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Abstract High-pressure metamorphic rocks occur as distinct belts along subduction zones and collisional orogens or as isolated blocks within orogens or mélanges and represent continental materials that were subducted to deep depths and subsequently exhumed to the shallow crust. Understanding the burial and exhumation processes and the sizes and shapes of the high-pressure blocks is important for providing insight into global geodynamics and plate tectonic processes. The South Beishan orogen of northwestern China is notable for the exposure of early Paleozoic high-pressure (HP), eclogite-facies metamorphic rocks, yet the tectonism associated with the HP metamorphism and mechanism of exhumation are poorly understood despite being key to understanding the tectonic evolution of the larger Central Asian Orogenic System. To address this issue, we examined the geometries, kinematics, and overprinting relationships of structures and determined the temperatures and timings of deformation and metamorphism of the HP rocks of the South Beishan orogen. Geochronological results show that the South Beishan orogen contains ca. 1.55–1.35 Ga basement metamorphic rocks and ca. 970–866 Ma granitoids generated during a regional tectono-magmatic event. Ca. 500–450 Ma crustal thickening and HP metamorphism may have been related to regional contraction in the South Beishan orogen. Ca. 900–800 Ma protoliths experienced eclogite-facies metamorphism (~1.2–2.1 GPa and ~700–800 °C) in thickened lower crust. These HP rocks were subsequently exhumed after ca. 450 Ma to mid-crustal depths in the footwall of a regional detachment fault during southeast-northwest–oriented crustal extension, possibly as the result of rollback of a subducted oceanic slab. Prior to ca. 438 Ma, north-south–oriented contraction resulted in isoclinal folding of the detachment fault and HP rocks. Following this contractional phase in the middle Mesozoic, the South Beishan orogen experienced thrusting interpreted to be the response to the closure of the Tethyan and Paleo-Asian Ocean domains. This contractional phase was followed by late Mesozoic extension and subsequent surface erosion that controlled exhumation of the HP rocks. 

The Beishan orogen is part of the Neoproterozoic to early Mesozoic Central Asian Orogenic System in central Asia that exposes ophiolitic complexes, passive-margin strata, arc assemblages, and Precambrian basement rocks. To better constrain the tectonic evolution of the Beishan orogen, we conducted field mapping, U-Pb zircon dating, whole-rock geochemical analysis, and Sr-Nd isotopic analysis. The new results, when interpreted in the context of the known geological setting, show that the Beishan region had experienced five phases of arc magmatism at ca. 1450−1395 Ma, ca. 1071−867 Ma, ca. 542−395 Ma, ca. 468−212 Ma, and ca. 307−212 Ma. In order to explain the geological, geochemical, and geochronological data from the Beishan region, we present a tectonic model that involves the following five phases of deformation: (1) Proterozoic rifting that separated the North Beishan block from the Greater North China craton that led to the opening of the Beishan Ocean, (2) early Paleozoic north-dipping subduction (ca. 530−430 Ma) of the Beishan oceanic plate associated with back-arc extension followed by collision between the North and South Beishan microcontinental blocks, (3) northward slab rollback of the south-dipping subducting Paleo-Asian oceanic plate at ca. 450−440 Ma along the northern margin of the North Beishan block that led to the formation of a northward-younging extensional continental arc (ca. 470−280 Ma) associated with bimodal igneous activity, which indicates that the westward extension of the Solonker suture is located north of the Hongshishan-Pengboshan tectonic zone, (4) Late Carboniferous opening and Permian north-dipping subduction of the Liuyuan Ocean in the southern Beishan orogen, and (5) Mesozoic-Cenozoic intracontinental deformation induced by the final closure of the Paleo-Asian Ocean system in the north and the Tethyan Ocean system in the south. 

The present topography of the northern Tibetan Plateau is characterized by the northwest-trending Eastern Kunlun Range, Qaidam Basin, and Qilian Shan, which figure importantly into the evolution and mechanism of Tibetan plateau development during Cenozoic Indo-Asian convergence. Understanding the Cenozoic deformation history and the source-to-sink relationship through time has significant implications for deciphering the growth history of the northern Tibetan Plateau. Despite decades of study, the timing, pattern, and mechanisms of deformation across the northern Tibetan Plateau are still vigorously debated. The North Qaidam thrust belt, located between the Qaidam Basin and Qilian Shan thrust belt, provides a valuable record of Cenozoic deformation in the northern Tibetan Plateau. Here, we present the results of new geologic mapping, structural and sedimentology analysis, and apatite fission track thermochronology to constrain the Cenozoic evolution history and reconstruct the paleogeomorphology of the eastern domain of the North Qaidam thrust belt and its foreland, the Wulan Basin. Our analyses reveal the North Qaidam thrust belt experienced multi-phase exhumation since the Cretaceous. A period of Eocene localized thrust-related uplift of the North Qaidam thrust belt initiated shortly after India-Asia collision, and lower erosion rates in the Oligocene allowed the thrust belt to expand along-strike eastward. Local uplift shed sediments to the southwest, directly into the Qaidam Basin. Reactivation of the proximal thrust faults and initiation of the northwest-striking right-slip Elashan fault at ca. 15−10 Ma drove the final accelerated mid-Miocene cooling and denudation to the surface. This phase of deformation established the overall framework morphology of the northeastern margin of the Tibetan Plateau, including the overall structure of the basins and ranges. 

The Proterozoic−Phanerozoic tectonic evolution of the Qilian Shan, Qaidam Basin, and Eastern Kunlun Range was key to the construction of the Asian continent, and understanding the paleogeography of these regions is critical to reconstructing the ancient oceanic domains of central Asia. This issue is particularly important regarding the paleogeography of the North China-Tarim continent and South China craton, which have experienced significant late Neoproterozoic rifting and Phanerozoic deformation. In this study, we integrated new and existing geologic field observations and geochronology across northern Tibet to examine the tectonic evolution of the Qilian-Qaidam-Kunlun continent and its relationships with the North China-Tarim continent to the north and South China craton to the south. Our results show that subduction and subsequent collision between the Tarim-North China, Qilian-Qaidam-Kunlun, and South China continents occurred in the early Neoproterozoic. Late Neoproterozoic rifting opened the North Qilian, South Qilian, and Paleo-Kunlun oceans. Opening of the South Qilian and Paleo-Kunlun oceans followed the trace of an early Neoproterozoic suture. The opening of the Paleo-Kunlun Ocean (ca. 600 Ma) occurred later than the opening of the North and South Qilian oceans (ca. 740−730 Ma). Closure of the North Qilian and South Qilian oceans occurred in the Early Silurian (ca. 440 Ma), whereas the final consumption of the Paleo-Kunlun Ocean occurred in the Devonian (ca. 360 Ma). Northward subduction of the Neo-Kunlun oceanic lithosphere initiated at ca. 270 Ma, followed by slab rollback beginning at ca. 225 Ma evidenced in the South Qilian Shan and at ca. 194 Ma evidenced in the Eastern Kunlun Range. This tectonic evolution is supported by spatial trends in the timing of magmatism and paleo-crustal thickness across the Qilian-Qaidam-Kunlun continent. Lastly, we suggest that two Greater North China and South China continents, located along the southern margin of Laurasia, were separated in the early Neoproterozoic along the future Kunlun-Qinling-Dabie suture. 

The growth history and formation mechanisms of the Cenozoic Tibetan Plateau are the subject of an intense debate with important implications for understanding the kinematics and dynamics of large-scale intracontinental deformation. Better constraints on the uplift and deformation history across the northern plateau are necessary to address how the Tibetan Plateau was constructed. To this end, we present updated field observations coupled with low-temperature thermochronology from the Qaidam basin in the south to the Qilian Shan foreland in the north. Our results show that the region experienced a late Mesozoic cooling event that is interpreted as a result of tectonic deformation prior to the India-Asia collision. Our results also reveal the onset of renewed cooling in the Eocene in the Qilian Shan region along the northern margin of the Tibetan Plateau, which we interpret to indicate the timing of initial thrusting and plateau formation along the plateau margin. The interpreted Eocene thrusting in the Qilian Shan predates Cenozoic thrust belts to the south (e.g., the Eastern Kunlun Range), which supports out-of-sequence rather than northward-migrating thrust belt development. The early Cenozoic deformation exploited the south-dipping early Paleozoic Qilian suture zone as indicated by our field mapping and the existing geophysical data. In the Miocene, strike-slip faulting was initiated along segments of the older Paleozoic suture zones in northern Tibet, which led to the development of the Kunlun and Haiyuan left-slip transpressional systems. Late Miocene deformation and uplift of the Hexi corridor and Longshou Shan directly north of the Qilian Shan thrust belt represent the most recent phase of outward plateau growth. 

Abstract Although the Cenozoic Indo-Asian collision is largely responsible for the formation of the Tibetan plateau, the role of pre-Cenozoic structures in controlling the timing and development of Cenozoic deformation remains poorly understood. In this study we address this problem by conducting an integrated investigation in the northern foreland of the Tibetan plateau, north of the Qilian Shan-Nan Shan thrust belt, NW China. The work involves field mapping, U-Pb detrital-zircon dating of Cretaceous strata in the northern foreland of the Tibetan plateau, examination of growth-strata relationships, and construction and restoration of balanced cross sections. Our field mapping reveals multiple phases of deformation in the area since the Early Cretaceous, which was expressed by northwest-trending folding and northwest-striking thrusting that occurred in the early stages of the Early Cretaceous. The compressional event was followed immediately by extension and kinematically linked right-slip faulting in the later stage of the Early Cretaceous. The area underwent gentle northwest-trending folding since the late Miocene. We estimate the magnitude of the Early Cretaceous crustal shortening to be ~35%, which we interpret to have resulted from a far-field response to the collision between the Lhasa and the Qiangtang terranes in the south. We suggest that the subsequent extension in the Early Cretaceous was induced by orogenic collapse. U-Pb dating of detrital zircons, sourced from Lower Cretaceous sedimentary clasts from the north and the south, implies that the current foreland region of the Tibetan plateau was a topographic depression between two highland regions in the Early Cretaceous. Our work also shows that the Miocene strata in the foreland region of the northern Tibetan plateau was dominantly sourced from the north, which implies that the rise of the Qilian Shan did not impact the sediment dispersal in the current foreland region of the Tibetan plateau where this study was conducted.