As a complex paleo-ocean located between the Tarim-North China and the Sibumasu/Baoshan blocks, the Proto-Tethys Ocean was opened from the rifting of the Supercontinent Rodinia and mainly closed at ...the end of the Early Paleozoic. The known studies suggest that there were many continents and/or micro-continents in the Proto-Tethys Ocean. During closure of the Proto-Tethys Ocean and assembly of these continents/micro-continents, some Early Paleozoic ophiolites and HP-UHP metamorphic rocks developed in East Asia similar to those Early Paleozoic orogens in Gondwana. However, some academic debates still remain on the boundaries of the Proto-Tethys Ocean and the nature, relationships and assembly processes of these continents/micro-continents to the Tarim-North China Continent to the north. These problems are important for revealing and reconstructing tectonic processes before the closure of the Proto-Tethys Ocean and the initial assembly of the Supercontinent Pangea. Not surprisingly, the Proto-Tethys tectonic domain is characterized by complex ocean-continent configurations, assemblies and dispersals of continents, from the rifting and drifting of the Supercontinent Rodinia to the assembly of the Supercontinent Pangea. Therefore, this paper mainly focuses on summarizing and discussing the northern part of the Proto-Tethys tectonic domain based on field geology, structural geology, magmatism, sedimentary formations, geochemical records, geochronology and tomography, in order to reveal three key aspects: 1) identifying the southern and northern boundaries of the Proto-Tethys Ocean; 2) establishing affinities of continents/micro-continents within the Proto-Tethys Ocean and its ocean-continent configuration; and 3) clarifying the temporal sequence and styles of micro-continental assembly and the closure of the Proto-Tethys Ocean. Integrated analysis results show that to the north the region is bounded by the paleo-Luonan-Luanchuan Suture (or Kuanping Suture) and its extension to West Kunlun; the southern boundary is marked by the Longmu Co-Shuanghu-Changning-Menglian Suture. The Tarim-Alax-North China Block to the north of the Proto-Tethys Ocean had a southward subduction polarity and collided with Gondwana along the northern margin of Gondwana in the Early Devonian. The southern branch of the Proto-Tethys Ocean may be closed, making the Greater South China Block, including the northern Qiangtang, Ruoergai, Yangtze and Cathaysia, Bureya-Jiamusi and Indochina blocks, southward subduction and accretion to the northern margin of Gondwana in the Early Devonian. The results also show that the North China Block had no clear affinity to Gondwana, whereas the other continental/micro-continental blocks, such as the Yangtze, Cathaysia, Tarim, Qaidam, Alax, North Qinling, Qilian, Oulongbuluke, South Qiangtang, Lhasa, Lanping-Simao and Indochina all have an affinity to Gondwana in the earlier part of the Early Paleozoic. During the interval 480–400Ma these series of continental blocks/micro-continental blocks experienced gradual southward subduction and accretion to the eastern segment of the northern margin of Gondwana, resulting in the closure of the Proto-Tethys Ocean and formation of the supercontinent called Proto-Pangea. The Greater South China Block and the Tarim-North China Block separated and drifted from Greater Gondwana of the Supercontinent Proto-Pangea since 380Ma, resulting in the formation of the Paleo-Tethys and the Mianlue oceanic crusts. After this minor adjustment and until 240–220Ma, they assembled northward gradually to develop Laurasia, which in turn resulted in the final formation of the Supercontinent Pangea.
The Mesozoic Western Pacific subduction system significantly impacted the North China and South China blocks along the East Asian continental margin and influenced the tectonic, magmatic, ...metallogenic and geomorphic evolution of the region. However, the dynamics and impact on the zone along the East Asian ocean-continent connection zone remain debated. Here we provide a comprehensive synthesis of the state-of-the-art information from deformation analysis, magmatism, geochronology, tomography and other fields from this region. We evaluate first the pre-Yanshanian (pre-Jurassic) final assembly of blocks and the Late Triassic formation of the unified continental margin in East China. We then focus on the Jurassic and Cretaceous geological processes in the East Asian ocean-continent connection zone. The temporal and spatial evolution of structural propagation, sedimentary depocentre, age zonation and migration of magmatism, as well as the large-scale tectono-morphological inversion in the Earth surface system combined with deep processes, are probed. In the early Yanshannian Period (Early and Middle Jurassic, 200–160 Ma), the destruction of the North China Craton (NCC) was mainly affected by the westward early-stage layered rollback, and stepwise delamination and thinning of its continental lithosphere, resulting in the early Yanshanian westward migration of tectonism and magmatism. Coevally, the combined effect of the closure of the Mongal-Okhotsk Ocean to the north and the subduction of the Bangong-Co- Nujiang Ocean to the south imparted an overall compressional setting in the East Asian Ocean-Continent Connection Zone (EAOCCZ). The centres of asthenospheric upwelling and mantle extrusion at depth continued to migrate eastward, driving the eastward lithospheric thinning with periodic and alternating extension and compression. The South China Block experienced a westward flat subduction during the early Yanshanian Period, resulting in the westward propagation of deformation and magmatism, followed by late two-stage delamination to induce the eastward tectono-magmatism. The difference in tectono-magmatic styles between the North China and South China blocks is a result of the different mechanisms and syles of the deep delamination processes under the superconvergence regime of the East Asian and adjacent plates. Especially delamination under North China generated the northwestward layered and fractured subcontinental lithospheric mantle, whereas under the eastern South China Block, were the oceanic lithospheric mantle of the Paleo- Pacific Plate that underwent flat subduction, or continental garnet peridotite mantle. In the middle Yanshanian Period (Late Jurassic to early Early Cretaceous, 160–125 Ma), the EAOCCZ underwent escape tectonics to form some basins related to strike slip faulting. Generally the extensional basins in the tails of the triangular-shaped escape blocks are perpendicular to the extrusion direction. The transtensional or transpressional basins are controlled by the strike slip faults distributed on both sides of the triangular block, and the flexural basins occur in front. In the late Yanshanian Period (late Early Cretaceous-Late Cretaceous, 125–65 Ma), the Paleo-Pacific (Izanagi) Plate subducted NNW-ward beneath the Eurasian continent, and the subduction angles changed gradually following eastward mantle extrusion induced by the closure of the Okhotsk Ocean to the north and Bangong-Nujiang Ocean to the south, as well as the rollback and subduction retreat of the Paleo-Pacific Plate to the east. The EAOCCZ gradually experienced lithospheric collapse and the formation of metamorphic core complexes, as well as obvious landscape reversal. During 70–45 Ma, the Izanagi-Pacific Ridge subducted beneath the EAOCCZ to induce wide uplift resulting in the formation of the Cenozoic dextral transtension-related basins.
Lithospheric subduction prior to the assembly of the South China and North China blocks is traditionally considered to be directed northward. However, some critical geological and geochemical data ...cannot be reconciled with this northward subduction. This paper presents new lines of evidence against the traditional models and proposes a new and revolutionary tectonic model to explain the distribution and exhumation of high pressure (HP)-ultrahigh pressure (UHP) metamorphic rocks of the Dabie-Sulu Belt. We emphasize the following: 1) The Triassic tectonic environment of the southern margin of the North China Block was passive, not active, based on the stratigraphy; 2) In the southern margin of the North China Block no arc magmatism was recorded. 3) Many Paleoproterozoic slices of Jiaobei affinity of the Jiao-Liao-Ji Belt in the North China Block were located in the Triassic Sulu Orogen. 4) Many 1.85Ga metamorphic zircons are preserved in the Dabie-Sulu high pressure-ultra-high pressure (HP-UHP) metamorphic rocks. 5) The geometric asymmetry of many structural patterns in the HP-UHP slices indicates top-to-the northwest thrusting during the exhumation of HP-UHP slices. 6) Blueschists occur in the south of the UHP eclogite slices. 7) In the eastern segment of the North Qinling Orogen, no components with an affinity of the South China Block have been found. Along the Shangdan Suture of the Qinling Orogen has been recorded an apparent northward subduction. We consider that the suture is just a lateral subduction zone rather than a major collisional zone. Along the Shangdan Suture, the rarity of I-type plutonism can be attributed to a transform-type continental margin. The Bureya-Jiamusi-Khanka Block has an affinity to the South China Block based on its similarity regarding the Paleozoic history of deformation and Triassic blueschist metamorphic facies metamorphism. The Bureya-Jiamusi-Khanka Block could be the northern extension of the Dabie-Sulu Belt, and this gigantic belt could be interpreted as an orocline related to the southeastward subduction of the North China Block beneath the Greater South China Block.
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.
► The southern segment of the Paleoproterozoic Jiao-Liao-Ji Belt underwent three distinct episodes of folding and two stage of ductile thrust shearing. ► The deformation developed at a period of ...about 1956Ma to 1875Ma. ► The syn-collisional extrusion and thrusting were possibly responsible for fast exhumation of the high pressure granulites. ► A southeastward-directed oblique subduction beneath the Rangrim Block led to collision between the two blocks.
The Paleoproterozoic Jiao-Liao-Ji Belt separates the Eastern Block of the North China Craton into two small sub-blocks: the northern Longgang and the southern Rangrim blocks. However, it still remains unknown or controversial about the subduction polarity, collisional deformation and kinematics between two sub-blocks. The southern segment of the belt consists of the Paleoproterozoic Fenzishan and Jingshan groups, and Paleoproterozoic high pressure mafic granulites and serpentinites blocks which are located in the Jiaodong Complex. All of which are separated from the Jiaodong Complex of Neoarchean TTG gneisses by STZ1 ductile shear zones. Structural analysis in this study indicates that most of the rocks in all the units of the southern segment of the Jiao-Liao-Ji Belt underwent three distinct episodes of folding (D1 to D3) and two stage of ductile thrust shearing (STZ1 coeval to D1 and D2, STZ2 between D2 and D3). The D1 deformation formed penetrative axial planar foliations (S1), bedding-parallel ductile shear zone, mineral stretching lineations (L1), and rarely preserved small isoclinal D1 folds in the Jingshan and Fenzishan groups. In the Jingshan Group, however, penetrative deformational transposition resulted in stacking of sedimentary compositional layers which are separated by bedding-parallel ductile shear zones (STZ1) at a period of about 1956Ma to 1914Ma. The kinematic indicators of STZ1 in the Jingshan Group with resultant prograde peak metamorphism up to granulite facies grade and the Fenzishan Group with peak metamorphism up to amphibolite facies grade indicate NW-directed compression. D2 resulted in crustal thickening with retrograded medium pressure granulite facies grade at about 1914–1893Ma. The D2 deformation produced NW-verging asymmetric and recumbent folds, interpreted to have resulted from basement-involved thicken-skin structures. The Jiaodong Complex was also involved into the development of WNW-verging asymmetric tight folds associated with D2 in the Jingshan and the Fenzishan groups. Ongoing collision led to the development of transpressional ductile shearing (STZ2), forming the transpressional Taipingzhuang dextral ductile shear zone between the Jingshan Group and the southern Archean Complex and the transpressional Tading-Xiadian sinistral ductile shear zone between the Jingshan Group and the northern Archean Complex. All three lithotectonic units were superposed during the late D3 deformation with amphibolite facies metamorphism. The D3 deformation developed WNW-trending open to tight upright folds at about 1893–1875Ma. The structural pattern resulting from superimposition of D2 and D3 is a composite synform in the Fenzishan and Jingshan groups. The structural events of D1 and STZ1, and D2 and STZ2 deformation were possibly responsible for fast syn-collisional exhumation of the high pressure mafic granulites. The structural patterns and deformational history of the Fenzishan and Jingshan groups suggest a southeastward-directed oblique subduction beneath the northwestern margin of the Rangrim Block, and that the final scissor-shaped closure of the rift led to collision between the two blocks to form the coherent basement of the Eastern Block of the North China Craton.
East China experienced alternating tectonic extension and compression with ambiguous tectonic settings in the Mesozoic-Cenozoic interval. Long-term extensional episodes associated with the subduction ...retreat of the Paleo-Pacific and Pacific slabs have been widely studied. The compressional events, of which basin inversion is a typical case, are less concerned, but important in understanding the tectonic evolution and geodynamics in East China. We made a systematic study, involving tectonics, sedimentation, apatite fission track, and dynamic topography, on the Mesozoic-Cenozoic basin inversion in East China. Four-phases of basin inversion were concluded: (1) Early-Late Cretaceous inversion occurred at 115-100 Ma in Southeast China and at 100-89 Ma in Northeast China, showing a northward migration due to the diachronous collision of the northward moving Okhotomorsk Block with East Asia. (2) The latest Cretaceous-Early Paleogene inversion was widely developed throughout East China. It is associated with the increasingly younger subducted oceanic crust of the Izanagi Plate, which caused the progressively increasing buoyancy beneath East China and an uplift in dynamic topography. Cenozoic inversion showed an eastward migration, from (3) the western part of each basin at the Late Paleogene to (4) the eastern part at the Neogene, due to the subduction retreat of the Pacific Plate.
Potential-field edge detection techniques are effective tools for identification of large-scale tectonic boundaries and geologic target bodies. Although a series of edge detectors have been ...developed, most of them suffer from a trade-off between edge resolution and noise immunity. To this end, we integrate multiple edge detectors such as normalized Harris filter (NHF) and ILTHG filter to propose a novel edge detector called ILGNH. The ILGNH edge detector takes advantage of both the enhanced noise immunity of NHF and the high resolution of ILTHG. Model experiments without/with noises both show that it is an alternative robust high-resolution edge detector. Afterwards, we apply this edge detection method to the Indo-China Peninsula and its adjacent areas to identify multi-phase tectonic boundaries. Combining the edge detection, residual crustal gravity anomalies (RCGA), and active faults, we identify four major NS transverse suture zones associated with microplates. These suture/boundary zones, together with deep faults, enclose 14 microplates with different interior feature of RCGA, while most of the boundaries are located in the gradient zones or the dislocation/distortion zones of the RCGA. Notably, inside the West Burma microplate, the ILGNH edge detection shows a distinct near NS-oriented arc-shaped deep boundary zone, which indicates that the underlying slab beneath the Indo-Burma Ranges was blocked during its eastward advance and shifted downward to form a high-angle deep subduction. Further, multi-scale edge detection at different depths confirms that the microplate boundary under the western Indo-China Peninsula vertically extends deeper than the eastern part. In addition, the seismicity below 50 km is concentrated to the west of the identified arc-shaped deep boundary zone and near the Naga-Kalaymyo-Arakan-Andaman Suture Zone.
•A new robust high-resolution potential-field edge detector is proposed.•Identification of NS transverse suture/boundary zones associated with 14 microplates.•Edge detection shows an arc-shaped deep boundary zone within the West Burma.•Differential seismicity to the east and west of the deep boundary zone.
► The Meso-Cenozoic basins in eastern China record structural processes of destruction of the North China Craton. ► Mesozoic shallow tectonism in eastern China is manifested by extrusion tectonics. ► ...The Mesozoic deep-seated tectonic processes are characterized by local delamination and magma underpalting.
Mesozoic basins occur widely in the Eastern Block and the neighboring area of the North China Craton, including the Bohai Bay, the Jiaolai, the Hefei and the North Yellow Sea in the north, and the Jianghan and the Subei-South Yellow Sea basins to the south. Their spatial–temporal framework is the consequence of the Indosinian and Yanshanian tectonic regimes in eastern China and record the events related to Mesozoic deconstruction of the North China Craton. Our results demonstrate that the Mesozoic tectonic evolution of the eastern North China Craton was related to both sub-crustal delamination and intra-crustal extrusion or escape tectonics. Thus, we propose that the mechanism of uplift of the Yanshanian North China Plateau and related lithosphere thinning in the eastern North China Craton were related to sub-crustal delamination at depth. However, the different distribution patterns of the basins on both sides of the Tan-Lu Fault System as well as the co-existence of both compressional and extensional basins in the Mesozoic indicate that these were controlled by escape tectonics in different tectonic parts of the crust.
The tectonic evolution history of the South China Sea (SCS) is important for understanding the interaction between the Pacific Tectonic Domain and the Tethyan Tectonic Domain, as well as the regional ...tectonics and geodynamics during the multi-plate convergence in the Cenozoic. Several Cenozoic basins formed in the northern margin of the SCS, which preserve the sedimentary tectonic records of the opening of the SCS. Due to the spatial non-uniformity among different basins, a systematic study on the various basins in the northern margin of the SCS constituting the Northern Cenozoic Basin Group (NCBG) is essential. Here we present results from a detailed evaluation of the spatial-temporal migration of the boundary faults and primary unconformities to unravel the mechanism of formation of the NCBG. The NCBG is composed of the Beibu Gulf Basin (BBGB), Qiongdongnan Basin (QDNB), Pearl River Mouth Basin (PRMB) and Taixinan Basin (TXNB). Based on seismic profiles and gravity-magnetic anomalies, we confirm that the NE-striking onshore boundary faults propagated into the northern margin of the SCS. Combining the fault slip rate, fault combination and a comparison of the unconformities in different basins, we identify NE-striking rift composed of two-stage rifting events in the NCBG: an early-stage rifting (from the Paleocene to the Early Oligocene) and a late-stage rifting (from the Late Eocene to the beginning of the Miocene). Spatially only the late-stage faults occurs in the western part of the NCBG (the BBGB, the QDNB and the western PRMB), but the early-stage rifting is distributed in the whole NCBG. Temporally, the early-stage rifting can be subdivided into three phases which show an eastward migration, resulting in the same trend of the primary unconformities and peak faulting within the NCBG. The late-stage rifting is subdivided into two phases, which took place simultaneously in different basins. The first and second phase of the early-stage rifting is related to back-arc extension of the Pacific subduction retreat system. The third phase of the early-stage rifting resulted from the joint effect of slab-pull force due to southward subduction of the proto-SCS and the back-arc extension of the Pacific subduction retreat system. In addition, the first phase of the late-stage faulting corresponds with the combined effect of the post-collision extension along the Red River Fault and slab-pull force of the proto-SCS subduction. The second phase of the late-stage faulting fits well with the sinistral faulting of the Red River Fault in response to the Indochina Block escape tectonics and the slab-pull force of the proto-SCS.
•NE-striking faults propagated from the South China Block into the NCBG.•Rifting is divided into three phases of early-stage and two phases of late-stage.•Early-stage rifting was younger eastward with diachronic features.•Late-stage rifting is synchronous with the slab-pull and activation of Red River Fault.
► Cenozoic structural patterns in the BBB resulted from normal faulting and transverse folding. ► The Cenozoic structures are controlled by stress, strain and Mesozoic basement structures. ► The NCC ...decratonization is related to an eastward jump of Cenozoic subduction of the Pacific Plate. ► The NCC decratonization is also the far-field effect of eastward extrusion of the Eurasia Plate.
The Cenozoic Bohai Bay Basin is located at the center of the Eastern Block of the North China Craton. The structural architecture of this basin provides important clues on the deep-seated lithosphere thinning of the North China Craton. The Cenozoic regional stress field is characterized by NW-oriented extension. However, the various Cenozoic structural patterns of normal faulting and related transverse folding in the Bohai Bay Basin are controlled not only by Cenozoic stress field, but also by strain field and Mesozoic basement fault assemblages in this area. Regionally, the Cenozoic tectonic features and the dynamic evolution of the eastern North China Craton are dominated by two lithosphere-penetrating fault systems including the sinistral Tan–Lu Fault System and the dextral Lan–Liao Fault System. To the west of the Lan–Liao Fault System, Cenozoic extensional tectonics includes NNE-trending listric normal faults that controlled half grabens. However, between these two fault systems are WNW-trending half grabens which show basement-involved faulting in the north and overlapping relations between sedimentary cover and basement in the south. To the east of the Tan–Lu fault, the North Yellow Sea Basin is a WNW-trending fault depression with faulting in the south and overlapping relations in the north. These structural features are inherited from the Mesozoic tectonic framework of this area, whose tectonic characteristics were completely controlled by two opposite strike-slipping faults, the trans-extensional or oblique rifting in the Paleogene, followed by extensional faulting and subsequent subsidence. Furthermore, the culmination of the decratonization of the North China Craton was also related to an eastward jump of Cenozoic subduction of the Pacific Plate and the far-field effect of eastward extrusion of Cenozoic subduction of the Indian Plate, and was not essentially restricted to the early Mesozoic processes. Therefore, the Cenozoic, especially ∼25Ma marks the time of cessation of the processes that led to lithosphere thinning and destruction of the Eastern Block of the North China Craton.
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