Understanding the active tectonic processes in the Nandakini Watershed is imperative for evaluating geological hazards and seismic risks,as well as for informing land-use planning and natural resource management strat...Understanding the active tectonic processes in the Nandakini Watershed is imperative for evaluating geological hazards and seismic risks,as well as for informing land-use planning and natural resource management strategies in the region.Tectonic geomorphology serves as a vital tool for characterizing recent tectonic movements.This research employs GIS techniques to elucidate tectonic activity and its influence on drainage patterns in the Nandakini Watershed,utilizing morphometric parameters derived from SRTM DEM data.Morphometric indices are employed to assess the tectonic movement within drainage basins,capturing both areal and linear factors such as drainage density,texture,circulatory and bifurcation ratios,and stream length ratios.The linear and areal morphometric indices are categorized into three classes representing varying degrees of active tectonic activity.These classifications are then utilized to compute the relative active tectonic index(IRAT).In addition,geomorphic parameters include hypsometric integral,stream length-gradient index,normalized steepness index,chi gradient index,and swath profiles.The majority of the studied region is in an extremely high to moderately active tectonic zone.Large-scale faults and thrusts within the basins are closely correlated with these zones that have been identified.The integrated methodology of GIS-based morphometric analysis and geomorphic study enables the identification of deformed landforms associated with ongoing tectonic activity.Furthermore,these results offer valuable insights for informing watershed management strategies and promoting sustainable land use planning initiatives.展开更多
0 INTRODUCTION.The global availability of digital elevation model(DEM)data,such as 90-m Shuttle Radar Topography Mission(SRTM)DEM and 30-m Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital ...0 INTRODUCTION.The global availability of digital elevation model(DEM)data,such as 90-m Shuttle Radar Topography Mission(SRTM)DEM and 30-m Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM),has been extensively utilized in morphotectonic analyses(e.g.,Wang et al.,2024;Cheng et al.,2018;Pérez-Pe?a et al.,2010;El Hamdouni et al.,2008).展开更多
The Ordos Basin(OB)in the western part of the North China Craton(NCC),was located at the jointed area of multi-plates and has recorded the Mesozoic tectonic characteristics.Its tectonic evolution in the Mesozoic is si...The Ordos Basin(OB)in the western part of the North China Craton(NCC),was located at the jointed area of multi-plates and has recorded the Mesozoic tectonic characteristics.Its tectonic evolution in the Mesozoic is significant to understand the tectonic transformation of the northern margin of the NCC.In this work,the detrital zircon and apatite(U-Th)/He chronological system were analyzed in the northern part of the OB,and have provided new evidence for the regional tectonic evolution.The(U-Th)/He chronological data states the weighted ages of 240‒235 Ma,141 Ma with the peak distribution of 244 Ma,219 Ma,173 Ma,147‒132 Ma.The thermal evolution,geochronological data,and regional unconformities have proved four stages of regional tectonic evolution for the OB and its surroundings in the Mesozoic:(1)The Late Permian-Early Triassic;(2)the Late Triassic-Early Jurassic;(3)the Late Jurassic-Early Cretaceous;(4)the Late Cretaceous-Early Paleogene.It is indicated that the multi-directional convergence from the surrounding tectonic units has controlled the Mesozoic tectonic evolution of the OB.Four-stage tectonic evolution reflected the activation or end of different plate movements and provided new time constraints for the regional tectonic evolution of the NCC in the Mesozoic.展开更多
0 INTRODUCTION The Qilian Mountain Belt,at the forefront of the Tibetan Plateau's expansion,offers key insights into the plateau's tectonic deformation(Zuza et al.,2018;Zheng et al.,2010;Zhang et al.,2004;Tapp...0 INTRODUCTION The Qilian Mountain Belt,at the forefront of the Tibetan Plateau's expansion,offers key insights into the plateau's tectonic deformation(Zuza et al.,2018;Zheng et al.,2010;Zhang et al.,2004;Tapponnier et al.,2001;Meyer et al.,1998).The northwest-trending mountain ranges in the Qilian Shan(“Shan”means“Mountain”in Chinese)have significantly influenced this deformation(Zheng et al.,2013).展开更多
The investigation of the tectonic deformation characteristics at the front margin of the Xu-Su arc tectonic belt provides important reference points for identifying and analyzing its genetic mechanism,tectonic evoluti...The investigation of the tectonic deformation characteristics at the front margin of the Xu-Su arc tectonic belt provides important reference points for identifying and analyzing its genetic mechanism,tectonic evolution process,and the latest evidence of tectonic deformation.In this study,two reflection seismic exploration profiles across the front margin of the Xu-Su arc tectonic belt are utilized to reveal that the Qinglongshan fault is the thrust fault of its front margin boundary.The kinematic properties and tectonic deformation characteristics of the internal faults in the front margin basin are also obtained.Using the Qinglongshan fault as the boundary,the middle and posterior margins of the Xu-Su arc tectonic belt are composed of numerous thrust faults,which suggest strong ancient tectonic movement.However,a large number of normal faults are developed within the front margin basin,with some faults exhibiting strike-slip and growth properties,which indicate strong neotectonic movement.Results reveal that the Xu-Su arc tectonic belt is a large-scale thrust-nappe structure that has undergone structural inversion.The Xu-Su arc tectonic belt experienced strong tectonic activity during the Middle Pleistocene,and the most recent tectonic deformation has extended into the front margin basin interior.展开更多
The Mohorovicic discontinuity(Moho)boundary separating the Earth’s crust and mantle reflects the evolutionary trajectory of the Earth’s crust,yielding crucial insights into crustal formation,tectonic evolution,and p...The Mohorovicic discontinuity(Moho)boundary separating the Earth’s crust and mantle reflects the evolutionary trajectory of the Earth’s crust,yielding crucial insights into crustal formation,tectonic evolution,and profound dynamic processes.However,the prevailing Moho models for China and its adjacent areas suffer from limited accuracy,owing to the irregular and sparse distribution of seismic data collection.In this study,we employ gravimetric data to derive Moho depth,and employ Bott’s regularization method,integrating gravity and seismic data to reconstruct the Moho structure with high precision in a three-dimensional framework across China and its adjacent areas.By optimizing gravity potential field separation and interface inversion techniques,we present a detailed and accurate zoning scheme for classifying China and its adjacent areas into 35 gradient belts,6 primary tectonic units,and 35 secondary tectonic units,based on the spatial distribution characteristics of the Moho discontinuity.Notably,our tectonic pattern division results surpass previous studies in terms of resolution,providing a wealth of tectonic information.Leveraging the Moho depth model of China and its adjacent areas,we discuss orogenic belts,sedimentary basins,fault systems,plate boundaries,and land-sea coupled tectonic patterns.We meticulously summarize the Moho depth distribution characteristics of each tectonic unit,while exploring the macrostructural framework and geological significance of the study area.Our findings highlight the close relationship between China and its adjacent areas Moho depth model and deep geodynamics,elucidating the tectonic evolution both between and within tectonic plates,as well as the tectonic effects induced by mantle dynamics.These insights have crucial implications for the study of deep geodynamics in China and its adjacent areas.展开更多
The Zongwulong Shan-Qinghai Nanshan tectonic belt of the northern Xizang Plateau experienced a protracted tectonica history,including the openings and closures of the Proto-and Paleo-Tethyan Oceans.Although the tecton...The Zongwulong Shan-Qinghai Nanshan tectonic belt of the northern Xizang Plateau experienced a protracted tectonica history,including the openings and closures of the Proto-and Paleo-Tethyan Oceans.Although the tectonic belt has been extensively studied,details regarding the tectonic processes involved in its development remain controversial.To better constrain the tectonic processes of this tectonic belt,we conducted detailed field geological mapping,zircon U-Pb geochronology,and whole-rock geochemical and Sr-Nd isotopic analyses.Our results show that intrusive rocks in the tectonic belt crystallized in ca.292-233 Ma,perhaps in an arc/subduction setting.Geochemical and Sr-Nd isotopic data suggest that Early Permian-Late Triassic ultramaficintermediate intrusions were sourced from the enriched mantle,whereas intermediate-acidic rocks were sourced from mixed crust-mantle.We present the tectonic model that involves:(1)Early Devonian-Early Permian intracontinental extension occurred in the northern margin of the Qaidam continent(ca.416-292 Ma);(2)Early Permian-Late Triassic northward subduction of the Paleo-Tethyan Ocean resulted in arc magmatism(ca.292-233 Ma);and(3)subsequent Late Triassic intracontinental extension(ca.233-215 Ma).Our results suggest that the Late Paleozoic-Early Mesozoic development of the Zongwulong Shan-Qinghai Nanshan was related to the opening,subduction,and slab retreat of the Paleo-Tethyan Ocean,which has key implications for the tectonic evolution of the northern Tibetan Plateau.展开更多
The Songliao Basin in northeast China is one of the largest petroliferous basins worldwide,and features the T_(2)fault system,which consists of numerous minor extensional normal faults.This study combines high-resolut...The Songliao Basin in northeast China is one of the largest petroliferous basins worldwide,and features the T_(2)fault system,which consists of numerous minor extensional normal faults.This study combines high-resolution 3D seismic datasets to detail the characteristics of the T_(2)fault system,contributing two key findings:(1)The T_(2)faults are confirmed as polygonal fault systems,characterized by closely spaced,layer-bounded faults with small throws,high dip angles,and random orientations,forming intricate polygonal networks.(2)The study reveals the influence of tectonic stresses on the fault system,showing spatial variations across different tectonic units.In depressions,T_(2)faults exhibit short lengths,small throws,high density,and multiple directions.In contrast,in inverted anticline belts,they have longer lengths,bigger throws,higher density,and concordant orientations.These variations demonstrate the impact of tectonic inversion on the development of T_(2)faults.The significance of this research lies in presenting a typical polygonal fault system developed in a deep lake succession and was superposed the influence by regional tectonic stress coeval with its development.The new insights facilitate a reevaluation of the T_(2)fault system's role in hydrocarbon migration and accumulation within the Songliao Basin.展开更多
0 INTRODUTION The Kuqa Depression,situated along the northern margin of the Tarim Basin,holds substantial geological significance due to its intricate sedimentary burial history,tectonic history,and the evolution of h...0 INTRODUTION The Kuqa Depression,situated along the northern margin of the Tarim Basin,holds substantial geological significance due to its intricate sedimentary burial history,tectonic history,and the evolution of hydrocarbon source rocks(Jiang et al.,2024;Zhang et al.,2023;Huang et al.,2019;Yang et al.,2017;Jia et al.,2003;Hendrix,2000).展开更多
This research investigates dynamic earth processes within the South Setifian allochthonous ensemble,providing insights into landscape evolution and seismotectonic activity within the Tellian mountain chain.Focusing on...This research investigates dynamic earth processes within the South Setifian allochthonous ensemble,providing insights into landscape evolution and seismotectonic activity within the Tellian mountain chain.Focusing on the Jebel Gustar and Kef Lahmar area,which includes 14 sub-basins,this research uses a DEM-based technique to assess Holocene activities,lineament characteristics,and stream systems.Five geomorphic indices are used to assess relative active tectonics:the stream lengthgradient index(SL),drainage basin asymmetry(AF),valley-floor width to valley height ratio(VF),drainage basin shape(BS),and mountain front sinuosity(SMF).A weighted overlay of these five indices produces the Index of Relative Active Tectonics(IRAT)map.The findings reveal significant neotectonic activity in the study area,supported by profound basement faulting.This research highlights the morpho-structural processes and neotectonics activity in the Jebel Gustar,providing a framework for investigating the evolution of this structure.Additionally,it enhances comprehension of the interactions between the alpine range's internal zones in Eastern Algeria and the Atlasic domain.This study proposes a systematic approach to evaluate the tectonic and geomorphological dynamics of the South Setif region.展开更多
Tectonic activities significantly impact deep reservoir properties via sedimentary and diagenetic processes,and this is particularly true for lacustrine rift basins.The tectonic-sedimentary-diageneticreservoir system ...Tectonic activities significantly impact deep reservoir properties via sedimentary and diagenetic processes,and this is particularly true for lacustrine rift basins.The tectonic-sedimentary-diageneticreservoir system is crucial in deep reservoir exploration.This study examined the first member and upper submember of the second member of the Dongying Formation in the Bodong Low Uplift in the Bohai Bay Basin(East China),documenting the petrologic features and physical properties of reservoirs in different tectonic sub-units through integrated analysis of log and rock data,along with core observation.A mechanism for deep reservoir formation in lacustrine rift basins was developed to elucidate the sedimentary and diagenetic processes in complex tectonic settings.The results show that tectonic activities result in the occurrence of provenances in multiple directions and the existence of reservoirs at varying burial depths,as well as the significant diversity in sedimentary and diagenetic processes.The grain sizes of the sandstones,influenced by transport pathways rather than the topography of the sedimentary area,exhibit spatial complexity due to tectonic frameworks,which determine the initial pore content of reservoirs.However,the burial depth,influenced by subsequent tectonic subsidence,significantly impacts pore evolution during diagenesis.Based on the significant differences of reservoirs in slope zone,low uplift and depression zone,we establish different tectonic-diagenetic models in deep complex tectonic units of lacustrine rift basins.展开更多
How the subduction direction of the Paleo-Pacific plate beneath the Eurasian plate changes in the Early Cretaceous remains highly controversial due to the disappearance of the subducted oceanic plate.Intraplate deform...How the subduction direction of the Paleo-Pacific plate beneath the Eurasian plate changes in the Early Cretaceous remains highly controversial due to the disappearance of the subducted oceanic plate.Intraplate deformation structures in the east Asian continent,however,provide excellent opportunities for reconstructing paleostress fields in continental interior in relation to the Paleo-Pacific/Eurasian plate interaction.Anisotropy of magnetic susceptibility(AMS),geological,and geochronological analyses of post-kinematic mafic dykes intruding the detachment fault zone of the Wulian metamorphic core complex(WL MCC)in Jiaodong Peninsula exemplify emplacement of mantle-sourced dykes in a WNW-ESE(301°-121°)oriented tectonic extensional setting at ca.120 Ma.In combination with the results from our previous kinematic analysis of the MCC,a ca.21°clockwise change in the direction of intraplate extension is obtained for early(135-122 Ma)extensional exhumation of the MCC to late(122-108 Ma)emplacement of the dykes.Such a change is suggested to be related to the variation in subduction direction of the Paleo-Pacific plate beneath the Eurasian plate,from westward(pre-122 Ma)to west-northwestward(post-122 Ma).展开更多
The extra-peninsular Gondwana Group rocks are exposed in narrow patches within the Lesser Himalayan sequence of the NE-Arunachal Himalayas,India.The bulk of sediments for the sandstones of the Gondwana Group were deri...The extra-peninsular Gondwana Group rocks are exposed in narrow patches within the Lesser Himalayan sequence of the NE-Arunachal Himalayas,India.The bulk of sediments for the sandstones of the Gondwana Group were derived from felsic/acidic to intermediate igneous rocks,with minor mafic input from the upper continental crust(UCC),as supported by various discrimination diagrams based on quantification of detrital minerals coupled with sandstone geochemistry.The inputs from metamorphic sources in subordinate amounts cannot be ruled out,as indicated by quantification of the quartz varieties.These sediments were found to be sourced from the interior part of a craton or shield and recycled platformal sediments which were derived from both passive and active margin settings.The sediments experienced a wide variance in climatic conditions,from arid to humid,suffering low-moderate-inten-sity weathering(CIA:63.43;CIW:86.18;WIP:44.84;PIA:75.37;ICV:2.39;C-value:0.42;PF:0.49;Sr/Cu:9.23 and Rb/Sr:1.68)within the vicinity of the low plains to moderate hills.Additionally,redox-sensitive elements indicate the deposition of sediments under oxygenated or oxygen-rich conditions(U_(au):−2.91;Th/U:7.37;U/Th:0.18;V/Cr:1.71;δU:0.67 and Ce/Ce^(*):0.93).展开更多
1.Objective The Songpan-Ganze terrane is a key region for understanding the tectonic evolution of the Tibetan Plateau and the Yangtze Craton.The Songpan-Ganzi complex comprises a thick succession of deformed Ladinian-...1.Objective The Songpan-Ganze terrane is a key region for understanding the tectonic evolution of the Tibetan Plateau and the Yangtze Craton.The Songpan-Ganzi complex comprises a thick succession of deformed Ladinian-Norian turbidites(ca.230-203 Ma),covering about 200000 km^(2)of the eastern Tibet Plateau with a volume of approximately 2.0×10^(6)km^(3)(Fig.1a).Furthermore,this complex has over 100 Permian-Cenozoic felsic plutons.展开更多
The Bijigou intrusion is one of the largest and most well-differentiated Fe–Ti oxide-bearing layered intrusions in the Hannan massif located in the northwestern margin of the Yangtze Block,South China.Besides the min...The Bijigou intrusion is one of the largest and most well-differentiated Fe–Ti oxide-bearing layered intrusions in the Hannan massif located in the northwestern margin of the Yangtze Block,South China.Besides the mineralization-related mafic-ultramafic rocks,the intermediate-acid intrusive rocks are also exposed in the mining area,which is of great significance for the understanding the Neoproterozoic tectonic evolution of the Yangtze Block,but studies on these intermediate-acid rocks are scarce.The Bijigou mafic-ultramafic layered intrusion is surrounded by granite and cut by syenite veins.Here,we report new zircon U-Pb ages,Lu-Hf isotope composition and bulk rock geochemical data of the Bijigou syenite vein and wall-rock granite in the northwestern margin of the Yangtze Block.Laser ablation inductively coupled plasma mass spectrometry(LAICP-MS)zircon U-Pb dating results show that the Bijigou syenite vein and wall-rock granite formed at 770±3.5 Ma(MSWD=0.17,n=28)and 810±4 Ma(MSWD=0.84,n=26),respectively.The zirconεHf(t)values of the syenite veins range from+1.52 to+5.33(average of+3.05),combined with its high potassium contents,negative Nb–Ta anomalies and positive Pb anomalies,suggesting that they may have originated from mantle-derived basaltic magma,which was modified by materials from subducting oceanic slab.The zirconεHf(t)and T_(DM2)ages of the wall-rock granite range from+0.71 to+5.71(average+3.06)and 1344 to 1659 Ma(average 1519 Ma),respectively,indicating that the granite was produced by partial melting of juvenile crust.The geochemical characteristics of the Bijigou syenite and granite indicate that they were formed in a continental margin arc setting.Thus,combined with previous studies,it suggests that there was a major subduction system along the northwestern margin of the Yangtze Block during 824-720 Ma,and the magmatism in the Hannan massif was divided into two episodes:(1)early magmatism(824-790 Ma),such as the Bijigou,Hongmiaozhen and Huangguanzhen granitoids,was derived from partial melting of the juvenile or pre-existing crust in a continental arc setting;(2)later magmatism(789-718 Ma),including Bijigou syenite,Wudumen,Erliba and Zushidian granitoids,formed in a subduction-related back-arc extensional environment.The long-term subduction system along the northwestern margin of the Yangtze Block during 824-720 Ma suggests that the Yangtze Block was previously located at the periphery of the Rodinia supercontinent.展开更多
In the context of complex tectonic evolution,due to the control of tectonic compression stress and faults on tectonic fractures,the formation and development of tectonic fractures in the T_3x~2 tight reservoirs presen...In the context of complex tectonic evolution,due to the control of tectonic compression stress and faults on tectonic fractures,the formation and development of tectonic fractures in the T_3x~2 tight reservoirs present significant variations across different tectonic segments in the Western Sichuan Foreland Basin.We clarified the control of differential tectonic evolution on the formation and development of tectonic fractures in different tectonic segments through field-based observations,core samples,image logging,as well as fluid inclusion petrography and temperature determinations of fracture-filling materials,combined with 2D balanced cross-section restoration.The study area primarily manifests two types of tectonic fractures in the tight reservoirs:orogen-related fractures(regional fractures)and fault-related fractures.The orientations of these fractures are predominantly E-W,nearly N-S,NE,and NW.Specifically,the northern segment area only shows the development of regional fractures,while the southern and middle segments exhibit the development of both regional and tectonic fractures.There are three phases of tectonic fractures in different tectonic segments,and their formation times are relatively consistent.The Mesozoic tectonic events had a significant impact on the northern and central segments,with the amount of tectonic shortening and the rate of stratigraphic shortening gradually decreasing from the northeast to the southwest.The compressional stress resulting from tectonic compression also decreases from the northeast to the southwest.As a result,the development of first-phase and second-phase tectonic shear fractures is more pronounced in the northern and middle segments compared to the southern segment.Under the significant control of faults,the development of N-S-and NE-oriented fault-related fractures is more pronounced in the southern segment,while the development of NE-oriented fault-related fractures is relatively higher in the middle segment.Overall,there is an increased density of fractures and an increasing trend in fracture scale from the northern to the middle and then to the southern segment.展开更多
Geodynamic processes following the Indo-Eurasian plate collision remain a key research focus,and the Jinshajiang-Red River tectonic zone(JRTZ),situated along this collision boundary,provides critical insights into pos...Geodynamic processes following the Indo-Eurasian plate collision remain a key research focus,and the Jinshajiang-Red River tectonic zone(JRTZ),situated along this collision boundary,provides critical insights into post-collision tectonic evolution.In this study,we identify a lithological assemblage in the JRTZ,including amphibolite,granite gneiss,and migmatite.These rocks exhibit contrasting geochemical signatures,reflecting multiple source regions:asthenospheric mantle,lithospheric mantle,mafic lower and upper crust.Specifically,amphibolite(28.5 Ma)formed through the partial melting of OIB-like mantle source,whereas S-type granite gneiss(28.2 Ma)originated from the dehydration melting of metamorphosed sedimentary rocks.Amphibole monzonite(28.9 Ma)records the mixing of ancient crustal material with mantle-derived components,while migmatite(37.9 Ma)resulted from deep melting processes of metasedimentary rocks under shear conditions.We propose that the ongoing Indo-Eurasian convergence progressively thickened the crust,ultimately driving large-scale lithospheric delamination between the Eocene and Oligocene.This delamination triggered asthenospheric upwelling,which provided the thermal input required for widespread melting.This lithospheric delamination event started around 38-37 Ma and lasted at least until 28 Ma.展开更多
There is significant debate concerning the tectonic characteristics and evolutionary understanding of the South China Block(SCB)during the Early Mesozoic.One of the key points of contention is the tectonic-magmatic ac...There is significant debate concerning the tectonic characteristics and evolutionary understanding of the South China Block(SCB)during the Early Mesozoic.One of the key points of contention is the tectonic-magmatic activity during the Triassic and its dynamic mechanisms.However,research on the detailed chronology and tectonic settings of granite plutons in key regions remains insuffi-cient,limiting the understanding of the tectonic-magmatic dynamic mechanisms in the interior of SCB during the Triassic.In this contribution,we present whole-rock major and trace elemental data,Sr-Nd isotope data,LA-ICP-MS zircon U-Pb age dating,and Lu-Hf isotope data for granites of Dashenshan pluton in the Xiangzhong,northwest part of SCB.The results indicate that the Dashenshan granite has an emplacement age of 208.4-212.5 Ma,characterized by high SiO_(2),Na_(2)O,and K_(2)O contents and low MgO and CaO.The Dashenshan granite is enriched in light rare-earth elements with a significant negative Eu anomaly(averageδEu=0.42).It is also enriched in Rb,K,and Th and shows pronounced depletion in Nb,Ta,and Ti,classifying it as peraluminous calc-alkaline granite,specifically of the I-type.The zircon ε_(Hf(t)) values range from−8.39 to−4.4,with an average of−5.82,and the Sr-Nd isotopes are relatively enriched[ε_(Nd)(t)=−9.31 to−6.8].Combining these geochemical characteristics,it is revealed that the Dashenshan granite was derived from the partial melting of middle to upper crustal metamorphic basement materials under medium-to low-temperature conditions,with possible minor contributions from mantle-derived materials.Furthermore,it underwent fractional crystallization,including plagioclase differentiation.By integrating the geochemical features and spatial distribution of Triassic granites in SCB,this study suggests that the regional tectonic evolution of SCB during the Triassic was primarily controlled by the collision of the SCB with the Indochina Block and the North China Block.In Xiangzhong,the tectonic setting transitioned from syn-collisional compression to post-collisional extension during the Late Triassic.The Dashenshan pluton formed in a post-collisional extensional setting,resulting from the decompression melting of middle-to-upper crustal rocks.The upwelling of the asthenosphere and upward heat transfer likely played a significant role in the formation of the Dashenshan granitic magma.展开更多
The study area is situated in the Tianshan region,specifically within the eastern segment of the North Qilian Orogenic Belt(NQLOB).The NQLOB is a critical region for understanding oceanic closure and continental colli...The study area is situated in the Tianshan region,specifically within the eastern segment of the North Qilian Orogenic Belt(NQLOB).The NQLOB is a critical region for understanding oceanic closure and continental collision processes driven by the Shangdan Ocean subduction-exhumation,which was a segment of the Proto-Tethys Ocean during the Early Paleozoic.Despite significant research,the Early Paleozoic tectonic background and subduction-related orogenic processes,particularly in the eastern NQLOB,remain subjects of debate.This study presents significant petrographic,geochemical,and geochronologic insights into the metavolcanic rocks of the Chenjiahe Group in the eastern NQLOB.Petrographic analysis reveals that these metavolcanic rocks originated in a low-grade metamorphic setting.Zircon laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)U-Pb dating yielded ages ranging between 449.7-443.4 Ma,indicating Late Ordovician formation.Geochemical signatures of felsic and intermediate rocks exhibit calc-alkaline to high-K calc-alkaline similarities,characterized by high light rare earth elements(LREEs),low heavy rare earth elements(HREEs),and moderate Eu anomalies,consistent with a continental arc setting.In contrast,basaltic rocks display tholeiitic features with elevated large-ion lithophile elements(LILEs),reduced high-field-strength elements(HFSEs),and weak Eu anomalies,suggesting an extensional environment.These findings imply that the metavolcanic rocks evolved in a continental arc-back-arc extension setting connected with the northward subduction and exhumation of the Huluhe back-arc oceanic basin.This process was likely triggered by the northward subduction and closure of the Shangdan Ocean,culminating in the Late Ordovician amalgamation of the Qilian Block and the southwestern North China Block.This study provides critical insight into the tectonic development of the NQLOB and the broader Proto-Tethys Ocean dynamics at the northern periphery of the Eastern Gondwana.展开更多
The Shuangwang Au deposit in the western Qinling Orogen is hosted by a WNW-ESE-trending breccia belt that is structurally controlled by the northern limb of the Yindonggou fold.Igneous rocks area in the deposit are pa...The Shuangwang Au deposit in the western Qinling Orogen is hosted by a WNW-ESE-trending breccia belt that is structurally controlled by the northern limb of the Yindonggou fold.Igneous rocks area in the deposit are part of the Xiba pluton,which comprises granodiorite and monzogranite that contains mafic microgranular envlaves(MMEs),and later mineralized granitic porphyry dikes.The mineralized granitic porphyry dikes were controlled by the same structures that controlled the ore bodies.Zircon LA-ICP-MS U-Pb dating yields ages of 220.0±1.9 Ma for the granodiorite,and 217.9±1.9 Ma for the granitic porphyry,which is consistent with the mineralization ages reported in previous studies(220-218 Ma).Together with the similarity of alteration mineral assemblages between ore and mineralized granitic porphyry,we suggest that the mineralization was controlled by structure and Xiba pluton.The geochemical data show that the granodiorite and granitic porphyry are subalkaline and the MMEs are alkaline in composition.All samples have similar chondrite-normalized rare earth element patterns with enrichment of light rare earth elements.The granodiorite and MMEs are depleted in Nb,Ta,Sr,P,and Ti and enriched in U,K,Pb,Zr,and Hf.The granitic porphyry is enriched in large-ion lithophile elements but depleted in high-field-strength elements.The granodiorite and MMEs have low whole-rockεNd(t)values(−10.90 to−2.32)and(^(87)Sr/^(86)Sr)i ratios(0.7000-0.7285),similar to coeval Triassic granites in the western Qinling Orogen.The(^(87)Sr/^(86)Sr)i ratios of the granitic porphyry have been affected by fluid metasomatism that results in higher(^(87)Sr/^(86)Sr)i values.The geochronological,geochemical,and isotopic evidence suggest that the Xiba pluton formed by partial melting of thickened lower crust that had been intruded by alkaline mafic magma,as documented by the MMEs,which were derived from a source metasomatized by subduction-related fluids.The granodioritic and granitic porphyry magmas were relatively oxidized(fayalite-magnetite-quartz[FMQ]to magnetite-hematite(MH)buffer conditions;zircon Ce^(4+)/Ce^(3+)=72-813;log(fO_(2))=−22 to−8).We propose that magma mixing between lower crust and mantle-derived mafic magma was triggered by the tectonic transition from a collisional to post-collision setting,which provided the metals,S,fluids,and increase in magma oxygen fugacity that enabled the formation of the Shuangwang Au deposit.Since the Late Triassic,the western Qinling Orogen evolved from a syn-collisional compressional to post-collisional extensional environment.The mineralization of the Shuangwang Au deposit involved early formation of a tectonic breccia in the compressional stage.Subsequently,hydrothermal fluids derived from a magma ascended,migrated,mixed,and precipitated ores in the tectonic breccia during the later extensional stage to form the Shuangwang Au deposit.展开更多
文摘Understanding the active tectonic processes in the Nandakini Watershed is imperative for evaluating geological hazards and seismic risks,as well as for informing land-use planning and natural resource management strategies in the region.Tectonic geomorphology serves as a vital tool for characterizing recent tectonic movements.This research employs GIS techniques to elucidate tectonic activity and its influence on drainage patterns in the Nandakini Watershed,utilizing morphometric parameters derived from SRTM DEM data.Morphometric indices are employed to assess the tectonic movement within drainage basins,capturing both areal and linear factors such as drainage density,texture,circulatory and bifurcation ratios,and stream length ratios.The linear and areal morphometric indices are categorized into three classes representing varying degrees of active tectonic activity.These classifications are then utilized to compute the relative active tectonic index(IRAT).In addition,geomorphic parameters include hypsometric integral,stream length-gradient index,normalized steepness index,chi gradient index,and swath profiles.The majority of the studied region is in an extremely high to moderately active tectonic zone.Large-scale faults and thrusts within the basins are closely correlated with these zones that have been identified.The integrated methodology of GIS-based morphometric analysis and geomorphic study enables the identification of deformed landforms associated with ongoing tectonic activity.Furthermore,these results offer valuable insights for informing watershed management strategies and promoting sustainable land use planning initiatives.
基金supported by the National Key Research and Development Project of China(No.2023YFC3007303)the Open Research Project of the Hubei Key Laboratory of Intelligent Geo-Information Processing(No.KLIGIP-2019B08)。
文摘0 INTRODUCTION.The global availability of digital elevation model(DEM)data,such as 90-m Shuttle Radar Topography Mission(SRTM)DEM and 30-m Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM),has been extensively utilized in morphotectonic analyses(e.g.,Wang et al.,2024;Cheng et al.,2018;Pérez-Pe?a et al.,2010;El Hamdouni et al.,2008).
基金This study was jointly supported by the Science&Technology Fundamental Resources Investigation Program(2022FY101800)National Science Foundation(92162212)+1 种基金the project from the Key Laboratory of Tectonics and Petroleum Resources(China University of Geosciences,Wuhan)(TPR-2022-22)the International Geoscience Programme(IGCP-675)。
文摘The Ordos Basin(OB)in the western part of the North China Craton(NCC),was located at the jointed area of multi-plates and has recorded the Mesozoic tectonic characteristics.Its tectonic evolution in the Mesozoic is significant to understand the tectonic transformation of the northern margin of the NCC.In this work,the detrital zircon and apatite(U-Th)/He chronological system were analyzed in the northern part of the OB,and have provided new evidence for the regional tectonic evolution.The(U-Th)/He chronological data states the weighted ages of 240‒235 Ma,141 Ma with the peak distribution of 244 Ma,219 Ma,173 Ma,147‒132 Ma.The thermal evolution,geochronological data,and regional unconformities have proved four stages of regional tectonic evolution for the OB and its surroundings in the Mesozoic:(1)The Late Permian-Early Triassic;(2)the Late Triassic-Early Jurassic;(3)the Late Jurassic-Early Cretaceous;(4)the Late Cretaceous-Early Paleogene.It is indicated that the multi-directional convergence from the surrounding tectonic units has controlled the Mesozoic tectonic evolution of the OB.Four-stage tectonic evolution reflected the activation or end of different plate movements and provided new time constraints for the regional tectonic evolution of the NCC in the Mesozoic.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0901)the State Key Laboratory of Earthquake Dynamics(No.LED2023B04)+1 种基金the National Natural Science Foundation of China(Nos.42272242,W2411033,W2521003)the Science and Technology Plan of Gansu Province(No.22JR11RA088)。
文摘0 INTRODUCTION The Qilian Mountain Belt,at the forefront of the Tibetan Plateau's expansion,offers key insights into the plateau's tectonic deformation(Zuza et al.,2018;Zheng et al.,2010;Zhang et al.,2004;Tapponnier et al.,2001;Meyer et al.,1998).The northwest-trending mountain ranges in the Qilian Shan(“Shan”means“Mountain”in Chinese)have significantly influenced this deformation(Zheng et al.,2013).
基金The active fault exploration and seismic risk assessment project of Huaibei and the research and development project of Beijing Disaster Prevention Technology Co.,Ltd.(FZKJYF202201)jointly funded this work。
文摘The investigation of the tectonic deformation characteristics at the front margin of the Xu-Su arc tectonic belt provides important reference points for identifying and analyzing its genetic mechanism,tectonic evolution process,and the latest evidence of tectonic deformation.In this study,two reflection seismic exploration profiles across the front margin of the Xu-Su arc tectonic belt are utilized to reveal that the Qinglongshan fault is the thrust fault of its front margin boundary.The kinematic properties and tectonic deformation characteristics of the internal faults in the front margin basin are also obtained.Using the Qinglongshan fault as the boundary,the middle and posterior margins of the Xu-Su arc tectonic belt are composed of numerous thrust faults,which suggest strong ancient tectonic movement.However,a large number of normal faults are developed within the front margin basin,with some faults exhibiting strike-slip and growth properties,which indicate strong neotectonic movement.Results reveal that the Xu-Su arc tectonic belt is a large-scale thrust-nappe structure that has undergone structural inversion.The Xu-Su arc tectonic belt experienced strong tectonic activity during the Middle Pleistocene,and the most recent tectonic deformation has extended into the front margin basin interior.
基金supported by the National Natural Science Foundation of China(Grant Nos.42474121 and 42192535)the Basic Frontier Science Research Program of the Chinese Academy of Sciences(Grant No.ZDBS-LY-DQC028).
文摘The Mohorovicic discontinuity(Moho)boundary separating the Earth’s crust and mantle reflects the evolutionary trajectory of the Earth’s crust,yielding crucial insights into crustal formation,tectonic evolution,and profound dynamic processes.However,the prevailing Moho models for China and its adjacent areas suffer from limited accuracy,owing to the irregular and sparse distribution of seismic data collection.In this study,we employ gravimetric data to derive Moho depth,and employ Bott’s regularization method,integrating gravity and seismic data to reconstruct the Moho structure with high precision in a three-dimensional framework across China and its adjacent areas.By optimizing gravity potential field separation and interface inversion techniques,we present a detailed and accurate zoning scheme for classifying China and its adjacent areas into 35 gradient belts,6 primary tectonic units,and 35 secondary tectonic units,based on the spatial distribution characteristics of the Moho discontinuity.Notably,our tectonic pattern division results surpass previous studies in terms of resolution,providing a wealth of tectonic information.Leveraging the Moho depth model of China and its adjacent areas,we discuss orogenic belts,sedimentary basins,fault systems,plate boundaries,and land-sea coupled tectonic patterns.We meticulously summarize the Moho depth distribution characteristics of each tectonic unit,while exploring the macrostructural framework and geological significance of the study area.Our findings highlight the close relationship between China and its adjacent areas Moho depth model and deep geodynamics,elucidating the tectonic evolution both between and within tectonic plates,as well as the tectonic effects induced by mantle dynamics.These insights have crucial implications for the study of deep geodynamics in China and its adjacent areas.
基金supported by the National Natural Science Foundation of China(No.42372256)the Basic Science Center for Tibetan Plateau Earth System(No.41988101)the Second Tibetan Plateau Scientific Expedition and Research Program(No.2019QZKK0708)。
文摘The Zongwulong Shan-Qinghai Nanshan tectonic belt of the northern Xizang Plateau experienced a protracted tectonica history,including the openings and closures of the Proto-and Paleo-Tethyan Oceans.Although the tectonic belt has been extensively studied,details regarding the tectonic processes involved in its development remain controversial.To better constrain the tectonic processes of this tectonic belt,we conducted detailed field geological mapping,zircon U-Pb geochronology,and whole-rock geochemical and Sr-Nd isotopic analyses.Our results show that intrusive rocks in the tectonic belt crystallized in ca.292-233 Ma,perhaps in an arc/subduction setting.Geochemical and Sr-Nd isotopic data suggest that Early Permian-Late Triassic ultramaficintermediate intrusions were sourced from the enriched mantle,whereas intermediate-acidic rocks were sourced from mixed crust-mantle.We present the tectonic model that involves:(1)Early Devonian-Early Permian intracontinental extension occurred in the northern margin of the Qaidam continent(ca.416-292 Ma);(2)Early Permian-Late Triassic northward subduction of the Paleo-Tethyan Ocean resulted in arc magmatism(ca.292-233 Ma);and(3)subsequent Late Triassic intracontinental extension(ca.233-215 Ma).Our results suggest that the Late Paleozoic-Early Mesozoic development of the Zongwulong Shan-Qinghai Nanshan was related to the opening,subduction,and slab retreat of the Paleo-Tethyan Ocean,which has key implications for the tectonic evolution of the northern Tibetan Plateau.
基金supported by the Open Funds for Hubei Key Laboratory of Marine Geological Resources,China University of Geosciences(No.MGR202303)the National Natural Science Foundation of China(No.41672110)。
文摘The Songliao Basin in northeast China is one of the largest petroliferous basins worldwide,and features the T_(2)fault system,which consists of numerous minor extensional normal faults.This study combines high-resolution 3D seismic datasets to detail the characteristics of the T_(2)fault system,contributing two key findings:(1)The T_(2)faults are confirmed as polygonal fault systems,characterized by closely spaced,layer-bounded faults with small throws,high dip angles,and random orientations,forming intricate polygonal networks.(2)The study reveals the influence of tectonic stresses on the fault system,showing spatial variations across different tectonic units.In depressions,T_(2)faults exhibit short lengths,small throws,high density,and multiple directions.In contrast,in inverted anticline belts,they have longer lengths,bigger throws,higher density,and concordant orientations.These variations demonstrate the impact of tectonic inversion on the development of T_(2)faults.The significance of this research lies in presenting a typical polygonal fault system developed in a deep lake succession and was superposed the influence by regional tectonic stress coeval with its development.The new insights facilitate a reevaluation of the T_(2)fault system's role in hydrocarbon migration and accumulation within the Songliao Basin.
基金supported by the National Key Research and Development Project(No.2019YFA0708601)the National Natural Science Foundation of China(No.4231101056)the Chinese Academy of Geological Sciences Basic Research Fund(No.JKYZD202402)。
文摘0 INTRODUTION The Kuqa Depression,situated along the northern margin of the Tarim Basin,holds substantial geological significance due to its intricate sedimentary burial history,tectonic history,and the evolution of hydrocarbon source rocks(Jiang et al.,2024;Zhang et al.,2023;Huang et al.,2019;Yang et al.,2017;Jia et al.,2003;Hendrix,2000).
文摘This research investigates dynamic earth processes within the South Setifian allochthonous ensemble,providing insights into landscape evolution and seismotectonic activity within the Tellian mountain chain.Focusing on the Jebel Gustar and Kef Lahmar area,which includes 14 sub-basins,this research uses a DEM-based technique to assess Holocene activities,lineament characteristics,and stream systems.Five geomorphic indices are used to assess relative active tectonics:the stream lengthgradient index(SL),drainage basin asymmetry(AF),valley-floor width to valley height ratio(VF),drainage basin shape(BS),and mountain front sinuosity(SMF).A weighted overlay of these five indices produces the Index of Relative Active Tectonics(IRAT)map.The findings reveal significant neotectonic activity in the study area,supported by profound basement faulting.This research highlights the morpho-structural processes and neotectonics activity in the Jebel Gustar,providing a framework for investigating the evolution of this structure.Additionally,it enhances comprehension of the interactions between the alpine range's internal zones in Eastern Algeria and the Atlasic domain.This study proposes a systematic approach to evaluate the tectonic and geomorphological dynamics of the South Setif region.
基金funded by the Open Fund of Key Laboratory of Marine Geology and Environment,Chinese Academy of Sciences(Grant No.MGE2020KG10)the Open Fund of Key Laboratory of Submarine Geosciences,Ministry of Natural Resources(Grant No.KLSG 2208)+2 种基金the Natural Science Basic Research Program of Shaanxi(Grant No.2024JC-YBMS-227,2023-JC-QN-0287)the Postgraduate Innovation and Practice Ability Development Fund of Xi'an Shiyou University(No.YCS23113046)the National Natural Science Foundation of China(Grant No.41802128,42076219)。
文摘Tectonic activities significantly impact deep reservoir properties via sedimentary and diagenetic processes,and this is particularly true for lacustrine rift basins.The tectonic-sedimentary-diageneticreservoir system is crucial in deep reservoir exploration.This study examined the first member and upper submember of the second member of the Dongying Formation in the Bodong Low Uplift in the Bohai Bay Basin(East China),documenting the petrologic features and physical properties of reservoirs in different tectonic sub-units through integrated analysis of log and rock data,along with core observation.A mechanism for deep reservoir formation in lacustrine rift basins was developed to elucidate the sedimentary and diagenetic processes in complex tectonic settings.The results show that tectonic activities result in the occurrence of provenances in multiple directions and the existence of reservoirs at varying burial depths,as well as the significant diversity in sedimentary and diagenetic processes.The grain sizes of the sandstones,influenced by transport pathways rather than the topography of the sedimentary area,exhibit spatial complexity due to tectonic frameworks,which determine the initial pore content of reservoirs.However,the burial depth,influenced by subsequent tectonic subsidence,significantly impacts pore evolution during diagenesis.Based on the significant differences of reservoirs in slope zone,low uplift and depression zone,we establish different tectonic-diagenetic models in deep complex tectonic units of lacustrine rift basins.
基金supported by the National Natural Science Foundation of China(Grant Nos:42130801,41430211,90814006,and 42072226)the“Deep-time Digital Earth”Science and Technology Leading Talents Team Funds for the Central Universities for the Frontiers Science Center for Deep-time Digital Earth,CUGB(Fundamental Research Funds for the Central UniversitiesGrant No:2652023001).
文摘How the subduction direction of the Paleo-Pacific plate beneath the Eurasian plate changes in the Early Cretaceous remains highly controversial due to the disappearance of the subducted oceanic plate.Intraplate deformation structures in the east Asian continent,however,provide excellent opportunities for reconstructing paleostress fields in continental interior in relation to the Paleo-Pacific/Eurasian plate interaction.Anisotropy of magnetic susceptibility(AMS),geological,and geochronological analyses of post-kinematic mafic dykes intruding the detachment fault zone of the Wulian metamorphic core complex(WL MCC)in Jiaodong Peninsula exemplify emplacement of mantle-sourced dykes in a WNW-ESE(301°-121°)oriented tectonic extensional setting at ca.120 Ma.In combination with the results from our previous kinematic analysis of the MCC,a ca.21°clockwise change in the direction of intraplate extension is obtained for early(135-122 Ma)extensional exhumation of the MCC to late(122-108 Ma)emplacement of the dykes.Such a change is suggested to be related to the variation in subduction direction of the Paleo-Pacific plate beneath the Eurasian plate,from westward(pre-122 Ma)to west-northwestward(post-122 Ma).
文摘The extra-peninsular Gondwana Group rocks are exposed in narrow patches within the Lesser Himalayan sequence of the NE-Arunachal Himalayas,India.The bulk of sediments for the sandstones of the Gondwana Group were derived from felsic/acidic to intermediate igneous rocks,with minor mafic input from the upper continental crust(UCC),as supported by various discrimination diagrams based on quantification of detrital minerals coupled with sandstone geochemistry.The inputs from metamorphic sources in subordinate amounts cannot be ruled out,as indicated by quantification of the quartz varieties.These sediments were found to be sourced from the interior part of a craton or shield and recycled platformal sediments which were derived from both passive and active margin settings.The sediments experienced a wide variance in climatic conditions,from arid to humid,suffering low-moderate-inten-sity weathering(CIA:63.43;CIW:86.18;WIP:44.84;PIA:75.37;ICV:2.39;C-value:0.42;PF:0.49;Sr/Cu:9.23 and Rb/Sr:1.68)within the vicinity of the low plains to moderate hills.Additionally,redox-sensitive elements indicate the deposition of sediments under oxygenated or oxygen-rich conditions(U_(au):−2.91;Th/U:7.37;U/Th:0.18;V/Cr:1.71;δU:0.67 and Ce/Ce^(*):0.93).
基金supported by the Science and Technology Major Project of the Sichuan Institute of Geological Survey(SCIGS-CZDXM-2023003)the National Natural Science Foundation of China(41603034).
文摘1.Objective The Songpan-Ganze terrane is a key region for understanding the tectonic evolution of the Tibetan Plateau and the Yangtze Craton.The Songpan-Ganzi complex comprises a thick succession of deformed Ladinian-Norian turbidites(ca.230-203 Ma),covering about 200000 km^(2)of the eastern Tibet Plateau with a volume of approximately 2.0×10^(6)km^(3)(Fig.1a).Furthermore,this complex has over 100 Permian-Cenozoic felsic plutons.
基金jointly supported financially by the National Natural Science Foundation of China(No.41603040)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2023-JC-YB-239)Fundamental Research Funds for the Central Universities(S202310710204)。
文摘The Bijigou intrusion is one of the largest and most well-differentiated Fe–Ti oxide-bearing layered intrusions in the Hannan massif located in the northwestern margin of the Yangtze Block,South China.Besides the mineralization-related mafic-ultramafic rocks,the intermediate-acid intrusive rocks are also exposed in the mining area,which is of great significance for the understanding the Neoproterozoic tectonic evolution of the Yangtze Block,but studies on these intermediate-acid rocks are scarce.The Bijigou mafic-ultramafic layered intrusion is surrounded by granite and cut by syenite veins.Here,we report new zircon U-Pb ages,Lu-Hf isotope composition and bulk rock geochemical data of the Bijigou syenite vein and wall-rock granite in the northwestern margin of the Yangtze Block.Laser ablation inductively coupled plasma mass spectrometry(LAICP-MS)zircon U-Pb dating results show that the Bijigou syenite vein and wall-rock granite formed at 770±3.5 Ma(MSWD=0.17,n=28)and 810±4 Ma(MSWD=0.84,n=26),respectively.The zirconεHf(t)values of the syenite veins range from+1.52 to+5.33(average of+3.05),combined with its high potassium contents,negative Nb–Ta anomalies and positive Pb anomalies,suggesting that they may have originated from mantle-derived basaltic magma,which was modified by materials from subducting oceanic slab.The zirconεHf(t)and T_(DM2)ages of the wall-rock granite range from+0.71 to+5.71(average+3.06)and 1344 to 1659 Ma(average 1519 Ma),respectively,indicating that the granite was produced by partial melting of juvenile crust.The geochemical characteristics of the Bijigou syenite and granite indicate that they were formed in a continental margin arc setting.Thus,combined with previous studies,it suggests that there was a major subduction system along the northwestern margin of the Yangtze Block during 824-720 Ma,and the magmatism in the Hannan massif was divided into two episodes:(1)early magmatism(824-790 Ma),such as the Bijigou,Hongmiaozhen and Huangguanzhen granitoids,was derived from partial melting of the juvenile or pre-existing crust in a continental arc setting;(2)later magmatism(789-718 Ma),including Bijigou syenite,Wudumen,Erliba and Zushidian granitoids,formed in a subduction-related back-arc extensional environment.The long-term subduction system along the northwestern margin of the Yangtze Block during 824-720 Ma suggests that the Yangtze Block was previously located at the periphery of the Rodinia supercontinent.
基金financially supported by the National Natural Science Foundation of China(No.42402171)the China Postdoctoral Science Foundation(No.2023MD744255)+6 种基金the Natural Science Basic Research Program of Shaanxi(No.2024JC-YBQN-0353)the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.23JK0600)the Shaanxi Postdoctoral Science Foundation(No.2023BSHEDZZ324)the project of Theory of Hydrocarbon Enrichment under Multi-Spheric Interactions of the Earth(No.THEMSIE04010107)the Key Research and Development Program of Shaanxi(No.2021KW-10)the Innovation Capability Support Program of Shaanxi(No.2022PT-08)the SINOPEC CCUS Fund Project(No.33550000-22ZC0613-0326)。
文摘In the context of complex tectonic evolution,due to the control of tectonic compression stress and faults on tectonic fractures,the formation and development of tectonic fractures in the T_3x~2 tight reservoirs present significant variations across different tectonic segments in the Western Sichuan Foreland Basin.We clarified the control of differential tectonic evolution on the formation and development of tectonic fractures in different tectonic segments through field-based observations,core samples,image logging,as well as fluid inclusion petrography and temperature determinations of fracture-filling materials,combined with 2D balanced cross-section restoration.The study area primarily manifests two types of tectonic fractures in the tight reservoirs:orogen-related fractures(regional fractures)and fault-related fractures.The orientations of these fractures are predominantly E-W,nearly N-S,NE,and NW.Specifically,the northern segment area only shows the development of regional fractures,while the southern and middle segments exhibit the development of both regional and tectonic fractures.There are three phases of tectonic fractures in different tectonic segments,and their formation times are relatively consistent.The Mesozoic tectonic events had a significant impact on the northern and central segments,with the amount of tectonic shortening and the rate of stratigraphic shortening gradually decreasing from the northeast to the southwest.The compressional stress resulting from tectonic compression also decreases from the northeast to the southwest.As a result,the development of first-phase and second-phase tectonic shear fractures is more pronounced in the northern and middle segments compared to the southern segment.Under the significant control of faults,the development of N-S-and NE-oriented fault-related fractures is more pronounced in the southern segment,while the development of NE-oriented fault-related fractures is relatively higher in the middle segment.Overall,there is an increased density of fractures and an increasing trend in fracture scale from the northern to the middle and then to the southern segment.
基金supported by the National Natural Science Foundation of China(Grant No.42472181)the National Key Research and Development Program of China(Grant No.2021YFA0719000)CNPC Innovation Fund(Grant No.2021DQ02-0103).
文摘Geodynamic processes following the Indo-Eurasian plate collision remain a key research focus,and the Jinshajiang-Red River tectonic zone(JRTZ),situated along this collision boundary,provides critical insights into post-collision tectonic evolution.In this study,we identify a lithological assemblage in the JRTZ,including amphibolite,granite gneiss,and migmatite.These rocks exhibit contrasting geochemical signatures,reflecting multiple source regions:asthenospheric mantle,lithospheric mantle,mafic lower and upper crust.Specifically,amphibolite(28.5 Ma)formed through the partial melting of OIB-like mantle source,whereas S-type granite gneiss(28.2 Ma)originated from the dehydration melting of metamorphosed sedimentary rocks.Amphibole monzonite(28.9 Ma)records the mixing of ancient crustal material with mantle-derived components,while migmatite(37.9 Ma)resulted from deep melting processes of metasedimentary rocks under shear conditions.We propose that the ongoing Indo-Eurasian convergence progressively thickened the crust,ultimately driving large-scale lithospheric delamination between the Eocene and Oligocene.This delamination triggered asthenospheric upwelling,which provided the thermal input required for widespread melting.This lithospheric delamination event started around 38-37 Ma and lasted at least until 28 Ma.
基金supported financially by the Research Foundation of the Department of Natural Resources of Hunan Province(20230135DZ)the Provincial Natural Science Foundation of Hunan(2024JJ7080)+1 种基金the Scientific Research Fund of Hunan Provincial Education Department(23C0320)Hunan Provincial College Student Innovation and Entrepreneurship Training Project(S202311527014).
文摘There is significant debate concerning the tectonic characteristics and evolutionary understanding of the South China Block(SCB)during the Early Mesozoic.One of the key points of contention is the tectonic-magmatic activity during the Triassic and its dynamic mechanisms.However,research on the detailed chronology and tectonic settings of granite plutons in key regions remains insuffi-cient,limiting the understanding of the tectonic-magmatic dynamic mechanisms in the interior of SCB during the Triassic.In this contribution,we present whole-rock major and trace elemental data,Sr-Nd isotope data,LA-ICP-MS zircon U-Pb age dating,and Lu-Hf isotope data for granites of Dashenshan pluton in the Xiangzhong,northwest part of SCB.The results indicate that the Dashenshan granite has an emplacement age of 208.4-212.5 Ma,characterized by high SiO_(2),Na_(2)O,and K_(2)O contents and low MgO and CaO.The Dashenshan granite is enriched in light rare-earth elements with a significant negative Eu anomaly(averageδEu=0.42).It is also enriched in Rb,K,and Th and shows pronounced depletion in Nb,Ta,and Ti,classifying it as peraluminous calc-alkaline granite,specifically of the I-type.The zircon ε_(Hf(t)) values range from−8.39 to−4.4,with an average of−5.82,and the Sr-Nd isotopes are relatively enriched[ε_(Nd)(t)=−9.31 to−6.8].Combining these geochemical characteristics,it is revealed that the Dashenshan granite was derived from the partial melting of middle to upper crustal metamorphic basement materials under medium-to low-temperature conditions,with possible minor contributions from mantle-derived materials.Furthermore,it underwent fractional crystallization,including plagioclase differentiation.By integrating the geochemical features and spatial distribution of Triassic granites in SCB,this study suggests that the regional tectonic evolution of SCB during the Triassic was primarily controlled by the collision of the SCB with the Indochina Block and the North China Block.In Xiangzhong,the tectonic setting transitioned from syn-collisional compression to post-collisional extension during the Late Triassic.The Dashenshan pluton formed in a post-collisional extensional setting,resulting from the decompression melting of middle-to-upper crustal rocks.The upwelling of the asthenosphere and upward heat transfer likely played a significant role in the formation of the Dashenshan granitic magma.
基金supported by the National Nature Science Foundation of China (Grant Nos. 41872235, 42172236, and 41872233)Double First-Class University Construction Special Project of Shaanxi (Grant No. 300111240014)+1 种基金the Youth Innovation Team of Shaanxi Universitiesthe Fundamental Research Funds for the Central Universities of China (Grant Nos. 300102270202, 202110710062, 300103183081, 300108231154, S202410710285, and 300102274808)
文摘The study area is situated in the Tianshan region,specifically within the eastern segment of the North Qilian Orogenic Belt(NQLOB).The NQLOB is a critical region for understanding oceanic closure and continental collision processes driven by the Shangdan Ocean subduction-exhumation,which was a segment of the Proto-Tethys Ocean during the Early Paleozoic.Despite significant research,the Early Paleozoic tectonic background and subduction-related orogenic processes,particularly in the eastern NQLOB,remain subjects of debate.This study presents significant petrographic,geochemical,and geochronologic insights into the metavolcanic rocks of the Chenjiahe Group in the eastern NQLOB.Petrographic analysis reveals that these metavolcanic rocks originated in a low-grade metamorphic setting.Zircon laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)U-Pb dating yielded ages ranging between 449.7-443.4 Ma,indicating Late Ordovician formation.Geochemical signatures of felsic and intermediate rocks exhibit calc-alkaline to high-K calc-alkaline similarities,characterized by high light rare earth elements(LREEs),low heavy rare earth elements(HREEs),and moderate Eu anomalies,consistent with a continental arc setting.In contrast,basaltic rocks display tholeiitic features with elevated large-ion lithophile elements(LILEs),reduced high-field-strength elements(HFSEs),and weak Eu anomalies,suggesting an extensional environment.These findings imply that the metavolcanic rocks evolved in a continental arc-back-arc extension setting connected with the northward subduction and exhumation of the Huluhe back-arc oceanic basin.This process was likely triggered by the northward subduction and closure of the Shangdan Ocean,culminating in the Late Ordovician amalgamation of the Qilian Block and the southwestern North China Block.This study provides critical insight into the tectonic development of the NQLOB and the broader Proto-Tethys Ocean dynamics at the northern periphery of the Eastern Gondwana.
基金supported by the Natural Science Foundation of Shaanxi Province(2023-JC-YB-222)National Natural Science Foundation of China(41872219)+1 种基金Opening Foundation of Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources(DBY-KF-19-12)Research on metallogenic structure and metallogenic structural plane of Shuangwang gold deposit(220227220347,220227230756).
文摘The Shuangwang Au deposit in the western Qinling Orogen is hosted by a WNW-ESE-trending breccia belt that is structurally controlled by the northern limb of the Yindonggou fold.Igneous rocks area in the deposit are part of the Xiba pluton,which comprises granodiorite and monzogranite that contains mafic microgranular envlaves(MMEs),and later mineralized granitic porphyry dikes.The mineralized granitic porphyry dikes were controlled by the same structures that controlled the ore bodies.Zircon LA-ICP-MS U-Pb dating yields ages of 220.0±1.9 Ma for the granodiorite,and 217.9±1.9 Ma for the granitic porphyry,which is consistent with the mineralization ages reported in previous studies(220-218 Ma).Together with the similarity of alteration mineral assemblages between ore and mineralized granitic porphyry,we suggest that the mineralization was controlled by structure and Xiba pluton.The geochemical data show that the granodiorite and granitic porphyry are subalkaline and the MMEs are alkaline in composition.All samples have similar chondrite-normalized rare earth element patterns with enrichment of light rare earth elements.The granodiorite and MMEs are depleted in Nb,Ta,Sr,P,and Ti and enriched in U,K,Pb,Zr,and Hf.The granitic porphyry is enriched in large-ion lithophile elements but depleted in high-field-strength elements.The granodiorite and MMEs have low whole-rockεNd(t)values(−10.90 to−2.32)and(^(87)Sr/^(86)Sr)i ratios(0.7000-0.7285),similar to coeval Triassic granites in the western Qinling Orogen.The(^(87)Sr/^(86)Sr)i ratios of the granitic porphyry have been affected by fluid metasomatism that results in higher(^(87)Sr/^(86)Sr)i values.The geochronological,geochemical,and isotopic evidence suggest that the Xiba pluton formed by partial melting of thickened lower crust that had been intruded by alkaline mafic magma,as documented by the MMEs,which were derived from a source metasomatized by subduction-related fluids.The granodioritic and granitic porphyry magmas were relatively oxidized(fayalite-magnetite-quartz[FMQ]to magnetite-hematite(MH)buffer conditions;zircon Ce^(4+)/Ce^(3+)=72-813;log(fO_(2))=−22 to−8).We propose that magma mixing between lower crust and mantle-derived mafic magma was triggered by the tectonic transition from a collisional to post-collision setting,which provided the metals,S,fluids,and increase in magma oxygen fugacity that enabled the formation of the Shuangwang Au deposit.Since the Late Triassic,the western Qinling Orogen evolved from a syn-collisional compressional to post-collisional extensional environment.The mineralization of the Shuangwang Au deposit involved early formation of a tectonic breccia in the compressional stage.Subsequently,hydrothermal fluids derived from a magma ascended,migrated,mixed,and precipitated ores in the tectonic breccia during the later extensional stage to form the Shuangwang Au deposit.
