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The curvilinear ~ E-W structures of the southern Thomson Orogen are approximately orthogonal to the general ~ N-S structural trend of the Tasmanides of eastern Australia. The origin of these orogen-perpendicular structures and their implications to tectonic reconstructions of eastern Gondwana are not fully understood. Here we use geophysical data to unravel the geometry, kinematics and possible timing of major structures along the boundary between the Thomson Orogen and the southern Tasmanides (Delamerian and Lachlan orogens). Aeromagnetic data from the southern Thomson Orogen show WNW, E-W and/or ENE trending structural grains, corresponding to relatively long wavelength linear geophysical anomalies. Kinematic analyses indicate strike-slip and transpressional deformation along these geophysically defined faults. Structural relationships indicate that faulting took place during the Benambran (Late Ordovician to Middle Silurian) and Tabberabberan (late Early to Middle Devonian) orogenies. However, some of the described crustal-scale structures may have developed in the Cambrian during the Delamerian Orogeny. Interpretation of deep seismic data shows that the crust of the southern Thomson Orogen is substantially thicker than the Lachlan Orogen crust, which is separated from the Thomson Orogen by the north-dipping Olepoloko Fault. A major lithospheric-scale change across this boundary is also indicated by a contrast in seismic velocities. Together with evidence for the occurrence of Delamerian deformation in both the Koonenberry Belt and northeastern Thomson Orogen, and a significant contrast in the width of the northern Tasmanides versus the southern Tasmanides, it appears that the southern Thomson Orogen may represent the locus of orogen-perpendicular segmentation, which may have occurred in response to along-strike plate boundary variations. [ABSTRACT FROM AUTHOR]

Knowledge of the crustal structure is important for understanding the tectonic framework and geological evolution of southeastern China and adjacent areas. In this study, we integrated the datasets from the TAIGER (TAiwan Integrated GEodynamic Research) and ATSEE (Across Taiwan Strait Explosion Experiment) projects to resolve onshore-offshore deep crustal seismic profiles from the Wuyi-Yunkai orogen to the Taiwan orogen in southeastern China. Three seismic profiles were resolved, and the longest profile was 850 km. Unlike 2D and 3D first arrival travel-time tomography from previous studies, we used both refracted and reflected phases (Pg, Pn, PcP, and PmP) to model the crustal structures and the crustal reflectors. In total, data from 40 shots, 2 earthquakes, and approximately 1,950 stations were used; 15,612 arrivals were selected among three transects. Using these data, we determined the complex crustal evolution since the Paleozoic era , involving the closed Paleozoic rift basin in central Fujian, the Cenozoic extension due to the South China Sea opening beneath the coastline of southern Fujian, and the on-going collision of the Taiwan orogen. The shape of the Moho, which also reflects the crustal evolution, can be summarized as follows: ~ 30 km deep to the west of Fujian, deepening toward central Fujian (~ 35 km), becoming shallower toward the Taiwan Strait (~ 28 km), deepening again toward the mountain belt of Taiwan (~ 42 km), and becoming shallower toward the Pacific Ocean (~ 10 km). [ABSTRACT FROM AUTHOR]

Abstract: The Solonker suture zone is one of the most important tectonic boundaries in the southeastern part of the Central Asian Orogenic Belt (CAOB). An ~630km-long reflection seismic profile across this suture was recently completed by the Chinese SinoProbe Project. The processed seismic data show clear crustal structures and provide new constraints on the tectonic and crustal evolution models. The Moho is delineated as a relatively flat boundary between a strongly reflective lower crust and a transparent mantle at a depth of ~40–45km (~14.5s two-way travel time), which is in agreement with the refraction data recorded along the same profile. In a broad view, the profile images an orogen that appears bivergent with, and approximately centered on, the Solonker suture zone. The southern portion of this profile is dominated by a crustal-scale, cratonward propagating fold-and-thrust system that formed during the late Permian and Triassic through collision and subsequent convergence in a post-collisional stage. The major thrust faults are truncated by Mesozoic granitoid plutons in the upper crust and by the Moho at the base of the crust. This geometry suggests that the Moho was formed after the thrusting event. The northern portion of the profile, although partially obliterated by post-collisional magmatic bodies, shows major south-dipping folding and thrusting. Bands of layered reflectors immediately overlying the Moho are interpreted as basaltic sills derived from the mantle. Episodic mafic underplating may have occurred in this region, giving rise to post-collisional magmatic events and renewal of the Moho. A few mantle reflectors are also visible. The overall geometry of these mantle reflectors supports the tectonic models that the southern orogen (Manchurides) experienced south-directed subduction and the northern orogen (Altaids) underwent north-directed subduction prior to collision along the Solonker suture zone. [Copyright &y& Elsevier]

Laterally extensive belts of mélange characterize Phanerozoic convergent plate margins, but are rare in Archean terranes. We document a late Archean mélange in the Zanhuang Massif of the North China Craton (NCC). The Zanhuang mélange separates a passive margin to foreland basin sequence developed on the western edge of the Eastern Block of the NCC from an arc terrane consisting of trondhjemitic, tonalitic and granodioritic (TTG) gneisses in the Central Orogenic Belt (COB) of the NCC. The mélange belt contains a structurally complex tectonic mixture of metapelites, metapsammites, marbles and quartzites mixed with exotic tectonic blocks of ultramafic and metagabbroic rocks, metabasalts that locally include relict pillow structures, and TTG gneisses. All units in the mélange have been intruded by mafic dikes that were subsequently deformed, and are now preserved as garnet–amphibolite boudins. We interpret the mélange to mark the suture zone between the Eastern Block and the arc terrane in the COB. Field relationships and geochemistry suggest that the exotic ultramafic–metagabbroic–metabasaltic blocks are possible slivers of an intra-oceanic arc or fore-arc ophiolite incorporated into the mélange during the arc–continent collision process. A circa 2.5Ga granitic pluton intrudes the mélange and undeformed circa 2.5Ga pegmatites cut the mélange. Tectonic models for the evolution of the COB are varied, but include models that favor collision at 2.5Ga, 2.1Ga, and 1.8Ga. This work shows clearly, from field structural relationships and geochronology, that the first collision must have occurred prior to 2.5Ga, consistent with late Archean suturing of the western margin of the Eastern Block with an arc terrane (Fuping terrane) during an arc–continent collision. The presence of an Archean mélange with exotic blocks in a suture zone between an Archean arc and continental margin is clear evidence for the operation of plate tectonics at circa 2.5Ga. [ABSTRACT FROM AUTHOR]

Abstract: The Tongbai orogen is located in a key tectonic position linking the Qinling orogen to the west and the Dabie-Sulu orogen to the east. This orogen comprises a Paleozoic accretionary orogenic system in the north and a Permo–Triassic collisional orogenic system in the south; hence it may serve as an ideal place to unravel the tectonic evolution from the initial oceanic subduction/accretion to the final continental collision between the Sino-Korean and Yangtze cratons. U Pb zircon geochronology of metasedimentary and metaigneous rocks and geochemical characterization of metabasalts indicate a close genetic relationship between the individual tectonic units of the Paleozoic accretionary orogenic system: (1) the Kuanping Group as a Neoproterozoic-Ordovician subduction-accretion complex which received sediments from the Qinling microcontinent, (2) the Erlangping Group and Huanggang diorite-granodiorite complex as an Ordovician–Silurian island arc evolving from backarc basin, (3) the Qinling Group as a Precambrian microcontinent converted into continental arc during the Ordovician, (4) the Guishan Complex as a mixture of the Qinling continental arc and Devonian forearc sediments, and (5) the Nanwan Flysch as a Devonian forearc sequence deposited on the newly accreted active margin of the Sino-Korean craton. Consequently, the northern and southern boundaries of the Paleozoic accretionary orogenic system represent two sutures of the Qinling microcontinent with the Sino-Korean and Yangtze cratons. The new and previously published data reveal that the tectonic evolution of the Tongbai orogen involved a series of events from Ordovician–Early Silurian (ca. 490–440Ma) oceanic subduction and arc magmatism, Silurian–Early Devonian (ca. 440–400Ma) arc-continent collision, Carboniferous (ca. 340–310Ma) oceanic subduction and accretion, Late Permian–Triassic (ca. 260–200Ma) continental subduction and collision, to Cretaceous (ca. 140–90Ma) extension and lateral eastward extrusion. The entire accretionary orogenic processes until the final collision between the Sino-Korean and Yangtze cratons may have lasted more than 200Ma. [Copyright &y& Elsevier]

Abstract: In the last years, the deep crustal structure of the North-Western part of the Iberian Peninsula has been explored using teleseismic receiver function (RF) analysis of P to S conversions at main crustal interfaces. This area has been previously investigated by seismic reflection and refraction experiments and therefore provides an excellent opportunity to compare the results of both approaches. The region shows the imprint of two orogenic events, the Variscan and Alpine ones that exhibit different, reverse intensities from west to east. In a first stage, a N–S transect across the Cantabrian Mountains was instrumented to study the area affected by the Alpine compressional tectonics. Later on, the limit between the undisturbed Variscan units and the reworked Alpine zones was explored by N–S and E–W transects. Finally, an array was deployed in the NW edge of Iberia, over the Variscan hinterland zone. The receiver functions are calculated by inverse filtering deconvolution of the L component from the Q component, and the resulting RF are processed using a simple form of migration to obtain images in depth of the lithosphere that can be compared to the 2-D velocity–depth models from active seismic experiments. The deep crustal structure constrained by both techniques is remarkably consistent, and provides further evidence on the crustal doubling and wedging between the Iberian and European crusts throughout the northern part of the Iberian Peninsula affected by the Alpine tectonics. The undisturbed Variscan domains, characterized by a clear subhorizontal Moho and few intracrustal convertors, show up at the southern edge of the N–S transects (southward of the Alpine deformation front) and over the Variscan hinterland in the E–W transect. The crust resulting from Alpine reworking presents a complex structure, with short and frequently dipping convertors, which in some cases seem to image preserved Variscan structures. [Copyright &y& Elsevier]