0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exe...0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).展开更多
The ocean crust remnants of the Proto-Tethys were preserved as the Kudi ophiolites in the West Kunlun Orogenic Belt(WKOB),and its evolutionary history was mainly constructed by research on igneous or metamorphic rocks...The ocean crust remnants of the Proto-Tethys were preserved as the Kudi ophiolites in the West Kunlun Orogenic Belt(WKOB),and its evolutionary history was mainly constructed by research on igneous or metamorphic rocks in the WKOB.Sedimentary rocks in the WKOB received little attention in the past;however,they could provide important constraints on the evolution of the oceanic lithosphere.Here,a series of shales and greywackes found in the Kudi area of WKOB were studied to constrain their deposition ages and explore their significance in the evolution of the ProtoTethys oceanic crust.The U-Pb dating and europium anomaly(Eu/Eu^(*))were analyzed for detrital zircons from greywackes interlayers,while bulk rare earth elements and yttrium(REY)of the shales were measured.Detrital zircons U-Pb ages yield a maximum deposition age of 436 Ma for the greywackes and black shales,while the REY distribution patterns of the black shales are similar to those of the Tarim Ordovician Saergan shales.Accordingly,the studied WKOB black shales were deposited in the Proto-Tethys Ocean during the Late Ordovician-Early Silurian period.The maximum deposition age at 436 Ma may represent a minimum closure time of the Proto-Tethys Ocean,which is also supported by the absence of increases in Eu/Eu^(*)values during the Late Ordovician-Early Silurian.Besides,our Eu/Eu^(*)values in detrital zircons indicate diminished orogenesis during the Archean to Meso-Proterozoic,subduction-related accretion at the margins of the supercontinent Rodinia during the Neoproterozoic.展开更多
0 INTRODUCTION The Haidewula uranium deposit is located in the Haidewula volcanic basin,which hosts a suite of basic,intermediate to felsic volcanic and subvolcanic rocks,including basalt,trachyte,trachyandesite.Previ...0 INTRODUCTION The Haidewula uranium deposit is located in the Haidewula volcanic basin,which hosts a suite of basic,intermediate to felsic volcanic and subvolcanic rocks,including basalt,trachyte,trachyandesite.Previous geochronological studies of the intrusions within this volcanic basin suggest that they primarily formed during the Silurian and Triassic periods(Dai et al.,2025;Sun et al.,2024;Wang et al.,2024;Zhu et al.,2022;Lei et al.,2021).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
A set of ultramafic-mafic-felsic rock assemblages was discovered in the Long-shenggeng area of the eastern part of the East Kunlun orogenic belt.Petrography,chronology and whole-rock geochemistry were conducted on thi...A set of ultramafic-mafic-felsic rock assemblages was discovered in the Long-shenggeng area of the eastern part of the East Kunlun orogenic belt.Petrography,chronology and whole-rock geochemistry were conducted on this set of intrusive rock assemblages.U-Pb dating of apatite shows that the lherzolite formed at 492±5 Ma,the granite at 473±6 Ma,and the diabase at 260±14 Ma,respectively.The lherzolites belong to a supra-subduction zone type(SSZ-type)ophiolite component above a subduction zone;the granites formed in an ocean-continent subduction setting;and the diabases represent products of partial melting of an asthenospheric mantle at shallow depth.The East Kunlun orogenic belt features the East Kunzhong and Buqingshan-Animaqing ophiolitic mélange belts,with the latter representing remnants of the Proto-Tethys Ocean.The Late Cambrian lherzolites and granites in the Longshenggeng area were magmatic products of the back-arc ocean basin and island arc formed during the northward subduction of the Proto-Tethys Ocean.Subsequently,extensive island arc magmatism occurred from the Late Permian to Middle Triassic,driven by the northward subduction of the Paleo-Tethys Ocean beneath the East Kunlun Block.The diabase may have formed during the transition from subduction to post-collisional extension.展开更多
We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and g...We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and geochemical data,the granitoids in the region can be divided into two age groups:ca.285 Ma and ca.269 Ma.The granitoids of the first group are mainly composed of calc-alkaline to high-K calc-alkaline,weakly peraluminous Ⅰ-type granodiorites with ε_(Hf)(t)values of-19.6 to-4.3,which demonstrates evidence of crustal reworking;the granitoids of the second group,however,mainly consist of A-type granites that are high-K calc-alkaline to shoshonite,metaluminous to weakly peraluminous,and have high 10,000×Ga/Al ratios(2.59-3.12)and ε_(Hf)(t)values ranging from-11.3 to-2.7,all of which demonstrates a mixed crust-mantle source.We interpret the granitoids of the first group to have formed during the subduction of Central Asian oceanic crust and the second group to have formed by the asthenospheric upwelling caused by the formation of slab windows during late ocean ridge subduction.展开更多
The Qinling orogenic belt in central China underwent long-term tectonic evolution during an amalgamation between the North China and South China cratons.However,intense compressional deformation and uplift erosion res...The Qinling orogenic belt in central China underwent long-term tectonic evolution during an amalgamation between the North China and South China cratons.However,intense compressional deformation and uplift erosion resulted in the transformation and disappearance of much geological record from the Qinling orogenic belt,and the tectonic evolution of this belt remains poorly constrained during the Triassic.Located in the northernmost margin of the South China Craton,the Sichuan Basin preserves the complete Triassic sedimentary succession,and can provide significant information for understanding the Triassic tectonic evolution of the Qinling orogenic belt.We present detrital zircon U-Pb dating,trace element and in situ Lu-Hf isotope data for the Middle Triassic Leikoupo Formation and the Late Triassic Xujiahe Formation samples from the eastern Sichuan Basin,South China.The detrital zircon U-Pb ages of the Leikoupo Formation show seven age clusters of 280-242,350-300,500-400,1000-800,2000-1750,2100-2000 and 2600-2400 Ma,while those of the Xujiahe Formation show five age clusters of 300-200,500-350,1050-950,2000-1750 and 2600-2400 Ma.Combined with published paleocurrent and paleogeographic data,the sediments of the Leikoupo Formation are interpreted to be sourced from the North China Craton,Yangtze Craton and North Qinling orogenic belt,and the potential main source regions of the Xujiahe Formation included the South and North Qinling orogenic belts.Provenance analysis indicates that the North Qinling orogenic belt was in inherited uplift and coeval denudation in the Middle Triassic.The proportion of the detritus formed in the South Qinling orogenic belt increases gradually from the Leikoupo to Xujiahe formations.This significant provenance change indicates that rapid tectonic uplift and extensive denudation of the South Qinling orogenic belt occurred in the early Late Triassic,which is related to the collision between the North China and South China cratons during the Triassic.展开更多
To explore the high heat flow anomalies from the Dabie orogenic belt,We have set up 15 Magnetotelluric(MT)stations.The stations have an average spacing of~2 km.Firstly,the phase tensor method is used to analyze MT dat...To explore the high heat flow anomalies from the Dabie orogenic belt,We have set up 15 Magnetotelluric(MT)stations.The stations have an average spacing of~2 km.Firstly,the phase tensor method is used to analyze MT data to estimate the dimensional characteristics of the underground resistivity structure.Then,based on the results of dimensional characteristics analysis,three-dimensional(3D)inversion was performed using ModEM,and a 3D resistivity structure from the surface to a depth of 30 km was obtained.It shows:that there are extensive low resistivity anomalies in the lower crust of the northern margin of the Dabie orogenic belt,which may be partial melting or water-bearing fluid.The high heat flow anomaly in the northern margin of the Dabie orogenic belt may be due to the increase of the background heat flow value caused by the orogenic belt delamination during post-collision,the thinning of the lithosphere and the upwelling of the asthenosphere.展开更多
Structure and composition of Earth are fundamental importance in exploring the dynamic evolution of the crust and mantle.The Qinling Orogenic Belt(QOB)is located between the North China plate and the South China Plate...Structure and composition of Earth are fundamental importance in exploring the dynamic evolution of the crust and mantle.The Qinling Orogenic Belt(QOB)is located between the North China plate and the South China Plate,and is one of the main orogenic belts in China.To explore the composition and origin of anisotropy and the low wave velocity zone of the QOB,ten rock samples(gneiss and schist)were collected from the five sites of the QOB and the P-and S-wave velocities of these samples were measured under 0.6 to 2.0 GPa and 100 to 550℃.The wave velocities increase with increasing pressure and decreasing temperature.The V_(P)and V_(S)of the schist and gneiss match the velocity of the middle and lower crust of the QOB,indicating that schist and gneiss are important component of the QOB.All the schist and gneiss samples exhibit obvious seismic anisotropy with 1.64%-17.42%for V_(S)and 2.93%-14.78%for V_(P)under conditions of crust and upper mantle.The CPO/LPO and layering distribution of mica in rock samples are the main reasons for this anisotropy.The V_(S)structures below the five sampled sites from seismic ambient noise tomography were built to explore the effect of schist and gneiss on the composition and structure of the QOB.The results indicate that orientation-arranged gneiss and schist driven by the tectonic stresses might be a new origin of the character of V_(P)/V_(S),seismic anisotropy,and the low velocity zone in the QOB.展开更多
The architecture and geodynamics of intracontinental orogens remain a fundamental geological challenge.The Xing’an-Mongolia intracontinental orogenic belt(XMIOB),superimposed on the eastern Central Asian Orogenic Bel...The architecture and geodynamics of intracontinental orogens remain a fundamental geological challenge.The Xing’an-Mongolia intracontinental orogenic belt(XMIOB),superimposed on the eastern Central Asian Orogenic Belt(CAOB),provides key insights into intracontinental orogenic belt dynamics.However,its architecture,deformation patterns,and geodynamic processes are poorly understood.This study integrates geological mapping,structural analysis,EBSD quartz c-axis fabrics,seismic reflection interpretation,and zircon U-Pb geochronology to unravel the XMIOB’s tectonic evolution and compare it with global intracontinental orogenic belts.Our findings reveal that the XMIOB is shaped by alternating fold-thrust belts and metamorphic zones,dominantly controlled by the inversion of pre-existing extensional structures.EBSD analysis indicates mid-temperature(400℃–500℃)ductile deformation in the deep crust,while seismic profiles highlight structural decoupling driven by a décollement zone.Integrated crustal thickness reconstructions from zircon Eu/Eu*ratios delineate three tectonic stages:Late Carboniferous-Permian asthenospheric upwelling induced crustal thinning from∼50 km to∼35 km,forming lithospheric weak zones with Buchan-type metamorphism and bimodal magmatism;Late Permian-Middle Triassic mantle subduction triggered compressional thickening(∼55 km),fold-thrust belt formation,and tectonic inversion of early extensional faults,exposing metamorphic zones;from the Middle Triassic continued mantle subduction and deep-crustal decoupling drove large-scale lateral extrusion and dextral shear,reshaping the XMIOB architecture.Comparisons with global intracontinental orogenic belts highlight two key traits of intracontinental orogenic belt evolution:pre-orogenic lithospheric thinning generates inherited weak zones that localize subsequent deformation;inherited extensional features dictate the final architecture,producing the systematic alternation of metamorphic zones and fold–thrust belts.展开更多
The Central Asian Orogenic Belt(CAOB),the Earth’s largest Phanerozoic accretionary orogenic belt,is located between the Siberian,Tarim and North China Cratons and the Kazakhstan composite continent(Fig.1a).It is ca.8...The Central Asian Orogenic Belt(CAOB),the Earth’s largest Phanerozoic accretionary orogenic belt,is located between the Siberian,Tarim and North China Cratons and the Kazakhstan composite continent(Fig.1a).It is ca.800 km wide and extends from the Ural Mountains in the west to the Pacific in the east(e.g.,Zonenshain et al.,1990;Mossakovsky et al.,1993;Jahn et al.,2000;Windley et al.,2007,Xiao et al.,2010;Safonova et al.,2011).In the past two decades,many studies have shown that the CAOB is composed of many terranes of different tectonic origins,and was formed by successive accretion of terranes,microcontinents,island arcs,seamounts,ophiolites,and accretionary prisms from the early Neoproterozoic to the late Palaeozoic(e.g.,Mossakovsky et al.,1994;Badarch et al.,2002;Xiao et al.,2003;Buslov et al.,2001;Kovalenko et al.,2004;Safonova,2009;Li,2006;Kröner et al.,2007,2014;Donskaya et al.,2013;Xu et al.,2013).展开更多
The eastern Central Asian Orogenic Belt(CAOB)in NE China is a key area for investigating continental growth.However,the complexity of its Paleozoic geological history has meant that the tectonic development of this be...The eastern Central Asian Orogenic Belt(CAOB)in NE China is a key area for investigating continental growth.However,the complexity of its Paleozoic geological history has meant that the tectonic development of this belt is not fully understood.NE China is composed of the Erguna and Jiamusi blocks in the northern and eastern parts and the Xing’an and Songliao-Xilinhot accretionary terranes in the central and southern parts.The Erguna and Jiamusi blocks have Precambrian basements with Siberia and Gondwana affinities,respectively.In contrast,the Xing’an and Songliao-Xilinhot accretionary terranes were formed via subduction and collision processes.These blocks and terranes were separated by the Xinlin-Xiguitu,Heilongjiang,Nenjiang,and Solonker oceans from north to south,and these oceans closed during the Cambrian(ca.500 Ma),Late Silurian(ca.420 Ma),early Late Carboniferous(ca.320 Ma),and Late Permian to Middle Triassic(260-240 Ma),respectively,forming the Xinlin-Xiguitu,Mudanjiang-Yilan,Hegenshan-Heihe,Solonker-Linxi,and Changchun-Yanji suture zones.Two oceanic tectonic cycles took place in the eastern Paleo-Asian Ocean(PAO),namely,the Early Paleozoic cycle involving the Xinlin-Xiguitu and Heilongjiang oceans and the late Paleozoic cycle involving the Nenjiang-Solonker oceans.The Paleozoic tectonic pattern of the eastern CAOB generally shows structural features that trend east-west.The timing of accretion and collision events of the eastern CAOB during the Paleozoic youngs progressively from north to south.The branch ocean basins of the eastern PAO closed from west to east in a scissor-like manner.A bi-directional subduction regime dominated during the narrowing and closure process of the eastern PAO,which led to“soft collision”of tectonic units on each side,forming huge accretionary orogenic belts in central Asia.展开更多
The Hongyanjing inter-arc basin, is located at the central part of Beishan Orogenic College （BOC）, Gansu Province, northwest China. Thick sequences of Permian sediments were strongly folded, forming extremely specta...The Hongyanjing inter-arc basin, is located at the central part of Beishan Orogenic College （BOC）, Gansu Province, northwest China. Thick sequences of Permian sediments were strongly folded, forming extremely spectacular superposed folds. To better understand the thermal history of Hongyanjing interarc basin and to potentially constrain the timing of deformation, apatite fission track thermochronology method was applied on two superposed folds in the Hongyanjing Basin. Samples from the basin, yield central AFT ages ranging from - 206 to 118 Ma. AFT peak ages were largely consistent between samples and can divided into three groups： 245, 204-170 and 112-131 Ma. Subsequent thermal history modeling of the samples from the Hongyanjing Basin can be summarized as follows： （1） thermal reheating by sedimentary burial at - 260 to -220 Ma; （2） major cooling from -220 to -180 Ma; （3） an episode of very slow subsequent cooling from -180 to 65 Ma （-80 ℃） to present-day outcrop temperatures. Sediments in the Hongyanjing Basin were folded forming F1 fold during the early to late Triassic （-240--220 Ma）, by regional stress, and at the time that the adjacent Xingxingxia shear zone started to become active. It is further suggested that the F2 folding occurred at -225-219 Ma. The deformation age of F2 should he extended to 180 Ma based on our thermal history modeling for the Hongyanjing Basin, which show a rapid exhumation and cooling at the late Triassic to early Jurassic （-220-- 180 Ma）. In our interpretations, the F1 folding is therefore thought to he related to the final closure of the Paleo-Asian Ocean, while the F2 folding occurred at - 225-180 Ma associated with a major pulse of orogenesis in the BOC.展开更多
A new concept of continental construction based on four main terms:(1)crustal growth,(2)crustal formation,(3)continental growth and(4)continental formation is presented here.Each of these terms reflects a certain proc...A new concept of continental construction based on four main terms:(1)crustal growth,(2)crustal formation,(3)continental growth and(4)continental formation is presented here.Each of these terms reflects a certain process responsible for the formation of what we call now“continental crust”.This concept is applied to the Central Asian Orogenic Belt(CAOB),which is a global major accretionary orogen formed after the closure of the Paleo-Asian Ocean,and to its actualistic analogues–orogenic belts and accretionary complexes of the Western Pacific.The main focuses of the paper are the state of activities in the study of the CAOB,the theoretical basics of the new concept of continental construction,its challenges,prospects and social impacts,main methods of investigation.The main issues of the paper are what has been done in this field of geoscience,which questions remained unaddressed and which problems should be solved.The most important challenges are:(a)dominantly Phanerozoic formation of the CAOB continental crust versus its dominantly Archean growth;(b)to what extent the CAOB continental crust was juvenile or recycled;(c)whether magmatic arcs or Gondwana-derived terranes were accreted to the Siberian,Kazakhstan,Tarim and North China cratons;(d)what was the balance between continental formation and tectonic erosion based on modern examples from the Western Pacific;(e)what social benefits(mineral deposits)and geohazards(seismicity and volcanism)can be inferred from the study of orogenic belts formed in place of former oceans.展开更多
Laser ablation–inductively coupled plasma–mass spectrometry（LA–ICP–MS） was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe（–Cu） deposits ...Laser ablation–inductively coupled plasma–mass spectrometry（LA–ICP–MS） was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe（–Cu） deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore–forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite： Ni–Mn–V–Ti（Factor 1）, Mg–Al–Zn（Factor 2）, and Ga– Co（Factor 3） magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe–Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore–forming fluids responsible for the Fe–Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe（–Cu） deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe（–Cu） deposits may be related to felsic magmatism.展开更多
The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics ...The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics comprise the prominent faulting along the northand south boundaries, the highly complicated petrological and petro-geochemical features of thevolcanic rock series, and the development of a new type of ophiolite suite. In terms of tectonicanalysis and the sequential analysis of tectonic settings of magmatic rocks, it is suggested thatthe Lajishan orogenic belt has undergone a complete 'opening-closing' cycle, which can be furtherdivided into 3 second-order 'opening-closing' cycles. The composite characteristics of the'opening-closing' movement show that Laji Mountain is a typical fault orogenic belt. The faultorogenic belt is one of the most important types of intracontinental orogens. It is of criticaltheoretical and practical significance to summarize the characteristics and the diagnostic criteriaof this kind of orogenic belts, and study the mechanism of their formation and build models of theirevolution.展开更多
The Qushi’ang granodiorite(QSG)is located at the central east of the ophiolitic melange belt in the East Kunlun Orogenic Belt(EKOB)in the northern margin of the Qinghai-Tibetan Plateau.LA-MC-ICP-MS zircon U–Pb datin...The Qushi’ang granodiorite(QSG)is located at the central east of the ophiolitic melange belt in the East Kunlun Orogenic Belt(EKOB)in the northern margin of the Qinghai-Tibetan Plateau.LA-MC-ICP-MS zircon U–Pb dating suggests that the granodiorite and mafic microgranular enclaves(MMEs)crystallized 246.61±0.62 and 245.45±0.9 Ma ago,respectively.Granodiorite,porphyritic diorite,and MMEs are metaluminous and medium-K calk-alkaline series,with island-arc magma features,such as LILE enrichment and HFSE depletion.The porphyritic diorite has high Cr(13.50 ppm to 59.01 ppm),Ni(228.53 ppm to 261.29 ppm),and Mg~#(46–54).Granodiorite and porphyritic diorite have similar mineral compositions and evolved major and trace elements contents,particularly Cr and Ni,both of which are significantly higher than that in granites of the same period.The crystallization age of MMEs is close to that of granodiorite,and their major and trace elements contents are in-between porphyritic diorite and granodiorite.The results suggest that the original mafic magma,which was the product of mantle melting by subduction process,intruded into the lower crust(Kuhai Rock Group),resulting in the formation of granodiorite.Countinous intrusion of mafic magma into the unconsolidated granodiorite formed MMEs and porphyritic diorite.The granodiorite reformed by late-stage strike-slip faulting tectonic event indicates that the strike-slip fault of Middle Kunlun and the collision of the Bayanhar block with East Kunlun were later than 246 Ma.Therefore,the formation of the QSG not only indicates the critical period of evolution of East Kunlun but also represents the tectonic transition from oceanic crust subduction to slab breaking.展开更多
In a re-study of regional geology by the China Geological Survey （CGS）, the key problem is in the stratigraphical division and correlation. According to the new isotopic dating of the Mesoand Neoproterozoic in China...In a re-study of regional geology by the China Geological Survey （CGS）, the key problem is in the stratigraphical division and correlation. According to the new isotopic dating of the Mesoand Neoproterozoic in China, there have been great changes in the strata correlation and tectonic explanation. The authors obtained four zircon sensitive high resolution ion micro-probe （SHRIMP） U- Pb datings from the bentonite of the Lengjiaxi Group （822±10 Ma, 823±12 Ma and 834±11 Ma） and Banxi Group （802.6±7.6 Ma） in north Hunan Province, which is considered to be the middle part of the Jiangnan Orogenic Belt. On the basis of the zircon dating mentioned above, the end of the Wuling orogen is first limited in the period from 822 Ma to 802 Ma in one continued outcrop （Lucheng section） in Linxiang city, Hunan Province. Combining a series of new zircon U-Pb datings in the Yangtze and Cathaysia blocks, several Neoproterozoic volcanic events and distribution of the metamorphic rocks in the Jiangnan Orogenic Belt have been distinguished. In the context of the global geodynamics, it is useful to set up a practical and high precision chronological framework and basic and unified late Precambrian section in South China.展开更多
Lithosphere extension and upwelling of asthenosphere at post-collisional stage of an orogenic cycle generally induce diverse magmatism and/or associated high-temperature metamorphism. Nevertheless, the intimate coexis...Lithosphere extension and upwelling of asthenosphere at post-collisional stage of an orogenic cycle generally induce diverse magmatism and/or associated high-temperature metamorphism. Nevertheless, the intimate coexistence of post-collisional magmatic activity and high-temperature metamorphism is rare.In this contribution, a lithological assemblage composing of diverse magmatic rocks deriving from distinct magma sources and coeval high-temperature metamorphism was identified in eastern Kunlun.Petrography, ages, mineral chemistry and whole-rock geochemistry demonstrated that those intimately coexistent diverse rocks were genetically related to post-collisional extension. The garnet-bearing mafic granulites in Jinshuikou area interior of the East Kunlun Orogenic Belt are mainly composed of garnet,orthopyroxene, and plagioclase, with peak metamorphic P–T conditions of ~ 701–756 ℃and 5.6–7.0 kbar,representing a granulite-facies metamorphism at 409.7 ± 1.7 Ma. The diverse contemporaneous magmatic rocks including hornblendites, gabbros and granites yield zircon U–Pb ages of 408.6 ± 2.5 Ma,413.4 ± 4.6 Ma, and 387–407 Ma, respectively. The hornblendites show N-MORB-like REE patterns with(La/Sm)Nvalues of 0.85–0.94. They have positive zircon εHf(t) values of 0.1–4.9 and whole-rock εNd(t) values of 3.9–4.7 but relatively high(^(87)Sr/^(86)Sr)_(i)values of 0.7081 to 0.7088. These features demonstrate that the hornblendites derived from a depleted asthenospheric mantle source with minor continental crustal materials in source. As for the gabbros, they exhibit arc-like elemental signatures, low zircon εHf(t) values(-4.3 to 2.5) and variable whole-rock εNd(t) values(-4.9 to 1.2) as well as high(^(87)Sr/86 Sr)ivalues(0.7068 to 0.7126), arguing for that they were originated from partial melting of heterogeneous lithospheric mantle anteriorly metasomatized by subducted-sediment released melts. Geochemistry of the granites defines their strongly peraluminous S-type signatures. Zircons from the granites yield a large range of εHf(t) values ranging from -30.8 to -5.1, while the whole-rock samples yield consistent(^(87)Sr/86 Sr)ivalues(0.7301 to 0.7342) and negative εNd(t) values(-10.1 to -12.4). These features indicate that the S-type granites could be generated by reworking of an ancient crust. Taken together, the penecontemporaneous magmatism and metamorphic event, demonstrated the early-middle Devonian transition from crustal thickening to extensional collapse. The post-collisional mantle-derived magmas serve as an essential driving force for the high-temperature granulite-facies metamorphism and anataxis of the crust associated with formation of S-type granite. This study not only constructs a more detail Proto-Tethys evolution process of the eastern Kunlun, but also sheds new light on better understanding the intimate relationship between magmatism and metamorphism during post-collisional extensional collapse.展开更多
The Drillhole ZK703 with a depth of 558 m is located in the Donghai area of the southern Sulu ultrahigh-pressure (UHP) metamorphic belt, eastern China, and penetrates typical UHP eclogites and various non-mafic rocks,...The Drillhole ZK703 with a depth of 558 m is located in the Donghai area of the southern Sulu ultrahigh-pressure (UHP) metamorphic belt, eastern China, and penetrates typical UHP eclogites and various non-mafic rocks, including peridotite, gneiss, schist and quartzite. Their protoliths include ultramafic, mafic, intermediate, intermediate-acidic, acidic igneous rocks and sediments. These rocks are intimately interlayered, which are meters to millimeters thick with sharp and nontectonic contacts, suggesting in-situ metamorphism under UHP eclogite facies conditions. The following petrologic features indicate that the non-mafic rocks have experienced early-stage UHP metamorphism together with the eclogites: (1) phengite relics in gneisses and schists contain a high content of Si, up to 3.52 p.f.u. (per formula unit), while amphibolite-facies phengites have considerably low Si content (<3.26 p.f.u.); (2) jadeite relics are found in quartzite and jadeitite; (3) various types of symplectitic coronas and pseud展开更多
基金supported by the National Key Research and Development Project(No.2022YFC2903302)the Second Tibet Plateau Scientific Expedition and Research Program(STEP),(No.2019QZKK0802)+2 种基金the National Natural Science Foundation of China(No.42361144841)the Chinese Academy of Geological Sciences Basal Research Fund(No.JKYZD202402)the Scientific Research Fund Project of BGRIMM Technology Group(No.JTKY202427822)。
文摘0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).
基金financially supported by the National Major Science and Technology Project of China(No.2016ZX05004-004)the State Scholarship Grant from the China Scholarship Council(CSC)to Yinggang Zhang。
文摘The ocean crust remnants of the Proto-Tethys were preserved as the Kudi ophiolites in the West Kunlun Orogenic Belt(WKOB),and its evolutionary history was mainly constructed by research on igneous or metamorphic rocks in the WKOB.Sedimentary rocks in the WKOB received little attention in the past;however,they could provide important constraints on the evolution of the oceanic lithosphere.Here,a series of shales and greywackes found in the Kudi area of WKOB were studied to constrain their deposition ages and explore their significance in the evolution of the ProtoTethys oceanic crust.The U-Pb dating and europium anomaly(Eu/Eu^(*))were analyzed for detrital zircons from greywackes interlayers,while bulk rare earth elements and yttrium(REY)of the shales were measured.Detrital zircons U-Pb ages yield a maximum deposition age of 436 Ma for the greywackes and black shales,while the REY distribution patterns of the black shales are similar to those of the Tarim Ordovician Saergan shales.Accordingly,the studied WKOB black shales were deposited in the Proto-Tethys Ocean during the Late Ordovician-Early Silurian period.The maximum deposition age at 436 Ma may represent a minimum closure time of the Proto-Tethys Ocean,which is also supported by the absence of increases in Eu/Eu^(*)values during the Late Ordovician-Early Silurian.Besides,our Eu/Eu^(*)values in detrital zircons indicate diminished orogenesis during the Archean to Meso-Proterozoic,subduction-related accretion at the margins of the supercontinent Rodinia during the Neoproterozoic.
基金financially supported by projects from the National Natural Science Foundation of China(No.42321001)the Qinghai Provincial Department of Science and Technology Key R&D Project(No.2025-SF-141)+1 种基金the Qinghai“Kunlun Talent”Program(Qing RC Talent Zi(2024)No.1)the Academician Zhao Pengda Innovation Center in Qinghai Geological Bureau of Nuclear Industry。
文摘0 INTRODUCTION The Haidewula uranium deposit is located in the Haidewula volcanic basin,which hosts a suite of basic,intermediate to felsic volcanic and subvolcanic rocks,including basalt,trachyte,trachyandesite.Previous geochronological studies of the intrusions within this volcanic basin suggest that they primarily formed during the Silurian and Triassic periods(Dai et al.,2025;Sun et al.,2024;Wang et al.,2024;Zhu et al.,2022;Lei et al.,2021).
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 Qinghai Provincial Special Fund for Geological Exploration-Deep Mineral Exploration Breakthrough Demonstration Project in Key Ore Concentration Areas of Qinghai Province(No.2023085029ky004)New Round of National Strategic Action for Mineral Exploration Breakthrough-Research and Demonstration of Air-Ground Collaborative Efficient Technologies for Copper-Nickel Sulfide Deposits in the East Kunlun Plateau Desert Region(No.ZKKJ202416)+1 种基金National Key R&D Program of China-Novel Geochemical Exploration Technologies for Desert Gobi and Alpine Grassland Shallow Overburden Terrains(No.2024ZD1002403)Kunlun Talent Program of Qinghai Province jointly support。
文摘A set of ultramafic-mafic-felsic rock assemblages was discovered in the Long-shenggeng area of the eastern part of the East Kunlun orogenic belt.Petrography,chronology and whole-rock geochemistry were conducted on this set of intrusive rock assemblages.U-Pb dating of apatite shows that the lherzolite formed at 492±5 Ma,the granite at 473±6 Ma,and the diabase at 260±14 Ma,respectively.The lherzolites belong to a supra-subduction zone type(SSZ-type)ophiolite component above a subduction zone;the granites formed in an ocean-continent subduction setting;and the diabases represent products of partial melting of an asthenospheric mantle at shallow depth.The East Kunlun orogenic belt features the East Kunzhong and Buqingshan-Animaqing ophiolitic mélange belts,with the latter representing remnants of the Proto-Tethys Ocean.The Late Cambrian lherzolites and granites in the Longshenggeng area were magmatic products of the back-arc ocean basin and island arc formed during the northward subduction of the Proto-Tethys Ocean.Subsequently,extensive island arc magmatism occurred from the Late Permian to Middle Triassic,driven by the northward subduction of the Paleo-Tethys Ocean beneath the East Kunlun Block.The diabase may have formed during the transition from subduction to post-collisional extension.
基金financially supported by the Geological Survey of China(Grant Nos.DD20240075,and DD20243516)the National Natural Science Foundation of China(Grant No.41872209)Basic Scientific Research Fund of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J2314)。
文摘We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and geochemical data,the granitoids in the region can be divided into two age groups:ca.285 Ma and ca.269 Ma.The granitoids of the first group are mainly composed of calc-alkaline to high-K calc-alkaline,weakly peraluminous Ⅰ-type granodiorites with ε_(Hf)(t)values of-19.6 to-4.3,which demonstrates evidence of crustal reworking;the granitoids of the second group,however,mainly consist of A-type granites that are high-K calc-alkaline to shoshonite,metaluminous to weakly peraluminous,and have high 10,000×Ga/Al ratios(2.59-3.12)and ε_(Hf)(t)values ranging from-11.3 to-2.7,all of which demonstrates a mixed crust-mantle source.We interpret the granitoids of the first group to have formed during the subduction of Central Asian oceanic crust and the second group to have formed by the asthenospheric upwelling caused by the formation of slab windows during late ocean ridge subduction.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC0602704)the National Natural Science Foundation of China(Grant No.U20B6001 and 91755211).
文摘The Qinling orogenic belt in central China underwent long-term tectonic evolution during an amalgamation between the North China and South China cratons.However,intense compressional deformation and uplift erosion resulted in the transformation and disappearance of much geological record from the Qinling orogenic belt,and the tectonic evolution of this belt remains poorly constrained during the Triassic.Located in the northernmost margin of the South China Craton,the Sichuan Basin preserves the complete Triassic sedimentary succession,and can provide significant information for understanding the Triassic tectonic evolution of the Qinling orogenic belt.We present detrital zircon U-Pb dating,trace element and in situ Lu-Hf isotope data for the Middle Triassic Leikoupo Formation and the Late Triassic Xujiahe Formation samples from the eastern Sichuan Basin,South China.The detrital zircon U-Pb ages of the Leikoupo Formation show seven age clusters of 280-242,350-300,500-400,1000-800,2000-1750,2100-2000 and 2600-2400 Ma,while those of the Xujiahe Formation show five age clusters of 300-200,500-350,1050-950,2000-1750 and 2600-2400 Ma.Combined with published paleocurrent and paleogeographic data,the sediments of the Leikoupo Formation are interpreted to be sourced from the North China Craton,Yangtze Craton and North Qinling orogenic belt,and the potential main source regions of the Xujiahe Formation included the South and North Qinling orogenic belts.Provenance analysis indicates that the North Qinling orogenic belt was in inherited uplift and coeval denudation in the Middle Triassic.The proportion of the detritus formed in the South Qinling orogenic belt increases gradually from the Leikoupo to Xujiahe formations.This significant provenance change indicates that rapid tectonic uplift and extensive denudation of the South Qinling orogenic belt occurred in the early Late Triassic,which is related to the collision between the North China and South China cratons during the Triassic.
基金supported by the National Key Research and Development Program of China(grant no.2023YFF0615101).
文摘To explore the high heat flow anomalies from the Dabie orogenic belt,We have set up 15 Magnetotelluric(MT)stations.The stations have an average spacing of~2 km.Firstly,the phase tensor method is used to analyze MT data to estimate the dimensional characteristics of the underground resistivity structure.Then,based on the results of dimensional characteristics analysis,three-dimensional(3D)inversion was performed using ModEM,and a 3D resistivity structure from the surface to a depth of 30 km was obtained.It shows:that there are extensive low resistivity anomalies in the lower crust of the northern margin of the Dabie orogenic belt,which may be partial melting or water-bearing fluid.The high heat flow anomaly in the northern margin of the Dabie orogenic belt may be due to the increase of the background heat flow value caused by the orogenic belt delamination during post-collision,the thinning of the lithosphere and the upwelling of the asthenosphere.
基金supported by the National Natural Science Foundation of China(42174115 and 42330311)the Special Fund of the Institute of Earthquake Forecasting,China Earthquake Administration(CEAIEF20230301)the State key laboratory of earthquake dynamics(LED2021B02).
文摘Structure and composition of Earth are fundamental importance in exploring the dynamic evolution of the crust and mantle.The Qinling Orogenic Belt(QOB)is located between the North China plate and the South China Plate,and is one of the main orogenic belts in China.To explore the composition and origin of anisotropy and the low wave velocity zone of the QOB,ten rock samples(gneiss and schist)were collected from the five sites of the QOB and the P-and S-wave velocities of these samples were measured under 0.6 to 2.0 GPa and 100 to 550℃.The wave velocities increase with increasing pressure and decreasing temperature.The V_(P)and V_(S)of the schist and gneiss match the velocity of the middle and lower crust of the QOB,indicating that schist and gneiss are important component of the QOB.All the schist and gneiss samples exhibit obvious seismic anisotropy with 1.64%-17.42%for V_(S)and 2.93%-14.78%for V_(P)under conditions of crust and upper mantle.The CPO/LPO and layering distribution of mica in rock samples are the main reasons for this anisotropy.The V_(S)structures below the five sampled sites from seismic ambient noise tomography were built to explore the effect of schist and gneiss on the composition and structure of the QOB.The results indicate that orientation-arranged gneiss and schist driven by the tectonic stresses might be a new origin of the character of V_(P)/V_(S),seismic anisotropy,and the low velocity zone in the QOB.
基金supports from National Natural Science Foundation of China,China(Grant Nos.42042029,42172248)the Department of Education of Hebei Province,China(Grant No.QN2024174)the Opening Foundation of Hebei Key Laboratory of Strategic Critical Mineral Resources,China(Grant Nos.HGU-SCMR2439,HGU-SCMR2440).
文摘The architecture and geodynamics of intracontinental orogens remain a fundamental geological challenge.The Xing’an-Mongolia intracontinental orogenic belt(XMIOB),superimposed on the eastern Central Asian Orogenic Belt(CAOB),provides key insights into intracontinental orogenic belt dynamics.However,its architecture,deformation patterns,and geodynamic processes are poorly understood.This study integrates geological mapping,structural analysis,EBSD quartz c-axis fabrics,seismic reflection interpretation,and zircon U-Pb geochronology to unravel the XMIOB’s tectonic evolution and compare it with global intracontinental orogenic belts.Our findings reveal that the XMIOB is shaped by alternating fold-thrust belts and metamorphic zones,dominantly controlled by the inversion of pre-existing extensional structures.EBSD analysis indicates mid-temperature(400℃–500℃)ductile deformation in the deep crust,while seismic profiles highlight structural decoupling driven by a décollement zone.Integrated crustal thickness reconstructions from zircon Eu/Eu*ratios delineate three tectonic stages:Late Carboniferous-Permian asthenospheric upwelling induced crustal thinning from∼50 km to∼35 km,forming lithospheric weak zones with Buchan-type metamorphism and bimodal magmatism;Late Permian-Middle Triassic mantle subduction triggered compressional thickening(∼55 km),fold-thrust belt formation,and tectonic inversion of early extensional faults,exposing metamorphic zones;from the Middle Triassic continued mantle subduction and deep-crustal decoupling drove large-scale lateral extrusion and dextral shear,reshaping the XMIOB architecture.Comparisons with global intracontinental orogenic belts highlight two key traits of intracontinental orogenic belt evolution:pre-orogenic lithospheric thinning generates inherited weak zones that localize subsequent deformation;inherited extensional features dictate the final architecture,producing the systematic alternation of metamorphic zones and fold–thrust belts.
文摘The Central Asian Orogenic Belt(CAOB),the Earth’s largest Phanerozoic accretionary orogenic belt,is located between the Siberian,Tarim and North China Cratons and the Kazakhstan composite continent(Fig.1a).It is ca.800 km wide and extends from the Ural Mountains in the west to the Pacific in the east(e.g.,Zonenshain et al.,1990;Mossakovsky et al.,1993;Jahn et al.,2000;Windley et al.,2007,Xiao et al.,2010;Safonova et al.,2011).In the past two decades,many studies have shown that the CAOB is composed of many terranes of different tectonic origins,and was formed by successive accretion of terranes,microcontinents,island arcs,seamounts,ophiolites,and accretionary prisms from the early Neoproterozoic to the late Palaeozoic(e.g.,Mossakovsky et al.,1994;Badarch et al.,2002;Xiao et al.,2003;Buslov et al.,2001;Kovalenko et al.,2004;Safonova,2009;Li,2006;Kröner et al.,2007,2014;Donskaya et al.,2013;Xu et al.,2013).
基金financially supported by the National Natural Science Foundation of China(42130305 and 42002227)project of the China Geological Survey(DD20190039-04,DD20179402,DD20190360 and DD20221632)+2 种基金National Key R&D Program of China(2017YFC0601300 and 2013CB429802)Taishan Scholars(ts20190918)Qingdao Leading Innovation Talents(19-3-2-19-zhc).
文摘The eastern Central Asian Orogenic Belt(CAOB)in NE China is a key area for investigating continental growth.However,the complexity of its Paleozoic geological history has meant that the tectonic development of this belt is not fully understood.NE China is composed of the Erguna and Jiamusi blocks in the northern and eastern parts and the Xing’an and Songliao-Xilinhot accretionary terranes in the central and southern parts.The Erguna and Jiamusi blocks have Precambrian basements with Siberia and Gondwana affinities,respectively.In contrast,the Xing’an and Songliao-Xilinhot accretionary terranes were formed via subduction and collision processes.These blocks and terranes were separated by the Xinlin-Xiguitu,Heilongjiang,Nenjiang,and Solonker oceans from north to south,and these oceans closed during the Cambrian(ca.500 Ma),Late Silurian(ca.420 Ma),early Late Carboniferous(ca.320 Ma),and Late Permian to Middle Triassic(260-240 Ma),respectively,forming the Xinlin-Xiguitu,Mudanjiang-Yilan,Hegenshan-Heihe,Solonker-Linxi,and Changchun-Yanji suture zones.Two oceanic tectonic cycles took place in the eastern Paleo-Asian Ocean(PAO),namely,the Early Paleozoic cycle involving the Xinlin-Xiguitu and Heilongjiang oceans and the late Paleozoic cycle involving the Nenjiang-Solonker oceans.The Paleozoic tectonic pattern of the eastern CAOB generally shows structural features that trend east-west.The timing of accretion and collision events of the eastern CAOB during the Paleozoic youngs progressively from north to south.The branch ocean basins of the eastern PAO closed from west to east in a scissor-like manner.A bi-directional subduction regime dominated during the narrowing and closure process of the eastern PAO,which led to“soft collision”of tectonic units on each side,forming huge accretionary orogenic belts in central Asia.
基金financially supported by 973 Program(2014CB440801)NSFC (41230207 and 41302167)sponsored by State Key Laboratory of Earthquake Dynamics(LED2013B03)
文摘The Hongyanjing inter-arc basin, is located at the central part of Beishan Orogenic College （BOC）, Gansu Province, northwest China. Thick sequences of Permian sediments were strongly folded, forming extremely spectacular superposed folds. To better understand the thermal history of Hongyanjing interarc basin and to potentially constrain the timing of deformation, apatite fission track thermochronology method was applied on two superposed folds in the Hongyanjing Basin. Samples from the basin, yield central AFT ages ranging from - 206 to 118 Ma. AFT peak ages were largely consistent between samples and can divided into three groups： 245, 204-170 and 112-131 Ma. Subsequent thermal history modeling of the samples from the Hongyanjing Basin can be summarized as follows： （1） thermal reheating by sedimentary burial at - 260 to -220 Ma; （2） major cooling from -220 to -180 Ma; （3） an episode of very slow subsequent cooling from -180 to 65 Ma （-80 ℃） to present-day outcrop temperatures. Sediments in the Hongyanjing Basin were folded forming F1 fold during the early to late Triassic （-240--220 Ma）, by regional stress, and at the time that the adjacent Xingxingxia shear zone started to become active. It is further suggested that the F2 folding occurred at -225-219 Ma. The deformation age of F2 should he extended to 180 Ma based on our thermal history modeling for the Hongyanjing Basin, which show a rapid exhumation and cooling at the late Triassic to early Jurassic （-220-- 180 Ma）. In our interpretations, the F1 folding is therefore thought to he related to the final closure of the Paleo-Asian Ocean, while the F2 folding occurred at - 225-180 Ma associated with a major pulse of orogenesis in the BOC.
基金continental construction served as a base of the IGCP Project no.592,which was submitted in October 2010supported by the Basic Research Project of KIGAM funded by the Ministry of Knowledge Economy of Korea+2 种基金the paper would like to express their cordial thanks to our Advisors,heads of research institutions and mining companies in both Asia and Europe,leaders of research teams and all our colleagues and friends who encouraged the proposers and helped the submission by their letters of supportInna Safonova is especially thankful to the hosting staff of KIGAM in Daejeon under the leadership of Dr.Sangheon Yi for his/their understanding and cooperationInna Safonova was supported by the Brain Pool Program of the Korean Federation of Science and Technology(KOFST).
文摘A new concept of continental construction based on four main terms:(1)crustal growth,(2)crustal formation,(3)continental growth and(4)continental formation is presented here.Each of these terms reflects a certain process responsible for the formation of what we call now“continental crust”.This concept is applied to the Central Asian Orogenic Belt(CAOB),which is a global major accretionary orogen formed after the closure of the Paleo-Asian Ocean,and to its actualistic analogues–orogenic belts and accretionary complexes of the Western Pacific.The main focuses of the paper are the state of activities in the study of the CAOB,the theoretical basics of the new concept of continental construction,its challenges,prospects and social impacts,main methods of investigation.The main issues of the paper are what has been done in this field of geoscience,which questions remained unaddressed and which problems should be solved.The most important challenges are:(a)dominantly Phanerozoic formation of the CAOB continental crust versus its dominantly Archean growth;(b)to what extent the CAOB continental crust was juvenile or recycled;(c)whether magmatic arcs or Gondwana-derived terranes were accreted to the Siberian,Kazakhstan,Tarim and North China cratons;(d)what was the balance between continental formation and tectonic erosion based on modern examples from the Western Pacific;(e)what social benefits(mineral deposits)and geohazards(seismicity and volcanism)can be inferred from the study of orogenic belts formed in place of former oceans.
基金financially supported by the Chinese 973 project(2012CB416804)the ‘‘CAS Hundred Talents’’ Project from the Chinese Academy of Sciences(KZCX2-YW-BR-09)to Qi Liang
文摘Laser ablation–inductively coupled plasma–mass spectrometry（LA–ICP–MS） was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe（–Cu） deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore–forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite： Ni–Mn–V–Ti（Factor 1）, Mg–Al–Zn（Factor 2）, and Ga– Co（Factor 3） magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe–Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore–forming fluids responsible for the Fe–Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe（–Cu） deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe（–Cu） deposits may be related to felsic magmatism.
基金the Doctoral Programme of Higher Education 97049119 the National Natural Science Foundation of China grant 40072062.
文摘The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics comprise the prominent faulting along the northand south boundaries, the highly complicated petrological and petro-geochemical features of thevolcanic rock series, and the development of a new type of ophiolite suite. In terms of tectonicanalysis and the sequential analysis of tectonic settings of magmatic rocks, it is suggested thatthe Lajishan orogenic belt has undergone a complete 'opening-closing' cycle, which can be furtherdivided into 3 second-order 'opening-closing' cycles. The composite characteristics of the'opening-closing' movement show that Laji Mountain is a typical fault orogenic belt. The faultorogenic belt is one of the most important types of intracontinental orogens. It is of criticaltheoretical and practical significance to summarize the characteristics and the diagnostic criteriaof this kind of orogenic belts, and study the mechanism of their formation and build models of theirevolution.
基金jointly supported by the National Science Foundation of China(Grant No.,41472191,41502191,41172186,40972136)the Special Fund for Basic Scientific Research of Central Colleages,Chang'an University(Grant Nos.310827161002,310827161006)the Commonweal Geological Survey,the Aluminum Corporation of China and the Land-Resources Department of Qinghai Province(Grant No.,200801)
文摘The Qushi’ang granodiorite(QSG)is located at the central east of the ophiolitic melange belt in the East Kunlun Orogenic Belt(EKOB)in the northern margin of the Qinghai-Tibetan Plateau.LA-MC-ICP-MS zircon U–Pb dating suggests that the granodiorite and mafic microgranular enclaves(MMEs)crystallized 246.61±0.62 and 245.45±0.9 Ma ago,respectively.Granodiorite,porphyritic diorite,and MMEs are metaluminous and medium-K calk-alkaline series,with island-arc magma features,such as LILE enrichment and HFSE depletion.The porphyritic diorite has high Cr(13.50 ppm to 59.01 ppm),Ni(228.53 ppm to 261.29 ppm),and Mg~#(46–54).Granodiorite and porphyritic diorite have similar mineral compositions and evolved major and trace elements contents,particularly Cr and Ni,both of which are significantly higher than that in granites of the same period.The crystallization age of MMEs is close to that of granodiorite,and their major and trace elements contents are in-between porphyritic diorite and granodiorite.The results suggest that the original mafic magma,which was the product of mantle melting by subduction process,intruded into the lower crust(Kuhai Rock Group),resulting in the formation of granodiorite.Countinous intrusion of mafic magma into the unconsolidated granodiorite formed MMEs and porphyritic diorite.The granodiorite reformed by late-stage strike-slip faulting tectonic event indicates that the strike-slip fault of Middle Kunlun and the collision of the Bayanhar block with East Kunlun were later than 246 Ma.Therefore,the formation of the QSG not only indicates the critical period of evolution of East Kunlun but also represents the tectonic transition from oceanic crust subduction to slab breaking.
基金supported by China Geological Survey(CGS) and IGMA 5000 (Grant No. 12120111200131)the ministry of Science and Technology (MST) (Grant No.,2011FY120100)
文摘In a re-study of regional geology by the China Geological Survey （CGS）, the key problem is in the stratigraphical division and correlation. According to the new isotopic dating of the Mesoand Neoproterozoic in China, there have been great changes in the strata correlation and tectonic explanation. The authors obtained four zircon sensitive high resolution ion micro-probe （SHRIMP） U- Pb datings from the bentonite of the Lengjiaxi Group （822±10 Ma, 823±12 Ma and 834±11 Ma） and Banxi Group （802.6±7.6 Ma） in north Hunan Province, which is considered to be the middle part of the Jiangnan Orogenic Belt. On the basis of the zircon dating mentioned above, the end of the Wuling orogen is first limited in the period from 822 Ma to 802 Ma in one continued outcrop （Lucheng section） in Linxiang city, Hunan Province. Combining a series of new zircon U-Pb datings in the Yangtze and Cathaysia blocks, several Neoproterozoic volcanic events and distribution of the metamorphic rocks in the Jiangnan Orogenic Belt have been distinguished. In the context of the global geodynamics, it is useful to set up a practical and high precision chronological framework and basic and unified late Precambrian section in South China.
基金supported by the Fundamental Research Funds for the Central Universities(No.2019B00414)Open Fund of the Key Laboratory of Marine Geology and Environment Chinese Academy of Sciences(No.MGE2020KG03)the PHD early development program of East China University of Technology(No.DHBK2018035)。
文摘Lithosphere extension and upwelling of asthenosphere at post-collisional stage of an orogenic cycle generally induce diverse magmatism and/or associated high-temperature metamorphism. Nevertheless, the intimate coexistence of post-collisional magmatic activity and high-temperature metamorphism is rare.In this contribution, a lithological assemblage composing of diverse magmatic rocks deriving from distinct magma sources and coeval high-temperature metamorphism was identified in eastern Kunlun.Petrography, ages, mineral chemistry and whole-rock geochemistry demonstrated that those intimately coexistent diverse rocks were genetically related to post-collisional extension. The garnet-bearing mafic granulites in Jinshuikou area interior of the East Kunlun Orogenic Belt are mainly composed of garnet,orthopyroxene, and plagioclase, with peak metamorphic P–T conditions of ~ 701–756 ℃and 5.6–7.0 kbar,representing a granulite-facies metamorphism at 409.7 ± 1.7 Ma. The diverse contemporaneous magmatic rocks including hornblendites, gabbros and granites yield zircon U–Pb ages of 408.6 ± 2.5 Ma,413.4 ± 4.6 Ma, and 387–407 Ma, respectively. The hornblendites show N-MORB-like REE patterns with(La/Sm)Nvalues of 0.85–0.94. They have positive zircon εHf(t) values of 0.1–4.9 and whole-rock εNd(t) values of 3.9–4.7 but relatively high(^(87)Sr/^(86)Sr)_(i)values of 0.7081 to 0.7088. These features demonstrate that the hornblendites derived from a depleted asthenospheric mantle source with minor continental crustal materials in source. As for the gabbros, they exhibit arc-like elemental signatures, low zircon εHf(t) values(-4.3 to 2.5) and variable whole-rock εNd(t) values(-4.9 to 1.2) as well as high(^(87)Sr/86 Sr)ivalues(0.7068 to 0.7126), arguing for that they were originated from partial melting of heterogeneous lithospheric mantle anteriorly metasomatized by subducted-sediment released melts. Geochemistry of the granites defines their strongly peraluminous S-type signatures. Zircons from the granites yield a large range of εHf(t) values ranging from -30.8 to -5.1, while the whole-rock samples yield consistent(^(87)Sr/86 Sr)ivalues(0.7301 to 0.7342) and negative εNd(t) values(-10.1 to -12.4). These features indicate that the S-type granites could be generated by reworking of an ancient crust. Taken together, the penecontemporaneous magmatism and metamorphic event, demonstrated the early-middle Devonian transition from crustal thickening to extensional collapse. The post-collisional mantle-derived magmas serve as an essential driving force for the high-temperature granulite-facies metamorphism and anataxis of the crust associated with formation of S-type granite. This study not only constructs a more detail Proto-Tethys evolution process of the eastern Kunlun, but also sheds new light on better understanding the intimate relationship between magmatism and metamorphism during post-collisional extensional collapse.
基金supported by the Chinese National Key Scientific Program--the Chinese Continental Seientitle Drilling Projectthe National Natural Science Foundation of China(NSFC Grant 49772142)1:250000 Regional Geological Survey of the Lianyungang Sheet(I50C002004)of P.R.China and the Laboratory of Continental Dynamics of the Land and Resource Ministry of China
文摘The Drillhole ZK703 with a depth of 558 m is located in the Donghai area of the southern Sulu ultrahigh-pressure (UHP) metamorphic belt, eastern China, and penetrates typical UHP eclogites and various non-mafic rocks, including peridotite, gneiss, schist and quartzite. Their protoliths include ultramafic, mafic, intermediate, intermediate-acidic, acidic igneous rocks and sediments. These rocks are intimately interlayered, which are meters to millimeters thick with sharp and nontectonic contacts, suggesting in-situ metamorphism under UHP eclogite facies conditions. The following petrologic features indicate that the non-mafic rocks have experienced early-stage UHP metamorphism together with the eclogites: (1) phengite relics in gneisses and schists contain a high content of Si, up to 3.52 p.f.u. (per formula unit), while amphibolite-facies phengites have considerably low Si content (<3.26 p.f.u.); (2) jadeite relics are found in quartzite and jadeitite; (3) various types of symplectitic coronas and pseud
