Ma contributed to continental arc magmatism. The Sevier orogen is characterized by thin-skinned thrust sheets while the Laramide is dominated by shallow slab dip and basement-core uplifts of Archean crust in the foreland. Significant sinistral strike-slip shearing at ~140–125 Ma is documented in the Early Cretaceous. Furthermore, widespread crustal shortening and emplacement of major batholiths (magmatic flare-up) were contemporaneous with accretion of the high pressure-low temperature (blueschist) Franciscan Complex at ca. 125–100 Ma during the Sevier orogeny. The EE extensional provinces constitute part of the retreating (Paleo-) Pacific-Eurasia subduction system, while crustal shortening along the WNA resulted from the advancing Farallon-North America subduction system. Stratified mantle convection is needed, however, when taking the tectonic evolution of the continental margins and the mid-ocean range as an integral system of the evolving globe. Shallow-mantle convection contributed to subduction of oceanic plates from 160 Ma, which resulted in Andean type subduction zones on both sides of the Ocean. Possibly from 160 Ma forward, eastward deep mantle flow occurred that induced migration of the shallow mantle convection systems. As a result, the west-dipping Paleo-Pacific slabs became steepened, stagnated and subsequently folded in the mantle transition zone, while the east-dipping Farallon slab became flattened, and subsequently penetrated the transition zone. The resultant eastward migration of shallow mantle convection systems continuously drove the retreating subduction of the Paleo-Pacific (or Izanagi) plate, advancing subduction of the Farallon plate and eastward migration of the Paleo-Pacific-Farallon mid-ocean ridge. As a consequence, multiple phases of tectonic extension dominated the deformation of the continental interior in EE and episodic compressional tectono-magmatic activities occurred along the continental margin of WNA.
Thesis
This thesis addresses several topics related to the tectonic history of the Sumatran-Andaman region. Firstly, I investigated the Martabe epithermal gold deposits using high-resolution 40Ar/39Ar geochronology in order to unravel the complex overprinting alteration system. The results indicate that there were five peak periods of alunite growth around the Martabe deposits at 1.40 to 1.70 Ma, 1.90 to 2.08 Ma, 2.12 to 2.51 Ma and 3.22 and 3.48 Ma. Analysis of the Arrhenius plots put the closure temperature of alunite ranging between 390C and 519C, which is above the temperature expected for the formation of the Martabe deposits. This result gives confidence that the measured ages from 40Ar/39Ar geochronology are for the formation of alunite and not an age at which the system has cooled below the closure temperature. Secondly, I created a 3D model of the subducted slab beneath Sumatra and the Andaman Sea, and restored the modelled slab geometry to the Earth's surface. This enabled recognition that the former spreading centres and transform faults of the Wharton Fossil Ridge localised a potential slab tear, thus circumventing otherwise enormous distortions that would have occurred during subduction. Seismotectonic analysis suggests continuing movement during subduction, in particular on the transform faults that once separated the spreading centres between the Indian and Australian plates. The emanation of fluids from the deforming lithosphere may have localised both the Toba supervolcano and the epithermal gold deposits at the Martabe. Thirdly, tomography in the Andaman region is not characteristic of a simple subducting slab. Instead there are unusual structures between 11N and 15N that have not been previously discussed. Tomographic anomalies can be misleading and might be erased with improvements in tomographic resolution. Nevertheless, we propose two interpretations of the slab morphology that explain a westward dip anomaly. Model 1 consists of overturning the subducted Indian slab, a geometry common for advancing hinges. However, an advancing Andaman trench is not consistent with the relative motion of the Indian plate. Instead, this morphology could arise from the northward motion of the Indian plate through the mantle rotating the edge of the Andaman slab, overturning the slab and producing slab tears. Model 2 interprets the anomaly as a westward dipping slab, required a slablet derived from the Andaman Sea to have punctured the subducted Indian plate. Model 1 fits within the tectonic reconstructions published for this region but requires a geodynamic mechanism to overturn the slab, while Model 2 requires an unrecognised sutured subduction zone within the Andaman Sea. Lastly, I report on a geomorphic analysis aimed at assessing a different hypothesis for the evolution of the Sumatran Fault System. Extensional structures in and adjacent to restraining bends on the Sumatran Fault System are unusual in an overall transpressive wrench regime. In addition, NW-SE trending tectonic lineaments appear to connect to offsets of the Sumatran Fault. Such features could be explained by westward rollback of the hinge of the subducting Indian plate driving NW-SE extension across northern Sumatra. Slab-tearing may have localised rollback and created NW-SE trending left-lateral strike-slip faults that offset the Sumatran Fault, eventually requiring the formation of new relay faults to accommodate the ongoing relative motion of the Sunda Block. The new relay faults eliminate the obstacles caused by offsets of the main fault strand. However, this model requires switching between extended periods during which transverse left-lateral strike-slip faults driven by differential slab rollback offset the Sumatran Fault, alternating with periods during which there is a renewal of transpressional wrenching. Inferred switches in the stress trajectories are complementary to those documented in the Andaman Sea.
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We present the first-generation full-waveform tomographic model (SinoScope 1.0) for the crust-mantle structure beneath China and adjacent regions. The three-component seismograms from 410 earthquakes recorded at 2,427 stations are employed in iterative gradient-based inversions for three successively broadened period bands of 70 - 120 s, 50 - 120 s, and 30 - 120 s. Synthetic seismograms were computed using GPU-accelerated spectral-element simulations of seismic wave propagation in 3-D anelastic models, and Fréchet derivatives were calculated based on an adjoint-state method facilitated by a checkpointing algorithm. The inversion involved 352 iterations, which required 18,600 wavefield simulations. SinoScope 1.0 is described in terms of isotropic P-wave (VP), horizontally and vertically polarized S-wave velocities (VSH and VSV), and mass density (ρ), which are independently constrained with the same data set coupled with a stochastic L-BFGS quasi-Newton optimization scheme. It systematically reduced differences between observed and synthetic full-length seismograms. We performed a detailed resolution analysis by repairing input random parametric perturbations, indicating that resolution lengths can approach the half propagated wavelength within the well-covered areas. SinoScope 1.0 reveals strong lateral heterogeneities in the lithosphere, and features correlate well with geological observations, such as sedimentary basins, Holocene volcanoes, Tibetan Plateau, Philippine Sea Plate, and various tectonic units. The asthenosphere lies below the lithosphere beneath East and Southeast Asia, bounded by subduction trenches and cratonic blocks. Furthermore, we observe an enhanced image of well-known slabs along strongly curved subduction zones, which does not exist in the initial model.
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Although Earth's surface motion is well known, the flow field in the underlying mantle is not. Mantle flow is typically calculated on the basis of inferred density variations, and flow directions can also be reflected in seismically observed anisotropy, but those observations leave ambiguity on the depth and direction of the deformation. Anisotropy orientations in East Asia, outside Tibet, have been interpreted in various ways and have often been linked to deformation in the asthenosphere related to absolute plate motion and/or mantle wedge deformation. Here, we re-analyze published seismic anisotropy data and find that orientations outside Tibet can be much better explained when considering absolute plate motion (APM) of the Earth's surface in addition to coherent sub-asthenospheric mantle flow, than when comparing orientations to APM alone. The direction and magnitude of the required sub-asthenospheric flow depend on the absolute reference frame used for the surface velocities, but when considering an APM frame with an intermediate global net-rotation we find an eastward flow of 1-2 cm/yr. This flow is faster than the surface motion, and generally in the same direction, from which we conclude that the mantle leads the plate motion. Our inferred flow is similar to those independently calculated based on buoyancy forces driven by density variations, most notably the high density anomalies associated with the western Pacific subduction zones, but possibly also the upwelling underneath Africa. Additionally, based on our predicted sub-asthenospheric flow and absolute motion of the lithosphere, we predict asthenospheric-based XKS orientations underneath all of east Asia and find it to differ significantly with observed XKS orientations where either the lithosphere is thick and/or strain rate is high, which suggests that at those places observed XKS orientations reflect the integrated deformation in both asthenosphere and lithosphere.
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We investigate how different crustal models can affect the stress field, velocities and associated deformation in the India–Eurasia collision zone. We calculate deviatoric stresses, which act as deformation indicators, from topographic load distribution and crustal heterogeneities coupled with density driven mantle convection constrained by tomography models. We use three different crustal models, CRUST2.0, CRUST1.0 and LITHO1.0 and observe that these models have different crustal thickness and densities. As a result, gravitational potential energy (GPE) calculated based on these densities and crustal thicknesses differ between these models and so do the associated deviatoric stresses. For GPE only models, LITHO1.0 provides a better constraint on deformation as it yields the least misfit (both orientation and relative magnitude) with the surface observations of strain rates, lithospheric stress, plate motions and earthquake moment tensors. However, when the stresses from GPE are added to those associated with mantle tractions arising from density-driven mantle convection, the coupled models in all cases provide a better fit to surface observations. The N–S tensional stresses predicted by CRUST2.0 in this area get reduced significantly due to addition of large N–S compressional stresses predicted by the tomography models S40RTS and SAW642AN leading to an overall strike-slip regime. On the other hand, the hybrid models, SINGH_S40RTS and SINGH_SAW that are obtained by embedding a regional P-wave model, Singh et al., in global models of S40RTS and SAW642AN, predict much lower compression within this area. These hybrid models provide a better constraint on surface observations when coupled with CRUST1.0 in central Tibet, whereas the combined LITHO1.0 plus mantle traction model provides a better fit in some other areas, but with a degradation of fit in central Tibet.
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The East Asian continental margin straddles the boundary between the Pacific Plate subduction Domain to the east and the Indo-Eurasian collision Domain to the west. The spatial and temporal interaction between these two dynamic domains induced dextral trans-tensional stress field, which resulted in generating nearly 75% of the globe's marginal seas and continental margin rifts during the Cenozoic. Among these, the South China Sea (SCS) and its northern margin are located in the core of the Pacific Tectonic Domain and the Tethyan Tectonic Domain. The evolution of the SCS and its northern margin are of prime interest because of the spectacular magnetic lineation and strong rifting. In spite of the several investigations on the Cenozoic marginal seas and rift basins occurred, their mechanisms of formation remain equivocal. Here we perform a comprehensive analysis of seismic profiles and fault architecture data with a view to understanding the Cenozoic tectonic evolution of the northern margin of the SCS. Based on detailed structural analysis of the geometry and kinematics, we demonstrate that the NE- and ENE-striking faults assembled to horsetail- or feather-shaped structures in plan view, with flower-like structures on seismic profiles. Two stages of faulting with NE-trending are identified along the northern margin of the SCS. The earlier oblique extension developed during the Paleocene to the early Middle Eocene (~44–42 Ma), accompanied by strong rifting and some left-stepping en echelon-like faults. The later trans-tensional faulting developed during the late Middle Eocene to the Early Miocene (~21 Ma), resulting in the formation of the dextral right-stepping trans-tensional fault system. Two stages of faulting were linked to the joint effect among the collision domain of Indian-Eurasian plates to the west, the subduction domain of the Pacific Plate to the east and the slab-pull system of the proto-SCS to the south. Our study provides important insights into the dynamics and tectonics that controlled the opening of the South China Sea. During the Late Eocene to the Oligocene, the later trans-extensional faulting and right-stepping strike-slip fault system caused the opening of the Northwest Sub-basin, East Sub-basin and Northeast Sub-basin. However, during the Early Miocene, the left-lateral strike-slip of the Ailao Shan-Red River (ASRR) shear zone and the slab-pull force of the Proto-SCS resulted in the opening of the Southwest Sub-basin and the change in the spreading direction of the East Sub-basin.
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Based on synthesizes basic Geological Survey, magnetotellurics, lithogeochemistry, and chronology, a case study of the Shiba-Huangshadong area in Huizhou was settled to reveal the evolution of geological tectonics since the Yanshanian (Jurassic and Cretaceous era) in Huizhou, Guangdong. The magnetotelluric data display that there are present the subterrane an bedrock of Yanshanian granite intrusions with a thickness of more than 5 km, and the graniteis sliced by the Cenozoic faults. The basal conglomerate minerals in the Danxia Formation have edges and corners, which show near-source sedimentary characteristics.The harmonic age and age spectrum show that the age of basal conglomerate is about 160 Ma.The REE pattern and spider diagram of granites in the study area with age more than 150 Ma indicate that the basal conglomerate is the product of denudation of Yanshanian granite. Based on the tectonic evolution of South China and its adjacent areas, we have established a conceptual model of geological evolution of the study area since the Yanshanian. The emplacement of the voluminous Yanshanian granite resulted in the uplift of the crust.The previously deposited strata suffered from long-term denudation, which caused the expose and denudation of granite that in the Paleozoic and Mesozoic strata. Combined with the Cenozoic large-scale Yue-Gui shearing caused by the collision of India-Eurasia plate and the northward drift of Philippine Plate, forming a series of deep-seated faults, for example, the Heyuan fault, the Zijin-Boluo fault, and the Lianhuashan fault.These faults are all cutting through the Yanshanian granite body. The current topography of the study area has been shaped by multiple activities.
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The opening of the East Vietnam Sea (EVS), leading to the activity of syn-spreading (33-16 Ma) and post-spreading (<16 Ma to today) volcanic activity. Syn-opening magma making up thick layers of tholeiitic basalt with a geochemical composition close to the refractory mid-ocean ridge basalt (MORB) is mainly distributed inside the EVS. The post-opening magma is widely spread not only inside the EVS, but also extends to South and SE China, Hainan Island, Southern Laos (Bolaven), Khorat Plateau (Thailand), and Vietnam showing typical intraplate geochemistry. Samples were collected at a number of places in 3 Indochina countries, coastal areas, and continental shelf of Vietnam to analyze for eruption age, petrographical, geochemical, and isotopic composition. The results together with compiled data from the literature sources are used for comparison to understand the similarities and differences between regions, which show that basalts in different areas have the different rare earth element characteristics. However, they all show signs of melting from spinel peridotite source to garnet peridotite over time. Radiogenic isotope data show that different basalts are distributed into different fields, regardless of the age of the eruption, indicating that the mantle source is largely dependent on space. That is, basalt eruptions of different areas have different source characteristics, not originating from a Hainan mantle plume, if it ever exists. From the results obtained in this report, we propose a suitable geodynamic model explaining the relationship between the opening of the East Vietnam Sea and volcanic activity following the collision tectonics of the Indian plate and Eurasia since the Eocene.
Chapter
An interesting subset of Earth's mountain ranges are those that are forming or have formed in continental interior regions, far from any active plate boundary. Intracontinental, intraplate mountain ranges may evolve in any kinematic mode, as evidenced today in Central Asia where diverse Miocene-Recent mountain ranges such as the Altai, Tien Shan, Gobi Altai, Beishan and Ordos Block ranges are actively developing over a wide region north of Tibet. These separate orogens represent an intraplate response to the continental interior force balance that is derived from the distant Indo-Eurasia collision, Asia's actively retreating Pacific margin, and stored gravitational potential energy in Central Asia's lithosphere. Mechanically weak, Phanerozoic terrane collages and Precambrian craton boundaries are susceptible to crustal reactivation with the kinematics of faulting largely driven by the angular relationship between SHmax (maximum horizontal stress) and the pre-existing structural “grain” in the region. The arid climate and low erosion rates in Central Asia, compared to more humid regions, allow the tectonic signal of Late Cenozoic crustal reactivation to be clearly expressed in the landscape. In addition to fault-driven orogenic processes, long-wavelength epeirogenic movements leading to differential erosion and isostatic adjustments may also generate mountainous relief in aseismic, intracontinental regions. Ancient intracontinental, intraplate mountain ranges may go un-noticed by tectonicists and geomorphologists, because their landscape expression may be geologically short-lived, with limited-to-no magmatic, metamorphic, and thermochronological signature.
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A combination of 60 years of seismicity, over 45 years of fault plane solutions of moderate-sized to large earthquakes, and recent databases of high-resolution topography delineate spatial patterns of seismogenic faulting in northeastern Asia. Here I synthesize new knowledge with known features in a regional context. Strike-slip faulting characterizes active deformation along the northern and southeastern margins, as well as the interior of this vast region; while normal and reserve faulting dominate its northwestern/southwestern and eastern margins, respectively. Consistent patterns of transpressive and reverse seismogenic faulting persist along the Sakhalin-Hokkaido shear zone and the Eastern Japan Sea fold-and-thrust belt over lengths of over 1000 km each, respectively, but not as throughgoing faults. The latter transitions into strike-slip faulting farther south along the North Chugoku shear zone in southwestern Japan and continues southward into Kyushu. Meanwhile, the true intra-continental, strike-slip Tanlu fault zone reaches an uninterrupted length of about 2000 km. Fault plane solutions, including one from a recent event near the great intra-continental earthquake of 1668, provided much-needed new evidence for the dextral-slip nature of this long fault and a paleo-seismic study confirmed that the entire fault is seismogenic. Meanwhile, active segments of strike-slip faults elsewhere in the North China basin, of lengths less than about 200 km, have been responsible for devastating earthquakes. These observations are noteworthy as the current speed of the ground, based on Global Navigation Satellite System (GNSS) measurements, is only 3–4 mm/yr over a length-scale of 3000 km in the entire area of study. Regions of particular concern include: 1) The east coast of South Korea where recent, moderate earthquakes ruptured small sections of an active fault system that has a set of sharp fault scarps extending southward near the metropolitan area of Busan; and 2) the North China basin where intense historical seismicity contrasts with quiescence that persisted since 1976. Overall, no continental block, including the Amurian microplate, is well defined and only the oceanic Japan Sea exhibits little internal deformation.
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The evolution of oroclines is often driven by the interplay of subduction and indentation associated with complex patterns of deformation transfer from shortening to strike-slip and extension. We study the kinematics and mechanics of indentation in an orocline with a backarc-convex geometry, the European Carpatho-Balkanides Mountains. Within this orocline, the kinematic evolution of the Serbian Carpathians segment is less understood. The results demonstrate that the overall deformation was accommodated by the Circum-Moesian Fault System surrounding the Moesian indenter, where strain was partitioned in a complex network of coeval strike-slip, thrust and normal faults. This system represents one of the largest European intracontinental strike-slip deformation zones, with a northward-increasing accumulated 140 km dextral offset along previously known and newly found faults. These strike-slip faults transfer a significant part of their offset eastwards to thrusting in the Balkanides and westwards to orogen-parallel extension and the formation of intramontane basins. The correlation with paleogeographic and geodynamic reconstructions demonstrates that the overall formation of the fault system is driven by subduction of the Carpathian embayment, resulting in laterally variable amounts of translation and rotation associated with indentation of the Moesian Platform. The onset of Carpathian slab retreat and backarc extension at 20 Ma has dramatically increased the rates of dextral deformation from ~3.5 mm/yr to ~2 cm/yr, facilitated by the pull exerted by the retreating slab. Our study demonstrates that indentation requires a strain partitioning analysis that is adapted to the specificity of deformation mechanics and is, therefore, able to quantify the observed kinematic patterns.
Article
The Korean Peninsula (KP), located along the eastern margin of the Eurasian and Amurian plates, has experienced continual earthquakes from small to moderate magnitudes. Various models to explain these earthquakes have been proposed, but the origins of the stress responsible for this region's seismicity remain unclear and debated. This study aims to understand the stress field of this region in terms of the contributions from crustal and upper-mantle heterogeneities imaged via seismic tomography using a series of numerical simulations. A crustal seismic velocity model can determine the crustal thickness and density. Upper-mantle seismic velocity anomalies from a regional tomography model were converted to a temperature field, which can determine the structures (e.g. lithospheric thickness, subducting slabs, their gaps, and stagnant features) and density. The heterogeneities in the crustal and upper mantle governed the buoyancy forces and rheology in our models. The modelled surface topography, mantle flow stress, and orientation of maximum horizontal stress, derived from the variations in the crustal thickness, suggest that model with the lithospheric and upper-mantle heterogeneities is required to improve these modelled quantities. The model with upper-mantle thermal anomalies and east–west compression of approximately 50 MPa developed a stress field consistent with the observed seismicity in the KP. However, the modelled and observed orientations of the maximum horizontal stress agree in the western KP but they are inconsistent in the eastern KP. Our analysis, based on the modelled quantities, suggested that compressional stress and mantle heterogeneities may mainly control the seismicity in the western area. In contrast, we found a clear correlation of the relatively thin lithosphere and strong upper-mantle upwelling with the observed seismicity in the Eastern KP, but it is unclear whether stress, driven by these heterogeneities, directly affects the seismicity of the upper crust.
Preprint
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Southeast Asia is surrounded by plate subduction zones, and very intense seismic and volcanic activities have been occurring there. Volcanic activity originating from the deep Earth, represented by the Hainan hotspot, also takes place. It is known that seafloor spreading and subduction have been repeated in the past, and the relationship between the slabs subducted deeply into the mantle and the plate movement on the surface is an important key to understanding the evolution history of this region. In this study, we apply an updated method of seismic tomography to investigate the whole mantle 3-D P-wave velocity structure beneath SE Asia. For the first time, a continuous whole-mantle plume is revealed beneath the Hainan hotspot with its root at the core-mantle boundary. Hot mantle upwellings above and below the subducting Australian slab are connected through a slab hole at depths of 280–430 km beneath eastern Java. The mixture of those hot mantle materials might have caused huge eruptions of the Tambora and Rinjani volcanoes in eastern Java.
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In the Cenozoic, the East Asian Continental Margin developed intense rifting, producing massive rift basins and marginal seas. Among these, the South China Sea (SCS) and adjacent continental margin have attracted attention due to the obscure opening mechanism and strong lithospheric thinning. Based on the seismic sections and fault architecture data in this paper, we perform a delicate study of fault geometry, kinematics, and dynamics in the Pearl River Mouth Basin (PRMB). Three-stage Cenozoic extension is identified in the PRMB. The earliest NNW-SSE-directed extension occurred as early as the Paleocene, resulting in the NE- and ENE-trending faulting with dextral oblique extension to continue until the Middle Eocene. The second extension in the N-S direction resulted in NE-trending dextral transtension in the Late Eocene to Early Oligocene (∼40-30 Ma). Subsequently, the latest extension with the NNW-SSE direction occurred during the Late Oligocene, resulting in the sinistral strike-slip of a large number of WNW-trending faults. This second-third extension produced a NE-striking transtensional fault system with dextral right-stepping characteristics. In the Oligocene, this fault system resulted in the scissor-type opening of the SCS with a progressively westward younging oceanic crust. During the Early Miocene, the dextral transtensional fault system disappeared due to the Pacific Plate subduction eastward retreat and the cease of the RRF sinistral strike-slipping. At this time, the SCS ridge spreading was controlled only by the NW-SE-oriented slab-pull linked to the proto-SCS.
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Q fever, caused by the zoonotic bacterium Coxiella burnetii, is a globally distributed emerging infectious disease. Livestock are the most important zoonotic transmission sources, yet infection in people without livestock exposure is common. Identifying potential exposure pathways is necessary to design effective interventions and aid outbreak prevention. We used natural language processing and graphical network methods to provide insights into how Q fever notifications are associated with variation in patient occupations or lifestyles. Using an 18‐year time‐series of Q fever notifications in Queensland, Australia, we used topic models to test whether compositions of patient answers to follow‐up exposure questionnaires varied between demographic groups or across geographical areas. To determine heterogeneity in possible zoonotic exposures, we explored patterns of livestock and game animal co‐exposures using Markov Random Fields models. Finally, to identify possible correlates of Q fever case severity, we modelled patient probabilities of being hospitalised as a function of particular exposures. Different demographic groups consistently reported distinct sets of exposure terms and were concentrated in different areas of the state, suggesting the presence of multiple transmission pathways. Macropod exposure was commonly reported among Q fever cases, even when exposure to cattle, sheep or goats was absent. Males, older patients and those that reported macropod exposure were more likely to be hospitalised due to Q fever infection. Our study indicates that follow‐up surveillance combined with text modelling is useful for unravelling exposure pathways in the battle to reduce Q fever incidence and associated morbidity.
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Numerous geoscientific investigations have been conducted on the southeastern Tibetan Plateau and adjacent areas for understanding crustal and mantle deformation associated with the indentation of the Indian Plate into Eurasia. A number of key issues, such as the causes of a sudden change of fast polarization orientations from N-S to almost E-W at approximately 26°N revealed by shear wave splitting (SWS) studies, and the geodynamic implications of the transition still remain enigmatic, partially due to the lack of sufficient SWS measurements on the Indochina Peninsula. Here we employ the SWS technique to systematically illuminate upper mantle anisotropy beneath the Indochina Peninsula with an unprecedented data coverage. The resulting 409 SWS measurements from 29 stations show that upper mantle anisotropy beneath the vast majority of the study area is characterized by dominantly E-W fast orientations which are nearly orthogonal to the strike of most of the major tectonic features in the study area, ruling out significant lithospheric contributions to the observed anisotropy. This observation, when combined with results from seismic tomography, numerical modeling, surface movement, and focal mechanism investigations, suggests that the observed azimuthal anisotropy is mostly the consequence of absolute plate motion or the westward rollback of the oceanic Indian slab. The flow system induced by the rollback or absolute plate motion may experience regional alteration from mantle upwelling along the eastern edge of the slab and through a previously detected slab window, leading to local variations in the observed splitting parameters.
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We present three-dimensional numerical models to investigate the dynamics of continental collision, and in particular what happens to the subducted continental lithosphere after oceanic slab break-off. We find that in some scenarios the subducting continental lithosphere underthrusts the overriding plate not immediately after it enters the trench, but after oceanic slab break-off. In this case, the continental plate first subducts with a steep angle and then, after the slab breaks off at depth, it rises back towards the surface and flattens below the overriding plate, forming a thick horizontal layer of continental crust that extends for about 200 km beyond the suture. This type of behaviour depends on the width of the oceanic plate marginal to the collision zone: wide oceanic margins promote continental underplating and marginal back-arc basins; narrow margins do not show such underplating unless a far field force is applied. Our models show that, as the subducted continental lithosphere rises, the mantle wedge progressively migrates away from the suture and the continental crust heats up, reaching temperatures >900 °C. This heating might lead to crustal melting, and resultant magmatism. We observe a sharp peak in the overriding plate rock uplift right after the occurrence of slab break-off. Afterwards, during underplating, the maximum rock uplift is smaller, but the affected area is much wider (up to 350 km). These results can be used to explain the dynamics that led to the present-day crustal configuration of the India–Eurasia collision zone and its consequences for the regional tectonic and magmatic evolution.
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Southeast Asia, located in the southeastern part of the Eurasian Plate, is surrounded by tectonically active margins, exhibiting intense seismicity and volcanism, contains complex geological units with a perplexing evolution history. Because tectonic evolution is closely related to the deep thermal structure, an accurate estimation of the lithosphere thermal structure and thickness is important in extracting information on tectonics and geodynamics. However, there are significant uncertainties in the calculated deep thermal state constrained only by the observed surface heat flow. In this study, in order to obtain a better-constrained deep thermal state, we first calculate the deep thermal structure of Southeast Asia by employing an empirical relation between S-velocity and temperature, and then we estimate the base of the thermal lithosphere from the calculated temperature-depth profiles. The results show that, in general, the temperature is higher than the dry mantle solidus below the top of the seismic low-velocity zone, possibly indicating the presence of partial melt in the asthenosphere, particularly beneath oceanic basins such as the South China Sea. The temperature at a depth of 80 km in rifted and oceanic basins such as the Thailand Rift Basin, Thailand Bay, Andaman Sea, and South China Sea is about 200 °C higher than in plateaus and subduction zones such as the Khorat Plateau, Sumatra Island, and Philippine Trench regions. We suggest that the relatively cold and thick lithosphere block of the Khorat Plateau has not experienced significant internal deformation and might be extruded and rotated as a rigid block in response to the Indo-Eurasia collision. Our results show that the surface heat flow in the South China Sea is mainly dominated by the deep thermal state. There is a thermal anomaly in the Leiqiong area and in the areas adjacent to the northern margin of the South China Sea, indicating the presence of a high-temperature and thin lithosphere in the area of the well-known and controversial Hainan plume. The thermal lithosphere-asthenosphere boundary uplift area along the Xisha and southeastern Vietnam margin, in the western margin of South China Sea, which corresponds to the volcanic belt around this area, might indicate upwelling of hot mantle materials. The temperature values at 100 and 120 km depths through most regions of Southeast Asia are about 1400–1500 and 1550–1600 °C, respectively, which are nearly uniform with a small temperature difference. Our results also show that the lithosphere becomes thinner from the continent blocks toward the oceanic basins, with the smaller thickness values of 65–70 km in the South China Sea. The estimated base of the lithosphere corresponds approximately to the 1400 °C isotherm and shows good correlation with the tectonic setting.
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Of the two debated, end-member models for the late-Cenozoic thickening of Tibetan crust, one invokes “channel flow” (rapid viscous flow of the mid-lower crust, driven by topography-induced pressure gradients and transporting crustal rocks eastward) and the other—“pure shear” (faulting and folding in the upper crust, with viscous shortening in the mid-lower crust). Deep-crustal deformation implied by each model is different and would produce different anisotropic rock fabric. Observations of seismic anisotropy can thus offer a discriminant. We use broadband phase-velocity curves—each a robust average of tens to hundreds of measurements—to determine azimuthal anisotropy in the entire lithosphere-asthenosphere depth range and constrain its amplitude. Inversions of the differential dispersion from path pairs, region-average inversions and phase-velocity tomography yield mutually consistent results, defining two highly anisotropic layers with different fast-propagation directions within each: the middle crust and the asthenosphere. In the asthenosphere beneath central and eastern Tibet, anisotropy is 2–4 per cent and has a NNE–SSW fast-propagation azimuth, indicating flow probably driven by the NNE-ward, shallow-angle subduction of India. The distribution and complexity of published shear-wave splitting measurements can be accounted for by the different anisotropy in the mid-lower crust and asthenosphere. The estimated splitting times that would be accumulated in the crust alone are 0.25–0.8 s; in the upper mantle—0.5–1.2 s, depending on location. In the middle crust (20–45 km depth) beneath southern and central Tibet, azimuthal anisotropy is 3–5 and 4–6 per cent, respectively, and its E–W fast-propagation directions are parallel to the current extension at the surface. The rate of the extension is relatively low, however, whereas the large radial anisotropy observed in the middle crust requires strong alignment of mica crystals, implying large finite strain and consistent with high-rate horizontal flow. Together, radial and azimuthal anisotropy suggest eastward mid-crustal channel flow in central Tibet, along the regional topography gradient. In NE high Tibet, mid-crustal azimuthal anisotropy is 4–8 per cent and has WNW–ESE and NW–SE fast-propagation directions, parallel to the net extension at the surface. These fast directions are inconsistent with channel flow following the SW–NE regional topography gradient. Instead, they suggest similar net deformation in the (decoupled) shallow and deep crust. In the brittle upper crust, it is accommodated by strike-slip faulting; in the ductile mid-lower crust—by shear oriented at ∼45° to the faults. Although mid-crustal flow beneath NE Tibet may transport some material towards the plateau periphery at a low region-average rate, the dominant mid-crust deformation pattern is shear parallel to the plateau boundary. This implies that channel flow from central Tibet is not the main cause of the on-going crustal thickening farther northeast.
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The stunningly increased resolution of the deep crustal levels in recent industrial seismic profiles acquired along most of the world's rifted margins leads to the unraveling of an unexpected variety of structures. It provides unprecedented access to the processes occurring in the middle and lower continental crust. We present a series of so far unreleased profiles that allows the identification of various rift-related geological processes such as crustal boudinage, ductile shear and low-angle detachment faulting, and a rifting history that differs from the classical models of oceanward-dipping normal faults. The lower crust in rifted margins appears much more intensely deformed than usually represented. At the foot of both magma-rich and magma-poor margins, we observe clear indications of ductile deformation of the deep continental crust along large-scale shallow dipping shear zones. These shear zones generally show a top-to-the-continent sense of shear consistent with the activity of Continentward Dipping Normal Faults (CDNF) observed in the upper crust. This pattern is responsible for a migration of the deformation and associated sedimentation and/or volcanic activity toward the ocean. We discuss the origin of these CDNF and investigate their implications and the effect of sediment thermal blanketing on crustal rheology. In some cases, low-angle shear zones define an anastomosed pattern that delineates boudin-like structures. The maximum deformation is localized in the inter-boudin areas. The upper crust is intensely boudinaged and the highly deformed lower crust fills the inter-boudins underneath. The boudinage pattern controls the position and dip of upper crustal normal faults. We present some of the most striking examples from the margins of Uruguay, West Africa, South China Sea and Barents Sea, and discuss their implications for the time-temperature history of the margins.
Data
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The World Stress Map (WSM) database is a global compilation of information on the crustal present-day stress field. It is a collaborative project between academia and industry that aims to characterize the stress pattern and to understand the stress sources. It commenced in 1986 as a project of the International Lithosphere Program under the leadership of Mary-Lou Zoback. From 1995-2008 it was a project of the Heidelberg Academy of Sciences and Humanities headed first by Karl Fuchs and then by Friedemann Wenzel. Since 2009 the WSM is maintained at the GFZ German Research Centre for Geosciences and since 2012 the WSM is a member of the ICSU World Data System. All stress information is analysed and compiled in a standardized format and quality-ranked for reliability and comparability on a global scale. The WSM database release 2016 contains 42,870 data records within the upper 40 km of the Earth’s crust. The data are provided in three formats: Excel (wsm2016.xlsx), Excel .csv (wsm2016.csv) and with a zipped google Earth input file (wsm2016_google.zip). Data records with reliable A-C quality are displayed in the World Stress Map (doi:10.5880/WSM.2016.002). Further detailed information on the WSM quality ranking scheme, guidelines for the various stress indicators, and software for stress map generation and the stress pattern analysis is available at http://www.world-stress-map.org.
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Using silicone slabs as a model analogue for lithospheric plates subducting into a box of glucose syrup, as an analogue of the mantle, we explore the subduction of continental lithosphere in a context of intercontinental collision. The continental indenter pushed by a piston, reproducing the collision, attached to a dense oceanic plate, subducts to two-thirds of the depth of the mantle box. We show that, surprisingly, the continental plate attached to the back wall of the box subducts, even if not attached to a dense oceanic slab. The engine of this subduction is not the weight of the slab, because the slab is lighter than the mantle, but the motion of the piston, which generates horizontal tectonic forces. These are transmitted to the back wall plate through the indenter and the upper plate at the surface, and by the advancing indenter slab through the mantle at shallow depth. We define this process as collisional subduction occurring in a compressional context. The collisional subduction absorbs between 14% and 20% of the convergence, and represents an unexplored component of collisional mass balance. The transmission of tectonic forces far from the collision front favors the formation of a wide plateau. Our experiments reproduce adequately the amount and geometry of the Asian lithosphere subduction episodes inferred during the collision, leading us to conclude that it reproduces adequately the physics of such process.
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This paper focuses on the processes of arc rifting in the context of the volcanic, structural, and sedimentologic evolution of the Izu-Bonin-Mariana arc-trench system. Sedimentation patterns were directly influenced by the productivity of the proximal arc volcanoes, with volcanic lulls recorded by hemipelagic interbeds. Many arc segments go through a cycle of (1) frequent volcanism before and during rifting; (2) reduced and/or less disseminated volcanism during latest rifting and early backarc spreading, as new frontal arc volcanoes are being constructed and growing to sea level; and (3) increasingly vigorous volcanism during middle and late stage backarc spreading, and until the next rift cycle begins. Differences in plate boundary forces at the ends, more than in the middle, of volcanic arcs may significantly influence their proclivity to rift. -from Author
Article
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Azimuthal seismic anisotropy, the dependence of seismic wave speeds on propagation azimuth, is largely due to fabrics within the Earth’s crust and mantle, produced by deformation. It thus provides constraints on the distribution and evolution of deformation within the upper mantle. Here, we present a new global, azimuthally anisotropic model of the crust, upper mantle and transition zone. Two versions of this new model are computed: the rough SL2016svAr and the smooth SL2016svA. Both are constrained by a very large dataset of waveform fits (∼750, 000 vertical component seismogram fits). Automated, multimode waveform inversion was used to extract structural information from surface and S wave forms in broad period ranges (dominantly from 11 to 450 s, with the best global sampling in the 20– 350 s range), yielding resolving power from the crust down to the transition zone. In our global tomographic inversion, regularization of anisotropy is implemented to more uniformly recover the amplitude and orientation of anisotropy, including near the poles. Our massive waveform dataset, with complementary large global networks and high-density regional array data, produces improved resolution of global azimuthal anisotropy patterns. We show that regional scale variations, related to regional lithospheric deformation and mantle flow, can now be resolved by the global models, in particular in densely sampled regions. For oceanic regions, we compare quantitatively the directions of past and present plate motions and the fast-propagation orientations of anisotropy. By doing so, we infer the depth of the boundary between the rigid, high-viscosity lithosphere (preserving ancient, frozen fabric) and the rheologically weak asthenosphere (characterized by fabric developed recently). The average depth of thus inferred rheological lithosphere-asthenosphere boundary (LAB) beneath the world’s oceans is ∼115 km. The LAB depth displays a clear dependence on the age of the oceanic lithosphere, closely matching the 1200◦C half-space cooling isotherm for all oceanic ages. In continental regions, azimuthal anisotropy is characterized by smaller-scale 3D variations. Quantitative comparisons of the tomographic models with global SKS splitting measurements confirm the basic agreement of the two types of anisotropy analysis; they also offer a new insight into the average rheological thickness of continental lithosphere. In spite of significant recent improvements in the resolution of upper mantle anisotropic structure, correlations between the anisotropic components of current global tomographic models remain much lower than between the isotropic ones. Our comparisons of the current models show which features are resolved consistently by different models, and therefore provide a means to estimate the robustness of anisotropic patterns and amplitudes. Significantly lower correlations are observed at depths greater than ∼300 km, compared to those shallower, which suggests that global azimuthal anisotropy models are yet to reach consensus on the nature of anisotropy in the transition zone.
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We compiled the most relevant data acquired throughout the Philippine Sea Plate (PSP) from the early expeditions to the most recent. We also analyzed the various explanatory models in light of this updated dataset. The following main conclusions are discussed in this study. (1) The Izanagi slab detachment beneath the East Asia margin around 60–55 Ma likely triggered the Oki-Daito plume occurrence, Mesozoic proto-PSP splitting, shortening and then failure across the paleo-transform boundary between the proto-PSP and the Pacific Plate, Izu-Bonin-Mariana subduction initiation and ultimately PSP inception. (2) The initial splitting phase of the composite proto-PSP under the plume influence at ∼54–48 Ma led to the formation of the long-lived West Philippine Basin and short-lived oceanic basins, part of whose crust has been ambiguously called “fore-arc basalts” (FABs). (3) Shortening across the paleo-transform boundary evolved into thrusting within the Pacific Plate at ∼52–50 Ma, allowing it to subduct beneath the newly formed PSP, which was composed of an alternance of thick Mesozoic terranes and thin oceanic lithosphere. (4) The first magmas rising from the shallow mantle corner, after being hydrated by the subducting Pacific crust beneath the young oceanic crust near the upper plate spreading centers at ∼49–48 Ma were boninites. Both the so-called FABs and the boninites formed at a significant distance from the incipient trench, not in a fore-arc position as previously claimed. The magmas erupted for 15 m.y. in some places, probably near the intersections between back-arc spreading centers and the arc. (5) As the Pacific crust reached greater depths and the oceanic basins cooled and thickened at ∼44–45 Ma, the composition of the lavas evolved into high-Mg andesites and then arc tholeiites and calc-alkaline andesites. (6) Tectonic erosion processes removed about 150–200 km of frontal margin during the Neogene, consuming most or all of the Pacific ophiolite initially accreted to the PSP. The result was exposure of the FABs, boninites, and early volcanics that are near the trench today. (7) Serpentinite mud volcanoes observed in the Mariana fore-arc may have formed above the remnants of the paleo-transform boundary between the proto-PSP and the Pacific Plate.
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Depuis le Mésozoïque, l’Afrique a été en extension avec de courtes périodes de compression associées a`l’obduction d’ophiolites sur sa marge nord. Moins fréquente que la subduction, l’obduction est néanmoins un phénomènede premier ordre qui reste énigmatique. La fermeture de la Neo-Téthys au Crétacé supérieur est caractérisée par un épisodemajeur d’obduction, depuis la Méditerranée jusqu’a` l’Himalaya, en particulier sur la marge de l’Arabie, de Chypre a` l’Oman.Ces ophiolites furent toutes mises en place dans un court laps de temps pendant le Crétacé supérieur, de 100 a` 75 Ma, dansun contexte de compression enregistré en de larges portions de l’Afrique et de l’Europe, au travers de la zone de convergence.L’échelle de ce processus requiert une explication a` l’échelle de plusieurs milliers de kilomètres et donc impliquantvraisemblablement l’ensemble du manteau convectif. Nous suggérons que l’alternance de périodes extensives et compressivesen Afrique résulte de changements du régime convectif. Les périodes extensives correspondraient a` la convectionimpliquant tout le manteau, l’Afrique étant portée par une grande cellule de type tapis-roulant, tandis que la compressionet l’obduction se produiraient quand le panneau plongeant africain pénètre la transition entre le manteau supérieur et lemanteau inférieur et quand la plaque Afrique accélère en conséquence d’une plus grande activité du panache, jusqu’a`pénétration complète, durant une période d’environ 25 Myr. Les archives géologiques sur lesquelles ce type de scenarios estfondé peuvent fournir des contraintes temporelles indépendantes pour tester les modèles numériques de convectionmantellique et les interactions panache–panneau plongeant.
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The East African Rift system (EARS) provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the pre-rift, syn-rift and post-rift far-field volcanic and tectonic activity show that the EARS formed in the context of the interaction between a deep mantle plume and a horizontally and vertically heterogeneous lithosphere under far-field tectonic extension. We bring quantitative insights into this evolution by implementing high-resolution 3D thermo-mechanical numerical deformation models of a lithosphere of realistic rheology. The models focus on the central part of the EARS. We explore scenarios of plume-lithosphere interaction with plumes of various size and initial position rising beneath a tectonically pre-stretched lithosphere. We test the impact of the inherited rheological discontinuities (suture zones) along the craton borders, of the rheological structure, of lithosphere plate thickness variations, and of physical and mechanical contrasts between the craton and the embedding lithosphere. Our experiments indicate that the ascending plume material is deflected by the cratonic keel and preferentially channeled along one of its sides, leading to the formation of a large rift zone along the eastern side of the craton, with significant magmatic activity and substantial melt amount derived from the mantle plume material. We show that the observed asymmetry of the central EARS, with coeval amagmatic (western) and magmatic (eastern) branches, can be explained by the splitting of warm material rising from a broad plume head whose initial position is slightly shifted to the eastern side of the craton. In that case, neither a mechanical weakness of the contact between the craton and the embedding lithosphere nor the presence of second plume are required to produce simulations that match observations. This result reconciles the passive and active rift models and demonstrates the possibility of evelopment of both magmatic and amagmatic rifts in identical geotectonic environments.
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Seismic travel-time tomography of the mantle under SE Asia reveals patterns of subduction-related seismic P-wave velocity anomalies that are of great value in helping to understand the region's tectonic development. We discuss tomography and tectonic interpretations of an area centred on Indonesia and including Malaysia, parts of the Philippines, New Guinea and northern Australia. We begin with an explanation of seismic tomography and causes of velocity anomalies in the mantle, and discuss assessment of model quality for tomographic models created from P-wave travel times. We then introduce the global P-wave velocity anomaly model UU-P07 and the tectonic model used in this paper and give an overview of previous interpretations of mantle structure. The slab-related velocity anomalies we identify in the upper and lower mantle based on the UU-P07 model are interpreted in terms of the tectonic model and illustrated with figures and movies. Finally, we discuss where tomographic and tectonic models for SE Asia converge or diverge, and identify the most important conclusions concerning the history of the region. The tomographic images of the mantle record subduction beneath the SE Asian region to depths of approximately 1600 km. In the upper mantle anomalies mainly record subduction during the last 10 to 25 Ma, depending on the region considered. We interpret a vertical slab tear crossing the entire upper mantle north of west Sumatra where there is a strong lateral kink in slab morphology, slab holes between c.200–400 km below East Java and Sumbawa, and offer a new three-slab explanation for subduction in the North Sulawesi region. There is a different structure in the lower mantle compared to the upper mantle and the deep structure changes from west to east. What was imaged in earlier models as a broad and deep anomaly below SE Asia has a clear internal structure and we argue that many features can be identified as older subduction zones. We identify remnants of slabs that detached in the Early Miocene such as the Sula slab, now found in the lower mantle north of Lombok, and the Proto-South China Sea slab now at depths below 700 km curving from northern Borneo to the Philippines. Based on our tectonic model we interpret virtually all features seen in upper mantle and lower mantle to depths of at least 1200 km to be the result of Cenozoic subduction.
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The formation and evolution of a backarc basin are linked to the dynamics of the subduction system. The opening of the central Mediterranean basins is a well-documented example of backarc extension characterized by short-lived episodes of spreading. The underlying reasons for this episodicity are obscured by the complexity of this subduction system, in which multiple continental blocks enter the subduction zone. We present results from three-dimensional numerical models of laterally varying subduction to explain the mechanism of backarc basin opening and the episodic style of spreading. Our results show that efficient backarc extension can be obtained with an along-trench variation in slab buoyancy that produces localized deformation within the overriding plate. We observe peaks in the trench retreating velocity corresponding first to the opening of the backarc basin, and later to the formation of slab windows. We suggest that the observed episodic trench retreat behavior in the central Mediterranean is caused by the formation of slab windows.
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Body wave seismic tomography is a successful technique for mapping lithospheric material sinking into the mantle. Focusing on the India/Asia collision zone, we postulate the existence of several Asian continental slabs, based on seismic global tomography. We observe a lower mantle positive anomaly between 1100 and 900 km depths, that we interpret as the signature of a past subduction process of Asian lithosphere, based on the anomaly position relative to positive anomalies related to Indian continental slab. We propose that this anomaly provides evidence for south dipping subduction of North Tibet lithospheric mantle, occurring along 3000 km parallel to the Southern Asian margin, and beginning soon after the 45 Ma break-off that detached the Tethys oceanic slab from the Indian continent. We estimate the maximum length of the slab related to the anomaly to be 400 km. Adding 200 km of presently Asian subducting slab beneath Central Tibet, the amount of Asian lithospheric mantle absorbed by continental subduction during the collision is at most 600 km. Using global seismic tomography to resolve the geometry of Asian continent at the onset of collision, we estimate that the convergence absorbed by Asia during the indentation process is similar to 1300 km. We conclude that Asian continental subduction could accommodate at most 45% of the Asian convergence. The rest of the convergence could have been accommodated by a combination of extrusion and shallow subduction/underthrusting processes. Continental subduction is therefore a major lithospheric process involved in intraplate tectonics of a supercontinent like Eurasia.
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