In the western Yangtze Block, widespread Mesoproterozoic to Neoproterozoic rocks are the key to understanding the Precambrian tectonic‐magmatic evolution of the region. However, their petrogenesis and tectonic setting are still controversial. In this paper, zircon U‐Pb ages, Sm‐Nd isotopic and whole‐rock geochemical data are reported from selected fresh samples in the southern Dechang county, southwestern China, in order to constrain their emplacement age and magma source, as well as their petrogenesis and tectonic setting. They are mainly composed of biotite monzogranite, monzonitic granite, biotite granodiorites, and quartz diorite. Two ages of 1055 ± 43 Ma and 837.6 ± 3.8 Ma were obtained through zircon U‐Pb dating by LA‐ICP‐MS and LA‐MC‐ICP‐MS, respectively. According to their major element compositions, the Grenville‐age granites are peraluminous calc‐alkaline series calcic S‐type granite. In contrast, the mid‐Neoproterozoic granites are metaluminous calc‐alkaline series alkalic I‐type granite. Furthermore, the S‐type granites are enriched in LREEs relative to HREEs with (La/Yb)N ratios of 3.85–18.56 and underwent major fractionation with strongly negative Eu anomalies (Eu/Eu* = 0.38–0.66). In the MORB‐normalized trace element variation diagram, all the samples are enriched in Ce and large ion lithophile elements such as Rb, Th, and K, and depleted in high field strength elements such as Nb, and Ti, with negative Sr and Ti anomalies. The I‐type granites are enriched in LREEs with slight negative Eu anomalies (Eu/Eu* = 0.83–0.93). They are characterized by the enrichment of highly incompatible elements (such as K, Rb, Ba, Th) and LREEs, relative to MORB. Neodymium isotopic data show that the S‐type granites display 143Nd/144Nd values of 0.51241–0.51256, and have εNd (t = 1055 Ma) values of (−3.29) to (−3.81). Calculated tDM ages yield values from 1.87 to 1.91 Ga with the tDM.2stg ages of 1.86 to 1.9 Ga. The I‐type granites have 143Nd/144Nd ratios between 0.51192 and 0.51195, corresponding to initial εNd (t = 837 Ma) values of 1.22 to 5.63. Calculated tDM ages yield values from 1.0 to 1.38 Ga and the tDM.2stg ages yield values from 0.99 to 1.06 Ga. The S‐type granites are distinguished as syn‐collision granite, whereas the I‐type granites were formed as arc magmas according to the Rb‐(Yb+Ta) and R1‐R2 tectonic discrimination diagrams. To conclude, there are two types of spatially associated granite, the Mesoproterozoic S‐type granite which were derived from re‐melting of upper crustal mudstone and/or clastics and resulted from the convergence of two continental plates, and the mid‐Neoproterozoic I‐type granite which formed in continental arc and resulted from mantle‐derived magma mixed crust material, in the western Yangtze Block. Furthermore, we suggest that collision between the Yangtze and Cathaysia blocks occurred at about 1055 Ma, and caused the S‐type granite. The I‐type granite related to the subduction of oceanic lithosphere eastward underneath the Yangtze Block in the mid‐Neoproterozoic.

On August 8, 2017, an earthquake of magnitude 7.0 on the Richter scale occurred in Jiuzhaigou, Sichuan, causing significant damage to both life and property. Traditional geological hazard investigation is difficult in Jiuzhaigou because of the high altitude, the high-altitude canyons, and the vegetation-covered seismic areas. This study explores the technical advantages of using airborne LiDAR technology to penetrate vegetation and gather information directly from the surface, rapidly acquiring airborne 3D point cloud data in difficult areas. Through the preprocessing of data, the high-precision digital terrain and landform results were obtained. Comparative research found that the DEM obtained by high-precision airborne LiDAR technology has significant advantages in terms of the accuracy, details, and microgeomorphology of the data collected. The results can be directly used in the early identification of disasters, such as during the initial collapse or for disaster management. Studies have shown that airborne LiDAR has the technical advantage of penetrating vegetation to the surface and can, therefore, be used to guide the early identification and management of geological disasters in similar areas in the future.

The triaxial cyclic loading and unloading test was carried out on a TAW-2000 rock mechanics to study the permeability characteristics of deep-buried sandstone. This paper analyzed the evolution laws of permeability, elastic modulus, rock damage, dissipated energy, and acoustic emission events of sandstone under different confining pressures. It also introduced the concept of relative strain and further discussed the relationship between relative strain and permeability. The test results showed that the permeability of sandstone under cyclic loading and unloading obviously experienced three stages. At a low strain level, the damage degree of sandstone was low. As a result, both the number of acoustic emission events and the proportion of the dissipated energy density were small. In this stage, with increasing the stress, the permeability decreased. With the increase of the relative strain, the propagation of fissure increased through rock interior and the damage of rock was accumulated. Consequently, the number of acoustic emission events grew slowly, and the proportion of dissipated energy density and the damage variable (D) increased gradually. In this stage, the permeability increases. As the axial strain reached the peak strain, the fissures developed into cracks and the rock failure happened. The number of acoustic emission events increased rapidly; both the proportion of the dissipated energy density and the damage variable (D) obtain the maximum value. In this stage, the permeability increased greatly. In this study, the point of fissure propagation of rock specimens was used as the point of demarcation. Before the fissures propagated, the permeability increased slowly and it was in accordance with a linear function. After the fissures propagated, the degree of rock damage increased, and the permeability increased in the form of an exponential function. The larger the confining pressure was, the smaller the relative strain corresponding to the point of fissure propagation was.

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This paper describes the Baibao landslide that occurred in October 2017 within a Jurassic formation in Guojiaba town, Zigui County, Yichang city, China. The factors leading to this landslide include complex geological conditions, slide-prone strata, and fluctuating water level of the Three Gorges Reservoir. Borehole and field investigations indicate that the landslide can be divided into two parts: a medium to deep rock landslide and a partial soil sliding landslide. A comprehensive analysis of the monitoring data, including GPS, precipitation, inclinometer, and water reservoir level measurements, indicates that the Baibao landslide was caused mostly by buoyancy, as well as seepage. Rising reservoir water levels and concentrated pore water pressure at the leading edge of the slope softened the sliding mass. The reduced anti-sliding force allowed the landslide to occur and ultimately drag the rear slope. This study illustrates the landslide deformation mechanism and provides a useful reference for engineering projects in similar regions.