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The Cenozoic Qilian Shan thrust belt is the northern margin of the Tibetan Plateau, which developed in part due to progressive India-Asia convergence during Himalayan-Tibetan orogeny. Available geologic observations suggest that this thrust belt started deforming shortly after initial India-Asia collision at 60-55 Ma, and thus its kinematic development is intrinsically related to the construction and evolution of the Tibetan Plateau. Here, we present new field observations from a geologic traverse across the Qilian Shan to elucidate the style of deformation across the active thrust belt. In particular, we infer protracted out-of-sequence deformation here that is consistent with this thrust system remaining a stationary northern boundary to the Tibetan Plateau since the early Cenozoic. We present a lithosphere-scale model for this region that highlights the following: (1) coupled distributed crustal shortening and underthrusting of the North China craton beneath Tibet, which explains the spatial and temporal distribution of observed crustal shortening and thickness, (2) this underthrusting exploited the south-dipping early Paleozoic Qilian suture paleo-subduction melange channel, and (3) development of a lower-crustal duplex at the lithospheric underthrusting ramp. This last inference can explain the relatively high elevation, low relief, and thickened crust of the central Qilian Shan, as well as the comparative aseismicity of the region, which experiences fewer earthquakes due to less upper-crustal faulting. Both the northern and southern margins of the Himalayan-Tibetan orogen appear to have developed similarly, with continental underthrusting and crustal-scale imbrication and duplexing, despite vastly different climatic and plate-velocity boundary conditions, which suggests that the orogen-scale architecture of the thrust belt is controlled by neither of these forcing mechanisms. Instead, strength anisotropies of the crust probably control the kinematics and style of deformation, including the development of northern Tibet, where thrust systems are concentrated along pre-Cenozoic suture zones.

The present-day Tibetan plateau, which is the largest highland on Earth, formed primarily due to the India-Asia collision since 50-60 Ma. The development of the plateau has been associated with the Cenozoic development of two large intra-plateau sedimentary basins in north-central Tibet: the Qaidam and Hoh Xil basins to the north and south of the Eastern Kunlun Range, respectively. We conducted an integrated study of these two basins and the Eastern Kunlun Range that separates them to understand the timing and mechanisms of their development in order to decipher the growth and uplift history of the plateau. Crustal shortening in the Fenghuoshan-Nangqian and Qilian Shan-Nan Shan thrust belts initiated no later than the early Eocene, which formed the northern and southern boundaries of the combined Hoh Xil and Qaidam basins in central Tibet. The distinct two-stage development of the Hoh Xil basin suggests emergence of a topographic barrier between the Hoh Xil basin in the south and Qaidam basin in the north in the early Neogene, which is supported by the existing and new apatite fission-track data from the Eastern Kunlun Range that suggest rapid cooling after ca. 20 Ma. Previous and newly collected geochronological, petrological, and thermochronological data are best interpreted in the context of the Paleogene Paleo-Qaidam hypothesis, which requires Hoh Xil and Qaidam basins to have been parts of a single integrated basin during the early stage of the Cenozoic Tibetan plateau development.

South China, composed of the Yangtze and Cathaysia Blocks and the intervening Jiangnan orogenic belt, has been central to the debate on the tectonic evolution of East Asia. Here we investigate the crustal structure and composition of South China from seismic data employing the H-k stacking technique. Our results show that the composition and seismic structure of the crust in the Jiangnan orogenic belt are identical to those of the Cathaysia Block. Our data reveal a distinct contrast in the crustal structure and composition between the two flanks of the Jiujiang-Shitai buried fault. We propose that the Jiujiang-Shitai buried fault defines a geosuture between the Yangtze and Cathaysia Blocks and that the felsic lower crust of the Cathaysia Block and the Jiangnan orogenic belt may represent fragments derived from the Gondwana supercontinent.

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.

Fifteen sandstone samples taken from pre-Cretaceous strata of the Yangtze Block are analysed to constrain the evolution of the South China Block, especially the assembly between the Yangtze and Cathaysia blocks. The results show that the maximum depositional age of the Neoproterozoic Lengjiaxi Group adjacent to the Cathaysia Block is c. 830 Ma, differing from that of the Kunyang and Dahongshan groups (> 960 Ma) on the southwestern margin of the Yangtze Block. The detrital zircons from Palaeozoic samples from the Yangtze Block have similar age populations to those in the Cathaysia Block, and they may originate from the Cathaysia Block according to palaeogeographic, palaeocurrent and former research data. The detrital zircons of Middle-Upper Jurassic sandstones in the southwestern and central Yangtze Block yield dominant age populations at 2.0-1.7 Ga and subordinate groups of 2.6-2.4 Ga, 0.8-0.7 Ga and 0.6-0.4 Ga. The Upper Triassic strata may be derived from the southern Yangtze and North China blocks due to the collisions between the Indosina, South China and North China blocks, whereas the Jurassic sediments may be partly derived from uplift and erosion of the Jiangnan Orogen due to an intracontinental orogeny induced by Pacific subduction towards the Eurasia Plate. The detrital age spectra and provenance data for basement in the South China Block are analysed and compared with each other. The South China Block has affinity with Australia not only in the Columbia supercontinent but also in the Rodinia supercontinent. We infer the existence of an ancient orogen under the western Jiangnan Orogen, which may have occurred during the Columbia age, earlier than the Sibao orogeny. This is supported by seismic profile proof from the SinoProbe.

The northern Alxa area is the southernmost segment of the southern Central Asian Orogenic Belt. Its tectonic environment during the Middle–Late Devonian is debated: post-collisional or subduction settings. Here, we conducted a combined study associated with the geochemistry, geochronology, and zircon Hf isotope in Middle–Late Devonian (386–375 Ma) granodiorites from the northern Alxa area for understanding their petrogenesis and tectonic setting. Our results show that these granodiorites are peraluminous (ACNK = 1.08–1.12) and (high-potassium) calc-alkaline I-type granites. Moreover, they exhibit light rare-earth elements (LREEs) and large ion lithophile elements (LILEs) enrichment as well as depletions in Nb, Ta, and Ti. The εHf(t) values of these granodiorites could be divided into two groups: the granodiorites with ages of 385–380 Ma yield mostly positive εHf(t) values (+0.2–+5.1) with young two-stage model ages of 1.78–1.33 Ga and few negative εHf(t) values (from − 0.2 to – 9.9) with old two-stage model ages of 2.69–1.80 Ga, suggesting that they were derived from juvenile oceanic crust materials mixed with older continental materials. In contrast, the Late Devonian granodiorite (375 Ma) yielded radiogenic εHf(t) values between − 12.6 and − 2.1 with old two-stage model ages of 2.91–1.98 Ga, indicating its origination of the partial melting of ancient crustal materials. Combined with sedimentary evidences, coeval adakites, and arc-related volcanic rocks in the northern Alxa area and the adjacent South Beishan Orogenic Belt, implying the Zhusileng–Hangwula Tectonic Zone underwent a subduction setting during the Middle–Late Devonian and this subduction was possibly associated with the Enger Us Ophiolitic Belt.

As the southernmost part of the central segment of the Central Asian Orogenic Belt, the northern Alxa area is characterized by abundant Permian magmatism and records key information on the geological evolution of the Palaeo-Asian Ocean. This study reports new zircon U-Pb and Lu-Hf isotopic and whole-rock geochemical data of the early Permian (285-286 Ma) Huisentala gabbro and Huodonghaer diorites from the Zhusileng-Hangwula Belt in the northern Alxa area. The gabbro is characterized by high Al, Ca, Mg# and light rare-earth elements, and low K, P and high field strength elements (e.g., Ti, Nb and Ta). Furthermore, the gabbro shows heterogeneous zircon εHf(t) value (-2.5 to +2.6). The Huodonghaer diorites show high MgO (3.46-6.32 wt%), Mg# (49-58), Sr (408-617 ppm) and Ba (223-419 ppm), and low FeOT/MgO (1.27-1.83) and TiO2 (0.48-0.90 wt%), with geochemical features similar to the high-Mg andesite/diorite. They show radiogenic zircon εHf(t) values of +1.2 to +4.9 and high Th/Nb ratios. These features suggest that the Huisentala gabbro and the Huodonghaer diorites were derived from the partial melting of mantle peridotite that was metasomatized by subduction-related fluids and by subducted sediment-derived melts, respectively.

The Jinshan gold deposit, located on the southern flank of the Keguqin Mountains in the western Tianshan orogen, is a typical low-grade, large to super-large epithermal system within a continental volcanic terrain. Although its genesis is linked to Late Palaeozoic volcanic-intrusive activity, controversies over ore-controlling structures have constrained deep and peripheral exploration. Through detailed field and outcrop observations, this study identifies multiple Carboniferous palaeo-volcanic edifices (pipes, depressions, necks), overprinted by NS-trending normal faults and conjugate NNW- and NE-trending strike-slip faults. Mineralisation is shown to be jointly controlled by these volcanic edifices, regional fault systems and the unconformity between Ordovician limestone and Carboniferous volcanic-clastic rocks – termed the ‘silica-calcite interface’. A corresponding ore-controlling model highlights favourable exploration targets at this unconformity within structural intersections of subsidiary vents and regional/ring/radial fractures. Subsequent drilling not only confirmed high-grade, thick orebodies (e.g. 6 m @ 3.56 g/t, peak 56.3 g/t) in predicted areas but also revealed anticipated mineralisation types in unexplored zones south of the mine. The study provides a validated structural model for epithermal exploration in similar volcanic terrains worldwide.

Mountainous areas have become among the most developed areas of geological hazards due to special geological environmental conditions and intensive human engineering activities. Geological hazards are a main threat to urbanization, rural revitalization, and new rural construction in complex mountainous areas. It is of great strategic significance to conduct large-scale geological hazard investigation and risk assessment in urban areas, control the risk of geological hazards at the source and propose risk control measures. In this paper, we established the technical methods of geologic hazard risk assessment and control in complex mountain towns by taking Longlin Town in the mountainous region of Gansu Longnan, China as the study area, with the Quanjia bay debris flows and Panping Village landslides as the typical pilot investigation and assessment. The methods consist of six stages—risk identification, hazard disaster model investigation, risk analysis, vulnerability assessment, risk evaluation and risk management and control measures and proposals. On this basis, the results of geological hazards with different precipitation frequencies (5%, 2%, 1%) are presented. The results show that 75.23% of the regions remained at low risk levels; 24.38% of the regions increased a risk level with decreasing precipitation frequency, and 0.39% of the regions remained at extremely high risk levels under different precipitation frequency conditions. For the Quanjia bay debris flows and Panping Village landslides case, we discussed the geological hazards risk source control contents, management and control technologies, engineering and non-engineering measures of disaster prevention and control for urban disasters and specific disaster areas. This research can provide technical support and reference for disaster prevention and mitigation, and territorial spatial planning.

The Jurassic shale in the northeastern Sichuan Basin is one of the main target intervals for continental shale gas exploitation. Research on the pore structure and gas-bearing properties of shales is the key issue in target interval optimization. Through core observation, geochemistry, bulk minerals, scanning electron microscopy, nitrogen adsorption, and isothermal adsorption experiments, various lithofacies with different pore structure characteristics were clarified. In addition, the factors that control gas-bearing properties were discussed, and a continental shale gas enrichment model was finally established. The results show that the Jurassic continental shale in the northeastern Sichuan Basin can be classified into six lithofacies. Organic pores, intergranular pores, interlayer pores in clay minerals, intercrystalline pores in pyrite framboids, and dissolution pores can be observed in shale samples. Pore structures varied in different shale lithofacies. The contact angle of shales is commonly less than 45°, leading to complex wettability of pores in the shales. Free gas content is mainly controlled by the organic matter (OM) content and the brittleness in the Jurassic shale. The adsorbed gas content is mainly controlled by the OM content, clay mineral type, and water saturation of the shales. The enrichment mode of the Lower Jurassic continental shale gas in the northeastern Sichuan Basin is established. Paleoenvironments control the formation of organic-rich shales in the center part of lakes. The “baffle” layer helps the confinement and high pressure, and the complex syncline controls the preservation, forming the enrichment pattern of the complex syncline-central baffle layer.