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, Available online , doi: 10.12090/j.issn.1006-6616.2025179
Abstract:
[Objective] The Cenozoic provenance evolution of the northern Yangtze River Delta remains poorly understood due to a scarcity of continuous, deep sedimentary records. [Methods] To address this knowledge gap, we present a comprehensive analysis of the upper 408 m unconsolidated succession from Core ZKA5, located in the Nantong area. Through integrated lithological observation, grain size analysis, and detailed heavy mineral identification, we reconstruct the sedimentary environmental history and delineate the provenance shifts since the late Cenozoic. [Results] Our results show that the stratigraphic sequence comprises six lithostratigraphic units, include the Yancheng, Haimen, Qidong, Kunshan, Gehu, and Rudong Formations, and is characterized by five sedimentary facies, include alluvial plain, channel, floodplain, delta plain, and intertidal facies. Heavy mineral assemblages reveal a significant provenance transition. Sediments during the late Neogene were predominantly sourced from the northern basin of the middle-upper Huai River. However, beginning in the early Quaternary (approximately at ~2.6 Ma), the dominant sediment source has progressively shifted from the Huai River basin to the middle‑lower reaches of the Yangtze River basin. [Conclusion] We interpret this provenance shift to be primarily driven by the southward migration of the regional depocenter from the Subei Basin to the Yangtze River Delta, coupled with changes in the East Asian monsoon precipitation regime during the Quaternary. [Significance] This study reveals the transformation of the provenance system driven by tectonic subsidence and climatic forcing, providing critical empirical evidence for the tectono-sedimentary-modification coupling mechanism in the Yangtze River Delta.
[Objective] The Cenozoic provenance evolution of the northern Yangtze River Delta remains poorly understood due to a scarcity of continuous, deep sedimentary records. [Methods] To address this knowledge gap, we present a comprehensive analysis of the upper 408 m unconsolidated succession from Core ZKA5, located in the Nantong area. Through integrated lithological observation, grain size analysis, and detailed heavy mineral identification, we reconstruct the sedimentary environmental history and delineate the provenance shifts since the late Cenozoic. [Results] Our results show that the stratigraphic sequence comprises six lithostratigraphic units, include the Yancheng, Haimen, Qidong, Kunshan, Gehu, and Rudong Formations, and is characterized by five sedimentary facies, include alluvial plain, channel, floodplain, delta plain, and intertidal facies. Heavy mineral assemblages reveal a significant provenance transition. Sediments during the late Neogene were predominantly sourced from the northern basin of the middle-upper Huai River. However, beginning in the early Quaternary (approximately at ~2.6 Ma), the dominant sediment source has progressively shifted from the Huai River basin to the middle‑lower reaches of the Yangtze River basin. [Conclusion] We interpret this provenance shift to be primarily driven by the southward migration of the regional depocenter from the Subei Basin to the Yangtze River Delta, coupled with changes in the East Asian monsoon precipitation regime during the Quaternary. [Significance] This study reveals the transformation of the provenance system driven by tectonic subsidence and climatic forcing, providing critical empirical evidence for the tectono-sedimentary-modification coupling mechanism in the Yangtze River Delta.
, Available online , doi: 10.12090/j.issn.1006-6616.2026006
Abstract:
[Objective] Landslide disasters represent complex geomorphological hazards occurring at the Earth's surface under the combined influence of internal and external geological dynamics. Although tectonic stress fields significantly affect the evolution and spatial distribution of landslides, quantitative research regarding the specific impact of tectonic stress on landslide development remains insufficient. This study aims to quantify the influencing effects of tectonic stress fields on landslide distribution across different geomorphological zones in the upper and middle reaches of the Dadu River area. Dadu River area lies in the transition zone between the eastern Tibetan Plateau and the Sichuan Basin—a region known for intense tectonic activity, rugged topography, and frequent landslides. [Methods] Focusing on four distinct zones (S1-S4) with concentrated landslide distributions, a newly developed in-situ stress depth–intensity model for the southeastern Tibetan Plateau was introduced. The horizontal tectonic stress fields and topography-induced stress fields (generated by gravity) were quantitatively calculated at grid points within the landslide boundaries of each zone. These calculated stress fields were subsequently integrated with slope geometric characteristics (slope length, gradient, and aspect), landslide attributes (area, frequency, and sliding direction), and regional geological-geomorphological backgrounds to analyze the differentiated mechanisms of tectonic stress on landslide evolution. [Results] Significant variations in the influence of tectonic stress on landslide development were observed across the four zones: (1) Upstream subdivision (S1): The proportion of tectonic stress is the lowest across the entire Dadu River area (approximately 50%). The landslide slope length probability (RL) increases monotonically with slope length (L), aligning closely with the theoretical curve dominated by topographic stress, which indicates that landslide development in S1 is primarily governed by gravitational topographic stress. (2) Midstream subdivisions (S2, S3):Situated at the intersection of multiple fault zones with frequent seismic activity, the proportion of tectonic stress increases markedly to approximately 63%. The landslide slope length probability (RL) exhibits a uniform and stable distribution within the 1 km to 3.5 km range. This pattern indicates a high proportion of earthquake-induced landslides, where instantaneous stress release from seismic events triggers slope instability that correlates weakly with slope length.; (3) Tributary (Liusha River) subdivision (S4): Although the calculated tectonic stress proportion approaches 80% with a peak landslide probability occurring at shorter slope lengths (approximately 1 km~2 km), wide exposures of low-strength mudstones and sandstones cause the calculated tectonic stress to be significantly overestimated compared to actual conditions; landslide development in S4 is ultimately influenced primarily by lithology, leading to the concentrated clustering of short-length and low-gradient landslides. [Conclusion] In conclusion, landslide development in the upstream subdivision (S1) is primarily influenced by topography-induced stress, while the midstream subdivisions (S2, S3) are significantly affected by tectonic stress. The instantaneous release of tectonic stress caused by earthquakes breaks the slope stress equilibrium, and the instability process has a weak correlation with slope length. The tributary subdivision (S4) is mainly influenced by weak lithology rather than tectonic stress. Overall, tectonic stress, as a component of the initial stress field, plays a crucial role in slope stress equilibrium. Under the continuous action of external forces such as weathering, rainfall, and earthquakes, the tectonic stress is weakened due to the reduction of the elastic modulus, leading to mechanical imbalance and subsequently influencing landslide development. [Significance] The differing characteristics of tectonic stress factors influencing landslide development across various subdivisions of the Dadu River basin offer new insights into understanding the spatial distribution patterns and mechanisms of landslides. Meanwhile, considering the impact of rock mass mechanical property degradation over time on the initial stress field may be a feasible direction to connect long-term geological evolution with short-term landslide triggering processes. This study employs a quantitative mechanical approach to reveal the key factors influencing landslide development in different sections of the Dadu River area, offering new insights into the role of tectonic stress in landslide spatial distribution patterns.
[Objective] Landslide disasters represent complex geomorphological hazards occurring at the Earth's surface under the combined influence of internal and external geological dynamics. Although tectonic stress fields significantly affect the evolution and spatial distribution of landslides, quantitative research regarding the specific impact of tectonic stress on landslide development remains insufficient. This study aims to quantify the influencing effects of tectonic stress fields on landslide distribution across different geomorphological zones in the upper and middle reaches of the Dadu River area. Dadu River area lies in the transition zone between the eastern Tibetan Plateau and the Sichuan Basin—a region known for intense tectonic activity, rugged topography, and frequent landslides. [Methods] Focusing on four distinct zones (S1-S4) with concentrated landslide distributions, a newly developed in-situ stress depth–intensity model for the southeastern Tibetan Plateau was introduced. The horizontal tectonic stress fields and topography-induced stress fields (generated by gravity) were quantitatively calculated at grid points within the landslide boundaries of each zone. These calculated stress fields were subsequently integrated with slope geometric characteristics (slope length, gradient, and aspect), landslide attributes (area, frequency, and sliding direction), and regional geological-geomorphological backgrounds to analyze the differentiated mechanisms of tectonic stress on landslide evolution. [Results] Significant variations in the influence of tectonic stress on landslide development were observed across the four zones: (1) Upstream subdivision (S1): The proportion of tectonic stress is the lowest across the entire Dadu River area (approximately 50%). The landslide slope length probability (RL) increases monotonically with slope length (L), aligning closely with the theoretical curve dominated by topographic stress, which indicates that landslide development in S1 is primarily governed by gravitational topographic stress. (2) Midstream subdivisions (S2, S3):Situated at the intersection of multiple fault zones with frequent seismic activity, the proportion of tectonic stress increases markedly to approximately 63%. The landslide slope length probability (RL) exhibits a uniform and stable distribution within the 1 km to 3.5 km range. This pattern indicates a high proportion of earthquake-induced landslides, where instantaneous stress release from seismic events triggers slope instability that correlates weakly with slope length.; (3) Tributary (Liusha River) subdivision (S4): Although the calculated tectonic stress proportion approaches 80% with a peak landslide probability occurring at shorter slope lengths (approximately 1 km~2 km), wide exposures of low-strength mudstones and sandstones cause the calculated tectonic stress to be significantly overestimated compared to actual conditions; landslide development in S4 is ultimately influenced primarily by lithology, leading to the concentrated clustering of short-length and low-gradient landslides. [Conclusion] In conclusion, landslide development in the upstream subdivision (S1) is primarily influenced by topography-induced stress, while the midstream subdivisions (S2, S3) are significantly affected by tectonic stress. The instantaneous release of tectonic stress caused by earthquakes breaks the slope stress equilibrium, and the instability process has a weak correlation with slope length. The tributary subdivision (S4) is mainly influenced by weak lithology rather than tectonic stress. Overall, tectonic stress, as a component of the initial stress field, plays a crucial role in slope stress equilibrium. Under the continuous action of external forces such as weathering, rainfall, and earthquakes, the tectonic stress is weakened due to the reduction of the elastic modulus, leading to mechanical imbalance and subsequently influencing landslide development. [Significance] The differing characteristics of tectonic stress factors influencing landslide development across various subdivisions of the Dadu River basin offer new insights into understanding the spatial distribution patterns and mechanisms of landslides. Meanwhile, considering the impact of rock mass mechanical property degradation over time on the initial stress field may be a feasible direction to connect long-term geological evolution with short-term landslide triggering processes. This study employs a quantitative mechanical approach to reveal the key factors influencing landslide development in different sections of the Dadu River area, offering new insights into the role of tectonic stress in landslide spatial distribution patterns.
, Available online , doi: 10.12090/j.issn.1006-6616.2025161
Abstract:
Abstract: [Objective] Aiming at the frequent wellbore collapse problems encountered in the drilling of highly deviated and horizontal wells in the hard brittle oil shale formation of the Shahejie Formation in the Jiyang Depression, this study clarifies the main controlling factors affecting wellbore stability and establishes a multi-field coupled evaluation and prediction method suitable for this formation. [Method] X-ray diffraction, scanning electron microscopy and CT scanning were used to analyze the mineral composition and micro-fracture characteristics of core samples. Petrophysical and mechanical parameters of the rock were determined by porosity-permeability tests and triaxial mechanical experiments. Wellbore stability evaluation was carried out by combining the effective stress field and seepage field around the wellbore, considering the coupling of fracture mechanical weak plane effect, drilling fluid pressure penetration and wellbore trajectory. [Results] The results show that the oil shale is dominated by quartz and clay minerals, and the clay minerals are mainly non-expansive illite, so water-based drilling fluids have little influence on rock mechanical properties. The rock mass is developed with multiple sets of micro-fractures with a width of about 2–3 μm, and is characterized by low porosity, low permeability and dense lithology. The compressive strength of homogeneous core samples is 183.5 MPa, while that of fractured core samples decreases to 37.2–62.5 MPa. After 12 days of immersion in drilling fluid, the strength reduction ranges from 3.87% to 20.51%. When drilling horizontal wells along the minimum horizontal principal stress direction, the collapse risk is high within the inclination angle range of 50°–90°, leading to wellbore instability. When drilling along the maximum horizontal principal stress direction, the high collapse pressure zone is concentrated at the inclination angle of 25°–45°. The drilling fluid pressure penetration effect increases the equivalent density of critical collapse pressure by 0.115–0.155 g/cm³. [Conclusion] The wellbore stability of the Shahejie Formation is jointly controlled by wellbore trajectory, mechanical weakness of fractures, and drilling fluid pressure penetration. Optimizing the wellbore trajectory along the maximum horizontal principal stress direction and enhancing the sealing performance of drilling fluid can effectively reduce the risk of wellbore collapse. [Significance] The research findings can provide guidance for achieving effective and safe drilling in oil shale formations.
Abstract: [Objective] Aiming at the frequent wellbore collapse problems encountered in the drilling of highly deviated and horizontal wells in the hard brittle oil shale formation of the Shahejie Formation in the Jiyang Depression, this study clarifies the main controlling factors affecting wellbore stability and establishes a multi-field coupled evaluation and prediction method suitable for this formation. [Method] X-ray diffraction, scanning electron microscopy and CT scanning were used to analyze the mineral composition and micro-fracture characteristics of core samples. Petrophysical and mechanical parameters of the rock were determined by porosity-permeability tests and triaxial mechanical experiments. Wellbore stability evaluation was carried out by combining the effective stress field and seepage field around the wellbore, considering the coupling of fracture mechanical weak plane effect, drilling fluid pressure penetration and wellbore trajectory. [Results] The results show that the oil shale is dominated by quartz and clay minerals, and the clay minerals are mainly non-expansive illite, so water-based drilling fluids have little influence on rock mechanical properties. The rock mass is developed with multiple sets of micro-fractures with a width of about 2–3 μm, and is characterized by low porosity, low permeability and dense lithology. The compressive strength of homogeneous core samples is 183.5 MPa, while that of fractured core samples decreases to 37.2–62.5 MPa. After 12 days of immersion in drilling fluid, the strength reduction ranges from 3.87% to 20.51%. When drilling horizontal wells along the minimum horizontal principal stress direction, the collapse risk is high within the inclination angle range of 50°–90°, leading to wellbore instability. When drilling along the maximum horizontal principal stress direction, the high collapse pressure zone is concentrated at the inclination angle of 25°–45°. The drilling fluid pressure penetration effect increases the equivalent density of critical collapse pressure by 0.115–0.155 g/cm³. [Conclusion] The wellbore stability of the Shahejie Formation is jointly controlled by wellbore trajectory, mechanical weakness of fractures, and drilling fluid pressure penetration. Optimizing the wellbore trajectory along the maximum horizontal principal stress direction and enhancing the sealing performance of drilling fluid can effectively reduce the risk of wellbore collapse. [Significance] The research findings can provide guidance for achieving effective and safe drilling in oil shale formations.
, Available online , doi: 10.12090/j.issn.1006-6616.2026091
Abstract:
T [Objective] To reveal the intrinsic link between manganese mineralization in the Kunlun-Altyn Tagh-Tianshan-Junggar region surrounding the Tarim Basin and the coupling mechanism among the crust, mantle, and inner core within the Earth's rotational system, and to elucidate the deep geodynamic mechanism responsible for manganese ore formation in this region. [Methods] The metallogenic ages and ore-forming material sources of the major manganese belts surrounding the Tarim Basin were compiled, and the paleogeographic positions of the Kunlun-Altyn Tagh-Tianshan orogenic belt during each metallogenic epoch were reconstructed based on paleomagnetic and paleogeographic data. The principles of rotational Earth dynamics were then applied to analyze angular momentum redistribution among the solid inner core, mantle, and crust during poleward or equatorward crustal migration, and its effects on mantle convection, magmatic activity, and geomagnetic field reversal. [Results] Manganese mineralization in the study area predominantly occurred during the Early-Middle Ordovician, Early Devonian, Early-Late Carboniferous, and Early Permian, with ore-forming materials primarily derived from manganese-bearing magmatic hydrothermal fluids or hot liquids. All identified metallogenic events coincided with periods of geomagnetic field reversal. During the Early-Middle Ordovician, Early Devonian, and Early-Late Carboniferous–Early Permian, the paleogeographic positions of the Kunlun-Altyn Tagh-Tianshan orogenic belt were situated near the equator, between 20°N and 20°S. According to the principles of rotational Earth dynamics, when the crust migrates poleward, angular momentum of the crust decreases while that of the mantle and solid inner core increases; the mantle, due to its rheological characteristics, undergoes extensional upwelling near the equator, facilitating the upward migration of magmatic hydrothermal fluids and intensifying magmatic activity. The positively charged solid inner core undergoes super-rotation, and when the velocity difference between the positively charged inner core and the negatively charged liquid outer core exceeds a critical threshold—at which point the observed surface geomagnetic field intensity drops to zero—a geomagnetic reversal is triggered. Conversely, when the crust migrates equatorward, angular momentum of the crust increases while that of the mantle and solid inner core decreases; the positively charged solid inner core decelerates, and the geomagnetic field recovers to its normal state, during which extensional upwelling in the mantle occurs at mid-to-high latitudes. [Conclusions] The formation of manganese deposits in the East-West Kunlun, East-West Tianshan, and Altyn Tagh regions is closely related to mantle extensional upwelling near the equator during geomagnetic reversal periods. This mineralization is the product of crust-mantle-inner core coupling within the Earth's rotational system, rather than a result of isolated shallow geological processes. [Significance] This study establishes, for the first time, a linkage between regional manganese mineralization and the crust-mantle-inner core angular momentum exchange mechanism within the framework of rotational Earth dynamics, providing a novel geodynamic perspective for understanding deep-time metallogenic events. It reveals the genetic association between geomagnetic reversal periods and mantle-derived mineralization, offering a theoretical basis for predicting concealed manganese deposits using paleomagnetic and paleogeographic data, and provides a representative case for the scientific proposition that deep Earth processes control shallow crustal mineralization, contributing significantly to the refinement of the global manganese metallogenic theory.
T [Objective] To reveal the intrinsic link between manganese mineralization in the Kunlun-Altyn Tagh-Tianshan-Junggar region surrounding the Tarim Basin and the coupling mechanism among the crust, mantle, and inner core within the Earth's rotational system, and to elucidate the deep geodynamic mechanism responsible for manganese ore formation in this region. [Methods] The metallogenic ages and ore-forming material sources of the major manganese belts surrounding the Tarim Basin were compiled, and the paleogeographic positions of the Kunlun-Altyn Tagh-Tianshan orogenic belt during each metallogenic epoch were reconstructed based on paleomagnetic and paleogeographic data. The principles of rotational Earth dynamics were then applied to analyze angular momentum redistribution among the solid inner core, mantle, and crust during poleward or equatorward crustal migration, and its effects on mantle convection, magmatic activity, and geomagnetic field reversal. [Results] Manganese mineralization in the study area predominantly occurred during the Early-Middle Ordovician, Early Devonian, Early-Late Carboniferous, and Early Permian, with ore-forming materials primarily derived from manganese-bearing magmatic hydrothermal fluids or hot liquids. All identified metallogenic events coincided with periods of geomagnetic field reversal. During the Early-Middle Ordovician, Early Devonian, and Early-Late Carboniferous–Early Permian, the paleogeographic positions of the Kunlun-Altyn Tagh-Tianshan orogenic belt were situated near the equator, between 20°N and 20°S. According to the principles of rotational Earth dynamics, when the crust migrates poleward, angular momentum of the crust decreases while that of the mantle and solid inner core increases; the mantle, due to its rheological characteristics, undergoes extensional upwelling near the equator, facilitating the upward migration of magmatic hydrothermal fluids and intensifying magmatic activity. The positively charged solid inner core undergoes super-rotation, and when the velocity difference between the positively charged inner core and the negatively charged liquid outer core exceeds a critical threshold—at which point the observed surface geomagnetic field intensity drops to zero—a geomagnetic reversal is triggered. Conversely, when the crust migrates equatorward, angular momentum of the crust increases while that of the mantle and solid inner core decreases; the positively charged solid inner core decelerates, and the geomagnetic field recovers to its normal state, during which extensional upwelling in the mantle occurs at mid-to-high latitudes. [Conclusions] The formation of manganese deposits in the East-West Kunlun, East-West Tianshan, and Altyn Tagh regions is closely related to mantle extensional upwelling near the equator during geomagnetic reversal periods. This mineralization is the product of crust-mantle-inner core coupling within the Earth's rotational system, rather than a result of isolated shallow geological processes. [Significance] This study establishes, for the first time, a linkage between regional manganese mineralization and the crust-mantle-inner core angular momentum exchange mechanism within the framework of rotational Earth dynamics, providing a novel geodynamic perspective for understanding deep-time metallogenic events. It reveals the genetic association between geomagnetic reversal periods and mantle-derived mineralization, offering a theoretical basis for predicting concealed manganese deposits using paleomagnetic and paleogeographic data, and provides a representative case for the scientific proposition that deep Earth processes control shallow crustal mineralization, contributing significantly to the refinement of the global manganese metallogenic theory.
, Available online , doi: 10.12090/j.issn.1006-6616.2025186
Abstract:
[Objective] China possesses abundant shale oil and gas resources, but frequent casing deformation (CD) during hydraulic fracturing in horizontal wells has become a critical constraint on the economic development of these resources. The industry gradually reaches an agreement on geomechanical mechanism of the casing shearing deformation of shale oil and gas, but lacks further knowledge on specific cause of CD (such as ‘pre-fracturing CD’) and predictive method for determining wellbore cleanout tool’s maximum diameter. [Methods] To solve these problems, by taking the Luzhou block deep shale gas reservoir as an example, (1) a predictive method for determining wellbore cleanout tool’s maximum diameter based on multi-perspective and quantitative confirmation of 3D CD morphology using 24-arm multi-finger logging tool (MIT) is proposed, and, (2) by comprehensive analysis of information from geological-engineering aspects, such as CD features, subseismic fault and large fracture location, fracturing events of specific stage, micro-seismic data and so on, [Results] specific causes of 225 CD sections in Luzhou are confirmed, and then new classification of four CD causes are proposed: objective-well-near CD, objective-well-far CD, offset-well-caused CD, and pre-fracturing CD. [Conclusion] (1) 3D imaging of CD intervals using non-centralized MIT logging not only reveals the true deformation morphology but also quantitatively characterizes shear displacement. (2) In deep shale gas development, the proportion of CD points caused by offset-well fracturing (55%) exceeds that caused by objective-well fracturing (45%). [Significance] (1) The propose of the predictive method for maximum wellbore cleanout tool diameter provides critical technical parameters for post-CD tool selection (e.g., bridge plug size). (2) The novel CD causation classification establishes a theoretical basis for optimizing fracturing sequence and scale of CD wells’ pad and adjacent pads, and CD-integrated mitigation strategies. This study has significant practical implications for shale oil and gas development.
[Objective] China possesses abundant shale oil and gas resources, but frequent casing deformation (CD) during hydraulic fracturing in horizontal wells has become a critical constraint on the economic development of these resources. The industry gradually reaches an agreement on geomechanical mechanism of the casing shearing deformation of shale oil and gas, but lacks further knowledge on specific cause of CD (such as ‘pre-fracturing CD’) and predictive method for determining wellbore cleanout tool’s maximum diameter. [Methods] To solve these problems, by taking the Luzhou block deep shale gas reservoir as an example, (1) a predictive method for determining wellbore cleanout tool’s maximum diameter based on multi-perspective and quantitative confirmation of 3D CD morphology using 24-arm multi-finger logging tool (MIT) is proposed, and, (2) by comprehensive analysis of information from geological-engineering aspects, such as CD features, subseismic fault and large fracture location, fracturing events of specific stage, micro-seismic data and so on, [Results] specific causes of 225 CD sections in Luzhou are confirmed, and then new classification of four CD causes are proposed: objective-well-near CD, objective-well-far CD, offset-well-caused CD, and pre-fracturing CD. [Conclusion] (1) 3D imaging of CD intervals using non-centralized MIT logging not only reveals the true deformation morphology but also quantitatively characterizes shear displacement. (2) In deep shale gas development, the proportion of CD points caused by offset-well fracturing (55%) exceeds that caused by objective-well fracturing (45%). [Significance] (1) The propose of the predictive method for maximum wellbore cleanout tool diameter provides critical technical parameters for post-CD tool selection (e.g., bridge plug size). (2) The novel CD causation classification establishes a theoretical basis for optimizing fracturing sequence and scale of CD wells’ pad and adjacent pads, and CD-integrated mitigation strategies. This study has significant practical implications for shale oil and gas development.
, Available online , doi: 10.12090/j.issn.1006-6616.2026001
Abstract:
[Objective] The Zhuguang uranium concentration area is the most important hard rock type uranium resource and industrial base in South China, which consists of Lujing, Sanjiu, Chengkou, Changjiang, Baishun, Lanhe and Quan 'an uranium fields. The ore deposits and orebodies are obviously controlled by the structures. The uranium deposits occur in the granite body and the early Paleozoic shallow metamorphic clastic rocks near the contact zone, and the host rocks are not selective. There are similarities and differences in ore-bearing structures in different uranium ore fields, which leads to disputes on the understanding of ore-controlling structures in the whole ore concentration area. [Methods] Based on the systematic analysis of the morphology, occurrence and combination characteristics of ore-bearing structures in major uranium ore fields, this paper uses the principal stress trace theory of material mechanics and the formation history of regional main faults in ore concentration area to inverse the formation mechanism of ore-bearing structures. [Results] The study shows that the morphological characteristics of ore-bearing structures in ore concentration area reflect the mechanical properties of compression and compression-torsion when they are formed. The occurrence of ore-bearing structures is generally dominated by near SN-trending, followed by NNE- and NNW-trending, a little NE-trending, some NW- and NEE-trending, and only theses ore-bearing structures of interlayer faults formed earlier in shallow metamorphic clastic rocks are NWW-trending. There is a significant regional law in the trend difference of ore-bearing structures in different uranium fields, that is, the ore-bearing structures in the central part of the ore concentration area are mainly NNW (near SN)-trending, while those in the northern and southern parts of the ore concentration area are mainly NNE-treading, which is S-shaped as a whole.[Conclusions] Combined with the regional tectonic setting, it is determined that the ore-controlling structure framework in the Zhuguang uranium concentration area is SN-trending, and it is considered that during the formation of ore-bearing structure, the relatively complete rock block as Zhuguangshan complex rock mass was subjected to the maximum principal compressive stress in the near EW-trending. There was no NE-trending concealed structure in the middle part of the ore-concentrated area, so the principal stress trace remained unchanged, that is, the compressive stress trace was near EW trending and the tensile stress trace was near SN-trending, forming a near SN-trending ore-bearing structure. Due to the existence of NE-trending concealed structures in the north and south parts of the ore concentration area, the direction of the main stress trace is changed and the NE-trending ore-bearing structures are formed. [Significane] This study not only reasonably explains the regular changes of ore-bearing structural trends in different uranium fields in Zhuguang uranium concentration area, but also provides theoretical guidance for prospecting prediction in different parts of the ore concentration area, enriching the structural ore-controlling theory of hydrothermal uranium deposits, and has a demonstration role in the structural ore-controlling research of other ore concentration areas and ore fields as well.
[Objective] The Zhuguang uranium concentration area is the most important hard rock type uranium resource and industrial base in South China, which consists of Lujing, Sanjiu, Chengkou, Changjiang, Baishun, Lanhe and Quan 'an uranium fields. The ore deposits and orebodies are obviously controlled by the structures. The uranium deposits occur in the granite body and the early Paleozoic shallow metamorphic clastic rocks near the contact zone, and the host rocks are not selective. There are similarities and differences in ore-bearing structures in different uranium ore fields, which leads to disputes on the understanding of ore-controlling structures in the whole ore concentration area. [Methods] Based on the systematic analysis of the morphology, occurrence and combination characteristics of ore-bearing structures in major uranium ore fields, this paper uses the principal stress trace theory of material mechanics and the formation history of regional main faults in ore concentration area to inverse the formation mechanism of ore-bearing structures. [Results] The study shows that the morphological characteristics of ore-bearing structures in ore concentration area reflect the mechanical properties of compression and compression-torsion when they are formed. The occurrence of ore-bearing structures is generally dominated by near SN-trending, followed by NNE- and NNW-trending, a little NE-trending, some NW- and NEE-trending, and only theses ore-bearing structures of interlayer faults formed earlier in shallow metamorphic clastic rocks are NWW-trending. There is a significant regional law in the trend difference of ore-bearing structures in different uranium fields, that is, the ore-bearing structures in the central part of the ore concentration area are mainly NNW (near SN)-trending, while those in the northern and southern parts of the ore concentration area are mainly NNE-treading, which is S-shaped as a whole.[Conclusions] Combined with the regional tectonic setting, it is determined that the ore-controlling structure framework in the Zhuguang uranium concentration area is SN-trending, and it is considered that during the formation of ore-bearing structure, the relatively complete rock block as Zhuguangshan complex rock mass was subjected to the maximum principal compressive stress in the near EW-trending. There was no NE-trending concealed structure in the middle part of the ore-concentrated area, so the principal stress trace remained unchanged, that is, the compressive stress trace was near EW trending and the tensile stress trace was near SN-trending, forming a near SN-trending ore-bearing structure. Due to the existence of NE-trending concealed structures in the north and south parts of the ore concentration area, the direction of the main stress trace is changed and the NE-trending ore-bearing structures are formed. [Significane] This study not only reasonably explains the regular changes of ore-bearing structural trends in different uranium fields in Zhuguang uranium concentration area, but also provides theoretical guidance for prospecting prediction in different parts of the ore concentration area, enriching the structural ore-controlling theory of hydrothermal uranium deposits, and has a demonstration role in the structural ore-controlling research of other ore concentration areas and ore fields as well.
, Available online , doi: 10.12090/j.issn.1006-6616.2026071
Abstract:
[Objective] High-elevation long-runout rock avalanches may undergo progressive damage, fragmentation, particle dilation, and a transition from block-dominated motion to debris-flow-like movement. Conventional equivalent-fluid models efficiently reproduce runout but do not explicitly resolve damage-induced disintegration, whereas fully discrete approaches are computationally expensive at field scale. This study aims to clarify how damage evolution and particle-state transition affect the post-failure dynamics of the 1991 Touzhai landslide in Yunnan, China. [Methods] Three numerical schemes were established under the same three-dimensional terrain and initial source geometry: a Dynamic Analysis of Landslides in Three Dimensions (DAN3D) equivalent-fluid model, a Landslide Post-Failure 3D (LPF3D) multiphase-state model without damage evolution and structural disintegration, and an LPF3D full-state model coupling the Holmquist-Johnson-Cook (HJC) damage model, explicit structural discontinuities, and particle-state transition. Their motion duration, velocity evolution, runout distance, run-up pattern, deposition characteristics, damage variable, and particle volume fraction were compared to evaluate the roles of structural degradation and state-dependent particle interactions. [Results] Four principal results were obtained. First, the LPF3D full-state model reproduced the main observed kinematic characteristics of the Touzhai event. The simulated motion lasted approximately 120 s and evolved from initial failure and rapid acceleration through impact-induced disintegration and channelized transport to deceleration and deposition. The maximum horizontal runout was approximately 3650 m, the vertical drop was nearly 960 m, and the peak velocity exceeded 23 m/s. The simulated mass also reproduced the observed run-up pattern on the opposite valley slope, where field investigations reported a maximum run-up of approximately 55 m. The final deposit was thicker in the central part and thinner toward both sides, broadly consistent with the mapped distribution of the source, transit, and deposition zones. Second, the damage field and particle volume-fraction field revealed a continuous mechanical-state transition rather than a thermodynamic phase change. The damage variable increased progressively from a relatively low initial level and approached 1.0 in highly damaged zones during repeated impact and shearing, indicating substantial degradation of the original load-bearing rock structure. Concurrently, the front of the moving mass experienced stronger stretching and impact, developed a lower particle volume fraction, and entered a dilute, collision- and inertia-influenced state, whereas the rear retained a higher volume fraction and a denser block- or granular-state structure. This produced a distinct longitudinal pattern characterized by a dilute front and a dense rear. As the mass entered the gentler deposition area, velocity and shear rate decreased, particle contacts were re-established, and the main body underwent re-compaction. Third, the comparison between the two LPF3D schemes isolated the influence of damage and structural disintegration under the adopted material and boundary settings. When HJC damage evolution and structural disintegration were disabled while the basic LPF3D material and contact parameters were kept unchanged, the mass stopped after a runout of approximately 1500 m. In contrast, the full-state scheme reached approximately 3650 m. The comparison indicates that damage accumulation, block separation, particle rearrangement, and dilation reduced persistent interlocking and frictional contacts and increased the relative contribution of collision and inertia, thereby modifying resistance and energy redistribution during motion. Fourth, the DAN3D equivalent-fluid scheme reproduced the macroscopic runout through a calibrated frictional rheology, demonstrating its efficiency for estimating velocity, runout, and deposition at the slope scale. However, its state variables did not directly represent rock damage, block disintegration, or particle-state transition. The three-scheme comparison therefore shows that similar macroscopic runout can be reproduced through different model representations, but only the full-state LPF3D framework explicitly links the simulated runout to progressive structural degradation and the subsequent transition among solid-like, dense granular, dilute granular, and deposition states. [Conclusions] Under the parameter and boundary conditions adopted for the Touzhai case, damage accumulation and structural disintegration are important factors promoting particle rearrangement, dilation, mechanical-state transition, and long-runout movement. The simulated transition is spatially non-uniform: the strongly disturbed front becomes dilute and increasingly collision- and inertia-influenced, whereas the rear remains comparatively dense and contact-dominated. DAN3D is suitable for efficient macroscopic runout analysis, while the LPF3D full-state model provides a more physically interpretable description of the coupled evolution from jointed rock mass to blocks and granular debris. These findings are case-specific and should not be interpreted as a universal threshold or a single mechanism applicable to all high-elevation landslides. [Significance] By integrating damage evolution, structural discontinuities, and particle-state-dependent dynamics within one computational framework, this study provides a physically constrained approach for reconstructing high-elevation rock avalanche-to-debris-flow processes. The framework can support case-specific runout assessment and hazard analysis while clarifying the model assumptions and mechanisms underlying the predicted movement range.
[Objective] High-elevation long-runout rock avalanches may undergo progressive damage, fragmentation, particle dilation, and a transition from block-dominated motion to debris-flow-like movement. Conventional equivalent-fluid models efficiently reproduce runout but do not explicitly resolve damage-induced disintegration, whereas fully discrete approaches are computationally expensive at field scale. This study aims to clarify how damage evolution and particle-state transition affect the post-failure dynamics of the 1991 Touzhai landslide in Yunnan, China. [Methods] Three numerical schemes were established under the same three-dimensional terrain and initial source geometry: a Dynamic Analysis of Landslides in Three Dimensions (DAN3D) equivalent-fluid model, a Landslide Post-Failure 3D (LPF3D) multiphase-state model without damage evolution and structural disintegration, and an LPF3D full-state model coupling the Holmquist-Johnson-Cook (HJC) damage model, explicit structural discontinuities, and particle-state transition. Their motion duration, velocity evolution, runout distance, run-up pattern, deposition characteristics, damage variable, and particle volume fraction were compared to evaluate the roles of structural degradation and state-dependent particle interactions. [Results] Four principal results were obtained. First, the LPF3D full-state model reproduced the main observed kinematic characteristics of the Touzhai event. The simulated motion lasted approximately 120 s and evolved from initial failure and rapid acceleration through impact-induced disintegration and channelized transport to deceleration and deposition. The maximum horizontal runout was approximately 3650 m, the vertical drop was nearly 960 m, and the peak velocity exceeded 23 m/s. The simulated mass also reproduced the observed run-up pattern on the opposite valley slope, where field investigations reported a maximum run-up of approximately 55 m. The final deposit was thicker in the central part and thinner toward both sides, broadly consistent with the mapped distribution of the source, transit, and deposition zones. Second, the damage field and particle volume-fraction field revealed a continuous mechanical-state transition rather than a thermodynamic phase change. The damage variable increased progressively from a relatively low initial level and approached 1.0 in highly damaged zones during repeated impact and shearing, indicating substantial degradation of the original load-bearing rock structure. Concurrently, the front of the moving mass experienced stronger stretching and impact, developed a lower particle volume fraction, and entered a dilute, collision- and inertia-influenced state, whereas the rear retained a higher volume fraction and a denser block- or granular-state structure. This produced a distinct longitudinal pattern characterized by a dilute front and a dense rear. As the mass entered the gentler deposition area, velocity and shear rate decreased, particle contacts were re-established, and the main body underwent re-compaction. Third, the comparison between the two LPF3D schemes isolated the influence of damage and structural disintegration under the adopted material and boundary settings. When HJC damage evolution and structural disintegration were disabled while the basic LPF3D material and contact parameters were kept unchanged, the mass stopped after a runout of approximately 1500 m. In contrast, the full-state scheme reached approximately 3650 m. The comparison indicates that damage accumulation, block separation, particle rearrangement, and dilation reduced persistent interlocking and frictional contacts and increased the relative contribution of collision and inertia, thereby modifying resistance and energy redistribution during motion. Fourth, the DAN3D equivalent-fluid scheme reproduced the macroscopic runout through a calibrated frictional rheology, demonstrating its efficiency for estimating velocity, runout, and deposition at the slope scale. However, its state variables did not directly represent rock damage, block disintegration, or particle-state transition. The three-scheme comparison therefore shows that similar macroscopic runout can be reproduced through different model representations, but only the full-state LPF3D framework explicitly links the simulated runout to progressive structural degradation and the subsequent transition among solid-like, dense granular, dilute granular, and deposition states. [Conclusions] Under the parameter and boundary conditions adopted for the Touzhai case, damage accumulation and structural disintegration are important factors promoting particle rearrangement, dilation, mechanical-state transition, and long-runout movement. The simulated transition is spatially non-uniform: the strongly disturbed front becomes dilute and increasingly collision- and inertia-influenced, whereas the rear remains comparatively dense and contact-dominated. DAN3D is suitable for efficient macroscopic runout analysis, while the LPF3D full-state model provides a more physically interpretable description of the coupled evolution from jointed rock mass to blocks and granular debris. These findings are case-specific and should not be interpreted as a universal threshold or a single mechanism applicable to all high-elevation landslides. [Significance] By integrating damage evolution, structural discontinuities, and particle-state-dependent dynamics within one computational framework, this study provides a physically constrained approach for reconstructing high-elevation rock avalanche-to-debris-flow processes. The framework can support case-specific runout assessment and hazard analysis while clarifying the model assumptions and mechanisms underlying the predicted movement range.
, Available online , doi: 10.12090/j.issn.1006-6616.2026020
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.
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.
, Available online , doi: 10.12090/j.issn.1006-6616.2026042
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.
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.
, Available online , doi: 10.12090/j.issn.1006-6616.2025181
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 (Dg) = 332.2°, Inclination (Ig) = 51.6°, precision parameter (kg) = 19.0, confidence cone half-angle of the mean direction (α95) = 9.4° before and of Declination (Ds) = 342.5°, Inclination (Is) = 25.7°, precision parameter (ks) = 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.
[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 (Dg) = 332.2°, Inclination (Ig) = 51.6°, precision parameter (kg) = 19.0, confidence cone half-angle of the mean direction (α95) = 9.4° before and of Declination (Ds) = 342.5°, Inclination (Is) = 25.7°, precision parameter (ks) = 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.
, Available online , doi: 10.12090/j.issn.1006-6616.2025077
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.
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.
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
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