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Unstable evolution of railway slope under the rainfall-vibration joint action

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Journal of Mountain Science 2024年第4期21卷 1419-1431页

作者： DONG Haoyu WANG Jiading ZHANG Dengfei LI Lin XU Yuanjun state key laboratory of continental dynamics Department of GeologyNorthwest UniversityXi’an 710069China

Understanding the unstable evolution of railway slopes is the premise for preventing slope failure and ensuring the safe operation of ***,as two major factors affecting the stability of railway slopes,few scholars have explored the unstable evolution of railway slopes under the joint action of *** on the model test of sandy soil slope,the unstable evolution process of slope under locomotive vibration,rainfall,and rainfall-vibration joint action conditions was simulated in this *** comparing and analyzing the variation trends of soil pressure and water content of slope under these conditions,the change laws of pore pressure under the influence of vibration and rainfall were *** main control factors affecting the stability of slope structure under the joint action conditions were further *** with the slope failure phenomena under these three conditions,the causes of slope instability resulting from each leading factor were ***,according to the above conclusions,the unstable evolution of the slope under the rainfall-vibration joint action was *** test results show that the unstable evolution process of sandy soil slope,under the rainfall-vibration joint action,can be divided into:rainfall erosion cracking,vibration promotion penetrating,and slope instability sliding three *** the process of slope unstable evolution,rainfall and vibration play the roles of inducing and promoting slide *** addition,the deep cracks,which are the premise for the formation of the sliding surface,and the violent irregular fluctuation of soil pressure,which reflects the near penetration of the sliding surface,constitute the instability characteristics of the railway slope *** paper reveals the unstable evolution of sandy soil slopes under the joint action of rainfall-vibration,hoping to provide the theoretical basis for the early warning and prevention technology of railway slopes.

关键词： Rainfall vibration joint action Small scale model tests Unstable evolution process Unstable characteristics Inducing sliding and promoting sliding

Primary and Secondary Calcite in Chinese Loess Distinguished by Crystallinity and Implications for Illuviation Depth and East Asian Summer Monsoon Intensity

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Journal of Earth Science 2024年

作者： Yan Zhao Kangjun Huang Yuanqiang Guo Pan Zhang Yawen Lu Long Ma state key laboratory of continental dynamics Shaanxi key laboratory of early life and Environment department of geology Northwest University

The crystallinity has the potential to distinguish the primary and secondary calcite in Chinese loess， which then provides insights into illuviation depth and variations of the East Asian summer monsoon. However， this aspect has been rarely investigated. In this study， we defined the crystallinity of calcite as the Height/Area (H/A) ratio of the diffracted peak at crystal face (1 0 4). The H/A ratio inversely correlates with the average width of the diffracted peak， where a higher H/A ratio indicates higher crystallinity of calcite. Through the mixing and synthetic experiments， we found that the H/A ratio is minimally affected by factors such as calcite content， deposition temperature or rate but significantly influenced by the ionic impurity and the mixing proportion of different calcites. Subsequently， we examined desert samples of loess sources and loess carbonate nodules. Desert samples predominantly consist of primary calcite which inherits characteristics from cryptocrystalline limestone with high levels of ionic impurities resulting in low H/A ratio of 4.30 ± 0.51. In contrast， loess carbonate nodules contain abundant secondary calcite precipitated within soil interstices with low levels of ionic impurities leading to a significantly higher H/A ratio of 7.76 ± 0.82. Consequently， higher H/A ratios during interglacial periods compared to glacial periods are attributed to variations in relative proportions between primary and secondary calcite in loess sequences. The thickness， between the glacial-interglacial boundary and the depth where the H/A ratio starts to increase from the bottom to the top in the loess layer， can be used to indicate the illuviation depth of upper-soil carbonates and the intensity of the East Asian summer monsoon. This proxy can be further applied in long-term loess sequences to uncover the summer monsoon evolution.

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Thermal History of Cambrian Burgess Shale-Type Deposits:New Insights from the early Cambrian Chengjiang and Qingjiang Fossils of South China

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Journal of Earth Science 2024年第4期35卷 1215-1223页

作者： Yuheng Qiao Linhao Cui Guangyuan Xing Dongjing Fu Chao Chang Robert Gaines Xingliang Zhang state key laboratory of continental dynamics Shaanxi Key laboratory of Early Life and EnvironmentsDepartment of GeologyNorthwest UniversityXi’an710069China department of geology Pomona CollegeClaremontCA91711USA

Burgess Shale-type deposits provide a wealth of information on the early evolution of *** that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s *** over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and early Cambrian *** alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been *** we investigate peak metamorphic temperatures of the two deposits using two independent *** gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the early Jurassic,corresponding to∼240°*** geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial *** two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°*** results from two independent methods are *** BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.

关键词： the Chengjiang Biota the Qingjiang Biota burial history Raman geothermometer thermal history Burgess Shale-type Lagerstätte

Structural geology and Chronology of Shear Zones along the Shangdan Suture in Qinling Orogenic Belt,China:Implications for Late Mesozoic Intra-continental Deformation of East Asia

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Journal of Earth Science 2024年第2期35卷 376-393页

作者： Falak Sheir Wei Li Le Zhang Basil Alabowsh Liuqing Jiang Li Liang Sainan Gao Shair Baz Umar Ashraf state key laboratory of continental dynamics Department of GeologyNorthwest UniversityXi’an710069China institute of geology University of PunjabLahore45590Pakistan

The Shangdan suture zone(SDZ)in the Qinling orogenic belt(QOB)is a key to understanding the East Asia tectonic *** SDZ gives information about convergent processes between the North China Block(NCB)and South China Block(SCB).In the Late Mesozoic,several shear zones evolved along the SDZ boundary that helps us comprehend the collisional deformation between the NCB and SCB,which was neglected in previous *** shear zones play an essential role in the tectonic evolution of the East Asia *** study focuses on the deformation and geochronology of two shear zones distributed along the SDZ,identified in the Shaliangzi and Maanqiao *** shear sense indicators and kinematic vorticity numbers(0.54–0.90)suggest these shear zones have sinistral shear and sub-simple shear deformation *** quartz’s dynamic recrystallization and c-axis fabric analysis in the Maanqiao shear zone(MSZ)revealed that the MSZ experienced deformation under green-schist facies conditions at∼400–500℃.The Shaliangzi shear zone deformed under amphibolite facies at∼500–700℃.The^(40)Ar/^(39)Ar(muscovite-biotite)dating of samples provided a plateau age of 121–123 *** with previously published data,our results concluded that QOB was dominated by compressional tectonics during the Late early ***,we suggested that the Siberian Block moved back to the south and Lhasa-Qiantang-Indochina Block to the north,which promoted intra-continental compressional tectonics.

关键词： Qinling orogenic belt Shangdan suture zone shear zone Late Mesozoic intra-continental deformation East Asia tectonics

Revisiting the Mg isotopic systematics of siliciclastic components of sediments and sedimentary rocks:A new geochemical proxy of continental weathering in Earth's history

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Science China Earth Sciences 2024年第2期67卷 620-633页

作者： Tianzheng HUANG Bing SHEN Kangjun HUANG Meng NING Chao LI Jinzhuang XUE Yuanlin SUN Baoqi HUANG key laboratory of Orogenic Belt and Crustal Evolution MOESchool of Earth and Space SciencesPeking UniversityBeijing100871China state key laboratory of continental dynamics Shaanxi Key Laboratory of Early Life and EnvironmentsDepartment of GeologyNorthwest UniversityXi’an710069China institute of Sedimentary geology Chengdu University of TechnologyChengdu610059China key laboratory of Rhenium-Osmium Isotopic Geochemistry Chinese Academy of Geological SciencesBeijing100037China

The Mg isotopic compositions of siliciclastic components(δ^(26)Mg_(sili))of sediments and sedimentary rocks have been commonly used to constrain the intensity of continental weathering,based on observations of,(1)an upward enrichment of26Mg in modern weathering profiles,(2)preferential uptake of26Mg in soil clays,and(3)general positive correlations between weathering intensities andδ^(26)Mg_(sili)***,not all weathering profiles display an upward increase ofδ^(26)Mg_(sili),and not all soil clays enrich in26Mg,complicating the interpretations ofδ^(26)Mg_(sili)data of sediments and sedimentary *** further explore the controls ofδ^(26)Mg_(sili)of sediments and sedimentary rocks,here we measuredδ^(26)Mg_(sili),mineralogical compositions and major element compositions of deep sea sediments from South China Sea(SCS)and carbonate rock samples from two late Paleozoic sections in South *** samples show decreasing trends of both normalized Mg concentration(Mgnorm)andδ^(26)Mg_(sili)values with the increase of weathering intensity,while SCS sediments samples do not show any correlation between Mgnormorδ^(26)Mg_(sili)values and weathering intensity.A three-stages weathering model is developed to explain the observed Mgnorm andδ^(26)Mg_(sili)*** the new model,weathering can be divided into three stages,(1)the preliminary weathering stage characterized by dissolution of primary minerals and formation of secondary clay minerals in saprolite,(2)the transitional stage with massive vermiculite and chlorite formation on the bottom of soil,and(3)the advanced stage showing dissolution of vermiculite and chlorite in the top of *** new model explains anδ^(26)Mg_(sili)increase and Mgnormdecrease with an increase weathering intensity in preliminary weathering stage and decrease of Mgnormandδ^(26)Mg_(sili)with increase weathering intensity in advanced weathering *** revised weathering model warrants the application of Mg isotope in the study of contin

关键词： Clay mineral Chemical weathering CIA Soil Weathering model

Polymetamorphism of the ultrahigh-temperature granulites in the Rauer Group,East Antarctica:new evidence from zircon SHRIMP U-Pb ages

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Advances in Polar Science 2024年第2期35卷 192-205页

作者： TONG Laixi LIU Zhao LI Chao LU Junsheng YANG Wenqiang WANG Yanbin state key laboratory of continental dynamics Department of GeologyNorthwest UniversityXi’an 710069China institute of geology Chinese Academy of Geological SciencesBejing 100037China

The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather ***,the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated,which is critical to understanding the tectonic nature and evolution history of the Prydz ***,both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age *** results show that metamorphic zircon mantles yield weighted mean^(206)Pb/^(238)U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites,respectively,while zircon rims and newly grown zircons yield weighted mean^(206)Pb/^(238)U ages of 523±9 Ma and 532±11 Ma,*** new zircon age data suggest that the UHT granulites may have experienced polymetamorphism,in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis(1000–900 Ma),whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis(580–460 Ma).This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events,which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively,and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.

关键词： ultrahigh-temperature granulites zircon SHRIMP U-Pb ages polymetamorphism Rauer Group East Antarctica

A tectono-thermal perspective on the petroleum generation,accumulation and preservation in the southern Ordos Basin, North China

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Petroleum Science 2024年第3期21卷 1459-1473页

作者： Peng Yang Zhan-Li Ren Jin-Hua Fu Hong-Ping Bao Hui Xiao Zheng Shi Kun Wang Yuan-Yuan Zhang Wen-Hui Liu Wen-Hou Li state key laboratory of continental dynamics Department of GeologyNorthwest UniversityXi'an710069ShanxiChina National Engineering laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields Exploration and Development Research Institute of PetroChina Changqing Oilfield CompanyXi'an710018ShaanxiChina Shaanxi key Lab of Petroleum Accumulation geology School of Earth Science and EngineeringXi'an Shiyou UniversityXian710065ShaanxiChina Wuxi Research institute of Petroleum geology Petroleum Exploration and Production Research InstituteSINOPECWuxi214126JiangsuChina

The southern Ordos Basin has excellent petroleum exploration ***,the tectono-thermal history and the controls on petroleum generation,accumulation and preservation conditions in southern basin are *** this study,we analyzed the present geothermal field,paleo-geothermal gradient,maturity of the hydrocarbon source rocks,uplift and cooling process and tectono-thermal evolution *** the study area,for the Ordovician,Permain and the Triassic strata,the present temperature is low(3070℃)in the southeastern area but high(80140℃)in the northwestern *** paleogeothermal gradient varied from 24℃/km to 30℃/km with a heat flow of 58—69 m W/m^(2)(i.e.,a medium-temperature basin).The paleo-temperatures are higher than the present temperatures and the maximum paleo-temperatures controlled the thermal maturity of the source *** vitrinite reflectance(Ro)values of the Triassic strata are>0.7%and the thermal maturity reached the middlemature oil generation *** Rovalues of the Permian-Ordovician strata are>1.8%and the thermal maturity reached the over-mature gas generation *** southern Ordos Basin has experienced the multiple tectonic events at the Late Ordovician Caledonian(452 Ma),Late Triassic(215 Ma),Late Jurassic(165160 Ma),End-early Cretaceous(110100 Ma)and Cenozoic(since 40 Ma).A large-scale tectonothermal event occurred at the End-early Cretaceous(110100 Ma),which was controlled by lithospheric extension,destruction and *** event led to the highest paleo-temperatures and thermal maturities and coeval with the peak period of petroleum generation and *** southern Ordos Basin has undergone rapid and large-scale uplift since the Late Cretaceous due to expansion of the northeastern margin of the Tibetan Plateau,uplift of the Qinling orogenic belt and thrust faulting in the Liupanshan tectonic *** southern Ordos Basin experienced tectonic overprinting that was strong in the south and weak in the *** str

关键词： Fission-track dating Vitrinitereflectance Geothermal field Tectono-thermal evolution Petroleum geology Ordos Basin

Regulation effect of the grille spacing of a funnel-type grating water–sediment separation structure on the debris flow performance

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Journal of Mountain Science 2024年第7期21卷 2283-2304页

作者： LI Shuai GU Tianfeng WANG Jiading WANG Fei LI Pu state key laboratory of continental dynamics/department of geology Northwest UniversityXi’an 710069China Chengdu institute of Mountain Hazards and Environment Ministry of Water Resources&Chinese Academy of SciencesChengdu 610299China

The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve the water–sediment separation ability of the *** new funnel-type grating water–sediment separation structure(FGWSS)combines vertical and horizontal structures and provides a satisfactory water–sediment separation ***,the regulation effect of the grille spacing of the structure on the debris flow performance has not been *** regulation effect of the structure grille spacing on the debris flow performance is studied through a flume test,and the optimal structure grille spacing is *** empirical equation of the relationship between the relative grille spacing of the structure and the sediment separation rate is ***,the influence of the water–sediment separation structure on the regulation effect of debris flows is examined from two aspects:external factors(properties of debris flows)and internal factors(structural factors).The experimental results show that the gradation characteristics of solid particles in debris flows constitute a key factor affecting the regulation effect of the structure on the debris flow *** optimum grille spacing of the FGWSS matches the particle size corresponding to the material distribution curves d85~d90 of the debris *** total separation rate of debris flow particles is related to the grille spacing of the structure and the content of coarse and fine particles in the debris flow.

关键词： Debris flow Water–sediment separation structure Grille spacing Performance regulation effect

Pre-Cryogenian integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

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Science China Earth Sciences 2024年第4期67卷 899-918页

作者： Peiyuan HU Qingguo ZHAI Guochun ZHAO Peter A.CAWOOD Yue TANG Yiming LIU institute of geology Chinese Academy of Geological SciencesBeijing 100037China department of Earth Sciences University of Hong KongPokfulam RoadHong Kong 999077China state key laboratory of continental dynamics Department of GeologyNorthwest UniversityXi’an 710069China School of Earth Atmosphere&EnvironmentMonash UniversityMelbourneVIC 3800Australia

The composition and geological evolution of pre-Cryogenian material in the Tibetan Plateau and its surrounding areas have played an important role in studying the formation and evolution of early supercontinents on *** paper systematically summarizes the characteristics of pre-Cryogenian sedimentation,paleontology,magmatism,and metamorphism in the Tibetan Plateau and its surrounding *** on existing data,the records of pre-Cryogenian sedimentation and paleontology are mainly concentrated in the Meso-Neoproterozoic,with relatively few records from the Paleoproterozoic or *** oldest geological record is the Hadean detrital zircons in the metamorphosed sedimentary rocks of the Himalaya and Qamdo areas(ca.4.0 Ga).The Tibetan Plateau and surrounding areas preserve records related to the formation and evolution of the Kenor supercraton,and the Columbia,Rodinia,and Gondwana ***-Cryogenian basements can be divided into three types:Tarim-,Yangtze-,and *** Tarim-type basement has a paleogeographic affinity with the northern margins of the Australian and Indian continents and lacks detrital zircon age peaks and magmatic-metamorphic records related to the Rodinia assembly(ca.1.3-0.9 Ga).The Yangtze-type basement records volcanic activity related to global cooling in the latest pre-Cryogenian period and contains Meso-Neoproterozoic stromatolite and micropaleoflora fossils,as well as magmaticmetamorphic records related to Rodinia assembly(ca.1.1-1.0 Ga).The Lhasa-type basement is characterized by Neoproterozoic rift-related sediment records(ca.900 Ma)and high-pressure metamorphic events(ca.650 Ma),with a prominent peak of detrital zircon ages of ca.1.2-1.1 *** is likely to have a paleogeographic affinity with the African continent.

关键词： Tibetan Plateau Pre-Cryogenian Sedimentation Fossils Paleogeographic evolution