The Paleo-Pacific Plate stagnated in the mantle transition zone beneath northeast Asia during the Late Mesozoic, resulting in the eastern Asian big mantle wedge (BMW). However, its formation mechanism remains unclear. Here, we analyzed elemental and isotopic compositions of 126–60 Ma intraplate basaltic rocks to map the mantle flow pattern and investigate the implications for the formation of the BMW. These rocks exhibit eastward an increase in Ba/Nb, Ba/La, ⁸⁷Sr/⁸⁶Sr, and ²⁰⁸Pb/²⁰⁴Pb ratios, while a decrease in Nb/Yb, Zr/Yb, Ta/Yb, and Nb/Nb^* ratios, indicating mixing between the fertile mantle and the depleted mantle modified by slab material, implying the occurrence of trench-perpendicular mantle flow. The coeval mantle flow and formation of the BMW, the similar directions of mantle flow and Paleo-Pacific Plate subduction, and migration of basin depocenters indicate trench-perpendicular mantle flow was a key factor in the formation of the BMW. Moreover, these basaltic rocks have elevated δ⁶⁶Zn values (0.22‰ to 0.52‰), indicating recycled carbonates have been added into their mantle source, which increased the mantle flow velocity. Combined with slab roll-back in the Late Mesozoic, it created the essential conditions for mantle flow to promote the formation of the eastern Asian BMW.

The mechanism of continental crust growth remains ambiguous. A key constraint is determining which tectonic settings were involved in the formation of the new continental crust. Because the basalts formed in intraplate (OIB, mean U/Pb = ~0.37 ± 0.11) and subduction (IAB, mean U/Pb = ~0.10 ± 0.06) settings have distinct U/Pb ratios, thus we back-calculate the present-day U/Pb ratios of the New Continental crust source [(U/Pb)_nc] based on our zircon-Hf and published whole rock-Pb isotope compositions of the Wulaga Ⅰ-type granite to unfold the mechanism of the crust growth in the Lesser Xing'an Range (LXR), of the eastern Central Asian orogenic belt (CAOB). The Wulaga granodiorite porphyry yields zircon U-Pb ages of 103 ± 1 Ma with ε_Hf(t) of +6.0 to +9.0 and T_DM2 of 590 to 784 Ma (averaging at 709 ± 100 Ma). This result indicates that the Early Cretaceous Wulaga granodiorite porphyry was derived from the Neoproterozoic juvenile basaltic crust. The back-calculated (U/Pb)_nc values (0.15–0.18) may approximately represent the U/Pb ratios of the basaltic protolith of the Wulaga granite. It is similar to the U/Pb ratios in the IAB magmas within the calculation errors. Therefore, the crust growth of the LXR may occur through subduction at ca. 700 Ma. In addition, this geochemical method also has been successfully applied to unfold the mechanism of the crust accretion of both the Jibei area in North China at ca. 2.0 Ga and the Hongol area in the eastern CAOB during ca. 1.1–0.8 Ga. The back-calculation of the present U/Pb ratio of the protolith of Ⅰ-type granites in this study may constitute a potential method to constrain the mechanism of continental crustal accretion.

Riedel shear system, which consists of some different oriented faults and derivative structures, is an important pattern of tectonic activity and stress regulation, which has been widely applied to the interpretation of intracontinental deformation. The Laolongwan Basin, located in the western Haiyuan fault zone at the northeastern Tibetan Plateau, is a key area to study the Cenozoic intracontinental deformation in the northeastern plateau, which formed a complex active fault system during the Cenozoic. However, the activity of these faults and their kinematic mechanism remain unclear. In this contribution, based on detailed structural interpretation of remote sensing image, field observations and OSL dating analysis, we propose a Riedel Shear model of active fault system in the Laolongwan Basin. Our observations show that this active fault system consist of four major faults, including the left strike-slip Hasi Shan fault and Zihong Shan fault with thrusting characteristics, the Southern Zihong Shan thrust fault and the Mijia Shan normal fault. The fault offset and OSL dating analyses suggest that the left-lateral slip rate of the Hasi Shan fault is ~2.60–3.01 mm/a since ca. 15 ka, whereas the Zihong Shan fault is ~1.10–1.13 mm/a since ca. 14 ka. Fault-slip vectors analyses indicate that the active fault system related to the Riedel Shear in the Laolongwan Basin was controlled by the regional ENE-WSW compressive stress. This compression also caused the significant left-lateral strike-slip movement along the Haiyuan fault zone at the same time, which might result from the northeastward continuous expanding of the Tibetan Plateau during the Late Cenozoic.

A DFN-DEC (discrete fracture network-distinct element code) method based on the MATLAB platform is developed to generate heterogeneous DFN. Subsequently, the effects of the spatial variability (the mean $ \mu $ and the standard deviation $ \sigma $) of the geometric properties (i.e., the fracture dip D, the trace length T and the spacing S) of both the gently-dipping (denoted with 1) and the steeply-dipping (denoted with 2) fractures on the stability of granite slope are investigated. Results indicate that the proposed DFN-DEC method is robust, generating fracture networks that resemble reality. In addition, the spatial variability of fracture geometry, influencing the structure of granite slope, plays a significant role in slope stability. The mean stability of the slope decreases with the increase of $ {\mu }_{{\mathrm{D}}_{1}} $ (the mean of gently-dipping fracture dip), $ {\sigma }_{{\mathrm{D}}_{2}} $ (the mean of steeply-dipping fracture dip), $ {\mu }_{{\mathrm{T}}_{1}} $ (the mean of gently-dipping fracture trace length), $ {\mu }_{{\mathrm{T}}_{2}} $ (the mean of steeply-dipping fracture trace length), $ {\sigma }_{{\mathrm{T}}_{1}} $ (the standard deviation of gently-dipping fracture trace length), $ {\sigma }_{{\mathrm{T}}_{2}} $ (the standard deviation of steeply-dipping fracture trace length), and the decrease of $ {\sigma }_{{\mathrm{D}}_{1}} $ (the standard deviation of gently-dipping fracture dip), $ {\mu }_{{\mathrm{D}}_{2}} $ (the standard deviation of steeply-dipping fracture dip), $ {\mu }_{{\mathrm{S}}_{1}} $ (the mean of gently-dipping fracture spacing) and $ {\mu }_{{\mathrm{S}}_{2}} $ (the mean of steeply-dipping fracture spacing). Among them, $ {\mu }_{{\mathrm{T}}_{1}} $, $ {\mu }_{{\mathrm{D}}_{1}} $ and $ {\mu }_{{\mathrm{S}}_{1}} $ have the major impact. When the fracture spacing is large, the variability in the fracture geometry becomes less relevant to slope stability. When within some ranges of the fracture spacing, the spatial varying of dips can increase the slope stability by forming an interlaced structure. The results also show that the effects of the variability of trace length on slope stability depend on the variability of dip. These findings highlight the importance of spatial variability in the geometry of fractures to rock slope stability analysis.

The reservoir landslide undergoes periodic saturation-drying cycles affected by reservoir fluctuation in hydropower project area, leading to the irreversible impact on the landslide materials. Sliding zone is the shearing part in formation of landslide and controls the further development of landslide. The mechanical behavior of sliding zone soil under compression is a crucial factor in the stability analysis in landslides. In this paper, the sliding zone soil from a giant landslide in the biggest hydropower project area, Three Gorges Reservoir Area, is taken as the research case. The particle-size distribution of the sliding zone soil from this landslide is studied and fractal dimension is adopted as representation. Periodic saturation-drying is introduced as the affecting factor on sliding zone soil properties. The triaxial compression test is conducted to reveal the mechanical behavior of the soil, including stress-strain behavior, elastic modulus, failure stress and strength parameters. These behavior of sliding zone soils with different fractal dimensions are studied under the effects of periodic saturation-drying cycles. The normalized stress-strain curves are displayed for further calculation. The data considering saturation-drying cycles are obtained and compared with the experimental results.

The rock masses in the hydro-fluctuation zone of reservoir banks sustain wetting-drying cycles (WDC), thereby affecting the stability of the reservoir bank slope. In this paper, rock masses with argillaceous siltstone and silty mudstone interbedded in Badong Formation were taken as the research object to investigate the variation of strength parameters of soft and hard interbedded rock masses with WDC and dip angle through laboratory experiments and numerical experiments. Some attempts were made to reveal the mechanical properties deterioration mechanism of interbedded rock masses by quantitatively analyzing the contribution of strength parameters deterioration of hard rocks, soft rocks, and bedding planes to the strength parameters deterioration of rock masses. The results indicate that the logarithmic function could be used to describe the deterioration of each strength parameter of both argillaceous siltstone and silty mudstone and bedding plane with the number of WDC. The strength parameters of interbedded rock masses decrease as the number of WDC increases, with the largest decrease after the first cycle and then slowing down in the later cycles. The strength parameters initially decrease and then increase as the dip angles increase. The impact of deteriorated strength parameters of bedding planes and rocks on the deterioration of strength parameters of interbedded rock masses differs significantly with the dip angle, which can be divided into four typical ranges of different controlling factors.

Granite residual soil slope is often destroyed, which poses great threats to Rong County in southeastern Guangxi, China. Heavy rainfall and fissures are the major triggering and internal factors. The fissure that controls the slope stability and the associated failure mechanisms remain unclear. The purpose of this study was to identify the controlling fissures through field investigation, elucidate the effect of its position, and analyze the failure process and hydrological response of residual soil slope through artificial flume model tests. The results comprised five aspects. (1) Surface weathering and unloading fissures could affect slope stability. (2) The failure processes with different fissure positions exhibited inconsistent characteristics. (3) The volume moisture content (VMC) had the most direct response at the fissure tip. The corresponding infiltration rate was the highest. The response time of pore water pressure (PWP) was longer than that of VMC. Fluctuations in PWP were associated with VMC and changes in the soil microstructure due to local deformation. (4) Slope failure was accompanied by serious soil erosion. This could be attributed to the infiltration direction and the interaction between soil and water. (5) Fissured soil slopes experienced five similar failure processes: sheet erosion and partial failure of the slope foot, occurrence of preferential flow and enlargement of the sliding area, creep deformation and tension fissure emergence, block sliding and gully erosion, and flow-slip.

The soil arching effect is an important factor affecting the internal load transfer of excavation-induced slopes. Physical model tests are usually used for studying the soil arching effect. Although physical model tests can monitor local point loads to demonstrate changes in local stresses, changes in force chains inside slopes are rarely demonstrated by physical modelling, which restricts the understanding of load transfer. To explore overall changes in stresses in slopes from a more microscopic perspective, a numerical simulation of the slope under excavation was carried out. Using built-in code and fish function programming in PFC^3D, the slope model was developed. Monitoring areas were set up to monitor the changes in stresses and force chains during excavation. The simulation results show that excavation width affects the size of deformation area, and the deformation area expands as excavation width increases. Excavation causes load transfer and the formation of soil arching in the slope. A mechanism is proposed to explain the effect of excavation on soil arching formation and load transfer. The numerical simulation is important for revealing the load transfer of slopes during excavation, and the research results have practical value for the prevention and mitigation of landslides caused by excavation.

In the physical model test of landslides, the selection of analogous materials is the key, and it is difficult to consider the similarity of mechanical properties and seepage performance at the same time. To develop a model material suitable for analysing the deformation and failure of reservoir landslides, based on the existing research foundation of analogous materials, 5 materials and 5 physical-mechanical parameters were selected to design an orthogonal test. The factor sensitivity of each component ratio and its influence on the physical-mechanical indices were studied by range analysis and stepwise regression analysis, and the proportioning method was determined. Finally, the model material was developed, and a model test was carried out considering Huangtupo as the prototype application. The results showed that (1) the model material composed of sand, barite powder, glass beads, clay, and bentonite had a wide distribution of physical-mechanical parameters, which could be applied to model tests under different conditions; (2) the physical-mechanical parameters of analogous materials matched the application prototype; and (3) the mechanical properties and seepage performance of the model material sample met the requirements of reservoir landslide model tests, which could be used to simulate landslide evolution and analyse the deformation process.

Active tectonic movements and geological disasters frequently occur in the upper reaches of the Jinsha River, increasing the likelihood of landslides obstructing the river. Taking the ancient Rongcharong landslide dam failure events in the Suwalong reach as an example, this paper first analyzes the accuracy and applicability of the commonly used methods in calculating the peak flow of the dam failure, such as the empirical formula, the numerical method based on the physical mechanism, and the computational fluid dynamics (CFD) method. Then, the peak flood flow of the Rongcharong-dammed lake when it overflows the dam is determined to be 28 393-64 272 m³/s. At the same time, the failure process of landslide dam due to flood erosion was elucidated using the CFD method, which can be divided into three stages: gradual erosion in the initial stage, rapid development in the middle stage, and gradual expansion in the final stage. Finally, the factors that affect the peak flow of floods are analyzed, and suggestions for emergency treatment of landslide dams are put forward. The findings of this research can serve as a valuable reference for disaster prevention and mitigation strategies to adapt to the increasing frequency of landslide-induced river blockages.

Quartz vein-type tungsten deposits are a common W deposit type. Their ore vein distribution was previously considered to be controlled by regional horizontal tectonic stress. In this paper, 14 tungsten deposits with fan-shaped mineralization in SE China are summarized, and the relations between their ore veins and granite and the ore-forming structural stress field are analyzed. These deposits have a post-magmatic hydrothermal genesis and involve the formation of two sets of veins with similar strike and opposite dips at the top of the ore-causative granite bodies, forming a vertical fan-shaped profile. Their ore veins were coeval with the underlying granite bodies, and generally extend along the long axis of the granite. In such fan-shaped ore formation, the stress is highly focused at the top of the granite and gradually weakens outward. The maximum principal stress (σ1) is perpendicular to the granite contact surface, and radiates outward from the pluton. Meanwhile, the minimum principal stress (σ3) forms an arc-shaped band parallel to the contact surface. Our findings, together with published numerical modeling indicate that the emplacement dynamics of granitic magma (rather than regional horizontal tectonic stress) are essential controls on the distribution of ore veins in quartz vein-type tungsten deposits.

To comprehensively utilize the valuable geological map, exploration profile, borehole, and geochemical logging data and the knowledge on the formation of the Jinshan Ag-Au deposit for forecasting the exploration targets of concealed ore bodies, three-dimensional Mineral Prospectivity Modeling (MPM) of the deposit has been conducted using the weights-of-evidence (WofE) method. Conditional independence between evidence layers was tested, and the outline results using the prediction-volume (P-V) and Student's t-statistic methods for delineating favorable mineralization areas from continuous posterior probability map were critically compared. Four exploration targets delineated ultimately by the Student's t-statistic method for the discovery of minable ore bodies in each of the target areas were discussed in detail. The main conclusions include: (1) three-dimensional modeling of a deposit using multi-source reconnaissance data is useful for MPM in interpreting their relationships with known ore bodies; (2) WofE modeling can be used as a straightforward tool for integrating deposit model and reconnaissance data in MPM; (3) the Student's t-statistic method is more applicable in binarizing the continuous prospectivity map for exploration targeting than the P-V approach; and (4) two target areas within high potential to find undiscovered ore bodies were diagnosed to guide future near-mine exploration activities of the Jinshan deposit.

The Erlian Basin is one of the most important multi-energy basins in China. The Baiyanhua area of the Chuanjing depression in the western Erlian Basin has recently become a favorable area for new progress in sandstone-type uranium prospecting. However, the Cretaceous source-to-sink evolution of the Chuanjing depression in the Erlian Basin is poorly known. This paper presents the systematic geochemical and zircon U-Pb studies on the Saihantala Formation and Erlian Formation in the Baiyanhua area. The data obtained are functionally important for revealing the provenance and tectonic setting of the source rocks. The results show that the upper part of the Saihantala Formation and the lower part of the Erlian Formation are mainly composed of felsic sedimentary rocks. The source rocks originated from a continental margin arc environment in terms of tectonic setting. The detrital zircons ages have the dominant populations at ca. 250–270 Ma, with two subdominant age groups at ca. 1 400–1 800 and 1 900–2 100 Ma, respectively. Combined with the tectono-sedimentary evolution of the Chuanjing depression, we conclude that: (1) the provenance of the Cretaceous strata was mostly sourced from the Baiyanhua uplift; (2) the water depth became shallow in the Southern Sangendalai sag during the middle period of Saihantala, further preventing the formation of coal beds; (3) the formation of Baiyanhua uplift might provide the beneficial tectonic condition for uranium mineralization in the upper Saihantala Formation in southern Sangendalai sag. This is significant for us to understand the space allocation of coal and uranium in Chuanjing depression and evaluate the uranium metallogenic prospects in southern Sangendalai sag.