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Insight into the evolution of Philippine Sea‐South China Sea (SCS) plate motions helps reveal the driving mechanisms of the long‐term tectonic complexity in Southeast Asia. Here, based on the integration of the most recent geological and seismic data, we present a new plate reconstruction model for this region characterized by back‐arc extension and subduction since the Eocene. We suggest that the western boundary of the Philippine Sea Plate was a constant sinistral strike‐slip fault at 55–22 Ma with a clockwise self‐rotation. The connection between the SCS and Shikoku Ridges possibly initiates at 30 Ma, when their spreading times overlapped indicating an affinitive origin and magma source. Regional‐scale geodynamic simulations interfaced with our reconstructed plate motion indicate that the seismic high‐velocity body under the SCS is likely to be the leading edge of the Pacific Slab. Plain Language Summary: Since 55 million years ago, East Asia has been going through a complex plate recombination. Several quantitative plate motion models have been published, but there remain several irrationalities, for example, a footwall plate was moving away from the trench. We established a new model for the Philippine Sea‐South China Sea (SCS) region as an improvement. Our model provides a smooth movement of the Philippine Sea Plate (PSP) from the equatorial zone to its present position, with a clockwise rotation. Based on it, we deduce: (a) the western boundary of the PSP was a sinistral strike‐slip fault; (b) the spreading ridges in SCS and Shikoku Basin were connected at 30 Ma; (c) the stagnant slab under the SCS is a part of the subducting Pacific Slab. Key Points: A new plate reconstruction model of Philippine Sea‐South China Sea (SCS) region since 55 Ma by integrating the latest geological geophysical dataThe western boundary of the Philippine Sea Plate was a constant sinistral strike‐slip fault at 55–22 MaThe geodynamic model indicates the seismic high‐velocity body under the SCS likely to be the leading edge of the Pacific Slab [ABSTRACT FROM AUTHOR]

The island-arc crustal growth rate (IACGR) is the island-arc magma production volume per 1 km width along the arc strike within one million years, and its variations are highly related to slab dehydration and mantle wedge melting. A novel method that includes Earth density modelling, gravity forward and inversion, and arc crustal growth thickness integration is designed to estimate the IACGR. This method can not only estimate the IACGR along the entire arc length but also assess the crustal growth of both remnant and active arcs. Therefore, the estimation result has high coverage and low uncertainty. Here, the Izu–Bonin–Mariana (IBM) subduction zone is taken as a case study region. The estimated time-averaged IACGR along the IBM arc changes between 16 and 59 km3 km−1 Myr−1, with a mean value of 40 km3 km−1 Myr−1, and this result matches the findings of previous studies well. The uncertainties due to crustal thickness inversion are relatively larger than those from flow line reconstruction. The rate results of the Mariana part have lower uncertainties than those of the Izu–Bonin parts since the arc boundaries can be delineated more accurately. The IACGR of the region where a plateau approaches the trench tends to be overestimated because the collision of the plateau with the island arc thickens the island arc crust and bias the uniform pre-existing crustal thickness assumption. [ABSTRACT FROM AUTHOR]

In this study, we for the first time applied a joint geodynamic‐geophysical inversion approach to oceanic plateau subduction models, and compared the subduction style and corresponding topography and Bouguer gravity of two representative subduction scenarios with passive or active collision. We showed that the case of passive collision of the Ontong Java Plateau (OJP) crust better explains the topography, gravity, and seismic data than the active collision scenario. This implies that the OJP did not control the regional dynamics during the collisional process. We conclude that previous studies may have overestimated the role of the OJP in triggering subduction initiation, subduction polarity reversal, and even Pacific Plate rotation. Plain Language Summary: The effect of the Ontong Java Plateau (OJP), the largest oceanic plateau on Earth, on subduction dynamics remains controversial. Proposed models for the evolution of the OJP range from dominantly "soft docking" that generates shallow subduction and little impact on nearby regions, to strong and active collision that results in deep plateau subduction, extensive accretion, subduction polarity reversal, and even major plate reorganization. Determining the subduction depth and accretion volume of OJP is the key to resolving this dispute. In the former, the oceanic plateau undergoes shallow subduction with its upper and middle crusts slightly accreted into the island arc, leading to relatively low topography and a flat Bouguer gravity profile, consistent with observation. The latter case leads to deep subduction of the plateau lithosphere, resulting in high topography, low Bouguer gravity, and crustal structures that all violate observation. Key Points: The joint geodynamic‐geophysical inversion approach can help distinguish ambiguous dynamic behaviors of oceanic plateau subductionThe Bouguer gravity and other observations of Ontong Java Plateau (OJP) favor the passive collision model over the active collision modelOJP should have played a passive role in the collision process, implying the overestimation in previous studies [ABSTRACT FROM AUTHOR]

The Amdo microcontinent which separates the Qiangtang terrane to the north and the Lhasa terrane to the south is a key terrane for reconstructing the tectonic evolution of Central Tibet. We report the new finding of retrograde eclogites within the Amdo microcontinent in this study. The eclogites are characterized by peak metamorphic mineral assemblages of garnet, omphacite, rutile and quartz and underwent a four‐stage metamorphic evolution, including a peak eclogite facies stage (M1) at ~20–24 kbar and 580–620°C, followed by an HP granulite facies decompression stage (M2) at ~13–15 kbar and 750–780°C, a subsequent MP‐UHT granulite facies heating stage (M3) at 8–10 kbar and >840°C and a final amphibolite facies retrogression (M4) at 5.3–6.0 kbar and 560–580°C. The eclogites exhibit rare earth element distribution patterns and trace element abundances similar to those of N‐MORB and arc‐related volcanics, with depleted whole‐rock εNd(t) values of 3.4 to 4.2, and are inferred to have formed in a back‐arc basin tectonic setting. Zircon and rutile U–Pb dating yields a protolith age of 226 ± 5 Ma, a peak eclogite facies metamorphic age of 190 ± 1 Ma, an HP granulite facies metamorphic age of 179 ± 1 Ma and an amphibolite facies retrograde age of 172 ± 1 Ma. The clockwise P–T–t paths and the oceanic protolith signature of retrograde eclogites suggest that part of the back arc basin was subducted to depths of ~80 km. Tectonic erosion associated with the subduction of the Amdo microcontinent beneath the Tethys Ocean accounts for the deep subduction of the back‐arc basin and the absence of arc magmatic rocks in the northern Amdo microcontinent. [ABSTRACT FROM AUTHOR]

The Amdo microcontinent located within the Bangong–Nujiang Suture Zone (BNSZ) holds one of the important keys to understand the tectonic evolution of Central Tibet before the Qiangtang‐Lhasa terrane collision during the Mesozoic. Newly discovered eclogites were reported within the Amdo microcontinent in this study, and their metamorphic evolution is deciphered by petrographic observations, pseudosection modelling, geochemistry, and zircon U–Pb dating. The eclogites are characterized by peak metamorphic mineral assemblages of garnet, omphacite, rutile, and quartz, and underwent a four‐stage metamorphic evolution, including eclogite facies stage (M1) at ~20–24 kbar and 580–620°C, followed by HP granulite facies decompression stage (M2) at ~13–15 kbar and 750–780°C, subsequent MP–HT granulite facies heating stage (M3) at 8–10 kbar and >840°C, and final amphibolite facies retrogression (M4) at 5.3–6.0 kbar and 560–580°C. The eclogites exhibit rare earth element (REE) distribution patterns and trace element abundance similar to those of N‐MORB and arc‐related volcanics, which are inferred to have formed in a back‐arc Basin tectonic setting. Zircon U–Pb dating yields eclogite facies metamorphic age of 190 ± 1 Ma. The clockwise P–T–t paths and the oceanic protolith signature of retrograde eclogites suggest that part of the back‐arc Basin was subducted to the depths of ~80 km. The subsequent ultra‐high temperature metamorphic overprinting may be related to the upwelling of the asthenosphere. Tectonic erosion associated with the subduction of the Amdo microcontinent beneath the Tethys Ocean accounts for the deep subduction of the back‐arc Basin and the absence of arc magmatic rocks in the northern Amdo microcontinent. [ABSTRACT FROM AUTHOR]

Cratons are generally defined as stable continental blocks with a strong cratonic root that typically is at least ∼200 km thick. Many cratons have undergone little internal tectonism and destruction since their formation, but some of them, such as the eastern part of the North China Craton (NCC), the Dharwar Craton and the Wyoming Craton, have lost their thick cratonic root and become reactivated in recent geological history, leading to widespread Meso-Cenozoic volcanisms. The mechanisms responsible for such decratonization remain debated. To provide new constraints on models leading to decratonization, in this study we stack 612 854 source-normalized P -to- S conversions (receiver functions or RFs) from the 410 and 660 km discontinuities (d410 and d660, respectively) bordering the mantle transition zone (MTZ) recorded at 1986 stations in the NCC. Both the number of RFs and the number of stations are unprecedented in the study area. The average apparent depths of the d410 and d660 and the thickness of the MTZ are 413 ± 6, 669 ± 8 and 255 ± 6 km, respectively. A depression of up to 37 km and mean 11 km of the d660 are clearly observed beneath the eastern NCC, mainly caused by the possible existence of a relatively large amount of water in the MTZ. Our study provides strong observational evidence for geodynamic modelling that suggests water in the MTZ can be driven out into the upper mantle by poloidal mantle flow induced by the subduction and retreat of subducted oceanic slabs. The results are consistent with the weakening of the lithosphere beneath the eastern NCC by the release of water (in the form of structurally bound H/OH) brought down to the MTZ by subduction of the Pacific slab. Continuous slab dehydration and the ascent of fluids would have triggered intraplate volcanism and mantle upwelling in the eastern NCC, as evidenced by the spatial correspondence among the lower-than-normal upper-mantle seismic velocities, unusually large depressions of the d660, Cenozoic basaltic volcanism and thinning of the cratonic lithosphere. [ABSTRACT FROM AUTHOR]

The buckling orocline is generally formed by buckling of an originally straight or nearly straight orogenic belt, which formed in the first stage and was buckled in the second stage either by mountain-parallel/oblique compression (e.g. Cantabrian orocline [[12]]) or by mountain-perpendicular/oblique indentation (e.g. Adriatic Orocline [[13]], Peruvian and Bolivian oroclines [[3]]). Therefore, the orocline structure plays a key role in the development of accretionary orogen architecture and contributes to the formation of a huge orogenic belt, such as the CAOB. The term "orocline" was first proposed by Carey [[1]] to describe the structure as 'an orogenic system which has been flexed in plane to a horse-shoe or elbow shape'; it usually emphasizes that a previous straight mountain belt or tectonic units have been bended horizontally. [Extracted from the article]

It is generally accepted that the subduction polarity reversal (SPR) results from the strong collision of two plates. Yet, the SPR of the Solomon Back‐arc Basin is started in the "soft docking" stage, and the mechanism by which the "soft docking" induced subduction initiation (SI) remains elusive. We find that the mass depletion of the plateau influences the evolution of the subduction patterns during SI. And the island arc rheological strength affects the development of the shear zone between an island arc and back‐arc basin which favors SI. What's more, with the increase of the rheological strength difference, the SI is more easily to occur, and the contribution of the plateau collision to SI weakens. Hence, by combining the available geological evidence, we suggest that the Solomon Island Arc rheological strength and the Ontong‐Java plateau collision jointly controlled the SI during the "soft docking" stage. Plain Language Summary: Plateau collision has been considered an important factor for the subduction initiation (SI). However, the SI of the Solomon Sea Basin occurred during the "soft docking" stage, which is unique from the traditional understanding of SI. Our numerical model shows that the rheological strength difference between the SIA and the Solomon Sea Basin results in the conjugate shear zone with a high strain rate during the "soft docking" stage. The conjugate shear zone with a high strain rate as a natural weak zone is conducive to inducing SI. Moreover, while the SI (the San Cristobal Trench) occurs, the OJP likes a "wall" has resulted in the uplift of the SIA and the distinct evolution of subduction patterns. Key Points: The subduction initiation at the SSB results from joint contributions of both SIA rheological strength and OJP collisionThe island arc affects the development of shear zone between an island arc and back‐arc basin, which favors subduction initiationThe mass depletion of the lithospheric mantle in the OJP influences the evolution of subduction patterns after subduction initiation [ABSTRACT FROM AUTHOR]

The extensive fast seismic anomalies in the mantle transition zone beneath East Asia are often interpreted as stagnant Pacific slabs, and a reason for the widespread tectonics since the Mesozoic. Previous hypotheses for their formation mostly emphasize vertical resistances to slab penetration or trench retreat. In this study, we investigate the origin of these stagnant slabs using global‐scale thermal‐chemical models with data‐assimilation. We find that subduction of the Izanagi‐Pacific mid‐ocean ridge marked the transition of mantle flow beneath western Pacific from being surface‐driven Couette‐type flow to pressure‐driven Poiseuille‐type flow, a result previously unrealized. This Cenozoic westward mantle wind driven by the pressure gradient independently explains seismic anisotropy in the region. We conclude that the mantle wind is the dominant mechanism for the formation of stagnant slabs by advecting them westward while the pressure gradient holds them in the transition zone. Plain Language Summary: The wide‐spread flat lying fast seismic anomalies in the mantle transition zone are often referred to as stagnant slabs. The mechanisms for their formation are debated. In this study we use Earth‐like global models to simulate slab geometry variation and reproduced the East Asian stagnant slabs. By running different tests we find that most previously proposed mechanisms are not the key reason, including the phase transformation at 660 km, viscosity increase in the lower mantle, seafloor age variation, and trench retreat. Instead, a westward mantle wind controlled the formation of stagnant slabs. This mantle wind occurred after the Izanagi‐Pacific mid‐ocean ridge began to subduct, and is driven by a long‐lasting horizontal pressure gradient induced by previously subducted slabs. Without this mantle wind the slabs sink directly into the lower mantle. Seismic anisotropy models further confirm the dominant role of this upper‐mantle flow in forming stagnant slabs. Key Points: Global thermal‐chemical subduction models with data‐assimilation reproduced the evolution of East Asian stagnant slabsThe key mechanism for slab stagnation is the westward mantle wind driven by continuous former Izanagi and Tethyan subductionAnisotropy calculations confirm the predominant upper‐mantle depth of the mantle wind since the early Cenozoic [ABSTRACT FROM AUTHOR]

Knowledge of the displacement history of the series of continental fragments in Northeast Asia is key to understanding the plate kinematic evolution of the western peri-Pacific tectonic domain. Palaeomagnetism is an effective approach for deciphering the horizontal movements of crustal elements, especially vertical-axis rotations. Here we present a set of new palaeomagnetic data from Lower Cretaceous volcanic rocks from the northeastern part of the North China Block (NCB), and from Lower Cretaceous sedimentary and volcaniclastic rocks from the Bureya-Jiamusi-Khanka terrane. The data suggest that the northeastern NCB crustal elements underwent a clockwise motion relative to the Eurasian continent after the Early Cretaceous, and in addition a substantial counterclockwise deformation component is observed in the Bureya-Jiamusi-Khanka terrane. Combined with the results of previous Cretaceous and Cenozoic palaeomagnetic studies, we suggest that the northeast part of the North China Block and the Korean Peninsula experienced ~20° of clockwise rotation during the Cenozoic. However, the Bureya-Jiamusi-Khanka terrane and its eastern neighbouring Pacific-related accretionary terranes, such as the Sikhote-Alin Orogenic belt, however, underwent a contemporaneous 40°counter-clockwise rotation. The Japanese Islands, with juvenile crust in the easternmost part of Asia, were divided into a pair of terranes, which rotated in opposite directions during the Middle Miocene. The opposing senses of rotation are attributed to mantle wedge convection. We suggest that tectonic rotations of parts of Northeast Asia are controlled by the subduction of the western Pacific Plate via lithospheric deep-shallow coupling. The two critical events were coeval with ridge subduction of the Izanagi-Pacific mid-ocean ridge under the continental margin during the Palaeocene, and the collision of the Izu-Bonin and Japanese Islands during the Middle Miocene, respectively. [ABSTRACT FROM AUTHOR]

Growing evidence supports that the widely developed Mesozoic folds and magmatism in the South China Block are attributed to the flat‐slab subduction, followed by slab steepening, of the Paleo‐Pacific Plate (PPP). However, the dynamics of the transition from flat‐ to steep‐slab subduction, as well as the relationship between tectonic processes and surface deformation and magmatic events, are poorly constrained. Using a 2‐D thermomechanical numerical model, we systematically investigate the effects of slab rollback or delamination following the eclogitization of a subducted oceanic plateau on the surficial topography, structural deformation, and magmatism. Our results indicate that the subduction of an oceanic plateau drives flat‐slab subduction, which further leads to the development of a wide thrust fault zone, an uplifted and magmatically active foreland, and the foreland basin subsidence. This model is further complicated by the transition from flat‐ to steep‐slab subduction through slab rollback or delamination which is controlled by the subduction rate and the timing of oceanic plateau eclogitization. The comparisons between our numerical results and the geological data from South China reveal that the slab delamination model reproduces the regional evolution of the Mesozoic South China. Based on our models, we suggest that the eclogitization during flat‐slab subduction is not instantaneous, which is instead at least 18 Myr after the oceanic plateau reaches the ideal conditions of phase change. Key Points: Eclogitization of oceanic plateau starts at 18 Myr after initial flat‐slab subductionSlab rollback versus delamination are controlled by subduction rate and timing of eclogitizationMesozoic South China was controlled by flat‐slab subduction and later slab delamination [ABSTRACT FROM AUTHOR]

The lithospheric "de‐rooting" of the Sulu‐Dabie Orogen (SDO) is an important tectonic mechanism for post‐orogenic tectono‐magmatism, which influenced the sedimentation, evolution, and development of oil–gas accumulation in the Hefei Basin (HB). Combined with seismic, geological, and sedimentary data of the HB and the SDO, this paper studies the coupling of the HB and the SDO since the Late Mesozoic. While the North China Block (NCB) indented south‐eastwards under the Greater South China Block (GSCB) since the Mesozoic, the SDO underwent three intense tectonic stages, i.e., subduction, exhumation, and uplift. The upwelling of deep mantle material causes the exhumation of the ultrahigh‐pressure metamorphic (UHPM) rocks to the upper crust or surface, forming the UHPM. Influenced by the indentation of the NCB, the "de‐rooting" of the SDO lithosphere, caused the delamination and thinning of the lithosphere, accompanied by the continuous flexural subsidence in the HB. The basin underwent at least four stages of tectonic evolution, involving sequentially: the flexural basin, the foreland basin, the strike‐slip‐related basin, and the faulted graben development periods. The tectonic evolution of the HB was closely coupled with the SDO orogeny. The "de‐rooting" of the SDO lithosphere resulted in a strong uplift and erosion of the orogen, providing abundant source of material for the HB and causing the successively northwards migration of basin depocenters at its early stage. Finally, influenced by the subduction retreat of the (Palaeo‐) Pacific Plate and the strike‐slip movement of the Tanlu Fault, the depocenters migrated to the east. [ABSTRACT FROM AUTHOR]

Submarine canyons are common features on the northern South China Sea (SCS) continental slope. Three main submarine canyon systems were observed by multi‐beam investigation and evaluated by a pre‐existing sedimentary dataset. They include the Xisha Canyon Zone, Shenhu Canyon Zone, and Taiwan Canyon Zone on the northern SCS continental slope which developed from the middle Miocene to the present‐day. Previous analysis implied that an enriched oil‐gas accumulation formed under this region with distinct gravity anomalies or active tectonic activity. Previous interpretation and geodynamics studies have revealed the detailed sedimentary records and the coupled tectonic‐sedimentary processes. However, the timing and mechanism of formation of the canyons on the northern SCS slope are still poorly constrained and vigorously debated, especially the differences among three submarine canyons from west to east that requires allowances for a variety of conflicting datasets. Here, we adopt the high‐resolution multi‐beam relief map and seismic profiles from these three canyon systems to estimate if the SCS slope controlled geometric segmentation and differentiation of canyon formation mechanisms and times. For this purpose, we ascertained that these canyons were initially controlled by the NE‐ to NW‐trending faults as a better constraint on the sediment flow direction. All the submarine canyons in the northern SCS slope extend in a range from NE‐/N–S‐ to NW‐ and E–W‐trending directions associated with the SCS oceanic spreading and the subsequent subduction‐related deformation along the Manila Trench. Furthermore, the present‐day morphology of these canyons implies a remarkable tectonic jump from west to east in the SCS continental slope and a north‐westward recession of the continental slope. Apart from the neo‐tectonic faults, the sea‐level fluctuation, gas hydrate disassociation, sediment source, and transportation channel also yielded dynamic processes and preservation for the submarine canyons. We finally propose a coupling model of the sedimentary and tectonic processes and confirm the spatial and temporal evolution of mechanisms of these canyons. [ABSTRACT FROM AUTHOR]

Lavas from back‐arc basins are generally diverse, and their geochemical compositions indicate that they received variable contributions from subduction components during petrogenesis. Obtaining comprehensive geochemistry characteristics for the entire back‐arc basin are helpful in gaining a better understanding of the complexities of back‐arc evolution. In this study, we systematically reviewed the major and trace element compositions of Lau Basin lavas. This data set covered all of the major tectonic units of the basin, for example, the Eastern Lau spreading center (ELSC), the Valu Fa ridge (VFR), the Central Lau spreading center (CLSC), the Northwestern Lau spreading center (NWLSC), the Northeastern Lau spreading center (NELSC), the Mangatolu Triple Junction (MTJ), and the Fonualei Spreading Center (FSC). The lava types from these locations are diverse, including tholeiitic basalts, alkali basalts, basaltic andesites, andesites, dacites, and rhyolites. In addition, the NELSC and FSC contain boninites. In this study, the geochemical compositions of these diverse rock types are used to investigate the spreading dynamics of the Lau Basin back‐arc. We conclude that (a) the subduction components mainly include hydrous fluids released from the subducted slab, and hydrous melt directly from the melting subducted sediment, and the influence of the subducted components on the mantle wedge and the petrogenesis of the central and southern Lau Basin lavas decreases with increasing distance from the Tonga Trench; (b) during the propagation and spreading of the Samoan mantle into the Lau Basin, lavas from the NELSC, NWLSC, MTJ, and even from the northern part of the FSC may receive variable degrees of influence from the Samoan plume; and (c) the migration of Indian MORB‐like mantle southwards into the Pacific mantle is consistent with the opening of the Lau Basin. With the gradual migration of Indian mantle into the Lau Basin, a series of spreading centers were formed, for example, in order, the NWLSC, CLSC, ELSC, and the propagating VFR. [ABSTRACT FROM AUTHOR]

A total of 431 well‐defined and 632 null shear–wave splitting measurements obtained from 115 broadband seismic stations located in the eastern Himalayan syntaxis and adjacent areas is largely inconsistent with predicted fast orientations by absolute plate motion models. Spatial coherency analysis of the splitting parameters suggests that the observed azimuthal anisotropy is mostly located in the upper asthenosphere or the transitional layer between the lithosphere and asthenosphere, and the disagreement between the fast orientations and regional tectonic fabrics suggests an insignificant lithospheric contribution to the observed anisotropy. The observations may be attributed to flow systems that are driven by the westward rollback of the Indian slab beneath the Indo‐Burma block and are modulated by a previously revealed gap between the northward and eastward subducting slabs of the Indian plate. Key Points: Seismic anisotropy may be explained by a rollback of the Indian slab and modulation by a slab gapThe rotational pattern of fast orientations in SE Tibetan Plateau may be attributed to flow in the mantle wedge escaped from the slab gapN‐S anisotropy in NE India and Burma block and E‐W anisotropy in Indochina may reflect sub‐slab trench parallel flow from slab rollback [ABSTRACT FROM AUTHOR]

Abstract The North Qaidam ultra-high pressure (UHP) metamorphic belt in the northern Tibetan Plateau is considered as a typical Alpine-type UHP metamorphic belt due to the Early Paleozoic subduction of the Qaidam Block beneath the Qilian Block. The well-preserved Paleozoic metatexite migmatite, diatexite migmatite, felsic sheet/dyke and anatectic granite in the North Qaidam UHP metamorphic belt provide us with an excellent opportunity to study the generation, transport and final fate of crustal melt and geodynamic processes associated with orogenesis. Based on structural relationships, petrology, geochronology, whole-rock geochemistry and Sr Nd isotope data, the Early Paleozoic anatexis during oceanic subduction to continental collision in the North Qaidam UHP metamorphic belt can be further divided into three stages of development ~470 Ma, 446–428 Ma and 432–420 Ma. The first-stage granitic leucosomes are rich in K, poor in Na with low Sr/Y and enrichment of large ion lithophile elements (LILEs), which were probably derived from partial melting of ancient felsic gneiss in continental arc circumstances during oceanic subduction. The second-stage Na-rich leucosomes and tonalite plutons are characterized by high Na, Sr, Sr/Y and La/Yb and low heavy rare earth elements (HREEs), with positive ε Nd (t) values of 0.1–4.3 and zircon ε Hf (t) values of 8.3–10.2, similar to typical tonalite-trondhjemite-granodiorites (TTGs). These TTG-like magmas were produced through partial melting of newly emplaced gabbroic rocks with arc affinity under high-pressure (HP) granulite-facies conditions in a thickened lower crust during continental collision. The volumetrically significant migrated plutons evolved from TTG-like melt will become segments of continental crust and contribute to crustal growth, with partial residual products of HP granulite and/or garnet pyroxenite to the mantle by delamination. The third stage of anatexis was preserved in both migmatitic UHP gneiss and eclogite in the Xitieshan and Luliangshan terranes. The Kfs-rich felsic leucosomes inside UHP gneisses in the third stage are characterized by high alkali contents and low mafic component with FeO T + MgO + TiO 2 <2%. In trace element distribution diagrams, these Kfs-rich leucosomes exhibit parallel patterns to their host gneisses but lower element contents and slightly positive Eu and Sr anomalies. The Pl-rich leucosomes within the retrograde eclogite have geochemical features as follows: (1) rich in CaO, Na 2 O and poor in K 2 O, with Na 2 O/K 2 O ratios >2.0; (2) high La/Yb and Sr/Y, and low Y and HREEs; (3) high Al 2 O 3 and low Mg# values; and (4) enriched in LILEs(e.g., Rb, Ba, K, Sr, Pb) and poor in high field strength elements (HFSEs). Partial melting of UHP eclogite and felsic gneiss during the initial retrogression stage with Pl-rich and Kfs-rich leucosome formation was triggered by dehydration melting involving predominant zoisite and muscovite. The anatectic melts from partial melting of deeply subducted UHP gneiss have accumulated and migrated outside the deeply subducted crustal slice in the form of syn -collisional plutons. The melt evolution from the leucosomes produced at the early exhumation stage to syn-collisional granitoids produced at the late exhumation, might contribute greatly to the exhumation of the North Qaidam UHP metamorphic belt from mantle depths to the lower crustal levels. [ABSTRACT FROM AUTHOR]

The Bangong–Nujiang Suture Zone (BNSZ) is one of the main suture zones in the Tibetan Plateau and indicates the existence of the Bangong–Nujiang Neo‐Tethys Ocean (BNO). It was formed by the collision between the Qiangtang and Lhasa blocks after the closure of the BNO. However, its evolutionary processes and subduction polarity remain controversial. Research on the BNSZ is of great significance for exploring plate tectonic evolution and ocean–continent connection. The scarcity of the BNSZ structural data is one of the most important reasons for the debate of the BNO tectonic evolution. Based on structural analysis in the field and combined with previous petrology and palaeomagnetic data, this paper has determined that the closure time of the BNO is progressive and scissor‐like, from Middle Jurassic in the east to Early Cretaceous in the middle and late Early Cretaceous to early Late Cretaceous in the west. There was a three‐stage deformation in the BNSZ: (a) N–S‐directed compression induced by the initial collision; (b) WNW–directed transpression related to the stress adjustment; and (c) NE–SW‐directed compression caused by the low‐angle NE‐directed subduction of the Indus–Yarlung Zangbo Ocean. The different structural pattern along the eastern segment of the BNSZ may have resulted from orogenic bending due to the later Himalayan Orocline caused by the India–Eurasia collision in the Cenozoic. [ABSTRACT FROM AUTHOR]

The Tan–Lu Fault Zone (TLFZ) is the largest continental‐scale strike‐slip fault zone in East China. It experienced a complex Meso‐Cenozoic deformation and controlled the development and evolution of the Bohai Bay Basin (BBB). Though its Mesozoic sinistral and Cenozoic dextral motions have been well documented, its strike‐slip transition history and mechanism from sinistral to dextral motions in the Early Paleogene remain poorly understood. To investigate these issues, we made a thorough analysis on the fault geometry and kinematics as well as the response of depocentre in the Early Paleogene of the sags adjacent to the TLFZ across the southeast BBB. The results show that the WNW‐/NW‐, E‐W‐, and ENE‐/NE‐trending extensional faults developed in the Early Paleogene of those sags share almost the same geometrical and kinematic features. Such features indicate that the TLFZ is sinistral in Ek3‐Ek2 depositional stage, extension dominated in Ek1 depositional stage, and dextral in Es4L depositional stage. Such strike‐slip transition of the TLFZ is a comprehensive effect of the plate events around the Eurasian Plate. The NNW‐directed subduction of the Pacific to the Eurasian plates triggers the sinistral motion of the TLFZ during 65–55 Ma, but this sinistral motion is terminated by the far‐field effect of the NNE‐directed India–Eurasia collision initiating at 55 Ma. Then, the kinematic adjustment of the Pacific Plate from NNW to WNW breaks the stress balance exerted on the TLFZ by the subduction of the Pacific to Eurasian plates and the India–Eurasia collision and makes it turn into dextral motion gradually during 48–42 Ma. [ABSTRACT FROM AUTHOR]

The East China Sea Shelf Basin (ECSSB) lies among the Eurasian Plate, the Pacific Plate, and the Indian Plate. Its formation and evolution since the Mesozoic was controlled by the combined effect of westward subduction of the Pacific Plate and actions of the large‐scale ductile shear zone on the South China Plate—the Changle–Nan'ao Fault Zone. This paper selects the southern ECSSB with well‐developed Mesozoic strata as the study area. By analysing the basin architectures and structures of each structural unit, calculating the fault growth index, and referring to the sandbox modelling results, we consider that the Oujiang Sag belongs to a strike‐slip pull‐apart basin controlled by the Changle–Nan'ao Fault Zone, while the Minjiang Sag and the Jilong Sag are extensional basins without strike‐slip property. The Mesozoic evolutionary process of the ECSSB can be divided into three stages on the basis of the three main strike‐slip movements of the fault zone. In the Middle–Late Jurassic, the subduction of the Izanagi Plate induced the dextral shearing in a ENE direction of the Changle–Nan'ao Fault Zone, which then formed NW‐SE‐directed transpressional structures inside the ECSSB. In the Late Jurassic–Early Cretaceous, the motion sense of the Izanagi Plate gradually shifted to the northwestwards, inducing the sinistral‐thrusting of the fault zone. Following this, the initial NW‐SE‐directed compressional structures were stretched into the original sag. By the Late Cretaceous, the retreat of the subducting Paleo‐Pacific Plate led to the turning of the regional stress field from compression to transtension. Being influenced by the dextral strike‐slip‐related structures of the Changle–Nan'ao Fault Zone, the Oujiang Sag developed extensive strike slipping‐related structures and was assembled into a left‐stepping en echelon pattern. The Minjiang and Jilong sags, however, gradually grew into extensional depressions under successive extension due to the great distance from the strike‐slip fault zone. [ABSTRACT FROM AUTHOR]

Abstract Any plate has a growth process from small to large. The micro-blocks or micro-plates are sometimes the precursors of large plates. The origin, growth, aborting, extinction and residual process of micro-blocks are of great significance for the study of plate tectonics and pre-plate tectonics. The micro-block can be divided into continental, oceanic and mantle micro-blocks according to their compositions. In this paper, the micro-blocks in the global oceans have been summarized according to the following five environments: mid-ocean ridge system, subduction system, transform fault system, deep-sea intraplate system and extension-rift system. We first propose a genetic classification of micro-blocks comprising: detachment-derived, rifting-derived, transform-derived, propagation-derived, ridge jumping-derived, subduction-derived, accretion-derived, collision-derived and delamination-derived micro-blocks. The different types of micro-block boundaries such as active or fossil detachment fault, subduction zone, mid-ocean ridge, transform fault, fracture zone, transfer fault, accommodation zone, lithosphere-scale strike-slip fault, pseudofault, intra-oceanic convergent zone, overlapping spreading centre, non-transform offset, rheological crustal or mantle discontinuity, are systematically discussed for different micro-blocks. Thus, the number of triple junctions will be more than the 16 in the traditional Plate Tectonic Theory. A stability analysis of these triple junctions is the key to understanding the causes of micro-blocks. However, the micro-block has no ultimate cause, so it is unnecessary to pursue one ultimate cause or initiation of plate tectonics. These micro-blocks within oceanic basins, along oceanic margins or within the deep mantle, can not only be used to develop deep ocean fine structural analysis and plate tectonic reconstruction, but also to explain the causes of micro-blocks in some orogens. This will enrich the research of more detailed pre-orogenic or syn-orogenic evolution of orogenic belts, and even extend to the study of early Precambrian pre-plate tectonic mechanisms. The micro-block can be a transition among microplate, plate and terrane under a plate tectonic regime. It can also be formed in inter-sphere tectonic processes. It helps better our understanding of regimes of cratonic basin formation and intra-continental deformation which are the difficulties faced by the Plate Tectonics Theory. We speculate that the Micro-block Tectonics Theory is a unified tectonic theory of cross-layer, cross-phase, cross-space-time scale and cross-planet. [ABSTRACT FROM AUTHOR]

The dynamics of formation and exhumation of high-pressure (HP) and ultra-high pressure (UHP) metamorphic orogens in double subduction-collision zones remain enigmatic. Here we employ two-dimensional thermo-mechanical numerical models to gain insights on the exhumation of HP-UHP metamorphic rocks, as well as their deformation during the collision of a micro-continent with pro- and retro-continental margins along two subduction zones. A three-stage collisional process with different convergence velocities is tested. In the initial collisional stage, a fold-and-thrust belt and locally rootless superimposed folds are developed in the micro-continent and subduction channel, respectively. In the second (exhumation) stage of HP-UHP rocks, a faster convergence model results in upwelling of the asthenosphere, which further leads to a detachment between the crust and lithospheric mantle of the micro-continent. A slower convergence model results in rapid exhumation of HP-UHP rocks along the north subduction channel and a typical piggy-back thrusting structure in the micro-continent. A non-convergence model produces a slab tear-off, leading to the rebound of residual lithosphere of the micro-continent. In the third and final stage, a series of back and ramp thrusts are formed in the micro-continent with the pro-continent re-subducted. Based on an analogy of our numerical results with the Western Dabie Orogen (WDO), we suggest that: (1) slab tear-off results in a rebound of residual lithosphere, which controls the two-stage syn-collisional exhumation process of HP-UHP rocks in the WDO; and (2) in contrast to the single subduction-collision system, the exhumation range of the partially molten rocks with lower viscosity and density is restricted to a specific region of the micro-continent by the Mianlue and Shangdan subduction zones, which generated the complex deformation features in the WDO. [ABSTRACT FROM AUTHOR]

Abstract: The East Asian geological setting has a long duration related to the superconvergence of the Paleo‐Asian, Tethyan and Paleo‐Pacific tectonic domains. The Triassic Indosinian Movement contributed to an unified passive continental margin in East Asia. The later ophiolites and I‐type granites associated with subduction of the Paleo‐Pacific Plate in the Late Triassic, suggest a transition from passive to active continental margins. With the presence of the ongoing westward migration of the Paleo‐Pacific Subduction Zone, the sinistral transpressional stress field could play an important role in the intraplate deformation in East Asia during the Late Triassic to Middle Jurassic, being characterized by the transition from the E‐W‐trending structural system controlled by the Tethys and Paleo‐Asian oceans to the NE‐trending structural system caused by the Paleo‐Pacific Ocean subduction. The continuously westward migration of the subduction zones resulted in the transpressional stress field in East Asia marked by the emergence of the Eastern North China Plateau and the formation of the Andean‐type active continental margin from late Late Jurassic to Early Cretaceous (160‐135 Ma), accompanied by the development of a small amount of adakites. In the Late Cretaceous (135‐90 Ma), due to the eastward retreat of the Paleo‐Pacific Subduction Zone, the regional stress field was replaced from sinistral transpression to transtension. Since a large amount of late‐stage adakites and metamorphic core complexes developed, the Andean‐type active continental margin was destroyed and the Eastern North China Plateau started to collapse. In the Late Cretaceous, the extension in East Asia gradually decreased the eastward retreat of the Paleo‐Pacific subduction zones. Futhermore, a significant topographic inversion had taken place during the Cenozoic that resulted from a rapid uplift of the Tibet Plateau resulting from the India‐Eurasian collision and the formation of the Bohai Bay Basin and other basins in the East Asian continental margin. The inversion caused a remarkable eastward migration of deformation, basin formation and magmatism. Meanwhile, the basins that mainly developed in the Paleogene resulted in a three‐step topography which typically appears to drop eastward in altitude. In the Neogene, the basins underwent a rapid subsidence in some depressions after basin‐controlled faulting, as well as the intracontinental extensional events in East Asia, and are likely to be a contribution to the uplift of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Statistics about the occurrence frequency of earthquakes (1973–2015) at shallow, intermediate and great depths along the Izu-Bonin-Mariana (IBM) Arc is presented and a percent perturbation relative to P-wave mean value (LLNL-G3Dv3) is adopted to show the deep structure. The correlation coefficient between the subduction rate and the frequency of shallow seismic events along the IBM is 0.605, proving that the subduction rate is an important factor for shallow seismic events. The relationship between relief amplitudes of the seafloor and earthquake occurrences implies that some seamount chains riding on the Pacific seafloor may have an effect on intermediate-depth seismic events along the IBM. A probable hypothesis is proposed that the seamounts or surrounding seafloor with high degree of fracture may bring numerous hydrous minerals into the deep and may result in a different thermal structure compared to the seafloor where no seamounts are subducted. Fluids from the seamounts or surrounding seafloor are released to trigger earthquakes at intermediate-depth. Deep events in the northern and southern Mariana arc are likely affected by a horizontal propagating tear parallel to the trench. [ABSTRACT FROM AUTHOR]

The eastern part of the North China Craton has experienced cratonic destruction during the Mesozoic-Cenozoic period. However, the mechanism and geodynamic process of cratonic destruction is still not clear. The Shandong Province is a typical region that suffered the Yanshanian (Jurassic to Cretaceous) tectono-thermal event relating to the cratonic destruction. In this paper, we focus on the Yanshanian deformation in Western Shandong and integrate the previous studies of contemporaneous magmatism. There are two-stage compressive structures developed in Western Shandong, NE- or NNE- trending open folds, which subsequently evolved the same trend as the thrust faults. A series of NW-trending normal faults converted from the pre-existing Indosinian (Triassic) thrusts controlled the formation of Mesozoic basins. These deformations are a tectonic response to the subduction of the Izanagi Plate (paleo-Pacific Plate) under the North China Craton during the Middle Jurassic and the Early Cretaceous. The Cretaceous magmatic rocks in Western Shandong mainly occurred between 130-125 Ma and have multi-magmatic sources, including enriched lithospheric mantle, delaminated lithosphere, and subducted oceanic slab. We propose that the subduction of the Izanagi Plate converting to the Pacific Plate occurred during the middle Early Cretaceous induced a delamination of the lower crust linked to the destruction of the eastern North China Craton. [ABSTRACT FROM AUTHOR]

The Indian Ocean and the West Pacific Ocean and their ocean-continent connection zones are the core area of 'the Belt and Road'. Scientific and in-depth recognition to the natural environment, disaster distribution, resources, energy potential of 'the Belt and Road' development, is the cut-in point of the current Earth science community to serve urgent national needs. This paper mainly discusses the following key tectonic problems in the West Pacific and North Indian oceans and their ocean-continent connection zones (OCCZs): 1. modern marine geodynamic problems related to the two oceans. Based on the research and development needs to the two oceans and the ocean-continent transition zones, this item includes the following questions. (1) Plate origin, growth, death and evolution in the two oceans, for example, 1) The initial origin and process of the triangle Pacific Plate including causes and difference of the Galapagos and West Shatsky microplates; 2) spatial and temporal process, present status and trends of the plates within the Paleo- or Present-day Pacific Ocean to the evolution of the East Asian Continental Domain; 3) origin and evolution of the Indian Ocean and assembly and dispersal of supercontinents. (2) Latest research progress and problems of mid-oceanic ridges: 1) the ridge-hot spot interaction and ridge accretion, how to think about the relationship between vertical accretion behavior of thousands years or tens of thousands years and lateral spreading of millions years at 0 Ma mid-oceanic ridges; 2) the difference of formation mechanisms between the back-arc basin extension and the normal mid-oceanic ridge spreading; 3) the differentials between ultra-slow Indian Ocean and the rapid Pacific spreading, whether there are active and passive spreading, and a push force in the mid-oceanic ridge; 4) mid-oceanic ridge jumping and termination: causes of the intra-oceanic plate reorganization, termination, and spatial jumps; 5) interaction of mantle plume and mid-oceanic ridge. (3) On the intra-oceanic subduction and tectonics: 1) the origin of intra-oceanic arc and subduction, ridge subduction and slab window on continental margins, transform faults and transform-type continental margin; 2) causes of the large igneous provinces, oceanic plateaus and seamount chains. (4) The oceanic core complex and rheology of oceanic crust in the Indian Ocean. (5) Advances on the driving force within oceanic plates, including mantle convection, negative buoyancy, trench suction and mid-oceanic ridge push, is reviewed and discussed. 2. The ocean-continent connection zones near the two oceans, including: (1) Property of continental margin basement: the crusts of the Okinawa Trough, the Okhotsk Sea, and east of New Zealand are the continental crusts or oceanic crusts, and origin of micro-continent within the oceans; (2) the ocean-continent transition and coupling process, revealing from the comparison of the major events between the West Pacific Ocean seamount chains and the continental margins, mantle exhumation and the ocean-continent transition zones, causes of transform fault within back-arc basin, formation and subduction of transform-type continental margin; (3) strike-slip faulting between the West Pacific Ocean and the East Asian Continent and its temporal and spatial range and scale; (4) connection between deep and surface processes within the two ocean and their connection zones, namely the assembly among the Eurasian, Pacific and India-Australia plates and the related effect from the deep mantle, lithosphere, to crust and surface Earth system, and some related issues within the connection zones of the two oceans under the super-convergent background. 3. On the relationship, especially their present relations and evolutionary trends, between the Paleo- or Present-day Pacific plates and the Tethyan Belt, the Eurasian Plate or the plates within the Indian Ocean. At last, this paper makes a perspective of the related marine geology, ocean-continent connection zone and in-depth geology for the two oceans and one zone. [ABSTRACT FROM AUTHOR]

The East China Sea Shelf Basin (ECSSB) is located on the southeastern continental margin of the Eurasian Plate. The basement of the ECSSB is an extension of the Cathaysian Block as well as an important part of the West Pacific or East Asian Continental Margin tectonic domain. By the analysis of global plate tectonic evolution, the ECSSB is situated in the eastern part of the West Pacific triangle region, as a huge convergence zone between the Indian-Australian, Pacific and Eurasian plates, as well as a global convergence centre. The ECSSB is closely related to the evolution of the Tethyan and West Pacific tectonic domains. Overall, the ECSSB is a pull-apart basin under the transtensional tectonic setting of a continental margin, which is contributed to by the combination of subduction retreat and back-arc spreading between the Eurasian Plate and the Pacific Plate, and the far-field effect of the collision and extrusion between the Indian-Australian and Eurasian plates, and deep mantle dynamics. The formation mechanism of the ECSSB is under passive extension. The eastward mantle flow and the asthenospheric upwelling in the deep Earth are the main driving forces of the basin jumping and eastward tectonic migration. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

East Asia suffered an important transformation from the Tethys to the Pacific tectonic domain during the early Mesozoic. Moreover, the South China Block (SCB) in East Asia has an obvious change from an Indosinian syn-orogenic compression to a post-orogenic extensional tectonic setting. The dynamic evolution of the SCB that caused this change is still unclear. Here, we combine the petrology and whole-rock geochemistry of the Daoxian mafic granulite xenoliths in basalts from South Hunan Province and the structural features of the Xuefengshan tectonic belt, to propose a late Triassic tectonic model in the central SCB. The Daoxian region is located in the eastern part of the Xuefengshan basement uplift belt. The Daoxian mafic granulite xenoliths, forming in the late Triassic, have high Mg# value, high MgO and low SiO2 contents. They have flat REE patterns with a positive Eu anomaly, enriched in Rb, Ba, and depleted in Th, U, Nb, Zr and Hf. These xenoliths are the product of pyroxene and plagioclase accumulation of the mafic melts. The mafic melts originated from the asthenosphere and then underplated to the bottom of the lower crust. In the Xuefengshan belt, it is observed that the unconformities during the Late Triassic changed from high-angle unconformity, through low-angle unconformity and para-unconformity, to conformity, from the central to western parts of the SCB. The detachment layer beneath the Xuefengshan belt displaying NW-trending thrusts cross-cuts the late Palaeozoic strata. We suggest that orogenic collapse happened beneath the central SCB during the Late Triassic, which was accompanied by lithospheric extension and asthenospheric upwelling. These dynamic processes induced different effects on the SCB. Beneath the central SCB, the mantle-derived melt underplated the lower crust, and subsequently influenced the deep crust. From central to western SCB, the regular westward change of the stratal unconformities is related to the weakening of the lithospheric extension. In the central and eastern SCB, the orogenic collapse and the subsequent asthenosphere upwelling could have contributed to the mantle disturbance to enhance the roll-back of the Palaeo-Pacific slab. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Tongbai-Hong'an orogen is located in a key tectonic position linking the Qinling orogen to the west and the Dabie-Sulu orogen to the east. Because the orogen preserves a Paleozoic accretionary orogenic system in the north and a latest Paleozoic-Mesozoic collisional orogenic system in the south, it may serve as an ideal place to study the tectonic evolution between the North and South China Blocks. The available literature data in the past 20 years indicate that the tectonic processes of the Tongbai-Hong'an orogen involved four stages during the Phanerozoic: (1) Early Paleozoic (490-420 Ma) oceanic subduction, arc magmatism and arc-continent collision created a new Andean-type active continental margin on the North China Block; (2) Late Paleozoic (340-310 Ma) oceanic subduction and accretion generated separated paired metamorphic belts: a medium P/T Wuguan-Guishan complex belt in the south of the Shandan-Songpa fault and a high P/T Xiongdian eclogite belt in the northern edge of the Mesozoic HP metamorphic terrane; (3) Latest Paleozoic-Early Mesozoic (255-200 Ma) continental subduction and collision formed the Tongbai HP terrane in the west and the Hong'an HP/UHP terrane in the east as a consequence of deep subduction towards the east and syn-subduction detachment/exhumation of the down-going slab; (4) Late Mesozoic (140-120 Ma) extension, voluminous magma intrusion and tectonic extrusion led to the final exhumation of the Tongbai-Hong'an-Dabie HP/UHP terrane and the wedge-shaped architecture of the terrane narrowing towards the west. However, many open questions still remain about the details of each evolutionary stage and earlier history of the orogen. Besides an extensive study directly on the Tongbai-Hong'an orogen in the future, integrated investigation on the 'soft-collisional' Qinling orogen in the west and the 'hard-collisional' Dabie-Sulu orogen in the east is required to establish a general tectonic model for the whole Qinling-Tongbai-Hong'an-Dabie-Sulu orogenic belt. [ABSTRACT FROM AUTHOR]

The North Luzon Trough, on the East Asian continental margin, is under transpression due to the oblique convergence between the Eurasian and Philippine Sea plates. Based on a seismic profile across the Manila subduction system and other geological data, we propose a strike-slip pull-apart basin model to account for the formation of the North Luzon Forearc Basin. The subduction system experienced four tectonic evolutionary stages: (1) initial subduction (~22–20 Ma): the Eurasian Plate began to subduct beneath the Philippine Sea Plate, and the incipient Manila Trench-North Luzon Volcanic Arc system started to form; (2) upper crustal deformation (~20–15 Ma): the overriding Philippine Sea Plate was strongly deformed by continuous subduction, and thrust faults, volcanic activity, and possibly strike-slip faulting weakened the forearc areas; (3) initiation of strike-slip faults (~15–6 Ma): continuous rotation of the Philippine Sea Plate initiated strike-slip faults in the weak zones of the forearc areas; (4) pull-apart basin formation (~6–0 Ma): the pull-apart basin formed in the forearc due to sinistral movement of two sets of strike-slip faults. We propose an indentation-escape process involving coupling between the sinistral strike-slip faults in the Taiwan-Luzon area and dextral strike-slip faults in the East Asia continental margin, for the evolution of the eastern South China Sea Basin margin. • Oblique convergence between the Eurasian and the Philippine Sea plates. • Strike-slip faulting along the Manila subduction system. • A strike-slip pull-apart basin model proposed for the forearc basins. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Nadanhada Terrane underwent four-stage deformation in the Mesozoic. • The accretion of oceanic seamounts resulted in the curved fold-and-thrust belt. • The subduction of a massif possibly made the Nadanhada Terrane preserved. The Nadanhada Terrane in Northeast China preserves important imprints of Mesozoic tectonic events and is therefore a key area to explore the evolutionary process of the Paleo-Pacific Plate along the northwestern Pacific continental margin. Here we present new results from detailed structural analysis of the Nadanhada Terrane. We also synthesize the previously published data from geochronology, geochemistry, petrology, paleobiology and paleomagnetism. The structural analysis reveals four-stage deformation in the Nadanhada area from late Early Jurassic to early Late Cretaceous. The first-stage deformation is represented by the ENE-striking tight folds or NNW-dipping schistosity during the late Early Jurassic, reflecting the northwestward subduction of the Paleo-Pacific Plate. The second-stage deformation occurred during the earliest Cretaceous and is characterized by chevron or asymmetric folds with some thrust faults, with varying strikes, and the regional structural lines indicate westward-protruding arcs in the plan view. The westward-protruding structural trend lines are probably caused by the combined influence of the difficultly-deformed Jurassic volcanic arcs in the south and the coevally-accreted seamounts in the middle. There was likely a small massif, probably the Pre-Nadanhada Massif, subducted and then stagnated beneath the Nadanhada Terrane later than this process, making the Nadanhada Terrane better preserved. The third-stage deformation is represented by some late Early Cretaceous top-to-the SW thrusts, which is likely related to the closure of the Mongol-Okhotsk Ocean. The fourth-stage deformation is characterized by NE-trending thrust faults with some fault-related folds in the early Late Cretaceous, indicating another stage of intense northwestward subduction of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

Based on bathymetric data and multichannel seismic data, the Manila subduction system is divided into three segments, the North Luzon segment, the seamount chain segment and the West Luzon segment starts in Southwest Taiwan and runs as far as Mindoro. The volume variations of the accretionary prism, the forearc slope angle, taper angle variations support the segmentation of the Manila subduction system. The accretionary prism is composed of the outer wedge and the inner wedge separated by the slope break. The backstop structure and a 0.5–1 km thick subduction channel are interpreted in the seismic Line 973 located in the northeastern South China Sea. The clear décollement horizon reveals the oceanic sediment has been subducted beneath the accretionary prism. A number of splay faults occur in the active outer wedge. Taper angles vary from 8.0° ± 1° in the North Luzon segment, 9.9° ± 1° in the seamount segment to 11° ± 1° in the West Luzon segment. Based on variations between the taper angle and orthogonal convergence rates in the world continental margins and comparison between our results and the global compilation, different segments of the Manila subduction system fit well the global pattern. It suggests that subduction accretion dominates the north Luzon and seamount chain segment, but the steep slope indicates in the West Luzon segment and implies that tectonic erosion could dominate the West Luzon segment. [ABSTRACT FROM AUTHOR]

The Jurassic subduction of the Bangong-Nujiang Tethys Ocean is recognized as a significant event in the geotectonic evolution of Tibetan Plateau. This study focuses on the Mesozoic ophiolites, magmatic rocks, sedimentary strata, and metamorphic features, and discusses their relationship with the evolution of the Bangong-Nujiang Ocean. Two stages of Jurassic northward subduction are identified. The first stage is represented by the Early Jurassic subduction of the Amdo-Jiayuqiao subterrane. Slab break-off triggered the Middle-Late Jurassic exhumation of the subducted subterrane as well as the eclogite and high-pressure granulite. This process promoted the initiation of the second stage subduction at the southern margin of the South Qiangtang and Amdo-Jiayuqiao subterranes. For the western-central Bangong-Nujiang Ocean, we interpret the second stage as flat or shallow angle subduction and suggested that it was triggered by break-off of the subducted slab. The Bangong-Nujiang Tethys Ocean experienced southward ocean-continent and intra-oceanic subduction in the eastern and central-western segments, respectively, which are represented by the Shiquanhe-Yongzhu-Jiali mélange zone. The western and central-eastern segments of the Shiquanhe-Yongzhu-Jiali oceanic basin represented an immature to mature back-arc basin. The Bangong-Nujiang Ocean experienced a complex subduction evolution during Jurassic. Both northward and southward subduction zones were initiated during Late Triassic perhaps in response to the closure of the Paleo-Tethys oceans to the south and north. [ABSTRACT FROM AUTHOR]

How deep the two opposite dipping subduction zones in the vicinity of Taiwan, northwestward-dipping Philippine Sea Plate (PSP) and eastward-dipping South China Sea Slab (SCS), penetrated down into mantle, are hotly on debate and insufficiently imaged by seismic tomographic inversions, either due to inadequate quantities of seismic data or limited vertical resolution of the techniques used by previous investigations. Here we employ an unprecedented number of 55,847 high-quality P-to-S radial receiver functions recorded by 304 broadband seismic stations located in SE China and adjacent areas to image the topography of the mantle transition zone (MTZ) discontinuities (d410 and d660) to delineate the configurations of the subducted slab segments and analyze the impacts of thermal and water content anomalies on the MTZ. The close-to-normal wavespeed-corrected d410 and a ~ 10 km depression of the corrected d660 to the east of northern Taiwan are revealed, indicating that the PSP breaks off above the d410 and the delaminated PSP drops into the lower MTZ along with slab dehydration. To the east of southern Taiwan, where the SCS begins to subduct eastward, the uplift of the apparent d410 is nearly twice as much as that of the d660. The positive wavespeed anomaly above the d410 and low temperature in the vicinity of the d410 are enough to contribute to the uplift of MTZ discontinuities, suggesting that the SCS just reaches the d410, rather than penetrating the entire MTZ. • The MTZ discontinuities in Taiwan and its adjacent regions are imaged using receiver functions of unprecedented resolution • The geometry of subducted slab segments in the vicinity of the MTZ is constrained • The break-off Philippine Sea Plate drops into the lower mantle transition zone along with dehydration • The eastward-dipping South China Sea Slab penetrates the d410 [ABSTRACT FROM AUTHOR]

East Asia is exceptionally rich in diverse geological phenomena related to processes of major global significance in Earth history. Its tectonic evolution is closely related to the subduction of the Izanagi and Pacific plates and the India-Eurasia collision. Thus, this domain presents a vast natural laboratory within which some of the most topical and fundamental problems in Pacific-Asian Tectonics can be addressed. Recent breakthroughs in understanding the tectonic evolution of East Asia have been achieved, involving intraplate deformation, plate fragmentation, plate boundary processes, orogenic collapse, and craton destruction. These advances have been achieved via multidisciplinary work including structural geology, basin research, land and marine geophysics, thermochronology, numerical modeling, geochemistry and classical field geology. In the current context of research in East Asia the time is ripe for a thematic volume of review papers. This special issue is focused on the theme "Pacific-Asian Tectonics". It describes interdisciplinary methods adopted to study Meso-Cenozoic basin-forming mechanisms and evolutionary processes, unravels the timing and characteristics of major intraplate deformation, depicts the spatial-temporal distribution of Meso-Cenozoic igneous rocks, discusses the deep lithospheric structures overlying the subducting oceanic plates, and probes the natures and fates of subduction or collision processes. [ABSTRACT FROM AUTHOR]

Abstract: Since Mesozoic, the South China region has been located at the center of a triangular area surrounded by westward subduction of the Pacific plate, northward subduction of the India Plate beneath the Eurasia Plate, and collision of the North and South China blocks along the Central China Orogen. This region thus marks the frontier of a super-convergent regime. Within the super-convergence domain, the compressional structures in the center of the South China Block are mainly characterized by shortening, thrusting and decollement. The block underwent inhomogeneous rejuvenation of the pre-existing crust and lithospheric structures through reactivation of late-stage activities. The surface deformation of the Xuefeng Intracontinental Tectonic System within the South China Block is possibly derived from intraplate tectonics. Particularly, the distinct magmatism between the west and east limbs of the Xuefeng Precambrian Uplift is a possible response of the rheological structure of the lithosphere. The deep structures as revealed from tomographic studies show marked difference of lithosphere architecture between the eastern and western sub-blocks of the South China Block. These data illustrate the long-term mosaic of multi-block convergence which led to present-day inhomogeneity in the continental lithosphere in South China. A comparison of the intensive contraction of the South China Block with the distinct features of rifting of the North China Block, brings out the contrasting structural and tectonic signatures developed in the same frontier of one of the largest super-convergent systems on the globe during the Mesozoic to Cenozoic. [Copyright &y& Elsevier]

Abstract: The Trans-North China Orogen separates the North China Craton into two small continental blocks: the Eastern and Western Blocks. As one of the largest exposure in the central part of the orogen, the Hengshan–Wutai–Fuping Complexes consist of four lithotectonic units: the Wutai, Hengshan and Fuping Complexes and the Hutuo Group. The Hengshan Complex contains high pressure mafic granulites and retrograded eclogites. Structural analysis indicates that most of the rocks in these complexes underwent three distinct episodes of folding (D1 to D3) and two stages of ductile thrust shearing (STZ1 between D1 and D2 and STZ2 after D3). The D1 deformation formed penetrative axial planar foliations (S1), mineral stretching lineations (L1), and rarely-preserved small isoclinal folds (F1) in the Hengshan and Fuping Complexes. In the Wutai Complex, however, large-scale F1 recumbent folds with SW-vergence are displayed by sedimentary compositional layers. Penetrative transposition resulted in stacking of thrust sheets which are separated by ductile shear zones (STZ1). The kinematic indicators of STZ1 in the Hengshan and Wutai Complexes show top-to-the-S230°W thrusting likely related to northeastward, oblique pre-collisional subduction. D1 resulted in crustal thickening with resultant prograde peak metamorphism. The Hutuo Group did not undergo the D1 deformation, either because sedimentation was coeval with the D1 deformation or because it was at a high structural level and was not influenced directly by the early deformation. The D2 deformation produced NW-verging asymmetric and recumbent folds. The D2 deformation is interpreted to have resulted from collision between the Eastern and Western Blocks of the North China Craton. In the Hutuo Group and the Fuping Complex, the development of ESE-verging asymmetric tight folds is associated with D2. The structural pattern resulting from superimposition of D1 and D2 is a composite synform in the Hengshan–Wutai–Fuping Complexes. All four lithotectonic units were superposed during the later D3 deformation. The D3 deformation developed NW-trending open upright folds. Ongoing collision led to development of transpressional ductile shearing (STZ2), forming the transpressional Zhujiafang dextral ductile shear zone between the northern Hengshan Complex and the southern Hengshan Complex, and generating the sinistral Longquanguan ductile shear zone between the Fuping Complex and the Wutai Complex, respectively. The STZ1 and D2 deformation were possibly responsible for fast syn-collisional exhumation of the high pressure mafic granulites and retrograded eclogites. The structural patterns and elucidation of the deformation history of the Hengshan–Wutai–Fuping Complexes places important constraints on the tectonic model suggesting that an oceanic lithosphere between the Eastern and Western Blocks underwent northeastward-directed oblique subduction beneath the western margin of the Eastern Block, and that the final closure of this ocean led to collision between the two blocks to form the coherent basement of the North China Craton. [Copyright &y& Elsevier]

Abstract: In a recent issue of Precambrian Research (vol. 170, pp. 73–87), Wang (2009) published a paper entitled ‘Tectonic evolution of the Hengshan–Wutai–Fuping complexes and its implication for the Trans-North China Orogen, in which he proposes that (1) the formation of arc-related igneous rocks in the Hengshan and Wutai Complexes formed by northwest-directed subduction, not by (south)east-directed subduction; and (2) the Wutai granitoids were the products of an intra-oceanic island arc, not formed in a continent-derived arc. However, we consider both the structural and geochemical approaches Wang (2009) adopted to determine the polarity of the subduction and the tectonic setting of the Wutai granitoids are inappropriate or invalid. Firstly, all his structural observations used to determine the polarity of subduction are restricted to the Zhujiafang and Longquanguan ductitle shear zones, both of which developed at the late stage. It is unreliable to use kinematic indicators from these later structures to infer the polarity of the pre-collisional subduction. Secondly, Wang (2009) assumed that the initial positive ɛ(Nd) values (+0.5 to +4.5) of the Wutai granitoids indicate their generation directly from a mantle source, forming in an intra-oceanic arc. Such an interpretation is incorrect because the positive ɛ(Nd) values of the Wutai granitoids merely indicate that the igneous protoliths of these granitoids originated from a depleted mantle source, not the Wutai granitoids themselves. As the products of the earliest arc magmatism in the Wutai arc, the Wutai granitoids could not be generated directly from a mantle source but must have been derived by partial melting of juvenile crust. [Copyright &y& Elsevier]

A simplified micro-blocks convergence model and seismogenic zone of the SE Asia. • A model involving "micro-block" convergence is put forward to explain the trigger of earthquakes in Borneo. • Occurrence of earthquakes is sequentially dominated by the Coulomb stress transfer. • Tingjar Fault and Red River Fault are identified as the boundary between the Sunda Block and the Borneo 'micro-block'. Earthquake geohazards that occur throughout the Borneo Block, especially in SW Borneo, cannot be reconciled within the classical earthquake mechanism and a uniform stress field, and unfulfilled earthquake forecast for many years. In this paper, we present a new inventory of 37 Borneo earthquakes, and focal mechanisms show that in NE Borneo earthquakes and aftershocks are dominated by NW-trending normal faults, in East Borneo earthquakes are controlled by the reactivation of NW-trending sinistral strike-slip faults, and the NE-trending thrusts acted as the main seismogenic faults in the SE Borneo seismicity zone. We calculated the Coulomb stress and observed the shallow faults exhibiting a high coefficient response to the Coulomb stress change and all these earthquakes under the Coulomb failure regime have decreased by the stress shadows or are triggered by dynamic stress increase and propagation. We performed a research using the horizontal GPS velocity displacements and vertical seismic sections and found that the micro-blocks convergence occurred here corresponding to the Coulomb stress distribution, and can best explain the earthquake mechanism within the "Borneo Block". Additionally, the earthquakes in SW Borneo showing a concordant focal mechanism along the Red-River Fault-Tinjar Fault-Sumatra Trench, are deduced to have formed along the "Sunda Block" boundary. Finally, the micro-block boundaries determined from the heatflux map can be effective in describing the main and aftershocks distribution in SE Asia, and the deep-shallow coupling dynamic model is proposed to solve the stress loading for these crustal-scale earthquakes and the responses to plate convergence in SE Asia. [ABSTRACT FROM AUTHOR]

A Mesozoic Andean-type active continental margin is believed to have developed along the Southeast China continental margin, which has been investigated in detail. However, the architecture and evolution of its retroarc-arc-forearc system, which is important for us to understand the interaction or connection between continental and oceanic lithospheres, are ambiguous. Using multiple disciplinary data comprising seismic profiles, field observations and numerical paleo-topographies, this study synthetically focused on the Jurassic-Cretaceous evolution and geodynamics of the Andean-type Southeast China continental margin. Subduction of the paleo-Pacific Plate was initiated during the Early Jurassic (~200 Ma), generating a NNE-striking Jurassic magmatic arc along the East China Sea, bounded by imbricate thrust faults on both sides and coinciding with a paleo-topographic coastal mountain range. While the Jurassic arc erupted along an ENE-striking Triassic suture zone in the northern South China Sea, dominated by the Tethyan tectonic domain and overprinted by the Pacific tectonic domain. The Jurassic coastal mountain range began to collapse and transited into a rift basin at ~135 Ma and then the Andean-type continental margin gradually switched to the western Pacific-type during the Late Cretaceous (100–72 Ma), accompanied by Jurassic thrust faults inverting into Cretaceous detachment faults and magmatic arc migrated eastward to the Taiwan-Rukyu areas. Such eastward tectonic migration and transition is associated with the eastward retreat of the subducted paleo-Pacific slab. Then a regional latest Cretaceous (72–66 Ma) compression prevailed Southeast China, probably related to "ridge subduction" when the Pacific Plate replaced the paleo-Pacific Plate to subduct beneath East Asia. [ABSTRACT FROM AUTHOR]

The generation of erosive and accretionary margins has yet to be determined. Here, we explore the variations in the forearc structures of the New Guinea Trench (NGT) based on the latest high-quality multichannel seismic profiles perpendicular or subparallel to the New Guinea Trench axis. Our results reveal that for the domain of the oceanic crust subducted beneath the NGT (O-NGT), the thickness of the sedimentary strata decreases from the forearc sedimentary basin to the forearc slope. The basement is generally characterized by homogeneous intra-basement reflections, and few discontinuous, prominent layered reflections in the basement are identified. On the forearc slope, arcward-dipping fault-plane reflections have been identified within the basement, and an abrupt topographic decrease occurs in the eastern part of the forearc basement uplift. Widespread sedimentary sequences are identified as the present, transparent and horizontal seismic reflections with high continuities and low amplitudes. The sedimentary sequences show a large lateral variation of thickness and present folded features near the seaward-dipping faults due to the development of slump bodies. However, the sedimentary sequences in the forearc slope of the domain of the oceanic plateau subducted beneath the NGT (P-NGT) are obviously thicker than those of the O-NGT and present folded features. The stratigraphic thickness from the forearc sedimentary basin to the forearc slope clearly increases. Our initial results initially indicate that the NGT might constitute an internal reverse polarity subduction zone that changes from an erosive margin in the O-NGT to an accretionary margin in the P-NGT. • The domain of the oceanic crust subducted beneath the NGT (O-NGT) shows erosive margin features. • The domain of the oceanic plateau subducted beneath the NGT (P-NGT) shows accretionary margin features. • NGT constitutes an internal reverse polarity subduction zone that changes from an erosive margin to an accretionary margin. [ABSTRACT FROM AUTHOR]

We study the age of the subducting Pacific slab beneath East Asia using a high-resolution model of P-wave tomography and paleo-age data of ancient seafloor. Our results show that the lithosphere age of the subducting slab becomes younger from the Japan Trench (∼130 Ma) to the slab's western edge (∼90 Ma) beneath East China, and the flat (stagnant) slab in the mantle transition zone (MTZ) is the subducted Pacific plate rather than the proposed Izanagi plate which should have already collapsed into the lower mantle. The flat Pacific slab has been in the MTZ for no more than ∼10–20 million years, considerably less than the age of the big mantle wedge beneath East Asia (>110 million years). Hence, the present flat Pacific slab in the MTZ has contributed to the Cenozoic destruction of the East Asian continental lithosphere with extensive intraplate volcanism and back-arc spreading, whereas the destruction of the North China Craton during the Early Cretaceous (∼140–110 Ma) was caused by the subduction of the Izanagi (or the Paleo-Pacific) plate. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) is one of the huge accretionary orogenic belts on the earth. NE China in the eastern segment of CAOB consists of several blocks connected by the accretionary belts and suture zones. The subduction and accretion of the Paleo-Asian Ocean (PAO) during the late Paleozoic around the Jiamusi Block and Zhangguangcailing Terrane (ZGCT) has been a subject of debate in terms of location, polarity, and timing. Our study found that the western margin of the ZGCT developed Early Carboniferous felsic magmatism with ages of 356–334 Ma newly obtained by LA–ICP–MS zircon U Pb dating. These igneous rocks, including strongly peraluminous rhyolites and I-type granites and rhyolites, display geochemical characteristics of medium- to high-K calc-alkaline series, and most of them have positive ε Hf (t) values, indicating an active continental margin setting. On the other hand, the Early Carboniferous magmatism was absent in the Jiamusi Block. Therefore, we suggest there existed a branch of the PAO that extended north-south along the western margin of the ZGCT. The magmatism in the western margin of the ZGCT migrated eastward to the western Jiamusi Block during the Carboniferous, accompanied by an increase in the depth of magma source, indicating an eastward advancing subduction of the PAO. The latest Carboniferous–earliest Permian marked a period of tectonic regime transition, during which the eastward-subducting plate along the western margin of the ZGCT began to roll back, resulting in the formation of bimodal volcanic rocks and A-type rhyolites across the ZGCT with a slight westward younging trend. Simultaneously, the eastern margin of the Jiamusi Block started to be controlled by the westward advancing subduction of the Panthalassa plate. • A newly found Early Carboniferous magmatic arc in western Zhangguangcailing Terrane. • There developed an eastward subduction along the western Zhangguangcailing • Terrane. • Zhangguangcailing Terrane was the western margin of Jiamusi Block in late Paleozoic. [ABSTRACT FROM AUTHOR]