The Early Cretaceous Sindong Group, a non-marine molasse, unconformably overlies the folded earliest Cretaceous Myogok Formation. The tectonism that folded the Jaseong Synthem including the Myogok and other formations...The Early Cretaceous Sindong Group, a non-marine molasse, unconformably overlies the folded earliest Cretaceous Myogok Formation. The tectonism that folded the Jaseong Synthem including the Myogok and other formations is here called the Nakdong-Jaeryeonggang （N-J） tectonism. The Oknyeobong and Dabokni Formations are discussed to show that they belong to the Jaseong Synthem. The Dabokni Formation yielded fossil diatoms whose age has been referred as the ＂earliest Cretaceous＂ based on the geologically constrained age of the fossil-bearing deposit. The age of the N-J tectonism appears Barremian as it is between the Hauterivian Myogok Formation and the Aptian Sindong Group with the TPN （Trigonioides-Plicatounio-Nippononaia） fauna. The N-J tectonism, an orogeny, quite deformed pre-Aptian strata in Korea, but can hardly find its reported equivalent in NE China. A revised correlation table shows that the Jaseong- Sindong sequence corresponds to the Jehol Group of China. The Sindong-Hayang transition was characterized by basin migration and dextral rotation probably caused by the Tan-Lu fault system in a broad sense.展开更多
Hydrothermal activity in mid-ocean ridges(MORs)is an important intermediary for the mass and heat exchange between the ocean and lithosphere.The development of hydrothermal activity on MORs is primarily controlled by ...Hydrothermal activity in mid-ocean ridges(MORs)is an important intermediary for the mass and heat exchange between the ocean and lithosphere.The development of hydrothermal activity on MORs is primarily controlled by coupled magmatic and tectonic activities.In ultraslow-spreading ridges,deepdipping low-angle normal faults with large offsets,typically detachment faults in the inside corners of ridge offsets,favor the formation of tectonic-related hydrothermal activities,whereas volcanic-related hydrothermal fields are typically developed in neovolcanic zones in this category of the ridge system.However,whether tectonic or magmatic activity is dominant and to what extent they control the formation of hydrothermal activities on ultraslow-spreading ridges remain unclear.Segments in the west and east of the Gallieni transform fault(TF)located in the ultraslow-spreading Southwest Indian Ridge(SWIR),namely,western area(WA)and eastern area(EA),exhibit distinct magma-supply conditions that provide favorable conditions for examining the influence of magmatic and tectonic activities.We generated prediction models for these areas using the spatial analysis of the water depth,minor faults,large faults,ridge axis,nontransform discontinuity(NTD)inside corners,TF inside corners,Bouguer gravity anomaly,magnetic anomalies,and seismic activities.By employing the weights of evidence method,we reported that the formation of seafloor hydrothermal systems in SWIR was primarily correlated to the NTD inside corner,ridge axis,and minor fault(i.e.,contrast values(C)of 4.186,3.727,and 3.482 in WA and 4.278,3.769,and 3.135 in EA).Furthermore,EA was significantly affected by the TF inside corner(C=3.501),whereas WA was influenced by large faults(C=4.062).Our results demonstrated that tectonism was the primary controlling factor in the development of hydrothermal activities in the study area,and the contribution of magmatism was secondary,even in WA,which has a relatively robust magma supply.We delimited prominent prospecting areas at each side based on posterior probability.Our results provided insights into the formation mechanisms of hydrothermal activities and support prospecting in MORs.展开更多
Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among ...Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among which the biggest altitude above river level is 401m and the formation age of the highest terrace is 1.57 Ma B.P. Based on comparative analysis of the Yellow River terraces located separately in the Mijiashan mountain, the Chemuxia gorge, the Heishanxia gorge and the other river terraces in the vast extent of the northern part of China, it has been found that the tectonic processes resulting in the formation of the terrace series is one of multi-gradational features, i.e., a terrace series can include the various terraces produced by tectonic uplifts of different scopes or scales and different ranks. The Yellow River terrace series in the study region can be divided into three grades. Among them, in the first grade there are 6 terraces which were formed separately at the same time in the vast extent of the northern part of China and represent the number and magnitude of uplift of the Qinghai-Xizang Plateau since 1.6 Ma B. P.; in the second grade there are 5 terraces which were separately and simultaneously developed within the Haiyuan-Tianjingshan tectonic region and represent the number and magnitude of uplift of this tectonic region itself since 1.6Ma B.P.; in the third grade there are 10 terraces which developed on the eastern slope of the Mijiashan mountain and represent the number and amplitude of uplift of the Haiyuan tectonic belt itself since 1.6Ma B.P. Comparison of the terrace ages with loess-paleosoil sequence has also showed that the first grade terraces reflecting the vast scope uplifts of the Qinghai-Xizang Plateau are very comparable with climatic changes and their formation ages all correspond to the interglacial epochs during which paleosoils were formed. This implies that the vast extent tectonic uplifts resulting in river down-cutting are closely related to the warm-humid climatic periods which can also result in river downward erosion after strong dry and cold climatic periods, and they have jointly formed the tectonic-climatic cycles. There exists no unanimous and specific relationship between the formation ages of the second and third grade terraces and climatic changes and it is shown that the formation of those terraces was most mainly controlled by tectonic uplifts of the Tianjingshan block and the Haiyuan belt. The river terraces in the study region, therefore, may belong to 2 kinds of formation cause. One is a tectonic-climatic cyclical terrace produced jointly by vast extent tectonic uplifts and climatic changes, and the terraces of this kind are extensively distributed and can be well compared with each other among regions. Another is a pulse-tectonic cyclical terrace produced by local tectonic uplifts as dominant elements, and their distribution is restricted within an active belt and can not be compared with among regions.展开更多
The Keshen gas field is one of the most important natural gas supply sources in the Tarim basin,western China.The main gas producing interval there is the Lower Cretaceous Bashijiqike Formation(K1bs),it is an ultra-de...The Keshen gas field is one of the most important natural gas supply sources in the Tarim basin,western China.The main gas producing interval there is the Lower Cretaceous Bashijiqike Formation(K1bs),it is an ultra-deep tight reservoir whose buried depth exceeds 6000 m,and it shows a low matrix porosity(<10%)and extremely low matrix permeability(<0.1mD).However,this reservoir can supply extremely high and stable gas production due to improvement of reservoir quality by tectonism and fluid.Based on tectonic evolution analysis by plenty of lab data of core plugs or thin sections,the enhancement models of tectonism and fluid are built,evidence suggests both tectonism and fluid improve the reservoir quality greatly.Tectonic evolution produces lots of natural fractures in 3stages which promote the ultra-deep tight reservoir permeability 10–200 times,then,testing results of new boreholes without fracturing show reservoir permeability underground can reach 20 mD.Furthermore,fluid dissolution increases reservoir porosity 1–2 times,the main dissolved mineral is feldspar,all fluid dissolution came from the unconformity controlling the dissolution distance.Tectonism and fluid interact on each other:Tectonism controls fracture distribution and types of diagenic fluid in reservoir,but fluids influence fracture cements and dissolution.Both tectonic folding and the fluid flow control the sweet point reservoir located in upper 150 m formation.展开更多
During the Ordovician-Silurian transition period,the Yangtze area experienced significant environmental changes,which were recorded by the widely distributed black shale of the Upper Ordovician Wufeng and Lower Siluri...During the Ordovician-Silurian transition period,the Yangtze area experienced significant environmental changes,which were recorded by the widely distributed black shale of the Upper Ordovician Wufeng and Lower Silurian Longmaxi formations.However,the petrological and geochemical analyses of the Upper Ordovician-Lower Silurian black shale in Well JY1(eastern Sichuan Basin)and Well YY2(western Hubei Province)drill cores show that there are some significant differences with respect to lithology,thickness,and geochemical characteristics despite the long-term similar variation trend in petrology and geochemistry.This may suggest some major environmental changes and their differential influence on black shale deposition in the Yangtze area.Based on the analyses of lithology,total organic carbon(TOC),Mo_(EF),and U_(EF),four long-term sedimentary cycles(one for the Wufeng Formation and three for the Longmaxi Formation)were identified in Well JY1.In Well YY2,only three long-term sedimentary cycles can be recognized(one for the Wufeng Formation and two for the Longmaxi Formation).Different from the gradual increase of the geochemical proxies(such as TOC,MoEF,and NiEF)followed by an abrupt decrease in the Wufeng Formation,these proxies of the Silurian sedimentary cycles in both wells exhibit an abrupt increase at the base followed by a gradual decrease,showing that controlling mechanisms for the Lower Silurian black shale deposition in the study areas were different from those of the Upper Ordovician black shale.However,the black shale of each Silurian cycle in Well JY1 is much thicker than that in Well YY2.Compared with the thick silty mudstone developed in Well JY1 during the Rhuddanian-Aeronian transition,there is a stratigraphic gap in Well YY2 except for a thin calcareous dolostone formed in a strongly restricted environment.These differences indicate that tectonism and glacial eustasy should be the key factors for black shale development,but their influences on the deposition of the Lower Silurian black shale varied between eastern Sichuan Basin and western Hubei province.Since the early Rhuddanian stage,continuous tectonic subsidence in eastern Sichuan Basin promoted the development of thick black shale,while a persistent tectonic uplift in western Hubei Province led to the formation of thin black shale.Meanwhile,the study areas experienced a significant sealevel drop related to intensified glaciation during the Rhuddanian-Aeronian transition,which is recorded by the low chemical index of alteration(CIA)values in both wells.This resulted in the formation of a stratigraphic gap in western Hubei Province and the deposition of thick silty mudstone in eastern Sichuan Basin.Moreover,abrupt increases in CIA,TOC,Mo_(EF),and Ni_(EF) observed in the lower part of the Aeronian black shale in the two wells suggest that eastern Sichuan Basin and western Hubei Province experienced a significant sealevel rise during the early Aeronian stage,which may be related to a global warming event.Subsequently,eastern Sichuan Basin and western Hubei Province both suffered a significant tectonic uplift related to the Kwangsian Movement leading to the termination of the Aeronian black shale formation.However,the thickness variations of the Aeronian black shale in the two study areas indicate that remarkable geomorphological differences persisted in these two areas until the middle Aeronian stage.Thus,this study not only reveals differences of the Upper Ordovician-Lower Silurian black shale in eastern Sichuan Basin and western Hubei Province,but also interprets the causes of these differences,which provide new data and perspectives for the understanding of global paleoclimate and sea-level changes during the Ordovician-Silurian transition.展开更多
The Tertiary Kuqa depression is a foreland basin generated by flexural subsidence resulting from the southward thrusting of the southern Tianshan Mountains. Tertiary basin fills of the depression can be classified int...The Tertiary Kuqa depression is a foreland basin generated by flexural subsidence resulting from the southward thrusting of the southern Tianshan Mountains. Tertiary basin fills of the depression can be classified into four tectonic sequences bounded by gentle angular unconformities. The sequences are composed of two parts, the lower transgressive and the upper progradational successions, which are separated by a regional maximum transgressive surface. The development of these sequences is attributed to the foreland tectonic process from flexural subsidence caused by thrust loading to rebounded uplift due to the erosion and stress release. The generation of the angular unconformities defining the tectonic sequences has been interpreted as the result of the rebounded uplift and the following thrusting. It has been found that there is a significant difference in depositional pattern between the northeastern and the northwestern margins. The relatively strong thrusting and mountain building occurring along the northwestern margin resulted in the development of thick-bedded alluvial fan and angular unconformities. The northeastern margin, in contract, lacks thick alluvial fan accumulation due to weak thrusting. This difference is likely related to the pre-existing east-west partition of the basin basement.展开更多
Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in ...Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in the southern Junggar Basin to comprehensively analyze the fracture characteristics and differential distribution and,ultimately,addressed the controlling mechanisms of tectonism and diagenesis on fracture effectiveness.Results revealed that the intensity of tectonic activities determines the complexity of tectonic fracture systems to create various fracture orientations when they have been stronger.The intense tectonic deformation would impact the stratum occurrence,which results in a wide range of fracture dip angles.Moreover,as the intensity of tectonic activities and deformations weakens,the scale and degree of tectonic fractures would decrease continuously.The control of tectonism on fracture effectiveness is reflected in the notable variations in the filling of multiple group fractures developed during different tectonic activity periods.Fractures formed in the early stages are more likely to be filled with minerals,causing their effectiveness to deteriorate significantly.Additionally,the strong cementation in the diagenetic evolution can cause more fractures to be filled with minerals and become barriers to fluid flow,which is detrimental to fracture effectiveness.However,dissolution is beneficial in improving their effectiveness by increasing fracture aperture and their connectivity to the pores.These insights can refine the development pattern of natural fractures and contribute to revealing the evolutionary mechanisms of fracture effectiveness in deep tight sandstone reservoirs of foreland thrust belts.展开更多
The Cretaceous gold deposits along the margins of the North China Craton(NCC),which formed in a craton destruction setting,display geological characteristics similar to traditional orogenic gold deposits typically ass...The Cretaceous gold deposits along the margins of the North China Craton(NCC),which formed in a craton destruction setting,display geological characteristics similar to traditional orogenic gold deposits typically associated with accretionary orogeny.These deposits,known as Jiaodong-type gold deposits,have attracted considerable attention.However,the lithospheric controls and formation mechanisms of these deposits remain unclear,as they cannot be fully explained by the supracrustal metamorphic genetic model commonly applied to classic orogenic gold deposits.In this study,the compiled S-Hg-Pb isotope ratios of gold deposits on different NCC margins display compatible variations to the Sr-Nd-Hg isotope ratios of mafic dikes spatial-temporally associated with the deposits.This implies that mantle lithosphere,metasomatized by variable proportions of oceanic and continental crust,was the source for both gold deposits and mafic dikes.Increase of oxygen fugacity and zirconεHf(t)from pre-to syn-gold granites suggests continuous basic magma underplating,which could induce concentrations of Au-rich sulfides and contribute additional Au to auriferous CO_(2)-rich fluids derived from metasomatized mantle lithosphere and basic magma.Localization of gold deposits was controlled by craton-margin sinistral shearing induced by clockwise rotation of the craton coincident with distal emplacement of metamorphic core complexes.Thus,the Cretaceous Jiaodong-type orogenic gold deposits were derived from fertilized mantle lithosphere through such crust-mantle processes within a lithosphere thinning background.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
The sedimentary geochemistry of St.Martin’s Island is important to determine the origin of the source rock,paleo weathering,tectonic setting,sediment recycling,maturity,sorting,redox condition,and paleo salinity of t...The sedimentary geochemistry of St.Martin’s Island is important to determine the origin of the source rock,paleo weathering,tectonic setting,sediment recycling,maturity,sorting,redox condition,and paleo salinity of the sediments.Major oxides,trace elements,and rare earth elements(REEs)obtained from the INAA technique are presented by analyzing the sediment samples collected from the shoreline of St.Martin’s Island,Bangladesh.The elemental ratios,comparison with average upper continental crust(UCC),binary diagrams(Th/Sc vs.Sc,La/Th vs.Hf,Th/Co vs.La/Sc),and chondrite normalized REE patterns exhibit substantial LREE enrichment,relatively fl at HREE fractionation,considerable negative Eu anomalies(average:0.72),indicates the derivation from a source dominated by felsic rock,with contribution from intermediate source and mafi c component.Sediments from St.Martin’s Island exhibit the deposition of sediments in transitional environments of active and passive continental margin settings.Weathering indices value of CIA,PIA,CIW,CIX,and K 2 O/Rb ratio show moderate chemical weathering,indicating that the sediments are chemically mature.Sedimentary redox indicative proxies,such as U/Th,V/Cr,and V/Sc,show an oxic depositional environment during sediment deposition.The intermediate CIA and other weathering index values of the St.Martin’s sediments show that the area had semiarid and humid climatic conditions throughout the deposition.The Rb/K ratio of the St.Martin’s sediments suggests that the development and deposition of the sedimentary sequence of St.Martin’s Island mainly occurred in a brackish water environment during the geological past.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
Since the Paleozoic,the tectonic evolution of northeastern Eurasia has been primarily influenced by the Paleo-Asian Ocean and the Paleo-Pacific tectonic domains.However,the spatial and temporal frameworks,as well as t...Since the Paleozoic,the tectonic evolution of northeastern Eurasia has been primarily influenced by the Paleo-Asian Ocean and the Paleo-Pacific tectonic domains.However,the spatial and temporal frameworks,as well as the timing of the tectonic transition between these two oceanic domains,remain unclear.For addressing these issues,we present petrological,geochronological,and geochemical data for andesite and sandstone samples from the Seluohe Group along the Jilin-Yanji Suture between the Jiamusi-Khanka Block and the North China Craton.The geochemical results indicate that the andesite sample is high-Mg andesite.Its magma source was generated by the metasomatized mantle wedge influenced by fluids derived from the subducted slab in a continental island arc setting.The high-Mg andesite gives the crystallization ages of Early Triassic(249±3 Ma).The sandstone is immature greywacke with a maximum depositional age of Early Triassic(247±1 Ma),and its sediments primarily originate from concurrent magmatic rocks within a juvenile continental arc.Based on our new findings,we propose that the Seluohe Group represents an Early Triassic volcanic-sedimentary association with continental island arc characteristics associated with the southwestward subduction of the Heilongjiang Ocean.We identified a sedimentary basin intimately associated with one or more continental arcs along the northeastern edge of the North China Craton.We suggest that the southwestward subduction of the Jilin-Heilongjiang Ocean in the Early Mesozoic accounts for this continental arc setting.There is a distinct temporal gap between the closure of the Paleo-Asian Ocean(ca.260 Ma)and the onset of Paleo-Pacific plate subduction(234–220 Ma),which is essentially coeval with the southwestward subduction of the Jilin-Heilongjiang Ocean between 255 Ma and 239 Ma.展开更多
Based on the analysis of surface geological survey,exploratory well,gravity-magnetic-electric and seismic data,and through mapping the sedimentary basin and its peripheral orogenic belts together,this paper explores s...Based on the analysis of surface geological survey,exploratory well,gravity-magnetic-electric and seismic data,and through mapping the sedimentary basin and its peripheral orogenic belts together,this paper explores systematically the boundary,distribution,geological structure,and tectonic attributes of the Ordos prototype basin in the geological historical periods.The results show that the Ordos block is bounded to the west by the Engorwusu Fault Zone,to the east by the Taihangshan Mountain Piedmont Fault Zone,to the north by the Solonker-Xilamuron Suture Zone,and to the south by the Shangnan-Danfeng Suture Zone.The Ordos Basin boundary was the plate tectonic boundary during the Middle Proterozoic to Paleozoic,and the intra-continental deformation boundary in the Meso-Cenozoic.The basin survived as a marine cratonic basin covering the entire Ordos block during the Middle Proterozoic to Ordovician,a marine-continental transitional depression basin enclosed by an island arc uplift belt at the plate margin during the Carboniferous to Permian,a unified intra-continental lacustrine depression basin in the Triassic,and an intra-continental cratonic basin circled by a rift system in the Cenozoic.The basin scope has been decreasing till the present.The large,widespread prototype basin controlled the exploration area far beyond the present-day sedimentary basin boundary,with multiple target plays vertically.The Ordos Basin has the characteristics of a whole petroleum(or deposition)system.The Middle Proterozoic wide-rift system as a typical basin under the overlying Phanerozoic basin and the Cambrian-Ordovician passive margin basin and intra-cratonic depression in the deep-sited basin will be the important successions for oil and gas exploration in the coming years.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 Irtysh tectonic belt lies on the southern margin of the Chinese Altai Orogen. Several secondary shear zones with NW-SE strikes have developed in this tectonic belt, and the deformation processes are of great signi...The Irtysh tectonic belt lies on the southern margin of the Chinese Altai Orogen. Several secondary shear zones with NW-SE strikes have developed in this tectonic belt, and the deformation processes are of great significance to understanding the tectonic regime of the Altai Orogen in the Late Paleozoic. The Tuerhongshate ductile shear zone is located in the eastern Irtysh tectonic belt with obvious deformed structures. The felsic rocks are strongly mylonitized, exhibiting S-C fabrics, asymmetric rotational porphyroclasts, and bookshelf structures of the plagioclases, indicating a sinistral shear sense. The deformation mechanisms, lattice preferred orientations (LPOs) of quartz, and opening angles of quartz c-axis suggest that the deformation temperatures range from 400 to 500 ℃, consistent with higher-greenschist to lower-amphibolite facies conditions. The calculated kinematic vorticity values (W_(k)) of the studied samples range from 0.53 to 0.89 and indicate general shear to simple shear, based on rotational rigid porphyroclast method and oblique grain-shaped/quartz c-axis fabric method. The U-Pb ages of magmatic zircons in felsic mylonites indicate that the sinistral shear occurred after 296.7 ± 3.0 Ma (Early Permian) in the Tuerhongshate shear zone and persisted for approximately 13 Ma. Combined with the tectonic setting and the observed sinistral strike-slip shear indicators in the mylonite zone, these features demonstrate that the Irtysh tectonic belt was in a post-orogenic and strike-slip environment following the closure of the Irtysh Ocean.展开更多
1.Objective,The Luang Prabang(Laos)-Loei(Thailand)metallogenetic belt,located along the northwestern margin of the Indochina Block(Fig.1a)and endowed nearly 200 t of gold and more than 106 t of copper,is one of the mo...1.Objective,The Luang Prabang(Laos)-Loei(Thailand)metallogenetic belt,located along the northwestern margin of the Indochina Block(Fig.1a)and endowed nearly 200 t of gold and more than 106 t of copper,is one of the most important gold-copper metallogenic belts in Indo-China Peninsula.It has undergone tectonic changes during the Early Paleozoic to Mesozoic Proto-Paleo Tethys tectonic evolution,recorded by the Luang Prabang tectonic belt,the Nan-Uttaradit suture,and the Dien Bien Phu-Loei suture.展开更多
Riedel shear system,which consists of some different oriented faults and derivative structures,is an important pattern of tectonic activity and stress regulation,which has been widely applied to the interpretation of ...Riedel shear system,which consists of some different oriented faults and derivative structures,is an important pattern of tectonic activity and stress regulation,which has been widely applied to the interpretation of intracontinental deformation.The Laolongwan Basin,located in the western Haiyuan fault zone at the northeastern Tibetan Plateau,is a key area to study the Cenozoic intracontinental deformation in the northeastern plateau,which formed a complex active fault system during the Cenozoic.However,the activity of these faults and their kinematic mechanism remain unclear.In this contribution,based on detailed structural interpretation of remote sensing image,field observations and OSL dating analysis,we propose a Riedel Shear model of active fault system in the Laolongwan Basin.Our observations show that this active fault system consist of four major faults,including the left strike-slip Hasi Shan fault and Zihong Shan fault with thrusting characteristics,the Southern Zihong Shan thrust fault and the Mijia Shan normal fault.The fault offset and OSL dating analyses suggest that the left-lateral slip rate of the Hasi Shan fault is~2.60-3.01 mm/a since ca.15 ka,whereas the Zihong Shan fault is~1.10-1.13 mm/a since ca.14 ka.Faultslip vectors analyses indicate that the active fault system related to the Riedel Shear in the Laolongwan Basin was controlled by the regional ENE-WSW compressive stress.This compression also caused the significant left-lateral strike-slip movement along the Haiyuan fault zone at the same time,which might result from the northeastward continuous expanding of the Tibetan Plateau during the Late Cenozoic.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
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
文摘The Early Cretaceous Sindong Group, a non-marine molasse, unconformably overlies the folded earliest Cretaceous Myogok Formation. The tectonism that folded the Jaseong Synthem including the Myogok and other formations is here called the Nakdong-Jaeryeonggang （N-J） tectonism. The Oknyeobong and Dabokni Formations are discussed to show that they belong to the Jaseong Synthem. The Dabokni Formation yielded fossil diatoms whose age has been referred as the ＂earliest Cretaceous＂ based on the geologically constrained age of the fossil-bearing deposit. The age of the N-J tectonism appears Barremian as it is between the Hauterivian Myogok Formation and the Aptian Sindong Group with the TPN （Trigonioides-Plicatounio-Nippononaia） fauna. The N-J tectonism, an orogeny, quite deformed pre-Aptian strata in Korea, but can hardly find its reported equivalent in NE China. A revised correlation table shows that the Jaseong- Sindong sequence corresponds to the Jehol Group of China. The Sindong-Hayang transition was characterized by basin migration and dextral rotation probably caused by the Tan-Lu fault system in a broad sense.
基金supported by the National Natural Science Foundation of China(Grant No.42127807)Key Research and Development Program of Zhejiang Province(Grant No.2021C03016)+1 种基金Scientific Research Fund of the Second Institute of Oceanography,MNR(Grant No.SZ2201)China Ocean Mineral Resources R&D Association Project(Grant No.DY135-S1-1-01).
文摘Hydrothermal activity in mid-ocean ridges(MORs)is an important intermediary for the mass and heat exchange between the ocean and lithosphere.The development of hydrothermal activity on MORs is primarily controlled by coupled magmatic and tectonic activities.In ultraslow-spreading ridges,deepdipping low-angle normal faults with large offsets,typically detachment faults in the inside corners of ridge offsets,favor the formation of tectonic-related hydrothermal activities,whereas volcanic-related hydrothermal fields are typically developed in neovolcanic zones in this category of the ridge system.However,whether tectonic or magmatic activity is dominant and to what extent they control the formation of hydrothermal activities on ultraslow-spreading ridges remain unclear.Segments in the west and east of the Gallieni transform fault(TF)located in the ultraslow-spreading Southwest Indian Ridge(SWIR),namely,western area(WA)and eastern area(EA),exhibit distinct magma-supply conditions that provide favorable conditions for examining the influence of magmatic and tectonic activities.We generated prediction models for these areas using the spatial analysis of the water depth,minor faults,large faults,ridge axis,nontransform discontinuity(NTD)inside corners,TF inside corners,Bouguer gravity anomaly,magnetic anomalies,and seismic activities.By employing the weights of evidence method,we reported that the formation of seafloor hydrothermal systems in SWIR was primarily correlated to the NTD inside corner,ridge axis,and minor fault(i.e.,contrast values(C)of 4.186,3.727,and 3.482 in WA and 4.278,3.769,and 3.135 in EA).Furthermore,EA was significantly affected by the TF inside corner(C=3.501),whereas WA was influenced by large faults(C=4.062).Our results demonstrated that tectonism was the primary controlling factor in the development of hydrothermal activities in the study area,and the contribution of magmatism was secondary,even in WA,which has a relatively robust magma supply.We delimited prominent prospecting areas at each side based on posterior probability.Our results provided insights into the formation mechanisms of hydrothermal activities and support prospecting in MORs.
文摘Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among which the biggest altitude above river level is 401m and the formation age of the highest terrace is 1.57 Ma B.P. Based on comparative analysis of the Yellow River terraces located separately in the Mijiashan mountain, the Chemuxia gorge, the Heishanxia gorge and the other river terraces in the vast extent of the northern part of China, it has been found that the tectonic processes resulting in the formation of the terrace series is one of multi-gradational features, i.e., a terrace series can include the various terraces produced by tectonic uplifts of different scopes or scales and different ranks. The Yellow River terrace series in the study region can be divided into three grades. Among them, in the first grade there are 6 terraces which were formed separately at the same time in the vast extent of the northern part of China and represent the number and magnitude of uplift of the Qinghai-Xizang Plateau since 1.6 Ma B. P.; in the second grade there are 5 terraces which were separately and simultaneously developed within the Haiyuan-Tianjingshan tectonic region and represent the number and magnitude of uplift of this tectonic region itself since 1.6Ma B.P.; in the third grade there are 10 terraces which developed on the eastern slope of the Mijiashan mountain and represent the number and amplitude of uplift of the Haiyuan tectonic belt itself since 1.6Ma B.P. Comparison of the terrace ages with loess-paleosoil sequence has also showed that the first grade terraces reflecting the vast scope uplifts of the Qinghai-Xizang Plateau are very comparable with climatic changes and their formation ages all correspond to the interglacial epochs during which paleosoils were formed. This implies that the vast extent tectonic uplifts resulting in river down-cutting are closely related to the warm-humid climatic periods which can also result in river downward erosion after strong dry and cold climatic periods, and they have jointly formed the tectonic-climatic cycles. There exists no unanimous and specific relationship between the formation ages of the second and third grade terraces and climatic changes and it is shown that the formation of those terraces was most mainly controlled by tectonic uplifts of the Tianjingshan block and the Haiyuan belt. The river terraces in the study region, therefore, may belong to 2 kinds of formation cause. One is a tectonic-climatic cyclical terrace produced jointly by vast extent tectonic uplifts and climatic changes, and the terraces of this kind are extensively distributed and can be well compared with each other among regions. Another is a pulse-tectonic cyclical terrace produced by local tectonic uplifts as dominant elements, and their distribution is restricted within an active belt and can not be compared with among regions.
基金reservoir research project of PetroChina(No.2021DJ0302).
文摘The Keshen gas field is one of the most important natural gas supply sources in the Tarim basin,western China.The main gas producing interval there is the Lower Cretaceous Bashijiqike Formation(K1bs),it is an ultra-deep tight reservoir whose buried depth exceeds 6000 m,and it shows a low matrix porosity(<10%)and extremely low matrix permeability(<0.1mD).However,this reservoir can supply extremely high and stable gas production due to improvement of reservoir quality by tectonism and fluid.Based on tectonic evolution analysis by plenty of lab data of core plugs or thin sections,the enhancement models of tectonism and fluid are built,evidence suggests both tectonism and fluid improve the reservoir quality greatly.Tectonic evolution produces lots of natural fractures in 3stages which promote the ultra-deep tight reservoir permeability 10–200 times,then,testing results of new boreholes without fracturing show reservoir permeability underground can reach 20 mD.Furthermore,fluid dissolution increases reservoir porosity 1–2 times,the main dissolved mineral is feldspar,all fluid dissolution came from the unconformity controlling the dissolution distance.Tectonism and fluid interact on each other:Tectonism controls fracture distribution and types of diagenic fluid in reservoir,but fluids influence fracture cements and dissolution.Both tectonic folding and the fluid flow control the sweet point reservoir located in upper 150 m formation.
基金sponsored by the China National Petroleum Corporation Innovation Found(Grant No.2021DQ02-0101)the Open Foundation of Cooperative Innovation Center of Unconventional Oil and Gas,Yangtze University(Ministry of Education and Hubei Province)(Grant No.UOG 2022-08)+2 种基金the Open Foundation of the Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences(Wuhan)(Grant No.TPR-2021-13)the Natural Gas Geology Key Laboratory of Sichuan Province(Grant No.2021trqdz02)the Hubei Provincial Natural Science Foundation of China(Grant No.2020CFB501).
文摘During the Ordovician-Silurian transition period,the Yangtze area experienced significant environmental changes,which were recorded by the widely distributed black shale of the Upper Ordovician Wufeng and Lower Silurian Longmaxi formations.However,the petrological and geochemical analyses of the Upper Ordovician-Lower Silurian black shale in Well JY1(eastern Sichuan Basin)and Well YY2(western Hubei Province)drill cores show that there are some significant differences with respect to lithology,thickness,and geochemical characteristics despite the long-term similar variation trend in petrology and geochemistry.This may suggest some major environmental changes and their differential influence on black shale deposition in the Yangtze area.Based on the analyses of lithology,total organic carbon(TOC),Mo_(EF),and U_(EF),four long-term sedimentary cycles(one for the Wufeng Formation and three for the Longmaxi Formation)were identified in Well JY1.In Well YY2,only three long-term sedimentary cycles can be recognized(one for the Wufeng Formation and two for the Longmaxi Formation).Different from the gradual increase of the geochemical proxies(such as TOC,MoEF,and NiEF)followed by an abrupt decrease in the Wufeng Formation,these proxies of the Silurian sedimentary cycles in both wells exhibit an abrupt increase at the base followed by a gradual decrease,showing that controlling mechanisms for the Lower Silurian black shale deposition in the study areas were different from those of the Upper Ordovician black shale.However,the black shale of each Silurian cycle in Well JY1 is much thicker than that in Well YY2.Compared with the thick silty mudstone developed in Well JY1 during the Rhuddanian-Aeronian transition,there is a stratigraphic gap in Well YY2 except for a thin calcareous dolostone formed in a strongly restricted environment.These differences indicate that tectonism and glacial eustasy should be the key factors for black shale development,but their influences on the deposition of the Lower Silurian black shale varied between eastern Sichuan Basin and western Hubei province.Since the early Rhuddanian stage,continuous tectonic subsidence in eastern Sichuan Basin promoted the development of thick black shale,while a persistent tectonic uplift in western Hubei Province led to the formation of thin black shale.Meanwhile,the study areas experienced a significant sealevel drop related to intensified glaciation during the Rhuddanian-Aeronian transition,which is recorded by the low chemical index of alteration(CIA)values in both wells.This resulted in the formation of a stratigraphic gap in western Hubei Province and the deposition of thick silty mudstone in eastern Sichuan Basin.Moreover,abrupt increases in CIA,TOC,Mo_(EF),and Ni_(EF) observed in the lower part of the Aeronian black shale in the two wells suggest that eastern Sichuan Basin and western Hubei Province experienced a significant sealevel rise during the early Aeronian stage,which may be related to a global warming event.Subsequently,eastern Sichuan Basin and western Hubei Province both suffered a significant tectonic uplift related to the Kwangsian Movement leading to the termination of the Aeronian black shale formation.However,the thickness variations of the Aeronian black shale in the two study areas indicate that remarkable geomorphological differences persisted in these two areas until the middle Aeronian stage.Thus,this study not only reveals differences of the Upper Ordovician-Lower Silurian black shale in eastern Sichuan Basin and western Hubei Province,but also interprets the causes of these differences,which provide new data and perspectives for the understanding of global paleoclimate and sea-level changes during the Ordovician-Silurian transition.
基金This work was supported by the Ministry of Science and Technology of China (Grant No.G1999043304).
文摘The Tertiary Kuqa depression is a foreland basin generated by flexural subsidence resulting from the southward thrusting of the southern Tianshan Mountains. Tertiary basin fills of the depression can be classified into four tectonic sequences bounded by gentle angular unconformities. The sequences are composed of two parts, the lower transgressive and the upper progradational successions, which are separated by a regional maximum transgressive surface. The development of these sequences is attributed to the foreland tectonic process from flexural subsidence caused by thrust loading to rebounded uplift due to the erosion and stress release. The generation of the angular unconformities defining the tectonic sequences has been interpreted as the result of the rebounded uplift and the following thrusting. It has been found that there is a significant difference in depositional pattern between the northeastern and the northwestern margins. The relatively strong thrusting and mountain building occurring along the northwestern margin resulted in the development of thick-bedded alluvial fan and angular unconformities. The northeastern margin, in contract, lacks thick alluvial fan accumulation due to weak thrusting. This difference is likely related to the pre-existing east-west partition of the basin basement.
基金supported by the CNPC Innovation Found(No.2023DQ02-0103)National Major Science and Technology Projects of China(No.2016ZX05003-001).
文摘Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts.This study focused on the Jurassic in the southern Junggar Basin to comprehensively analyze the fracture characteristics and differential distribution and,ultimately,addressed the controlling mechanisms of tectonism and diagenesis on fracture effectiveness.Results revealed that the intensity of tectonic activities determines the complexity of tectonic fracture systems to create various fracture orientations when they have been stronger.The intense tectonic deformation would impact the stratum occurrence,which results in a wide range of fracture dip angles.Moreover,as the intensity of tectonic activities and deformations weakens,the scale and degree of tectonic fractures would decrease continuously.The control of tectonism on fracture effectiveness is reflected in the notable variations in the filling of multiple group fractures developed during different tectonic activity periods.Fractures formed in the early stages are more likely to be filled with minerals,causing their effectiveness to deteriorate significantly.Additionally,the strong cementation in the diagenetic evolution can cause more fractures to be filled with minerals and become barriers to fluid flow,which is detrimental to fracture effectiveness.However,dissolution is beneficial in improving their effectiveness by increasing fracture aperture and their connectivity to the pores.These insights can refine the development pattern of natural fractures and contribute to revealing the evolutionary mechanisms of fracture effectiveness in deep tight sandstone reservoirs of foreland thrust belts.
基金funded by the National Natural Science Foundation of China(42125203,42330809)the 111 project of the Ministry of Science and Technology(BP0719021).
文摘The Cretaceous gold deposits along the margins of the North China Craton(NCC),which formed in a craton destruction setting,display geological characteristics similar to traditional orogenic gold deposits typically associated with accretionary orogeny.These deposits,known as Jiaodong-type gold deposits,have attracted considerable attention.However,the lithospheric controls and formation mechanisms of these deposits remain unclear,as they cannot be fully explained by the supracrustal metamorphic genetic model commonly applied to classic orogenic gold deposits.In this study,the compiled S-Hg-Pb isotope ratios of gold deposits on different NCC margins display compatible variations to the Sr-Nd-Hg isotope ratios of mafic dikes spatial-temporally associated with the deposits.This implies that mantle lithosphere,metasomatized by variable proportions of oceanic and continental crust,was the source for both gold deposits and mafic dikes.Increase of oxygen fugacity and zirconεHf(t)from pre-to syn-gold granites suggests continuous basic magma underplating,which could induce concentrations of Au-rich sulfides and contribute additional Au to auriferous CO_(2)-rich fluids derived from metasomatized mantle lithosphere and basic magma.Localization of gold deposits was controlled by craton-margin sinistral shearing induced by clockwise rotation of the craton coincident with distal emplacement of metamorphic core complexes.Thus,the Cretaceous Jiaodong-type orogenic gold deposits were derived from fertilized mantle lithosphere through such crust-mantle processes within a lithosphere thinning background.
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Supporting Program for funding this work under Project number(RSP2024R328),King Saud University,Riyadh,Saudi Arabia.
文摘The sedimentary geochemistry of St.Martin’s Island is important to determine the origin of the source rock,paleo weathering,tectonic setting,sediment recycling,maturity,sorting,redox condition,and paleo salinity of the sediments.Major oxides,trace elements,and rare earth elements(REEs)obtained from the INAA technique are presented by analyzing the sediment samples collected from the shoreline of St.Martin’s Island,Bangladesh.The elemental ratios,comparison with average upper continental crust(UCC),binary diagrams(Th/Sc vs.Sc,La/Th vs.Hf,Th/Co vs.La/Sc),and chondrite normalized REE patterns exhibit substantial LREE enrichment,relatively fl at HREE fractionation,considerable negative Eu anomalies(average:0.72),indicates the derivation from a source dominated by felsic rock,with contribution from intermediate source and mafi c component.Sediments from St.Martin’s Island exhibit the deposition of sediments in transitional environments of active and passive continental margin settings.Weathering indices value of CIA,PIA,CIW,CIX,and K 2 O/Rb ratio show moderate chemical weathering,indicating that the sediments are chemically mature.Sedimentary redox indicative proxies,such as U/Th,V/Cr,and V/Sc,show an oxic depositional environment during sediment deposition.The intermediate CIA and other weathering index values of the St.Martin’s sediments show that the area had semiarid and humid climatic conditions throughout the deposition.The Rb/K ratio of the St.Martin’s sediments suggests that the development and deposition of the sedimentary sequence of St.Martin’s Island mainly occurred in a brackish water environment during the geological past.
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 Nos.42230303,42430305 and 42302236Graduate Innovation Fund of Jilin University Number:2024CX109.
文摘Since the Paleozoic,the tectonic evolution of northeastern Eurasia has been primarily influenced by the Paleo-Asian Ocean and the Paleo-Pacific tectonic domains.However,the spatial and temporal frameworks,as well as the timing of the tectonic transition between these two oceanic domains,remain unclear.For addressing these issues,we present petrological,geochronological,and geochemical data for andesite and sandstone samples from the Seluohe Group along the Jilin-Yanji Suture between the Jiamusi-Khanka Block and the North China Craton.The geochemical results indicate that the andesite sample is high-Mg andesite.Its magma source was generated by the metasomatized mantle wedge influenced by fluids derived from the subducted slab in a continental island arc setting.The high-Mg andesite gives the crystallization ages of Early Triassic(249±3 Ma).The sandstone is immature greywacke with a maximum depositional age of Early Triassic(247±1 Ma),and its sediments primarily originate from concurrent magmatic rocks within a juvenile continental arc.Based on our new findings,we propose that the Seluohe Group represents an Early Triassic volcanic-sedimentary association with continental island arc characteristics associated with the southwestward subduction of the Heilongjiang Ocean.We identified a sedimentary basin intimately associated with one or more continental arcs along the northeastern edge of the North China Craton.We suggest that the southwestward subduction of the Jilin-Heilongjiang Ocean in the Early Mesozoic accounts for this continental arc setting.There is a distinct temporal gap between the closure of the Paleo-Asian Ocean(ca.260 Ma)and the onset of Paleo-Pacific plate subduction(234–220 Ma),which is essentially coeval with the southwestward subduction of the Jilin-Heilongjiang Ocean between 255 Ma and 239 Ma.
基金Supported by the National Natural Science Foundation of China(42330810)Major Science and Technology Project of PetroChina Changqing Oilfield Company(ZDZX2021-01).
文摘Based on the analysis of surface geological survey,exploratory well,gravity-magnetic-electric and seismic data,and through mapping the sedimentary basin and its peripheral orogenic belts together,this paper explores systematically the boundary,distribution,geological structure,and tectonic attributes of the Ordos prototype basin in the geological historical periods.The results show that the Ordos block is bounded to the west by the Engorwusu Fault Zone,to the east by the Taihangshan Mountain Piedmont Fault Zone,to the north by the Solonker-Xilamuron Suture Zone,and to the south by the Shangnan-Danfeng Suture Zone.The Ordos Basin boundary was the plate tectonic boundary during the Middle Proterozoic to Paleozoic,and the intra-continental deformation boundary in the Meso-Cenozoic.The basin survived as a marine cratonic basin covering the entire Ordos block during the Middle Proterozoic to Ordovician,a marine-continental transitional depression basin enclosed by an island arc uplift belt at the plate margin during the Carboniferous to Permian,a unified intra-continental lacustrine depression basin in the Triassic,and an intra-continental cratonic basin circled by a rift system in the Cenozoic.The basin scope has been decreasing till the present.The large,widespread prototype basin controlled the exploration area far beyond the present-day sedimentary basin boundary,with multiple target plays vertically.The Ordos Basin has the characteristics of a whole petroleum(or deposition)system.The Middle Proterozoic wide-rift system as a typical basin under the overlying Phanerozoic basin and the Cambrian-Ordovician passive margin basin and intra-cratonic depression in the deep-sited basin will be the important successions for oil and gas exploration in the coming years.
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).
基金support for this study was provided by the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(No.XDB18030601)the One Hundred Talents Project of Shaanxi Province to Laixi Tongthe Natural Science Foundation of Shaanxi Province(No.2023-JC-QN-0283)granted to Chao Li.
文摘The Irtysh tectonic belt lies on the southern margin of the Chinese Altai Orogen. Several secondary shear zones with NW-SE strikes have developed in this tectonic belt, and the deformation processes are of great significance to understanding the tectonic regime of the Altai Orogen in the Late Paleozoic. The Tuerhongshate ductile shear zone is located in the eastern Irtysh tectonic belt with obvious deformed structures. The felsic rocks are strongly mylonitized, exhibiting S-C fabrics, asymmetric rotational porphyroclasts, and bookshelf structures of the plagioclases, indicating a sinistral shear sense. The deformation mechanisms, lattice preferred orientations (LPOs) of quartz, and opening angles of quartz c-axis suggest that the deformation temperatures range from 400 to 500 ℃, consistent with higher-greenschist to lower-amphibolite facies conditions. The calculated kinematic vorticity values (W_(k)) of the studied samples range from 0.53 to 0.89 and indicate general shear to simple shear, based on rotational rigid porphyroclast method and oblique grain-shaped/quartz c-axis fabric method. The U-Pb ages of magmatic zircons in felsic mylonites indicate that the sinistral shear occurred after 296.7 ± 3.0 Ma (Early Permian) in the Tuerhongshate shear zone and persisted for approximately 13 Ma. Combined with the tectonic setting and the observed sinistral strike-slip shear indicators in the mylonite zone, these features demonstrate that the Irtysh tectonic belt was in a post-orogenic and strike-slip environment following the closure of the Irtysh Ocean.
基金supported by the National Natural Science Foundation of China(Grant No.42102113)the National Key Research and Development Program of China(Grant No.2021YFC2901803)+1 种基金the China Geological Survey Project(Grant No.DD20230579)China Scholarship Council(File No.202108575008).
文摘1.Objective,The Luang Prabang(Laos)-Loei(Thailand)metallogenetic belt,located along the northwestern margin of the Indochina Block(Fig.1a)and endowed nearly 200 t of gold and more than 106 t of copper,is one of the most important gold-copper metallogenic belts in Indo-China Peninsula.It has undergone tectonic changes during the Early Paleozoic to Mesozoic Proto-Paleo Tethys tectonic evolution,recorded by the Luang Prabang tectonic belt,the Nan-Uttaradit suture,and the Dien Bien Phu-Loei suture.
基金financially supported by the Natural Science Foundation of Chongqing,China(No.cstc2020jcyj-msxm X0487)the Open Fund of Key Laboratory of Sedimentary Basins and Oil and Gas Resources,the Ministry of Natural Resources(No.cdcgs2022006)+2 种基金the National Natural Science Foundation of China(No.42072001)the China Geological Survey(No.DD20190018)the Science and Technology Innovation Fund for Postgraduates of Chongqing University of Science and Technology(No.YKJCX2220101)。
文摘Riedel shear system,which consists of some different oriented faults and derivative structures,is an important pattern of tectonic activity and stress regulation,which has been widely applied to the interpretation of intracontinental deformation.The Laolongwan Basin,located in the western Haiyuan fault zone at the northeastern Tibetan Plateau,is a key area to study the Cenozoic intracontinental deformation in the northeastern plateau,which formed a complex active fault system during the Cenozoic.However,the activity of these faults and their kinematic mechanism remain unclear.In this contribution,based on detailed structural interpretation of remote sensing image,field observations and OSL dating analysis,we propose a Riedel Shear model of active fault system in the Laolongwan Basin.Our observations show that this active fault system consist of four major faults,including the left strike-slip Hasi Shan fault and Zihong Shan fault with thrusting characteristics,the Southern Zihong Shan thrust fault and the Mijia Shan normal fault.The fault offset and OSL dating analyses suggest that the left-lateral slip rate of the Hasi Shan fault is~2.60-3.01 mm/a since ca.15 ka,whereas the Zihong Shan fault is~1.10-1.13 mm/a since ca.14 ka.Faultslip vectors analyses indicate that the active fault system related to the Riedel Shear in the Laolongwan Basin was controlled by the regional ENE-WSW compressive stress.This compression also caused the significant left-lateral strike-slip movement along the Haiyuan fault zone at the same time,which might result from the northeastward continuous expanding of the Tibetan Plateau during the Late Cenozoic.
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 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).
