Multistage Strike-Slip Fault in the Narrowest Portion of the Qinling Orogen, Central China: Deformation Mechanism and Tectonic Significance

The North Huicheng Basin strike-slip fault system is on the northeastern frontier of the Tibetan Plateau and separates the West and East Qinling differential orogeny. However, the deformation mechanism of this strike-slip fault system and its exact tectonic significance are unclear. Here, we carried out systematic field structural analysis, physical analog modeling, and multiproxy geochronological dating to address these issues. The field structural analysis indicates that the North Huicheng Basin strike-slip fault system was induced from the plate-like movement of the West and East Qinling Orogens, which underwent multiple left-lateral strike-slip faulting and controlled salient and recessed structures. The scaled physical analog experiment results confirm this hypothesis and reveal the primary spatial-temporal deformational kinematic process. Combined with published works, multiproxy geochronological dating (zircon U‒Pb age of 213 Ma, biotite 40Ar/39Ar age of 203 Ma, and apatite fission-track age of 56 Ma) outlines the main thermal history of the hanging wall. Based on the above facts, the integrated research suggests that multistage strike-slip faulting played a significant role in the main tectonic events, that is, late Triassic magmatic emplacement, Jurassic/Cretaceous local pull-apart, and Cenozoic rapid exhumation driven by Tibetan Plateau growth

Late Cenozoic Volcanism in the Hövsgöl Rift Basin: Source, Genesis, and Evolution of Intraplate Volcanism in Mongolia

Diffuse, intraplate volcanic deposits are prevalent throughout Mongolia. This study sought to examine Late Cenozoic lavas (9.5-17.1 Ma) from the Hövsgöl rift basin in order to better understand their source, genesis, and evolution. The relationship of these volcanic rocks to the Baikal Rift Zone (BRZ) and the extent to which these lavas are involved in, or derived from, rifting has important implications for lithospheric development of Mongolia and Central Asia. The alkaline basalts have similar light rare earth element enrichments (La/Yb = 9.1-31.9) and 87Sr/86Sr ratios in the range of .7039 to .7050. Major and trace element and isotopic data reveal that low degrees of partial melting of garnet lherzolite occurred at depths greater than 65 km. Enrichment in fluid-mobile elements (e.g. Sr and Ba), lower La/Nb ratios, and a calc-alkaline trend suggest that hydrous minerals may have contributed to the melt. Nb enrichment (>35 ppm), along with the melting of hydrous minerals, may be attributed to the melting of a metasomatically enriched lithospheric mantle source. The mixing of minor asthenospheric upwelling with a volatile-rich, metasomatized lithospheric mantle may have produced melts without requiring extremely elevated temperatures, consistent with other published studies that show a small, shallow thermal anomaly under Mongolia

Hot Cordilleran hinterland promoted lower crust mobility and decoupling of Laramide deformation

Raman spectroscopy of carbonaceous material thermometry. Compilation of temperature versus depth data across the Cordilleran hinterland

Supplemental Material: Metamorphic Core Complex Dichotomy in the North American Cordillera Explained by Buoyant Upwelling in Variably Thick Crust

 A synthesis of timing constraints for the North American Cordillera metamorphic core complexes, a brief discussion the Conjugate Shatsky Rise, details of zircon Hf compilation, and methods and results of numerical simulations.  </p

Linking source and sink: The timing of deposition of Paleogene syntectonic strata in Central Asia

International audienceDetermining the age of siliciclastic continental sequences in the absence of comprehensive biostratigraphy or radiometric dating of geological markers (e.g., volcanic layers) is inherently challenging. This issue is well exemplified in the current debate on the age of Cenozoic terrestrial strata in Central Asia, where competing age models constrained by non-unique paleomagnetic correlations are interpreted to reflect the growth of the Tibetan Plateau and its impact on Central Asian climate change. Here we present a new approach to evaluate competing age models by comparing the onset of rapid basement exhumation constrained by low-temperature thermochronology in the sediment source region with the initiation of growth strata in the adjacent sedimentary sink. We first validate this method in regions with well-constrained age models and subsequently apply this approach to the Tarim and Qaidam Basins in the northern Tibetan Plateau. The results of this analysis show that syntectonic sedimentation had already initiated during the Paleocene−Eocene and was followed by intensified Oligocene−Miocene mountain building along the northern margin of the plateau. Based on this refined Paleogene tectonic history, we further arrive at a temporal correlation between Paleogene tectonism in Northern Tibet and the retreat of the Proto-Paratethys Sea, a major water body that extended across Eurasia and was closely associated with climatic and biodiversity changes. We thus highlight the previously underestimated role tectonics in Northern Tibet had in the evolution and demise of the Proto-Paratethys Sea during the Paleogene

Paleoproterozoic Plate Tectonics Recorded in the Northern Margin Orogen, North China Craton

Abstract The occurrence of plate tectonic processes on Earth during the Paleoproterozoic is supported by ca. 2.2–1.8 Ga subduction‐collision orogens associated with the assembly of the Columbia‐Nuna supercontinent. Subsequent supercontinent breakup is evidence by global ca. 1.8–1.6 Ga large igneous provinces. The North China craton is notable for containing Paleoproterozoic orogens along its margins, herein named the Northern Margin orogen, yet the nature and timing of orogenic and extensional processes of these orogens and their role in the supercontinent cycle remain unclear. In this contribution, we present new field observations, U‐Pb zircon and baddeleyite geochronology dates, and major/trace‐element and isotope geochemical analyses from the northern margin of the North China craton that detail its Paleoproterozoic tectonic and magmatic history. Specifically, we record the occurrence of ca. 2.2–2.0 Ga magmatic arc rocks, ca. 1.9–1.88 Ga tectonic mélange and mylonitic shear zones, and folded lower Paleoproterozoic strata. These rocks were affected by ca. 1.9–1.8 Ga granulite‐facies metamorphism and ca. 1.87–1.78 Ga post‐collisional, extension‐related magmatism along the cratonal northern margin. We interpret that the generation and emplacement of these rocks, and the coupled metamorphic and magmatic processes, were related to oceanic subduction and subsequent continent‐continent collision during the Paleoproterozoic. The occurrence of ca. 1.77–1.73 Ga mafic dykes and ca. 1.75 Ga mylonitic shear zones along the northern margin of the North China craton may have been related to a regional mantle plume event. Our results are consistent with modern style plate tectonics, including oceanic subduction‐related plate convergence and continent‐continent collision, operating in the Paleoproterozoic

Controls of mantle subduction on crustal-level architecture of intraplate orogens, insights from sandbox modeling

Subduction of mantle lithosphere can initiate in the continental interior and acts as an important mechanism for intraplate orogeny. However, the associated kinematic response in the upper crust is still poorly resolved, hindering identification and investigation of mantle subduction during intraplate orogeny. Here we conducted sandbox experiments incorporating mantle-subduction-type and traditional indentation-type convergence to explore their difference in crustal-level orogenic architecture and deformation kinematics. We demonstrate that mantle-subduction-type convergence enhances orogen expansion above the subducting plate, whereas indentation-type convergence promotes deformation propagation toward the overriding plate. Such contrast leads to systematic variations in deformation sequence, structural style, and the first-order orogen geometry. We also show that changes of convergence mode leave distinct structural relics. Out-of-sequence faulting occurs when indentationtype convergence replaces the mantle-subduction-type mode. Conversely, the overprinting of mantle subduction on an earlier indentation mode triggers immediate in-sequence, foreland-propagating thrusting. Additionally, the influence of mantle-subduction-type convergence concentrates within the subducting plate when under a combined convergence involving opposite-direction indentation and mantle-subduction. This creates a special pattern of deformation localization comparable to the distribution of present-day seismicity and topography observed in the active Qilian Shan fold-thrust (northern Tibetan Plateau), confirming a bi-directional compression state during its recent evolution. Our modeling results can provide insights into the geodynamics of other intraplate orogens. (C) 2022 The Author(s). Published by Elsevier B.V

Geochronology and geochemistry of Neoproterozoic granitoids in the central Qilian Shan of northern Tibet: Reconstructing the amalgamation processes and tectonic history of Asia

Our understanding of the assembly history of Asia depends critically on the tectonic relationships between its major cratons, including Siberia, North China, South China, and Tarim. The intervening microcontinents between these cratons can provide insight into the paleogeographic and paleotectonic relationships of the cratons, but there is currently a general lack of knowledge regarding the basement geology of these microcontinents. Here we present results from systematic geologic mapping, U-Pb zircon dating, whole-rock geochemical analysis, and synthesis of existing data to establish the Proterozoic to early Paleozoic evolution of the central Qilian basement to the south of the North China craton in northwest China. Our results indicate that the region underwent three major periods of magmatic activity at 960-880, 877-710, and 550-375 Ma. Our geochemical analysis suggests that the ca. 900 Ma plutons were generated during arc magmatism and/or syncollisional crustal melting, whereas the ca. 820 Ma plutons are A-type granitoids, which are typically associated with extensional tectonism. Igneous zircons from a high-and ultrahigh-pressure eclogite in the north-central Qilian Shan have a U-Pb age of ca. 916 Ma, whereas dating of the recrystallized rims suggests that eclogite facies metamorphism occurred at ca. 485 Ma. Our detrital zircon geochronology also indicates that a widespread metasedimentary unit in the region was deposited between ca. 1200 and ca. 960 Ma, prior to the onset of a rift-drift event at ca. 750 Ma. Based on regional geologic constraints and the magmatic history, we propose the following tectonic history: (1) the paleo-Qilian Ocean bound the combined North Tarim-North China craton to the south (present-day coordinates) in the Mesoproterozoic(2) the paleo-Qilian Ocean closed between 900 and 820 Ma following the collision of North Tarim-North China craton and the South Tarim-Qaidam-Kunlun continent(3) the younger Qilian Ocean opened at ca. 775 Ma along the previous suture trace of the paleo-Qilian Ocean as a marginal sea within southern Laurasiaand (4) this ocean closed by ca. 445-440 Ma as a result of collision between the Tarim-North China cratons and the Qaidam-Kunlun continent along a south-dipping subduction system

Accommodation of India-Asia convergence via strike-slip faulting and block rotation in the Qilian Shan fold-thrust belt, northern margin of the Tibetan Plateau

Existing models of intracontinental deformation have focused on plate-like rigid body motion v. viscous-flow-like distributed deformation. To elucidate how plate convergence is accommodated by intracontinental strike-slip faulting and block rotation within a fold-thrust belt, we examine the Cenozoic structural framework of the central Qilian Shan of northeastern Tibet, where the NW-striking, right-slip Elashan and Riyueshan faults terminate at the WNW-striking, left-slip Haiyuan and Kunlun faults. Field- and satellite-based observations of discrete right-slip fault segments, releasing bends, horsetail termination splays and off-fault normal faulting suggest that the right-slip faults accommodate block rotation and distributed west-east crustal stretching between the Haiyuan and Kunlun faults. Luminescence dating of offset terrace risers along the Riyueshan fault yields a Quaternary slip rate of c. 1.1 mm a(-1), which is similar to previous estimates. By integrating our results with regional deformation constraints, we propose that the pattern of Cenozoic deformation in northeastern Tibet is compatible with west-east crustal stretching/lateral displacement, non-rigid off-fault deformation and broad clockwise rotation and bookshelf faulting, which together accommodate NE-SW India-Asia convergence. In this model, the faults represent strain localization that approximates continuum deformation during regional clockwise lithospheric flow against the rigid Eurasian continent. Supplementary material: Luminescence dating procedures and protocols is available at Thematic collection: This article is part of the Fold-and-thrust belts and associated basins collection available at