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.
Unsupervised feature selection is a dimensionality reduction method and has been widely used as an important and indispensable preprocessing step in many tasks. However, real‐world data are not only ...high‐dimensional, but also have intrinsic correlations between data points, which are not fully utilized in feature selection. Furthermore, real‐world data usually inevitably contain noise or outliers. In order to select features from data more effectively, a sparse regression model based on latent low‐rank representation with the symmetric constraint for unsupervised feature selection is proposed. With the coefficient matrix of non‐negative symmetric low‐rank representation, an affinity matrix characterized by the correlation relationship between data points is adaptively obtained, which reveals the intrinsic geometric relationship, global structure, and discrimination of data points. A latent representation of all data points obtained from this affinity matrix is employed as a pseudo‐label, and feature selection is carried out by sparse linear regression. This method performs feature selection in the learned latent space instead of the original data space. An alternating iteration algorithm is designed to solve the proposed model, and its effectiveness and efficiency are verified on several benchmark data sets.
An affinity matrix is adaptively obtained by the low‐rank self‐representation with symmetric constrain; Take the latent representation obtained from the affinity matrix as a pseudo‐label in the sparse linear regression model and perform feature selection in the learned latent space instead of the original data space; Provide an alternating iteration solver for the proposed model, and its effectiveness and efficiency are verified on several benchmark data sets.
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.
The East Asian continental margin straddles the boundary between the Pacific Subduction Domain to the east and the Tethyan Collision Domain to the west. The spatial and temporal interaction between ...these two dynamic domains induced a dextral trans-tensional stress field, generating nearly 75% of the globe's marginal seas and continental margin rifts during the Cenozoic. Among these, the South China Sea (SCS) and its northern margin are located in the core of the Pacific Subduction Domain and the Tethyan Collision Domain. The evolution of the SCS and its northern margin are of prime interest because of their spectacular magnetic lineations and strong rifting. In spite of the several investigations carried out on the Cenozoic marginal seas and rift basins, their formation mechanisms remain equivocal. Here we perform a comprehensive analysis of seismic profiles and fault architecture data with a view to understand the Cenozoic tectonic evolution of the northern margin of the SCS. Based on detailed structural analysis of the geometry and kinematics, we demonstrate that the NE- and ENE-striking faults assembled to horsetail- or feather-shaped structures in plan view, which display flower-like structures in seismic profiles. Two stages of faulting along NE-trending faults are identified along the northern margin of the SCS. The earlier oblique extension occurred during the Paleocene to the early Middle Eocene (~44–42 Ma), accompanied by strong rifting and formation of some left-step en echelon-like faults. The later trans-tensional faulting developed during the late Middle Eocene to the Early Miocene (~21 Ma), resulting in the formation of the dextral right-step trans-tensional fault system. Two stages of faulting were linked to the joint effect among the Indo-Eurasian collision to the west, the subduction of the Pacific Plate to the east and the slab pull of the proto-SCS to the south. Our study provides important insights into the dynamics and tectonics controlling the opening of the South China Sea. During the Late Eocene to the Oligocene, the dextral trans-extensional faulting along the right-step strike-slip fault system caused the opening of the Northwest Sub-basin, the East Sub-basin and the Northeast Sub-basin. However, during the Early Miocene, the sinistral strike slipping of the Ailao Shan-Red River (ASRR) shear zone and the slab-pull force of the proto-SCS resulted in the opening of the Southwest Sub-basin and the change of the spreading direction of the East Sub-basin.
Soil reconstruction is at the core of mine land reclamation. Reconstructed soil from an opencast mine dump in a loess area is a complex composite that was assembled by humans, using multiple ...reconstruction technologies. The soil is composed of varied soil particles with irregular shapes and has self-similar structure. To better quantify the characterization of reconstructed soil in this dump, the soil particle-size distribution from four modes of soil reconstruction in the Shanxi Pingshuo Antaibao opencast coal-mine dump was analyzed using multi-fractal theory. Soil reconstruction modes included loess material containing gravel (LG), loess material containing coal gangue (CG), total loess material (AL) and loess material containing ginger stone (LGS). Soil particle composition, gravel content, field water capacity, soil bulk density, soil organic matter, total nitrogen (TN), soil pH and electrical conductivity (EC) of different soil layers from different reconstruction modes were measured. A generalized dimension spectrum D(q), multi-fractal singularity exponent α(q) and multi-fractal spectrum function f(α(q)) were calculated. Relationships between soil properties and fractal parameters were analyzed. The results led to the following conclusions: (1) the soil particle distribution of reconstructed soil had significant multi-fractal characteristics in an opencast coal-mine dump in a loess area. D(0), D(1), D(1)/D(0), Δα and Δf can reflect the non-uniform particle-size distribution characteristics. D(0), D(1)/D(0) and Δf (or D(0), D(1)/D(0) and Δα) can be simplified as three parameters to quantify the multi-fractal characterization of the reconstructed soil particle distribution. (2) After reclamation, the soil quality from different layers of different profiles in different reconstruction modes shows some improvement. (3) There were strong correlations between multi-fractal parameters and soil properties. D(1) and Δα increased and D(1)/D(0) and Δf decreased with increasing gravel content, soil bulk density, organic matter, TN and soil EC; however, it was opposite for pH and field water capacity. Gangue and gravel have a definite impact on the dispersion degree of soil particles in reconstruction. This study provides a theoretical basis for land reclamation and quantitative expression of reconstructed soil particles’ distribution in opencast coal-mine dumps in loess areas.
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•Experiments reproduced the evolutionary process of tectonic inversion in the Xihu Sag.•Previous transtensional basin influenced the deformation of inversion basin.•Pacific subduction ...and Indian-Eurasian collision controlled the tectonic inversion.
The East China Sea Shelf Basin lies between the Pacific Subduction and Indian-Eurasian Collision tectonic domains and records Cenozoic tectonic inversion, especially in the Xihu Sag. To improve the understanding of the evolution and mechanism of tectonic inversion, this paper employs analogue modelling to reproduce the evolutionary process. Combined with the structural analysis of seismic profile, this paper determines the pattern of basement-involved faults. Simulation results show that under the transtension, two subsidence centers developed and a number of normal faults assembled in two flower structures. When the stress field turned into transpression, the geometry and deformation of inversion basin inherited the previous transtensional basin and pre-existing faults, respectively. The geometry and fault patterns in models are well consistent with those observed in the Xihu Sag, which indicates the plausibility of similar deformation controls. The formation of the tectonic inversion is related to the variation in stress field caused by the changes in the rates and directions of the subduction of the Pacific Plate and the collision of the Indian Plate with Eurasian Plate.
•The Late Palaeoproterozoic (∼1.93Ga) granulite facies metamorphism and anatexis.•Link with the assembly of supercontinent Columbia.•Similar early Precambrian evolutionary history to the TC.
The ...Oulongbuluke Block, which is located in the northeastern margin of the Tibet Plateau, has traditionally been considered to be a fragment of the Tarim Craton. Here we present a systematic petrologic, geochemical, and zircon U-Pb and Hf isotopic investigation on mafic granulite and migmatite in the Oulongbuluke Block. The mafic granulite is mainly composed of clinopyroxene, orthopyroxene, plagioclase, amphibole and quartz, with peak metamorphic P-T contions of 6.5–8.8kbar, 745–770°C. Macroscopic and microscopic observations provide strong evidence for in situ partial melting of the felsic gneiss involving breakdown of biotite within the Oulongbuluke Block. The Pl-rich leucosomes with positive Eu anomalies and higher Sr contents were generated as the early-formed feldspar cumulate, and the Kfs-rich pegmatite with negative Eu anomalies and lower Sr contents may represent percolating fractionated melt that was trapped during cooling. Zircon U–Pb dating and Hf isotopic analyses on the mafic granulite and migmatite of the Oulongbuluke Block reveal two distinct age populations: the early Paleoproterozoic (∼2.37Ga) and late Paleoproterozoic (1.93–1.92Ga). The ∼2.37Ga magmatic zircon cores of the migmatite have εHf(t) values between −4.3 and 0.4, with two-stage Hf model ages (TDMC) mainly between 2.82Ga and 3.05Ga. The age of 1.93–1.92Ga obtained from the mafic granulite and migmatite is interpreted as the age of Late Paleoproterozoic metamorphism and anatexis. Most of the 1.93–1.92Ga metamorphic and anatectic zircons have significantly lower 176Lu/177Hf ratios but higher 176Hf/177Hf (t) values than the inherited magmatic zircon cores, which demonstrates that both the zircon U–Pb and Lu–Hf isotope compositions were significantly reset during metamorphism and anatexis. The late Paleoproterozoic metamorphic and anatectic event coincided with global orogenic events that are recorded in many continental fragments, which suggests their link to the Columbia supercontinent.
The NE China region involves a complex accretionary belt formed by multiple stages of assembly of micro-blocks from the Paleozoic to Mesozoic, the tectonics of which provides important clues on the ...evolution of the East Asian continental margin. With a view to evaluating the micro-block evolution in NE China, we used gravity and magnetic methods to analyze the geophysical characteristics of the micro-blocks and their boundaries. Combining with regional geology, paleomagnetism and paleontology, we reconstructed the micro-block assembly history in the eastern Central Asian Orogenic Belt. Five Paleozoic to Mesozoic micro-blocks are recognized in NE China: the Erguna, Xing'an, Songnen, Jiamusi and Nadanhada, and their boundaries show significant differences in gravity and magnetic fields. The boundary between the Erguna Block (EB) and the Xing'an Block (XB) shows as a continuous tectonic line in the gravity field, whereas the one between the XB and the Songnen Block (SB) exhibits a rather discrete but strong magnetic anomaly belt. The boundary between the SB and the Jiamusi Block (JB) is characterized by both distinct gravity and magnetic anomalies. The Nadanhada Micro-block (NMB) appears as an independent micro-block in the fourth-order detail field of the Bouguer gravity anomaly, where it shows as a short axis or circinate structure in this anomaly field. The Paleozoic to Mesozoic tectonic evolution of these micro-blocks in NE China is closely related to five sutures in the eastern Central Asian Orogenic Belt. The Xinlin-Xiguitu Suture was first formed at ~500 Ma, leading to the assembly of the EB and the XB, the Heihe-Hegenshan Suture was formed at 320–290 Ma, marking the amalgamation of the XB and the SB, the Mudanjiang-Yilan Suture was formed at ~200 Ma, marking the collision of the JB and the SB. The Paleo-Asian Ocean closed during 250–230 Ma in a scissor style. The subduction of the Paleo-Pacific Ocean was initiated at ~200 Ma. Based on the deep structural architecture imaged from gravity and magnetic anomalies, we propose an evolutionary model of the micro-blocks in the NE China, which provides important insights into the tectonic evolution of the NE China region during the Paleozoic to Mesozoic.
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•Micro-block boundaries in NE China defined by gravity and magnetic anomalies•Paleozoic to Mesozoic evolutionary history of micro-blocks from breakup to assembly•Plate reconstruction of micro-blocks based on geophysical and paleomagnetic data
Crustal instability to induce the geohazards often results from both the internal tectonic dynamics and external sediment processes. Thus, the detailed geodynamics and kinematics of geohazards are ...important for understanding the tectonic evolutionary process and evaluating potential geohazards. This paper focuses on the active faults, submarine landslides, earthquakes as well as submarine canyons geomorphology description and kinetics explanation in the northern South China Sea (SCS) continental margin. Firstly, we have estimated the spatial extent, fault-plane geometry and faulting behaviors of the submarine active faults, such as the Littoral Fault Zone, based on cumulative deformation recorded by geophysical seismic reflections and geomorphic markers. We also analyzed the reactivation of preexisting structures, as well as the spatial and temporal distribution and migration of the submarine landslides and canyons. Then, several conceptual models and a comprehensive study of some of the different factors that contributed to the geohazard chain are conducted based on pre-existing theory and available literature. This review study indicates: (i) geohazards of different phases and geohazard chain are generally triggered by both early-phase tectonics-dominated and later-phase sedimentation-dominated processes; (ii) the fault geometric and stress segmentation may have played an important role in controlling on the uneven and asymmetric distribution of earthquakes and submarine canyons of the northern SCS, Especially, the ENE-striking preexisting Littoral Fault Zone is the major seismogenic structure along the Southchina coastline; (iii) the tectono-sedimentary coupling induced landslide and slope failure that has help to shape the modern coastal and slope geomorphology.
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