Chinese Academy of Geological Sciences
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This study aims to assess the sensitivity of landslide susceptibility mapping (LSM) to various sampling strategies used for non-landslide samples. The study area is Tianshui city, Gansu province, China. Three types of landslide samples, combined with four machine learning models, resulted in a total of 12 scenarios. The receiver operating characteristic curve (ROC), landslide susceptibility index and the mapping distribution characteristics were calculated to access the influences of different sampling strategies and models. The results indicate that the low susceptibility areas sampling strategy yields the highest accuracy for the landslide susceptibility prediction model, followed by the stratified sampling from engineering geological petrofabric (EGP) strategy, and lastly, the random sampling strategy. Analyzing from the perspective of factor importance and the distribution law of landslide susceptibility index under each model, the models employing the stratified sampling from EGP strategy demonstrate greater robustness. In contrast, the models using the random sampling strategy exhibit lower precision and more randomness. In general, the coupled model exhibits strong performance, the frequency ratio coupled adaptive boosting model (FR-AB) demonstrates high sensitivity, while the other models are characterized by their generaliz-ability and robustness. The results reveal the effects of non-landslide sampling strategies and different coupled models on the prediction performance of landslide susceptibility mapping, which provides a reference for subsequent researchers to obtain more reasonable landslide susceptibility mapping.
  • Yanfeng Zhang
    Yanfeng Zhang
  • Yueping Yin
    Yueping Yin
  • Bin Li
    Bin Li
  • [...]
  • Luqi Wang
    Luqi Wang
The Qinghai–Tibet Plateau has some of the most complex geological structures, the most intense tectonic activity, and the most severe geological disasters in the world. Under the control of multidynamic and cross-scale coupling effects such as plate interaction, plateau uplifting, climate change, and human engineering activities, the mechanism of major slope failure disasters is complex. There have been multiple occurrences of giant landslides and subsequent formation of giant barrier lakes in the Yigong Zangbo River Basin in the eastern Himalayan tectonic zone. After barrier-lake outburst, a basin-wide disaster chain occurred, seriously endangering the hydropower projects along the river and the safety of human life and property. This research explores the disaster environments, sliding structures, and failure mechanisms of the Benduo mountain slope in the Yigong Zangbo basin of the Qinghai–Tibet Plateau via field surveys, high-resolution unmanned aerial vehicle (UAV) surveys, adit explorations, and interferometric synthetic aperture radar (InSAR) monitoring. The results show that the Benduo mountain slope has a high-steep slope, good free-face conditions, a strong rock-mass unloading effect, and developed faults. Under the influence of faults, freeze–thaw cycles, earthquakes, and rock-mass unloading, multiple sets of discontinuous structural planes are developed in the shallow surfaces and deep rock mass. Owing to the structural planes, the rock mass exhibits various textures and clear zoning characteristics. Under these disaster environment conditions, the deformation and failure phenomena of the Benduo mountain slope are obvious. The slope is divided into three zones based on the shallow-surface deformation and failure phenomena. The most intense deformation areas are located at the rear edge and the leading edge of the Benduo mountain slope, and their maximum annual deformation rates are 85 and 80 mm/yr, respectively. Under the control of the structural planes, the deformation and failure modes of the Benduo mountain slope primarily include toppling, sliding–fracturing, and locking. The findings of this study provide a scientific basis for the deformation and failure mechanism of high-steep mountains and the risk prevention and control of basin disaster chains in the Qinghai–Tibet Plateau.
Soil nitrogen status is tightly related to vegetation productivity and ecosystem carbon sequestration. Therefore, how increasing plant species diversity (PSD) during vegetation restoration or afforestation affects soil nitrogen pool would ultimately determine its effects on vegetation productivity and ecosystem carbon sequestration. Though diversifying plant species has been found to benefit soil nitrogen accumulation, how it influences soil microbial necromass nitrogen (MNN), which is a major constituent of soil nitrogen pool, remains unexplored. Forty‐five plots with different PSD were selected in a subtropical forest with the soil being calcareous. Soil MNN was indexed by amino sugars and microbial growth, microbial nitrogen use efficiency, and other soil biotic or abiotic variables were simultaneously measured to explore the influence of increasing PSD on soil MNN pool. Increasing PSD significantly (p < 0.05) stimulated soil microbial growth and contents of fungal, bacterial, and total MNN, but only marginally (p = 0.07) enhanced microbial nitrogen use efficiency. Structural equation modelling revealed that increasing PSD‐stimulated soil MNN content by enhancing microbial biomass through three paths, that is, promoting microbial growth via increasing soil nitrogen availability and the relative abundance of copiotrophic microbial taxa, increasing the inputs of plant‐derived available substrates, and improving mineral protection through elevating soil exchangeable calcium and magnesium levels. However, increasing PSD did not alter the contribution of MNN to soil nitrogen pool, likely owing to the proportional increase of plant‐derived organic nitrogen and the marginal increase in microbial nitrogen use efficiency. Synthesis and applications: These findings highlight that increasing plant species diversity is an effective measure for promoting soil microbial necromass nitrogen accumulation. Considering the importance of soil nitrogen in supporting vegetation productivity and ecosystem carbon sequestration, the current study advocates for the incorporation of diversifying plant species during vegetation restoration or afforestation.
In seismically disturbed regions, sufficient landslide sediments are continuously transported from hillslopes to channels and affect debris flow activity. Existing studies on the prolonged impact of the Wenchuan earthquake are primarily aimed at landslide activity, detailed analysis of differences in the change of landslide sediment transfer at a large scale is quite lacking in different regions. To fill this substantial knowledge gap, we selected three typical regions (Wenchuan region, Beichuan region, and Qingping region) to investigate the temporal and spatial evolution of landslide sediment transfer potential. In this study, a first-order indicator of the transport potential of landslide sediments on hillslopes was used to monitor the spatiotemporal changes in the transport potential of landslide sediment on hillslopes in three regions. The results suggest that the landslide sediment transfer potential in the hanging wall area of the Yingxiu–Beichuan fault zone was greater than that in other areas in the first 5 years of the Wenchuan earthquake, but the areas with higher landslide sediment transfer potential were mainly concentrated in the middle and upper reaches of each basin in recent years. The landslide sediment transfer potential gradually evolves from extreme and high level to moderate, slight, and low levels, and the decay rate of landslide sediment transfer potential is the fastest in Wenchuan regions, followed by Qingping region and Beichuan region. Generally, the landslide sediment transport potential in the Wenchuan, Qingping, and Beichuan regions may recover to pre-seismic levels by 2038, 2028, and 2025, respectively, without the impact of extreme rainfall. Importantly, the landslide sediment transfer potential in Wenchuan region was dominated by moderate and slight, which accounting for 78.33% of the Wenchuan region. However, the Qingping and Beichuan regions were dominated by slight and low landslide sediment transfer potential, which accounting for 94.21% and 82.78% of the region, respectively, in recent years.
The Qinghai-Xizang Plateau (QXP) in China is a geological treasure trove known for its complex structures and rich mineral resources. Among these, copper stands out as a critical metal for economic development. However, the exploitation of these resources is not without challenges, particularly in balancing the need for economic growth with the preservation of the plateau’s delicate ecosystem. In this study, we take into account the intricate interplay between human activities, environmental conditions, and economic strategies. By applying a pressure-state-response (PSR) framework and innovatively establishing a comprehensive potential evaluation index, we are able to quantify the development potential of copper deposits on the QXP and to identify key factors influencing the development potential. The results indicate a varied landscape of copper deposit development potential across the QXP. The state layer in the PSR model represents the most significant obstacle to the development potential of copper resources on the QXP. Certain areas, specifically central Xizang, eastern Xizang, and northwestern Yunnan, show high development potential for copper deposits due to favorable geological conditions and policy environments, and strong infrastructure.
The Ediacaran Period records a significant turning point in the evolution of life on Earth, witnessing the rise to ecological dominance of macroscopic tissue-grade organisms. The Wenghui biota from the Doushantuo Formation of South China hosts abundant multicellular algal macrofossils and problematica, some of which might be closely related to taxa from classic Late Ediacaran assemblages from South Australia and the White Sea biota of Russia. However, a lack of well-resolved isotopic age estimates has hampered efforts to constrain the timing of appearance of the Wenghui biota, obfuscating its significance to our understanding of Ediacaran macroevolution in the aftermath of the Snowball Earth events. Here, we present the first SHRIMP zircon U-Pb dating results for samples obtained from a laminated tuff ash layer at the base of the Wenghui biota in the Doushantuo Formation, Jiangkou County, Tongren City, Guizhou Province, China. Our analyses yield an age of 595.4 ± 5.3 Ma for the first appearance of Wenghui biota, suggesting that its appearance postdated that of the Lantian and Weng’an biotas, but preceded that of the Miaohe biota. These newly obtained age proxies offer an independent test of previous isotopic estimates for the age of the Wenghui biota, providing new chronostratigraphic evidence to map the succession of Ediacaran fossil assemblages on the Yangtze Platform during the Doushantuo interval. These data suggest that the Lantian, Weng’an, Wenghui, and Miaohe biotas may record a sequence of biotic assemblages attesting to successive phases in the radiation of Ediacaran macroscopic organisms, particularly macroalgae.
The return of the young Chang'e‐5 (CE‐5) samples provide new insights into the lunar thermal evolution. In this study, we present a new type of exotic low‐Ti basalt in CE‐5 breccia, which has a magmatic equigranular texture with low Ti content and high Mg bulk composition and minerals. Low rare earth elements (REEs) imply that the clast was probably derived from a primitive source, which may originate from western ancient mare unit. Based on fractional crystallisation modelling, the exotic basalt source is considered as low‐Ti high‐Al, opposing the source of CE‐5 basalts. Our partial melting and REE modelling further imply that the addition of 8% plagioclase and only 1% KREEP contributes to the formation of this specific magma source. This low degree of KREEP involvement in mantle sources may be widespread in Chang'e‐5 terrane and its surrounding units, playing an important role in prolonging lunar magmatism.
In the Wenchuan seismic disturbed region, the landslide sediment transfer has seriously damaged the vegetation. On the contrary, the vegetation recovery can improve the post-seismic slope instability by the root reinforcement effect and reduce landslide sediment transfer. However, due to limited earth observations, it remains elusive that the dynamic response of hillslope landslide sediment transfer to ecological environment recovery in earthquake disturbed area. We analyzed the prolonged evolution of landslide sediment transfer potential (LSTP) and surface recovery in epicentre of Wenchuan earthquake using the standardization landslide sediment transfer potential index (SIH) and normalized difference vegetation index (NDVI), respectively. As well, the dynamic relationship between landslide sediment transfer and vegetation recovery is discussed. We found that the LSTP in regions between Gengda and Caopo was dominated by high and extreme levels between 2008 and 2013, and it gradually enhanced during this period, which poses a negative impact on vegetation recovery. On the contrary, the LSTP continued to decline after 2013, which provided a positive impact on vegetation recovery, and average NDVI recovered at a rate of 0.05 yr−1. In recent years, more than 78.33% of the study area was dominated by moderate and slight LSTP, and the NDVI has almost returned to pre-earthquake levels, which provides a linear impact on decay of landslide erosion and landslide sediment supply for channel. However, the species that breed slowly (trees) will gradually rehabilitate for a longer period, so the impact of vegetation restoration on landslide sediment reduction needs further long-term observation.
Geochemistry of the fault gouge record information on fault behaviors and environmental conditions. We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margin zone (MZ) to the slip central zone (CZ) of the fault gouge in the Beichuan-Yingxiu surface rupture zone of the Wenchuan Earthquake. Results show that the clay minerals contents increase from the MZ to CZ, and the quartz and plagioclase contents slight decrease. An increasing enrichment in Al2O3, Fe2O3, and K2O are observed toward the CZ; the decomposition of quartz and plagioclase, as well as the depletion of SiO2, CaO, Na2O, and P2O5 suggest that the alkaline-earth elements are carried away by the fluids. It can be explained that the stronger coseismic actions in the CZ allow more clay minerals to form, decompose quartz and plagioclase, and alter plagioclase to chlorite. The mass loss in the CZ is larger than that in MZ, which is maybe due to the more concentrated stress in the strongly deformed CZ, however other causes will not be excluded.
The Salt Lake Mahai in Qaidam Basin, western China contains large and thick lithium-rich clay sediments that exhibit great economic potential for lithium exploration. This study analyzed the occurrence of lithium and related dissolution mechanisms in these clay through mineral identification, chemical analyses, and monitoring of brine composition evolution. Our results show that lithium-rich clay mainly occurred as interbeds between salt layers and fillings between salt crystals. The dominant clay mineral is illite, followed by chlorite, kaolinite, and an illite–smectite mixed layer. The leached lithium content in brine was less than 10% of the total lithium content in the clay samples. Lithium commonly occurred as structurally incorporated or adsorbed pattern within the clay minerals, particularly illite, leading to a relatively slow dissolution rate in brine during leaching. Consequently, optimizing the solvent injection points based on the distribution of silt-bearing and clay-bearing halite, particularly in the eastern and northwestern sections of Salt Lake Mahai where leached lithium concentrations are higher (45 ~ 70 mg/L), and extending the contact time between solvent and ore layers could further enhance lithium recovery.
The rare earth elements Sm and Nd significantly address fundamental questions about crustal growth, such as its spatiotemporal evolution and the interplay between orogenesis and crustal accretion. Their relative immobility during high-grade metamorphism makes the Sm-Nd isotopic system crucial for inferring crustal formation times. Historically, data have been disseminated sporadically in the scientific literature due to complicated and costly sampling procedures, resulting in a fragmented knowledge base. However, the scattering of critical geoscience data across multiple publications poses significant challenges regarding human capital and time. In response, we present an automated tabular extraction method for harvesting tabular geoscience data. We collect 10,624 Sm-Nd data entries from 9,138 tables in over 20,000 geoscience publications using this method. We manually selected 2,118 data points from it to supplement the previously constructed global Sm-Nd dataset, increasing its sample count by over 20%. Our automatic data collection methodology enhances the efficiency of data acquisition processes spanning various scientific domains.
Debris flow is a significant geological hazard in the mountainous regions of China, characterized by its sudden onset, high mobility, and considerable destructive potential. In the Helan Mountains, debris flows primarily consist of coarse-grained materials transported by water flows, exhibiting both high destructive potential and a broad impact range. Therefore, understanding the dynamics of debris flows in this region is of crucial importance. This study focuses on the Zhengguangou debris flow, utilizing the DAN-3D software based on Smoothed Particle Hydrodynamics (SPH) to construct a dynamic debris flow model. The movement characteristics of the debris flow were investigated by simulating various operating conditions, including differences in formation area conditions and rainfall intensity. The simulation results indicate that under extreme conditions (with a pore pressure coefficient of 0.8), the debris flow with the same initial volume traveled an average distance of 1503 m, significantly farther than the 1323 m travelled under normal conditions (with a pore pressure coefficient of 0.3). Under normal conditions, the final average deposition thickness of the debris flow was 8.9 m, which was thicker than the 8.3 m observed under extreme conditions. Regarding movement speed, the debris flow initially accelerated and then decelerated, with the extreme condition resulting in a greater travel distance compared to the normal condition. Additionally, the debris flow exhibited greater erosion depth and volume under normal conditions. In contrast, under extreme conditions, the debris flow had a larger scraping width, with the maximum width occurring at the point where the flow direction changed. This study enhances our understanding of the dynamic characteristics of debris flows in northern Ningxia and provides valuable insights for hazard prediction and mitigation efforts in the region.
The fault fracture zone is closely related to groundwater activity, which is a common target for water exploration and well drilling. It is often located below the cover layer, which is difficult to identify solely through geological surveys due to its concealment. Geophysical methods are a common and effective means of quickly identifying fault fracture zones. The fault fracture zones and the developed fissures within them often manifest as low-resistivity anomalies. When under low-resistivity background conditions, the identification difficulty of the fault fracture zone increases. A single geophysical method often has ambiguity and uncertainty in identifying fault fracture zones. Therefore, this paper uses integrated geophysical methods to determine the location, depth, and properties of a fault fracture zone and further assess it based on geological data, achieving good results. First, electrical resistivity tomography is used to determine the approximate location and range of the fault fracture zone. The abnormal feature is a low-resistivity strip with a localized low-resistivity trap. The low-resistivity trap area is a concentrated zone of fault fracture with fractured lithology. The audio-frequency magnetotelluric method is used to determine the depth of the bottom boundary of the fault fracture zone The anomalous feature presents a wide and gentle U-shaped low resistivity. The drilling depth is determined by inferring the depth of the bottom boundary of the fault fracture zone using the audio-frequency magnetotelluric method. The composite profiling method is used to accurately locate the fault fracture zone and determine the drilling position. The anomalous feature is determined to be a synchronous low-resistivity anomaly, which changes from a V-shaped to a U-shaped from shallow to deep. As the electrode distance increases, the inferred width of the fault fracture zones change from narrow to wide. To reduce the ambiguity and uncertainty in identifying fault fracture zones in low-resistivity environments using conventional electrical and electromagnetic methods, the microtremor horizontal-to-vertical spectral ratio (HVSR) method is used to further review the location of the fault fracture and fissure zones. The abnormal feature is a horizontal-to-vertical (H/V) high-value trap. The apparent resistivity sounding curve is used to determine the burial depth of water-bearing fissure zones in the fault fracture zone. The anomalous feature is a V-shaped low-resistivity anomaly. Then, the water content of the hanging and foot walls of the fault based on hydrogeological conditions is analyzed. Finally, on the basis of the construction site conditions, a drilled hole is performed near the fault fracture zone (342.5 measuring points), with a depth of 160.3 m. When the water level drawdown is 6.90 m, the water inflow is 107.40 m³/day. After drilling verification, the selection and application process of the above method is a scientifically reasonable water exploration model that can be applied to the same geological background conditions. The case study results show that the combination of geophysical prospecting methods, namely, electrical resistivity tomography, audio-frequency magnetotelluric method, composite profiling method, microtremor HVSR method and apparent resistivity sounding curve can effectively explore the fault fracture zones under low-resistivity background conditions.
Loess is extensively developed on both sides of the Longwu River, a tributary of the Yellow River, Tongren County, Qinghai Province. The engineering geological characteristics are complex, and landslide disasters are highly developed. Based on field geological surveys and physical property analysis of the loess in this area, this study analyzes the influence of water content, consolidation pressure, and soil disturbance on the dynamic characteristics of loess using GDS dynamic triaxial tests. The results show that Tongren loess has strong structural properties. Its dynamic constitutive relationship conforms to the Hardin-Dinevich hyperbolic model, where the parameters a and b decrease with increasing confining pressure and increase with increasing water content. The dynamic cohesion and dynamic friction angle both decrease with increasing water content, with the dynamic cohesion significantly affected, decreasing by 77% ~ 83% when saturated. However, the dynamic friction angle is less affected by water content changes, decreasing by 18% ~ 25% when saturated. Under dynamic conditions, the dynamic friction angle of Tongren loess is only 12 ~ 16°, making slopes composed of Tongren loess highly susceptible to instability and sliding under strong earthquake conditions. The dynamic structural properties of Tongren loess are significantly influenced by water content, with increasing water content destroying the joint structural strength of intact loess. Before reaching the plastic limit water content, the joint structural strength of intact loess decreases sharply with increasing water content, and then decreases slowly. The frictional structural strength shows an opposite trend. Under the same experimental conditions, the failure dynamic stress, maximum dynamic elastic modulus, and dynamic shear strength parameters of intact loess are generally greater than those of remolded loess, and the differences between them decrease with increasing water content. This study provides insights into the dynamic structural characteristics of Tongren loess, which can serve as a reference for understanding the formation mechanisms, stability analysis, and seismic design of loess landslides in the region.
To study the correlation between the mesoscopic damage evolution and macroscopic failure characteristics of anisotropic shale, an in situ high-resolution micro-computed tomography (micro-CT) was used to conduct a uniaxial loading experiment with real-time scanning on Carboniferous shale from the eastern Qaidam Basin. The subvoxel displacement field of each specimen was calculated based on the correlation coefficient interpolation of the image subset with the digital volume correlation method, and the high-precision strain field was obtained to evaluate the deformation localization characteristics of shale specimens with low and high bedding inclination angles during loading. The research results show that the stable cracks expansion is caused by the synergistic effect of tension and shear. However, the unstable cracks expansion in low bedding inclination angle shale is controlled by tension and shear, whereas in high bedding inclination angle shale, it is dominated by tension. The evolution of the axial strain field of the low bedding inclination angle shale confirms the compaction of the bedding defects, strengthening bedding planes and inhibiting the formation of cracks along bedding. Conversely, high bedding inclination angle shale experiences concentrated tensile and shear strains due to damage to original bedding defects, leading to rapid strain increase and localized strain band formation consistent with subsequent splitting failure. The strain localization can predict the development location of cracks before they become macroscopically visible in CT images.
Corystosperms, an extinct group of “seed ferns” that lived from the late Permian to the Cretaceous or Eocene, are significant for seed plant phylogeny for their unique roles in partially resolving the long-standing question of angiosperm origins. A new fossil wood taxon, Fengweioxylon sinense gen. et sp. nov. is reported here based on exceptionally preserved wood material from the Jurassic in western Liaoning, China, whose peculiar wood structure enables it to be recognized as the first unequivocal fossil wood record of a corystosperm plant in Laurasia. The anatomical structures of this corystosperm wood show gymnospermous characters. The discovery of the new specimen will provide more anatomical evidence for understanding the systematic and affinity of this seed plants.
Sedimentary manganese (Mn) mineralization requires a switch between anoxic and oxic water column conditions, which is commonly explained by the “bathtub ring” model and more recently interpreted by the emerging “episodic ventilation” model. To date, however, it remains unclear regarding how to distinguish between these two mechanisms, profoundly influencing Mn ore prospecting. Here, we conducted a comprehensive investigation on the Muhu Mn deposit in northwestern China. The upward lithological variations from breccia-dominated to fine-grained siliciclastic units (e.g., black shales) are typical of sequence characteristics of rifted basins. Black shales were deposited in deep waters due to continued tectonic subsidence that resulted in hydrographic restriction and bottom water euxinia, as indicated by their high ratios of FeHR/FeT and FePy/FeHR, as well as relatively low Mo/TOC ratios. The Mn ore beds are interbedded with black shales and consist of divalent Mn minerals (e.g., rhodochrosite). They display shale-normalized positive cerium anomalies and negative inorganic carbon isotopes and Mo isotopes, suggesting that these Mn carbonate minerals originated from the diagenetic conversion of primary buried Mn oxides deposited under oxic benthic conditions. Taken together, the intimate spatial association between Mn ore beds and black shales records a dynamic temporal redox change. Such a redox shift is consistent with the “episodic ventilation” scenario, where incursions of oxygenated seawater triggered the deposition of initial Mn oxides. In contrast with the “bathtub ring” model, the ventilation scenario represents distinct spatial-temporal configurations of redox-hydrological conditions. Therefore, deciphering the detailed redox variations of Mn-hosting sedimentary successions, in conjunction with paleogeographic reconstruction, is the key to distinguishing between these two mechanisms.
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479 members
Marie Luce Chevalier
  • Institute of Geology
Jian Sun
  • Institute of Geology
Lingsen Zeng
  • Continental Dynamics
Jianxin Zhang
  • Institute of Geology
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