Chiyang Liu’s research while affiliated with Northwest University and other places

Middle Triassic paleogeography is essential for the paleoclimate change and ecosystem recovery after the end-Permian mass extinction, but is highly debated in the Paleo-Tethys Ocean and North China Craton, eastern Pangaea. Here we report a detailed provenance fingerprinting dataset from Middle Triassic sediments across the North China Craton, Qinling and Songpan-Ganzi and identify the paleo-uplift in the northern North China Craton as a primary sediment source. We propose that a Middle Triassic transcontinental drainage system flowed from the northern North China Craton through the central Qinling into the eastern Paleo-Tethys Ocean along the gradually descending landform, challenging the suggestion that the North China Craton was a great endorheic basin. The finding of this study will provide a better understanding of Middle Triassic physiography and paleogeography of the North China Craton. Such heterogeneous paleotopography and transcontinental drainage played a critical role in the marine-terrestrial ecosystems of the eastern Pangaea.

The Ordos Basin is among China's largest petroliferous basins, with its southwestern part being a key exploration area. Prior studies indicated that the basin's internal structure was relatively simple, featuring minor developmental faults and primarily stratigraphic–lithologic reservoirs. However, recent research has identified numerous strike‐slip faults in the basin, and their relationship to oil and gas accumulations remains unclear. This study, using integrated interpretations of field outcrops, imaging logging and 3D seismic reflection data, clarifies the characteristics, morphology and formation mechanisms of multi‐period faults in the southwestern Ordos basin. Additionally, the study investigates the relationship between these faults and oil and gas accumulations. Results show that Mesozoic fractures in the southwestern basin are primarily NE‐ and NW‐trending. Seismic profiles reveal that these faults exhibit complex geometries, including upright structures in the Middle to Upper Triassic and floral structures in the Cretaceous. Coherence slices show that Lower Jurassic faults have linear structures NE‐ and NW‐trending, while Cretaceous faults exhibit parallel linear structures ENE‐trending. The study of fault displacement and morphology suggests two evolutionary patterns for Mesozoic faults in the basin: layered development and basement‐activated faulting. The widespread ENE‐ and NW‐trending faults represent a specific mode of tectonic stress transfer in stable cratonic areas with minimal basement fault influence. Conversely, some ENE‐trending faults are significantly influenced by basement activation during various geological periods, penetrating deeply into strata and exhibiting distinct segmentation on a planar scale. This differential fault development results in an uneven distribution of Jurassic oil and gas reservoirs. Significant accumulations of Jurassic oil and gas are found in the ENE‐trending tension–torsional strike‐slip sections, whereas many NW‐trending faults may negatively impact oil and gas reservoirs. This study elucidates the characteristics of Mesozoic faults in the southwestern Ordos Basin, offering valuable guidance for oil and gas exploration and development in the region.

The northern South China Sea (SCS) divergent margin developed on a heterogeneous crust that inherited the structures of the Mesozoic convergent margin. However, in the past, studies focused mainly on Cenozoic structures and neglected Mesozoic basement structures. On the basis of the latest high–resolution 3D seismic volumes, we first identify the fault features and evidence in the granite basement. We then identify three sets of Mesozoic fault systems in the northern SCS and discuss their properties and genesis. The NE–trending thrust system (Seismic Reflection 1), formed by forward compression, corresponds to the NW‐ward subduction of the palaeo‐Pacific plate; the NE–trending extensional system (Seismic Reflection 2 and small residual half‐grabens) is related to post‐orogenic extension caused by slab rollback and retreat of the palaeo‐Pacific plate; and the NNE–trending thrust system (Seismic Reflection 3) formed by a transpressional effect related to the palaeo‐Pacific plate and the Eurasian plate changed from the long‐term NW‐ward orthogonal convergence to a NNW‐ward oblique convergence. Finally, by combining previous results on the regional tectonic evolution of onshore and offshore South China, we establish a model for the late Mesozoic evolution of the northern SCS from the Andean‐type margins to the western Pacific‐type margins.

Stable intraplate cratonic blocks usually have less structural deformation and fewer earthquakes than other locations on Earth, but with strong compressional deformation around their periphery. Investigating how and why this different deformation occurred is beneficial for understanding why the cratonic block is so stable and how the intraplate in-plane stress is transmitted. In this work, we first investigated the structural deformation changes from the margin to the interior of the western Ordos block (one of the most tectonically stable areas in China) via seismic data. The results show abrupt structural deformation changes from the margin to the interior of the Ordos block in terms of the deformation strength (from strong to weak), structural orientation (high-angle oblique relationships), and kinematics (from compression to wrenching). Our investigation also shows that such phenomena are widespread in cratonic blocks worldwide. The abrupt changes are probably induced by special in-plane stress transfer inside the cratonic block: When far-field stress is transmitted into continental interiors from active plate margins, the weak belt around the cratonic block filters and accommodates the in-plane stress. Consequently, this decreases the stress, changes the stress direction, and transmits the in-plane stress along a shallower layer (probably less than 1500 m). Furthermore, the compressional stress from the plate margin is converted into shear stress within the cratonic block. This stress transmission manner makes reactivation of deep preexisting faults difficult under far-field horizontal plate-boundary stresses in the cratonic block without vertical forces from the mantle, guaranteeing long-term stability and low seismicity. This understanding can provide a new perspective for the interpretation of earthquakes in stable continental regions. It can also be applied to appraise the long-term stability of sites for the storage of CO2.

Saline giants are thick, regionally extensive marine evaporites composed primarily of gypsum (CaSO4·2H2O), anhydrite (CaSO4) and halite (NaCl) that crystallize from hypersaline solutions known as brine. Remarkably, though evaporites account for less than 2 % of the world’s sedimentary rocks, one-half of the largest oilfields are hosted by saline giants. Given possess a relatively low compressive strength and Young’s moduli, and a generally high Poisson’s ratio, evaporites therefore are susceptible to a change shape and plastic flow at low effective confining pressure. Therefore, basinwide saline giants are commonly preserved as halokinetic bodies (e.g., salt domes) or dissolution breccias, rather than bedded evaporites. Here, we report the discovery of a remarkably preserved ∼170-million-year-old marine evaporite succession more than 60 m thick in the Qiangtang basin in the hinterland of Tibetan Plateau. In consistency with typical epeiric platform evaporite successions dominated by thick CaSO4 beds intercalated with normal shallow marine carbonates, the thick anhydrites in the studied section are also both underlain and overlain with thick marine carbonate rocks, suggesting that depositional setting starts off shallow and remains shallow throughout the deposition of the evaporite sequence. Assuming a thickness of ca. 60 m and an average crustal shortening of 40 %, we estimate an evaporite volume of around 22,000 km3. Although that estimate is much less than that of the Gulf of Mexico basin (∼160 Ma), the largest saline giant in Earth’s history with 2,400,000 km3 of salt, it is at least comparable with the volume of the Alan Anhydrite in Arabia (∼180 Ma), the largest Early Jurassic saline giant with 20,000 km3 of evaporite. Therefore, the development of thick anhydrites in the Quemo Co Formation suggests that the Qiangtang basin seems to have been the largest Middle Jurassic saline giant yet discovered.

The Daihai Cenozoic intraplate basalts are distributed in the western North China Craton (NCC), which is a part of the Cenozoic volcanic province in eastern China, and they are all alkaline basalts. The fine-scale determination of their mantle source region properties, partial melting mechanisms, and petrogenesis can provide crucial information for exploring lithospheric destruction and thinning in the western NCC. 40Ar-39Ar dating of potassium feldspar grains from the Daihai alkaline basalts yielded plateau ages of 18.22 ± 1.84 Ma and 26.86 ± 0.72 Ma, indicating that the Daihai basalts underwent multiple eruptive cycles during the Late Oligocene-Middle Miocene. These basalts exhibit ocean island basalt (OIB)-like geochemical features and were subjected to negligible crustal contamination. Moreover, basaltic magmas underwent intense fractional crystallization of olivine and clinopyroxene. The geochemical differences in the Daihai basalts were controlled by partial melting. The Daihai basaltic magmas were composed of at least two types (type I-enriched mantle and prevalent mantle) of mantle end-members that partially melted and then mixed, and the lithology of the mantle source region was predominantly peridotite. Under enriched mantle conditions, the mixing of garnet lherzolite partial melts (<1%) and spinel lherzolite partial melts (2-5%) can reasonably explain the elemental variations characteristic of the Daihai basalts. Most importantly, the melting depth and lithospheric thickness of the Daihai basalts were < 70 km or even close to 50 km, implying that the western NCC underwent lithospheric destruction and thinning during the Cenozoic. However, these effects were spatially heterogeneous. The most plausible genetic mechanism for the generation of the Daihai basalts was the coupled effects of subduction of the Pacific slab and subduction–collision of the Indo–Eurasian Plate since the Oligocene. The mantle flows generated by these two events convected, blocked and triggered upwelling mantle flows at the eastern margin of the Ordos Block. The upwelling mantle flows resulted in frequent magmatism in the region.

The Yushuwan fault is located in the transition zone among the Yimeng uplift, Jinxi fold belt and Shanbei slope in the northeastern Ordos basin and marks the boundary between Palaeozoic and Mesozoic strata. According to the field geological survey and geophysical data, this study shows that the Yushuwan fault is a deep-cut northwest-southeast-oriented strike-slip basement fault. A total of 17 apatite and zircon fission track points show that the basin experienced several stages of uplift at 190 Ma, 150–170 Ma, 110–130 Ma, 60–80 Ma, and 20–40 Ma. The characteristics of the Yushuwan fault indicate that the northeastern part of the basin is not a simple slope but rather a step with a large drop. Therefore, in the area to the southwest of the Yushuwan fault, there should be high natural gas resource potential and good exploration prospects. The contour values of the magnetic anomaly on the southwestern side of the fault are high, and the contours are dense; in contrast, the contour values of the northwest magnetic anomaly are low, and the gradient is gentle. Therefore, the fault represents the eastern boundary of the Yimeng uplift, and restricts the eastward extent of the high magnetic anomaly zone in the Yimeng uplift area.