地质力学学报

Deformation characteristics and ⁴⁰Ar/³⁹Ar geochronology of the Shili ductile shear zone at the northwestern margin of the Yunkai Block

GUO Shangyu, WU Xiangke, ZHAO Bing, LI Dan

Objective The Yunkai Massif is one of the Precambrian metamorphic crystalline basements within the South China Block. To better understand the Indosinian deformation characteristics in the Yunkai area, the Shili ductile shear zone at the northwestern margin of the Yunkai Massif was selected for this study. Methods Through detailed field investigations, finite strain measurements, kinematic vorticity analyses, and ⁴⁰Ar/³⁹Ar geochronology, the structural characteristics and evolutionary process of the shear zone were constrained. Results The Shili ductile shear zone generally strikes WNW–ESE with NNE-directed thrusting. It has undergone four phases of deformation. Among which, the D2 to D4 deformations all indicate movement from SSW to NNE. D2 to D4 formed under a unified tectonic stress field, reflecting an evolution from ductile shear through brittle-ductile deformation to folding during the Late Triassic. Mylonites formed synchronously with the ductile shear deformation yield a muscovite ⁴⁰Ar/³⁹Ar plateau age of 232 ± 2.3 Ma (MSWD = 3.65). The Flinn index (K) is 0.06–0.77, the Lode parameter (ν) is 0.13–0.89, the Effective strain (E_s) is 0.41–0.51, and the kinematic vorticity value (W_k) is 0.70–0.78. These parameters indicate a flattening-type strain regime dominated by general shear, with comparable contributions of pure shear and simple shear. The dynamic recrystallization of minerals suggests that the deformation environment reached the upper greenschist facies. Conclusions This study indicates that the mylonitization, crenulation cleavage development, and folding within the Shili ductile shear zone were dynamically driven by the propagation of far-field stress resulting from the NE–SW collision between the Indochina and South China blocks during the Indosinian period. Significance These findings provide critical constraints on the Indosinian tectono-thermal event and its geodynamic framework in South China.

Tectonic stress field characteristics in Wushi, Xinjiang, and the stress impact of the M 7.1 Wushi earthquake

SONG Zeyao, WAN Yongge, GU Peiyuan, ZHOU Mingyue

Objective The Wushi region in Xinjiang is located at the intersection of multiple tectonic units, characterized by frequent tectonic activity, making it a critical region for stress concentration and release. On January 23, 2024, an M 7.1 earthquake struck Wushi (epicenter: 41.26°N, 78.63°E; depth: 22 km), representing the largest event in this area over the past decade. To better understand the regional seismogenic environment and assess future seismic hazards, this study utilizes comprehensive focal mechanism data to investigate the regional tectonic stress field and quantitatively evaluate the impact of the M 7.1 Wushi earthquake on the stress regime. Methods Based on 148 focal mechanism solutions (January 1976 to March 2025) compiled from multiple domestic and international institutions, we applied the damped stress tensor inversion method to determine the stress field characteristics across subregions and systematically evaluate changes in the stress field before and after the earthquake. Results Stress tensor inversion reveals that the Wushi region is dominated by a compressional stress regime under N–S compression. Except for the area near the Jiashi earthquake cluster where R > 0.5, the azimuth of the maximum principal compressive stress (σ₁) gradually rotates from NNW in the south to approximately N–S in the north (azimuth range: 168.75°–183.45°; plunge range: 6.85°–19.58°). The Jiashi seismic cluster exhibits a strike-slip stress regime characterized by NNE–SSW compression and NWW–SEE extension, with thrust faulting dominating to its north and strike-slip faulting to its south. Comparative analysis shows that the optimal σ₁ direction adjusted from an azimuth/plunge of 178.91°/6.24° before the earthquake to 167.61°/7.98° after the earthquake, corresponding to an azimuth deviation of 12.53° and a total spatial rotation of 15.06°. This indicates that the mainshock exerted a relatively minor impact on the regional stress field, which remains under the dominant compressional regime. Conclusions The tectonic stress field in the Wushi region is driven by the northward collision of the Indian plate against Eurasia, which transmits near-N–S horizontal compression northeastward into the Tianshan orogenic belt, causing crustal shortening and thrusting between the Tarim Basin and the Tianshan Mountains. The M 7.1 earthquake caused only localized adjustments, leaving the overall regional stress regime controlled by deep-seated tectonic processes. Furthermore, the northern Jiashi earthquake cluster, located at the boundary between the northern Tarim plate and the Tianshan Mountains, exhibits a strike-slip stress mechanism, marking a major tectonic transition zone between the Tarim Basin and the Tianshan orogenic belt. Significance This study provides a refined characterization of the tectonic stress field in the Wushi region and clarifies the limited impact of the M 7.1 mainshock on regional stress states. These findings deepen our understanding of the tectonic interactions between the Tianshan orogenic belt and the Tarim Basin, providing critical scientific constraints for regional tectonic segmentation and seismic hazard assessment.

Remote sensing image characteristics and seismic hazard of the Baiganhu Fault on the south side of the central Altyn Tagh Fault

LIU Hanlin, CHEN Tao, YUAN Zhaode

Objective Accurately delineating the spatial distribution and geometric scale of active faults is essential for understanding crustal deformation and assessing regional seismic hazards. While the Altyn Tagh Fault (ATF) has been extensively studied, its adjacent secondary structures—such as the Baiganhu Fault—remain poorly constrained regarding their geometry, slip history, and seismic potential. This study aims to systematically characterize the offset geomorphology of the Baiganhu Fault, establish its segmentation, and evaluate its potential for generating large earthquakes, including multi-fault cascading ruptures with the ATF. Methods Using multi-source high-resolution satellite imagery and digital topographic data, we conducted detailed geomorphic mapping of the Baiganhu Fault. Displaced landforms (e.g., offset gullies, alluvial fans, pressure ridges, and sag ponds) were measured. We constrained displacement variations at individual measurement points using Gaussian cumulative probability density (COPD) distributions to interpret the displacement accumulation pattern and evaluate coseismic slip. Results The Baiganhu Fault extends for approximately 247 km along a general northeast–east (NEE) strike, displaying prominent left-lateral strike-slip geomorphic features. Based on fault geometry and deformation patterns, it is divided into western, central, and eastern segments. The central segment hosts a well-preserved ~50-km-long surface rupture zone with an average coseismic displacement of 4.8 m. Statistical analysis of 99 offset gullies yields an average horizontal offset of 4.3–4.8 m for the most recent event, corresponding to a moment magnitude of M_W 7.4±0.3. A full-segment rupture could generate an earthquake of M_W 7.8±0.3. Furthermore, the ~5-km-wide stepover separating the Baiganhu Fault from the main strand of the ATF is unlikely to act as a permanent barrier, making a cascading rupture mechanically plausible. Conclusions The Baiganhu Fault is a highly active left-lateral structure capable of generating M_W 7.4 events. Regional seismic hazard models must incorporate the scenario of cascading ruptures between the Baiganhu Fault and the Altyn Tagh Fault to avoid underestimating seismic risk to surrounding infrastructure. Significance This study provides critical quantitative constraints on the geometry, slip behavior, and seismic potential of a previously under-studied secondary structure within the ATF system. By highlighting the potential for multi-fault cascading ruptures, our findings underscore the need to update regional seismic hazard models, which is vital for risk mitigation and infrastructure safety in the region.

Tectonic evolution of the western Yangtze Block during the Ediacaran–Cambrian: evidence from detrital zircon U-Pb geochronology

SHI Zhiqiang, SUN Le, ZHANG Hong, PEI Jinyun, LI Wei

Objective The Yangtze Block was a crucial component of the Gondwana supercontinent. During the Ediacaran–Early Cambrian, its western margin underwent a marked transition from carbonate- to siliciclastic-dominated depositional environments. However, the tectonic dynamics and geotectonic setting governing this pronounced sedimentary facies shift remain poorly constrained. Thick Lower Cambrian terrigenous clastic rocks widely exposed along the western margin of the Yangtze Block (Western Yangtze) serve as a key archive for tracing sediment provenance and deciphering Early Cambrian geotectonic evolution. Methods This study presents systematic detrital zircon U–Pb geochronological and whole-rock major- and trace-element geochemical analyses of the Lower Cambrian Qiongzhusi Formation in the Western Yangtze to constrain its provenance and tectonic background. Results Whole-rock geochemical data indicate that high-field-strength elements (HFSEs) and large-ion lithophile elements (LILEs; e.g., Th, Zr, Hf, Ba, Pb) in the Qiongzhusi Formation clastic rocks align closely with upper continental crust (UCC) values. Conversely, elements such as Co, Ni, Y, Nb, Cs, Hf, and Ta are depleted relative to UCC, with Co, Cs, and Ta showing the most significant depletion. Characteristics of immobile elements (Th, Sc, Hf, Zr, Ho) and rare earth elements (REEs; e.g., La, Ce, Yb) consistently indicate a predominantly felsic igneous source. Detrital zircon U–Pb age spectra exhibit two primary population peaks at ca. 590–500 Ma and ca. 880–720 Ma, alongside two subordinate clusters at ca. 1900–1500 Ma and ca. 2500–2400 Ma. Conclusions Integrated with regional geological evidence, we propose that the Early Cambrian detritus was primarily derived from Ediacaran–Early Cambrian magmatic rocks within the Longmenshan tectonic belt, as well as weathering products of late Neoproterozoic felsic magmatic rocks from the Panxi–Hannan and Ailaoshan magmatic arcs. Subduction of the Proto-Tethys Ocean beneath the Western Yangtze during the latest Ediacaran–Early Cambrian established a Late Ediacaran–Early Cambrian magmatic arc. This tectonic event converted the Western Yangtze from a passive margin into an active continental margin, supplying voluminous Early Cambrian detritus that drove the major depositional transition from carbonates to siliciclastics. [ Significance ]These findings establish key provenance links between the Western Yangtze and surrounding orogenic belts, providing critical constraints for reconstructing the tectonic and paleogeographic evolution of the South China Block during the Ediacaran–Early Cambrian transition.

Genesis of Ordovician Kelimoli Formation dolomites in the complex tectonic zone along the western margin of the Ordos Basin

MA Zhanrong, LI Zhenhong, LIU Jianping, HU Aiping, KOU Linlin

Objective The dolomite in the Ordovician Kelimoli Formation of the complex tectonic zone along the western Ordos Basin margin is a high-quality reservoir for natural gas exploration. However, its genetic mechanism and the relationships among the sedimentary environment, multi-stage tectonic superimposition, and diagenetic alteration remain controversial, limiting effective guidance for oil and gas exploration. Methods To elucidate the genesis of this dolomite, a comprehensive analytical approach was applied, incorporating thin-section petrography, cathodoluminescence (CL), C–O isotopes, X-ray diffraction (XRD) ordering degrees, trace and rare earth element (REE) geochemistry, and Sr isotopes, integrated with regional tectonic evolution. Results Under CL, the dolomites generally exhibit weak dark-brown luminescence with distinct zonation, alongside authigenic quartz and saddle dolomite, indicating hydrothermal involvement and multi-stage recrystallization during deep burial. Carbon and oxygen isotopic signatures further support a burial origin. XRD data reveal a relatively low ordering degree in dolomites, which decreases with increasing temperature, suggesting rapid crystallization under elevated temperatures. REE patterns display positive Ce and Eu anomalies, indicating that dolomitization occurred in a relatively closed, high-temperature, and high-pressure diagenetic system via internal fluid readjustment and material redistribution. Overall, the dolomite shows a relatively low degree of order, and the order decreases with higher temperatures, suggesting that the dolomite formed in an environment with relatively high temperature and rapid crystallization rate. Geochemically, lower Sr contents correlate with higher Fe and Mn concentrations, reflecting multi-stage superimposed alteration under deep burial conditions. Furthermore, strontium isotope values of medium-to coarse-grained dolomite closely approach average crustal values, likely influenced by crustal Sr transported along coeval tectonic conduits. Conclusions This research attributes the dolomite formation primarily to deep burial and the coeval superimposition of tectonic fluid modification. The origin and evolution of the Ordovician Kelimoli Formation dolomite were strongly controlled by deep fault systems. During the co-deposition period, this fault system controlled the development of high-energy terraces. In the subsequent tectonic activity phase, the deep fault system became a fluid migration channel, facilitating the superimposed modification of dolomite bodies. Significance The research results provide fundamental support for the efficient exploration of oil and gas resources.

Cover

2026, 32(4).

Abstract (51) PDF (2211KB)(18)

Contents

2026, 32(4): 1-2.

Abstract (69) HTML (30) PDF (434KB)(75)

Tectonic System & Structural Geology

Deformation characteristics and ⁴⁰Ar/³⁹Ar geochronology of the Shili ductile shear zone at the northwestern margin of the Yunkai Block

GUO Shangyu, WU Xiangke, ZHAO Bing, LI Dan

2026, 32(4): 771-785. doi: 10.12090/j.issn.1006-6616.2025052

Abstract (150) HTML (27) PDF (6154KB)(59)

Formation and modification of the Minle Basin in the Hexi Corridor: Insights into Cretaceous tectonic characteristics of the northeastern Tibetan Plateau

ADINA Alimu, ZHANG Beihang, YANG Yan, ZHAO Heng, JIANG Hai, LIU Yugang, DING Zhe

2026, 32(4): 786-805. doi: 10.12090/j.issn.1006-6616.2025154

Abstract (224) HTML (41) PDF (9189KB)(119)

Fractal characteristics of karst geology in large-scale thrust-nappe tectonic settings

SHI Xiaodi, YAO Jianxin, ZHAO Biyi, YAO Dan, KUANG Li

2026, 32(4): 806-816. doi: 10.12090/j.issn.1006-6616.2025039

Abstract (108) HTML (24) PDF (1130KB)(68)

Crustal Stress & Tectonic Stress Field

Tectonic stress field characteristics in Wushi, Xinjiang, and the stress impact of the M 7.1 Wushi earthquake

SONG Zeyao, WAN Yongge, GU Peiyuan, ZHOU Mingyue

2026, 32(4): 817-828. doi: 10.12090/j.issn.1006-6616.2025085

Abstract (506) HTML (93) PDF (6970KB)(573)

Mechanical property prediction and 3D modeling via statistical regression and prestack inversion: a case study from the Bonan Sag

WANG Bin, XIAO Han, NIU Xuemin, ZHANG Ruixuan, GE Xing

2026, 32(4): 829-841. doi: 10.12090/j.issn.1006-6616.2025084

Abstract (295) HTML (63) PDF (4282KB)(378)

Energy Resources Geology

Evaluation of hydrocarbon source rocks and oil-source correlation of the Chang 7 and Chang 6 Members of the Yanchang Formation in the Jingbian area, Ordos Basin

TANG Siwei, XUE Hui, TANG Youjun, WANG Shumin, HU Guangming, LI Geng, SHI Fangtingyu

2026, 32(4): 842-860. doi: 10.12090/j.issn.1006-6616.2025050

Abstract (282) HTML (61) PDF (2679KB)(297)

Permian–Triassic reservoir characteristics and controls on their differences in the Pen-1 West Sag, Junggar Basin

ZHANG Fushun

2026, 32(4): 861-876. doi: 10.12090/j.issn.1006-6616.2026027

Abstract (188) HTML (41) PDF (11903KB)(113)

Diffusion coefficients and multi-scale diffusion models of shale oil and gas

ZHANG Mingdi, ZHANG Guangdong, ZHU Langtao, MENG Sijin

2026, 32(4): 877-888. doi: 10.12090/j.issn.1006-6616.2025140

Abstract (244) HTML (48) PDF (1174KB)(146)

Geo-hazards & Engineering Geology

Slope engineering in the deeply incised valleys of the Tibetan Plateau: key challenges and strategic considerations

WANG Jiming, QI Bangshen

2026, 32(4): 889-898. doi: 10.12090/j.issn.1006-6616.2025061

Abstract (127) HTML (27) PDF (5098KB)(66)

Reactivation mechanism and stability trend prediction of the Huangci No.2 landslide, Heifangtai, Gansu Province, China

DOU Xiaodong, LI Yushan, MENG Yateng, CONG Kai, ZHANG Yongjun, JIA Qiang

2026, 32(4): 899-918. doi: 10.12090/j.issn.1006-6616.2026014

Abstract (447) HTML (44) PDF (11819KB)(288)

Active Tectonics & Earthquake

Remote sensing image characteristics and seismic hazard of the Baiganhu Fault on the south side of the central Altyn Tagh Fault

LIU Hanlin, CHEN Tao, YUAN Zhaode

2026, 32(4): 919-932. doi: 10.12090/j.issn.1006-6616.2025187

Abstract (179) HTML (36) PDF (21838KB)(120)

Numerical simulation analysis of seismically triggered load and ball-and-pillow structures in the lacustrine sediment

YAN Zelong, FAN Ruixiang, LIANG Lianji, ZHONG Ning, ZHANG Junjie

2026, 32(4): 933-941. doi: 10.12090/j.issn.1006-6616.2026005

Abstract (175) HTML (33) PDF (1775KB)(112)

Fundamental Geology & Regional Geology

Tectonic evolution of the western Yangtze Block during the Ediacaran–Cambrian: evidence from detrital zircon U-Pb geochronology

SHI Zhiqiang, SUN Le, ZHANG Hong, PEI Jinyun, LI Wei

2026, 32(4): 942-957. doi: 10.12090/j.issn.1006-6616.2025065

Abstract (357) HTML (72) PDF (2674KB)(273)

Genesis of Ordovician Kelimoli Formation dolomites in the complex tectonic zone along the western margin of the Ordos Basin

MA Zhanrong, LI Zhenhong, LIU Jianping, HU Aiping, KOU Linlin

2026, 32(4): 958-979. doi: 10.12090/j.issn.1006-6616.2025031

Abstract (245) HTML (73) PDF (17456KB)(381)

Study on the cooling history of Pliocene basalt columns in Kanchanaburi, Thailand

ZHOU Enxiong, YAN Yonggang, LAI Zhenyang, LI Danxin, FU Yalan, DENG Xiaotai, ANCHANA Thanakan, VEERAVINANTANAKUL Apivut, CHARUSIRI Punya, WANG Weitao, HUANG Baochun, ZHANG Peizhen

2026, 32(4): 980-998. doi: 10.12090/j.issn.1006-6616.2025169

Abstract (220) HTML (45) PDF (6100KB)(171)

More>

ncc-audit-test-1e8ebb15

[Abstract](4) [PDF 0KB](0)

Abstract:

Application and Prospect of Geophysical Exploration Technologies in Large-Scale Oil and Gas Engineering Construction

JING Shaodong, MA Xuedong, YAN Yuefeng, SUN Huaifeng

doi: 10.12090/j.issn.1006-6616.2026054

[Abstract](32) [PDF 2526KB](11)

Abstract:
The construction of large-scale oil and gas engineering projects serves as a strategic cornerstone for ensuring national energy security. Various types of projects, including long-distance pipelines, refining and chemical engineering, and underground storage facilities, are being advanced synergistically, playing an irreplaceable supporting role in the national economy and people's livelihoods. Integrated site investigation, running through from site selection and design to construction and operation. Its core tasks are accurately identifying geological hazards along long-distance pipelines, foundation conditions of refining and chemical plant sites, rock mass integrity and stability in underground spaces. However, poor adaptability to complex terrains, limited detection range, disturbance and damage to the site, high costs and long time remain the shortcomings of current drilling technologies. Engineering geophysical, leveraging the unique advantages of non-destructive, rapid, and capable of 3D exploration, have become the answer of the aforementioned challenges. Methods such as Controlled Source Audio-frequency Magnetotellurics (CSAMT), Electrical Resistivity Tomography (ERT), shallow seismic exploration, Ground Penetrating Radar (GPR), and microtremor surveys have been widely applied in oil and gas projects. Appropriate combinations of geophysical methods have demonstrated significant effectiveness in pipeline investigation, foundation exploration in karst-developed areas, and underground storage facility investigation. With the maturation of Unmanned Aerial Vehicle (UAV) technology, semi-airborne and fully airborne geophysics will effectively address personnel safety and exploration efficiency issues in complex terrains. Artificial Intelligence (AI)-driven geophysical data processing and inversion techniques are expected to achieve computational acceleration by tens of thousands of times. Airborne-ground-borehole joint inversion will enable 3D high-precision imaging. The development of Distributed Acoustic Sensing (DAS) technology provides a new method for real-time dynamic monitoring of geological. Engineering geophysical is advancing towards intelligence, multi-dimensionality, and real-time capability, which will provide more robust technical support for the construction of large-scale oil and gas engineering projects.

Artificial Intelligence-Empowered Coal Geology: Advances, Challenges, and Prospects

dai shifeng, XU Na, ZHU Wei, li pengfei, qi anliangyu, LIU Yu, yan ruiwen, ZHAO Zhengfu

doi: 10.12090/j.issn.1006-6616.2026060

[Abstract](42) [PDF 603KB](23)

Abstract:
[Objective] The rapid development of artificial intelligence has reshaped the research paradigm of geosciences. Coal geology focuses on coal, coal seams, coal-bearing strata, coal basins, and coexisting and associated mineral resources in coal-bearing strata. These research objects exhibit highly complex material compositions, multiscale characteristics, and pronounced spatiotemporal variability. Consequently, the major research directions of coal geology, including coal petrology, coal geology, critical metals in coal-bearing strata, and coalbed methane exploration and development, are highly compatible with artificial intelligence.[Methods] Artificial intelligence is driving coal geology beyond traditional experience-based identification and local statistical analysis toward a new paradigm integrating multi-source data fusion, intelligent prediction, and mechanistic interpretation. It also provides new opportunities for discovering previously unrecognized geological phenomena.[Results] This paper systematically reviews recent advances in the application of artificial intelligence to the intelligent identification of coal macerals, intelligent prediction of coal quality, intelligent assessment of the occurrence modes and resource potential of critical metals in coal, and coalbed methane prediction. Artificial intelligence technologies have significantly improved the efficiency and accuracy of maceral image recognition, coal quality parameter prediction, identification of occurrence patterns of critical metals in coal, and comprehensive resource evaluation. However, several challenges remain, including the scarcity of high-quality datasets, limited cross-regional generalization capability, weak model interpretability, insufficient consistency with geological mechanisms, inadequate knowledge constraints, and limited implementation in engineering scenarios.[Conclusions] Future research should strengthen the construction of standardized large-scale databases, promote the deep integration of geological knowledge with data-driven models, develop interpretable and transferable intelligent models, and establish an intelligent research paradigm oriented toward major scientific questions in coal geology and the green and efficient development of coal-related resources.[Significance] This review highlights the transformative role of artificial intelligence in advancing coal geology from experience-driven analysis toward knowledge-guided intelligent research, providing methodological support for major scientific discovery and the green, efficient development of coal-related resources.

Early Paleozoic Tectonic Transition and Metallogenic Implications in the Eastern Kunlun Orogenic Belt, Qinghai: Evidence from Kunlun River Granites

ZU Muretiabuliyimiti, JIAO He, WANG Yong, huang guobiao

doi: 10.12090/j.issn.1006-6616.2026020

[Abstract](57) [PDF 2095KB](29)

Abstract:
Abstract: [Objective] The East Kunlun Orogenic Belt (EKOB) is a fundamental component of the Tethyan tectonic domain and preserves crucial records of the orogen’s evolution. Although remarkable progress has been achieved in tectonic evolution of the EKOB, systematic studies on its western segment remains insufficient. In particular, no unified consensus has been reached on the closure timing of the Proto-Tethyan Ocean, shift of tectonic regimes, provenance of crustal material, and associated metallogenic processes. [Methods] To better constrain the timing of tectonic transition and assess its metallogenic significance for regional polymetallic mineralization, this study conducts integrated petrological, geochemical and zircon geochronological analyses on three representative plutons (North Heihai, Jiadong, and Suhaitu) in the Kunlun River area, with comparisons to coeval granitoids in the eastern EKOB. [Results] Zircon U–Pb dating yields formation ages of 437.7–428.8 Ma for the monzogranites. Geochemically, these rocks belong to calc-alkaline series with weak peraluminosity, and exhibit higher A/NK ratios than coeval monzogranites of the Baitonggou pluton in eastern EKOB. The monzogranites have total REE contents of 212–256 ppm, with (La/Yb)_N = 8.78–21.05 and LREE/HREE = 8.15–14.13, reflecting LREE enrichment, flat HREE patterns, and pronounced negative Eu anomalies (0.23–0.73). Primitive mantle-normalized trace element patterns reveal enrichment in large-ion lithophile elements (Rb, K) and depletion in high field strength elements (Nb, Ta, Ti, P). [Conclusions]These characteristics indicate that the monzogranites are highly fractionated I-type granites derived from partial melting of ancient mid–upper crustal basement, and emplaced during a post-collisional extensional transition following Proto-Tethyan Ocean closure. This magmatic event records the tectonic switch from compression to extension and provides potential thermal and material conditions for polymetallic mineralization. The eastern and western EKOB experienced this tectonic transition nearly synchronously, demonstrating synchronous and unified evolutionary processes of the Proto-Tethyan Ocean across the whole EKOB.

Structural Characteristics and Quantitative Deformation Analysis of the Central Segment of the Western Sichuan Depression

LONG Yi, WANG Renfu, DUAN Wenshen, kong xuanlin, DING Yunan, wang chun, zhou xiaorong, QIU Jianhua

doi: 10.12090/j.issn.1006-6616.2026042

[Abstract](123) [PDF 4729KB](101)

Abstract:
The central segment of the Western Sichuan Depression, located on the western margin of the Sichuan Basin, has been influenced by the Longmen Shan orogenic belt and has experienced multiple phases of tectonic movement and superimposed modification, resulting in the formation of a complex deep-shallow dual-layer structural system. Based on high-precision three-dimensional seismic data from the central segment of the Western Sichuan Depression, this study conducts fine structural interpretation, selects profiles of typical buried detachment anticlines, and applies the area-depth-strain (ADS) method to perform quantitative analysis of multi-phase structural deformation. In combination with regional structural deformation characteristics, it systematically investigates the structural deformation mechanisms and basin-mountain coupling processes in the central segment of the Western Sichuan Depression. The results show that, bounded by the Middle-Lower Triassic gypsum-salt detachment layer, the central segment of the Western Sichuan Depression is vertically decoupled into a shallow frontal thrust-nappe system in the piedmont and a deep buried detachment deformation system within the basin. The structural deformation in the study area exhibits a segmented pattern along strike, with deep deformation weakening from south to north and shallow deformation strengthening from south to north. This segmentation results from the combined effects of heterogeneous compression of the orogenic belt, differences in basement structure, and spatial variations in the detachment layer. Combined with the ADS quantitative analysis results of detachment anticlines, this study suggests that the multi-phase deformation of detachment anticlines in the central segment of the Western Sichuan Depression displays a pulsed distribution pattern of “early Indosinian deep-level initiation (217 m), middle Indosinian shallow-level dominance (142 m), and late Indosinian overall waning (≤31 m)”, quantitatively revealing an episodic pattern in which the basin-mountain compressional deformation was transferred from deep to shallow levels and from early to late stages. Meanwhile, the differences in shortening amounts between the deep and shallow deformation systems in anticlines A and B indicate a “staggered peak” response over time: the deep deformation system experienced significant shortening during the early Indosinian (anticline B shortening of 217 m), whereas the shallow deformation system responded most strongly to compression during the middle Indosinian (Anxian Movement), together forming a unique coupling style of “deep pre-existing folding–shallow thrust nappe”. The “vertical layering–lateral segmentation–multi-phase quantification” structural understanding system established in this study not only provides a quantitative structural basis for deep to ultra-deep petroleum exploration in foreland basins, but is also of great significance for deepening the understanding of the basin-mountain coupling processes in the central segment of the Western Sichuan Depression.

Paleomagnetic constraints on a two-stage Cenozoic tectonic framework of the South China Block and the southeastern Tibetan Plateau

LIAO Yilian, HUANG Baochun, WANG Jianhua, LU Hongliang, SUN Qishun, CHEN Zaixu

doi: 10.12090/j.issn.1006-6616.2025181

[Abstract](200) [PDF 5569KB](56)

Abstract:
[Objective] The kinematic history of the South China Block (SCB) following the breakup of Gondwana is of critical significance for constraining the timing of the initial opening of the Ailao Shan–Song Ma Paleo-Tethys Ocean basin. However, the understanding of this process has been limited by the scarcity of reliable paleomagnetic data. [Methods] In this study, systematic paleomagnetic, rock magnetic, and petrographic analyses were conducted on red beds and limestones of the Upper Silurian Kuanti Formation from the Qujing area, Yunnan Province. [Results] The samples were, however, very likely remagnetized during the Cenozoic. Rock magnetic analyses indicate that the red beds are predominated by hematite as the primary carrier of magnetization, with minor contributions possibly from magnetite/titanomagnetite. Anisotropy of magnetic susceptibility (AMS) results reveal combined features of sedimentary, incipient deformation and strong cleavage fabrics, suggesting that the sediments may have undergone significant syn-depositional or post-depositional tectonic deformation. Lithological observations indicate that the magnetic minerals within both the red beds and limestones are primarily authigenic. From 14 sites (85 red bed and limestone specimens), a stable, high-temperature or high-field characteristic remanent magnetization (ChRM) component, converging towards the origin, was isolated, yielding a mean direction of Declination (D_g)= 332.2°, Inclination (I_g)= 51.6°, precision parameter (k_g)= 19.0, confidence cone half-angle of the mean direction (α₉₅)= 9.4° before and of Declination (D_s)= 342.5°, Inclination (I_s)= 25.7°, precision parameter (k_s)= 15.8, confidence cone half-angle of the mean direction (α₉₅) = 10.3° after the tilt-adjustment. Several fold tests indicate a negative result. The corresponding paleomagnetic pole calculated from the in-situ ChRM direction is located at 64.9°N, 35.2°E (A₉₅=7.9°). This paleomagnetic pole is consistent with reference poles for the SCB between 20~5 Ma, suggesting that the Kuanti Formation underwent remagnetization at approximately 20 Ma. [Conclusion] Integrating these results with previously reported reliable paleomagnetic data from small blocks within the southeastern Tibetan Plateau and the SCB since 50 Ma, as well as prior studies on the tectonic evolution of the southeastern Tibetan Plateau, a two-stage model of co-evolution between the SCB and the southeastern Tibetan Plateau is proposed. During 50~20 Ma, collision between the Indian and Eurasian plates resulted in the uplift and crustal shortening of the southeastern Tibetan Plateau. The fault systems along the southeastern Tibetan Plateau exhibited left-lateral strike-slip motion, which induced clockwise rotation of the SCB relative to stable Eurasia. The amount of clockwise rotation varied across different locations of the SCB, with sites closer to the southeastern Tibetan Plateau fault systems experiencing larger rotations. Since 20 Ma, continuous northward subduction of the Indian Plate beneath Eurasia, combined with multiple dynamic processes, including lower to middle crustal flow, gravitational spreading, mantle convection inducing by the tearing of the Indian Plate, and Pacific–Indian Ocean subduction, has driven clockwise rotation and extrusion of the southeastern Tibetan Plateau. During this stage, the fault systems exhibit right-lateral strike-slip motion, while the SCB underwent counterclockwise rotation relative to stable Eurasia. The magnitude of rotation is generally consistent across different locations. [Significance] Therefore, the transition of the SCB from a “clockwise rotation” to a “counterclockwise rotation” behavior essentially represents a direct manifestation of the shift in the geodynamic regime along the southeastern Tibetan Plateau from vertical uplift to tectonic extrusion. The ~20 Ma paleomagnetic data in this study provide robust evidence for a regional reversal of the tectonic framework along the southeastern Tibetan Plateau.

Wu Chengjie^1,2，Zeng Huaien^1,2,3，Chen Jun⁴，FengYu⁵ , Li xi^2,3，WeiPengcheng^2,3,Yan Baorui^1,2

chengjie wu, HuaiEn CENG, jun chen, Yu FENG, xi li, pengcheng wei, baorui yan

doi: 10.12090/j.issn.1006-6616.2025077

[Abstract](514) [PDF 1363KB](648)

Abstract:
Accurate prediction of landslide displacement is a crucial component of landslide early warning systems. This paper proposes a landslide displacement prediction model based on Gaussian Process Regression (GPR) combined with diverse time-series feature engineering, achieving high-precision displacement prediction and uncertainty quantification. TAKING THE BAZIMEN LANDSLIDE AS AN EXAMPLE, During the feature engineering phase, displacement lag features, rolling mean of rainfall, rolling variance of reservoir water level, and displacement change rate are constructed. Additionally, temporal decomposition features including monthly and quarterly components are extracted. SUBSEQUENTLY, EMPLOY THREE-FOLD TIME SERIES CROSS-VALIDATION, ALONG WITH A GRID SEARCH SCHEME, TO OPTIMIZE HYPERPARAMETERS IN CONJUNCTION WITH THE TIME SERIES CROSS-VALIDATION STRATEGY, THEREBY MITIGATING THE RISK OF OVERFITTING IN THE SMALL-SAMPLE SCENARIO. The results demonstrate that after incorporating multi-source temporal features, the prediction coefficients of determination (R²) for monitoring points ZG110 and ZG111 at the Bazimen Landslide significantly increase to above 0.99. Metrics such as MAE, RMSE, and MAPE are substantially reduced, indicating a significant improvement in prediction accuracy. This study integrates probabilistic modeling with feature interpretability analysis. The proposed method achieves high-precision landslide displacement prediction in small-sample environments while simultaneously quantifying prediction uncertainty. It provides effective decision support for landslide risk early warning and engineering safety assessment.

More>

TopicMore>

Supervisor： China Geological Survey

Sponsor： Institute of Geomechanics, Chinese Academy of Geological Sciences; Geological Society of China (GSC)

Editor-in-Chief： DENG Jun

ISSN 1006-6616

CN 11-3672/P

Post Issue Number 82-124

TopicMore>

News

Notice

Download

Conference

Links

Papers by research area