Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inve...Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inverted metamorphism. The present study, based on structural, petrological and geochronological investigations in the Kinnar Kailas Granite (KKG) and surrounding HHC sequence, evidences a discordant intrusive contact of the Ordovician KKG with respect to Pre\|Alpine high grade deformed HHC sequence in the Sutlej valley.Four main phases of deformation are recorded in this HHC sequence and pre\|Ordovician sediments. The first three phases of deformation occurred under high\|grade metamorphic conditions, before the intrusion of the KKG. The geometry of the main progressive ductile deformation (D2—D3) results from SW vergent doming and migmatisation. The latest deformation is expressed by local shearing under greenschist facies conditions. This late D4 deformation corresponds to N—S oriented ductile normal faults lowering the eastern blocks. The KKG is a shallow depth intrusion, showing discordant contacts with the surrounding basement rocks and large scale magmatic stoping. The KKG crosscuts the high\|grade deformation structures (D2—D3) but is locally affected by the local late D4 extensional deformation. The granite textures reflect only slight orientation related to magmatic deformation and even at few centimetres from the intrusion contact, the granite appears undeformed in contrast to the surrounding highly foliated rocks. Furthermore, xenoliths of Kyanite\|Sillimanite bearing basement rocks are present within the KKG.展开更多
The main types of intrusive rocks in the Kelameili-Harlik Hercynian orogenic belt include calc-alkaline granites, diabase dykes, kaligranites and alkaline granites. Investigation in field geology, petrology, mineralog...The main types of intrusive rocks in the Kelameili-Harlik Hercynian orogenic belt include calc-alkaline granites, diabase dykes, kaligranites and alkaline granites. Investigation in field geology, petrology, mineralogy and geochemistry shows that the calc-alkaline granites belong to the syntexis-type (or I-type) and were formed in a pre-collisional magmatic arc environment. In consideration of the fact that kaligranites have many features of alkaline granites with higher consolidation temperatures than the calc-alkaline granites and show a discontinuity of minor element and REE evolution in respect to the calc-alkaline granites, they could not have been derived by differentiation of magmas for the calc-alkaline granites, but are likely to have been generated in an environment analogous to that for alkaline granites. The triplet of basic dyke swarms, kaligranites and alkaline granites could be regarded as a prominent indication of the initial stage of post-collisional delamination and extension. These rocks might have originated from underplating and intraplating of mantle-derived magmas at varying levels with varying degrees of partial melting, mixing, and interchange of crustal and mantle materials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
Lamprophyre dykes that crosscut different types of ultrahigh pressure(UHP)metamorphic rocks are widely distributed in the Triassic Sulu UHP orogenic belt.Although abundant studies have been performed on these dykes,th...Lamprophyre dykes that crosscut different types of ultrahigh pressure(UHP)metamorphic rocks are widely distributed in the Triassic Sulu UHP orogenic belt.Although abundant studies have been performed on these dykes,their origin and petrogenesis remain topics of controversy.This study presents the results of a detailed field-based study of petrology,whole-rock geochemistry and zircon U-Pb and Lu-Hf isotopes on lamprophyre dykes exposed in the central Sulu UHP zone,aiming at shedding lights on their petrogenesis and providing clues on the geological evolution of eastern continental China during the Cretaceous.The lamprophyres are typically porphyritic,with phenocrysts dominantly composed of amphibole and clinopyroxene set in a lamprophyric matrix.The dykes have moderate Si O2(47.70 wt.%–60.44 wt.%),variably high Mg O(2.58 wt.%–8.28 wt.%)and Fe2 O3 T(4.88 wt.%–9.26 wt.%)contents with high Mg#of 49–66.Geochemically,they have enriched light rare earth element(REE)and flat heavy REE patterns((La/Gd)N=5.14–10.56;(Dy/Yb)N=1.43–1.54)with negligible Eu anomalies(Eu/Eu*=0.83–1.10),and they show enrichment in large ion lithophile elements(e.g.,Ba and K)but depletion in high-field strength elements(e.g.,Nb,Ti and P).In-situ zircon U-Pb geochronology reveals that the lamprophyres have concordant ages of 120–115 Ma,demonstrating that the dykes emplaced in the Early Cretaceous.These zircons have?Hf(t)values ranging from-26.0 to-11.0.Inherited zircons that occur in the dykes are dated to be Neoproterozoic,in line with the protolith ages of their host(i.e.,the UHP rocks).An integration of these data allows us to propose that the lamprophyres were generated during the Cretaceous,by melting of subcontinental lithospheric mantle-derived metasomatite with enriched chemical compositions underneath the North China Craton.The metasomatite was formed mainly by peridotite-fluid/melt reactions,with the fluids/melts mainly liberated from subducted Yangtze continental crust during the Triassic.Regional extension,lithospheric thinning and mantle upwelling caused by rollback of the subducted paleoPacific plate is considered to account for the generation of the lamprophyres as well as the extensive arc-like magmatic rocks in eastern continental China during the Early Cretaceous.展开更多
The Indosinian and Yanshanian orogenic movements are both important Mesozoic orogenies in eastern China.The resulted tectonic belts are neither products of the third stage of crustal evolution,as proposed by Chen Guod...The Indosinian and Yanshanian orogenic movements are both important Mesozoic orogenies in eastern China.The resulted tectonic belts are neither products of the third stage of crustal evolution,as proposed by Chen Guoda,nor intra-continental(or intraplate)orogenic belts generated by intraplate dynamics,as argued by some scholars-rather,they are superposed orogenic belts formed on the pre-existing continental crust in eastern China due to Mesozoic Paleo-Pacific dynamic system.In the past,these orogenic belts were called the marginal Pacific epicontinental activation belts of eastern China.In the Mesozoic,under the effect of Paleo-Pacific dynamic system,the East Asia margin orogenic system formed along Northeast Russia-Sikhote Alin(Russia)-Japan-Ryukyu-Taiwan(China)-Palawan(Philippines)regions,while simultaneously the Mesozoic superposed orogenic system formed in the pre-existing continental crust in eastern China adjacent to the East Asia continental margin.The two orogenic systems,both driven by Mesozoic Paleo-Pacific dynamic system,developed synchronously to form the giant Mesozoic orogenic system in the Pacific tectonic domain in eastern Asia,radically changing the pre-Indosian tectonic framework of the area.展开更多
The alkali feldspar granite of Gabal El Atawi is post orogenic granite originated from subalkaline magma in extensional suite. It is developed within plate tectonic setting and has A2-type character which generated fr...The alkali feldspar granite of Gabal El Atawi is post orogenic granite originated from subalkaline magma in extensional suite. It is developed within plate tectonic setting and has A2-type character which generated from apparent crustal source. The petrographic, geochemical and radioactive characteristics of El Atawi granite meet and fulfill the requirements of being fertile granite and it can be considered as promising uraniferous granite. Fluid inclusion studies of the altered granite elucidated two different solutions acting on the host granitic pluton. The first is NaCl-CaCl low temperature fluid with a wide range of salinity. The second is high temperature and salinity Fe-Mg-Na chloride solution. Different fractures in the granite acted as good channels for the hydrothermal fluids that leached uranium from its bearing minerals disseminated all over the host granite and redeposited it in the alteration zones.展开更多
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 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
A wealth of retrogressive microstructures have been discovered from the UHP metamorphic rocks in Dabie orogenic belt, namely, the ultrahigh-pressure (URP) eclogites, jadeite quartzites and kyanite-zoisite-quartz vein....A wealth of retrogressive microstructures have been discovered from the UHP metamorphic rocks in Dabie orogenic belt, namely, the ultrahigh-pressure (URP) eclogites, jadeite quartzites and kyanite-zoisite-quartz vein. The most important are pseudomorphic replacements of UHP minerals like coesite, the corona reaction textures iuduced by solid-solid reactions as well as the corona and symplectites induced by reactions involving fluid. According to the textural relationships the sequence of mineral Paragenesis and the metamorphic stages in the UHP eclogites can be delineated; the mineral geobarothermometry of the various stages of retrograde metamorphism is studied and a clockwise, nearly isothermal decompressive metamorphic PT-trajectory for the UHP eclogites can be reconstructed. In terms of the PT-trajectory the two stage post collision uplirt and exhumation processes are reflected. When the UHP metumorphic rocks extruded to the lower-middle crust partial melting happened which bad in turn caused tke crustal extension and the further exhumation or the UHP metomorphic rocks. Based on the field strain analysis combined with geochronological data a scenario or post collision uplift aud exhumation model is presented.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
Subducting slabs transport carbon to deep mantle depths and release it into the overlying mantle wedge and lithospheric mantle through multiple mechanisms,including mechanical removal via diapirism,metamorphic decarbo...Subducting slabs transport carbon to deep mantle depths and release it into the overlying mantle wedge and lithospheric mantle through multiple mechanisms,including mechanical removal via diapirism,metamorphic decarbonization,carbonate dissolution and parting melting.Identifying the dominant carbon recycling mechanism responsible for carbonation of subcontinental lithospheric mantle(SCLM)remains challenging,yet it is critical for understanding the genesis of post-collisional carbonatites and associated rare earth element deposits.To address this issue,we investigate the Li isotopic systematics of typical post-collisional carbonatite-alkalic complexes from Mianning-Dechang(MD),Southeast Xizang.Our results show that the less-evolved magmas(lamprophyres)have mantle-like or slightly lowerδ^(7)Li values(0.3‰–3.6‰)with limited variability,contrasting sharply with the widerδ^(7)Li range observed in associated carbonatites and syenites.We interpret this dichotomy as reflecting distinct processes:while the variable and anomalousδ^(7)Li values in differentiated rocks(carbonatites and syenites)were caused by late-stage magmatic-hydrothermal processes(including biotite fractionation,fluid exsolution and hydrothermal alteration),the lamprophyres retain the primary Li isotopic signature of their mantle source.Together with their arc-like trace element and EM1-EM2-type Sr-Nd-Pb isotopic signatures,such mantle-like or slightly lowerδ^(7)Li values of the lamprophyres preclude carbon derivation from high-δ^(7)Li reservoirs(altered oceanic crust,serpentinites)and recycling of sedimentary carbon through metamorphic decarbonization or dissolution.Instead,these features indicate that the carbon was predominantly transported into the mantle source via partial melting of subducted carbonate-bearing sediments.This study demonstrates that Li isotopes can serve as a tracer for identifying the mechanism of carbon recycling in collision zones.展开更多
The study area is situated in the Tianshan region,specifically within the eastern segment of the North Qilian Orogenic Belt(NQLOB).The NQLOB is a critical region for understanding oceanic closure and continental colli...The study area is situated in the Tianshan region,specifically within the eastern segment of the North Qilian Orogenic Belt(NQLOB).The NQLOB is a critical region for understanding oceanic closure and continental collision processes driven by the Shangdan Ocean subduction-exhumation,which was a segment of the Proto-Tethys Ocean during the Early Paleozoic.Despite significant research,the Early Paleozoic tectonic background and subduction-related orogenic processes,particularly in the eastern NQLOB,remain subjects of debate.This study presents significant petrographic,geochemical,and geochronologic insights into the metavolcanic rocks of the Chenjiahe Group in the eastern NQLOB.Petrographic analysis reveals that these metavolcanic rocks originated in a low-grade metamorphic setting.Zircon laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)U-Pb dating yielded ages ranging between 449.7-443.4 Ma,indicating Late Ordovician formation.Geochemical signatures of felsic and intermediate rocks exhibit calc-alkaline to high-K calc-alkaline similarities,characterized by high light rare earth elements(LREEs),low heavy rare earth elements(HREEs),and moderate Eu anomalies,consistent with a continental arc setting.In contrast,basaltic rocks display tholeiitic features with elevated large-ion lithophile elements(LILEs),reduced high-field-strength elements(HFSEs),and weak Eu anomalies,suggesting an extensional environment.These findings imply that the metavolcanic rocks evolved in a continental arc-back-arc extension setting connected with the northward subduction and exhumation of the Huluhe back-arc oceanic basin.This process was likely triggered by the northward subduction and closure of the Shangdan Ocean,culminating in the Late Ordovician amalgamation of the Qilian Block and the southwestern North China Block.This study provides critical insight into the tectonic development of the NQLOB and the broader Proto-Tethys Ocean dynamics at the northern periphery of the Eastern Gondwana.展开更多
The 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
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
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
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
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
Post-collisional magmatism contains important clues for understanding the reworking and growth of continental crust,as well as lithospheric delamination and orogenic collapse.Early Devonian magmatism has been identifi...Post-collisional magmatism contains important clues for understanding the reworking and growth of continental crust,as well as lithospheric delamination and orogenic collapse.Early Devonian magmatism has been identified in the North Qilian Orogenic Belt(NQOB).This paper reports an integrated study of petrology,whole-rock geochemistry,Sm-Nd isotope and zircon U-Pb dating,as well as Lu-Hf isotopic data,for two Early Devonian intrusive plutons.The Yongchang and Chijin granites yield zircon U-Pb ages of 394-407 Ma and 414 Ma,respectively.Both of them are characterized by weakly peraluminous to metaluminous without typical aluminium-rich minerals,LREE-enriched patterns with negative Eu anomalies and a negative correlation between P_(2)O_(5) and SiO_(2) contents,consistent with geochemical features of I-type granitoids.Zircons from the studied granites display negative to weak positive ε_(Hf)(t)values(−5.7 to 2.1),which agree well with those of negative ε_(Nd)(t)values(−6.4 to−2.9)for the whole-rock samples,indicating that they were derived from the partial melting of Mesoproterozoic crust.Furthermore,low Sr/Y ratios(1.13-21.28)and high zircon saturation temperatures(745℃ to 839℃,with the majority being>800℃)demonstrated a relatively shallow depth level below the garnet stability field and an additional heat source.Taken together,the Early Devonian granitic magmatism could have been produced by the partial melting of ancient crustal materials heated by mantle-derived magmas at high-temperature and low-pressure conditions during postcollisional extensional collapse.The data obtained in this study,when viewed in conjunction with previous studies,provides more information about the tectonic processes that followed the closure of the North Qilian Ocean.The tectonic transition from continental collision to post-collisional delamination could be constrained to~430 Ma,which is provided by the sudden decrease of Sr/Y and La/Yb ratios and an increase in zircon ε_(Hf)(t)values for granitoids.A two-stage tectonic evolution model from continental collision to post-collisional extensional collapse for the NQOB includes(a)continental collision and crustal thickening during ca.455-430 Ma,characterized by granulite-facies metamorphism and widespread low-Mg adakitic magmatism;(b)post-collisional delamination of thickened continental crust and extensional collapse of orogen during ca.430-390 Ma,provided by coeval high-Mg adakitic magmatism,A-type granites and I-type granitoids with low Sr-Y ratios.展开更多
The Xikuangshan antimony deposit in central Hunan, South China, is the largest antimony deposit ever known in the world. The ore bodies are strictly confined to the footwalls of mafor high-angle normal faults which tr...The Xikuangshan antimony deposit in central Hunan, South China, is the largest antimony deposit ever known in the world. The ore bodies are strictly confined to the footwalls of mafor high-angle normal faults which transect the inclined folds in the flank;away from the fault planes,both the homogenization temperatures of inclusions in gangue minerals and the intensity of antimony mineralization decrease.These characteristics strongly demonstrate that the faults are used as the conduit for the metal-bearing fluid in mineralization.The normal faults,striking the NE to NNE,are interpreted to be generated by the postmgenic extension in the time from Cretaceous to Paleogene.Crustal or lithospheric thinning, directly resulting from regional extension inevitably increase the geothermal gradient, Which is likely to cause large-scale convection of underground water that may leach out and transport valuablemetals such as Sb from source rocks.Focussed discharge along the fault zones contributes to the formation of the supergiant antimony deposit in Xikuangshan under the appropriate sedimentary barrier.展开更多
文摘Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inverted metamorphism. The present study, based on structural, petrological and geochronological investigations in the Kinnar Kailas Granite (KKG) and surrounding HHC sequence, evidences a discordant intrusive contact of the Ordovician KKG with respect to Pre\|Alpine high grade deformed HHC sequence in the Sutlej valley.Four main phases of deformation are recorded in this HHC sequence and pre\|Ordovician sediments. The first three phases of deformation occurred under high\|grade metamorphic conditions, before the intrusion of the KKG. The geometry of the main progressive ductile deformation (D2—D3) results from SW vergent doming and migmatisation. The latest deformation is expressed by local shearing under greenschist facies conditions. This late D4 deformation corresponds to N—S oriented ductile normal faults lowering the eastern blocks. The KKG is a shallow depth intrusion, showing discordant contacts with the surrounding basement rocks and large scale magmatic stoping. The KKG crosscuts the high\|grade deformation structures (D2—D3) but is locally affected by the local late D4 extensional deformation. The granite textures reflect only slight orientation related to magmatic deformation and even at few centimetres from the intrusion contact, the granite appears undeformed in contrast to the surrounding highly foliated rocks. Furthermore, xenoliths of Kyanite\|Sillimanite bearing basement rocks are present within the KKG.
基金This rescarch was jointly supported by the NationalNatural Science Foundation of China Grant No.4917-2094National Key Project No.305with additionalsuppor for the analyses from the Modern AnalysisCentre of Nanjing University.
文摘The main types of intrusive rocks in the Kelameili-Harlik Hercynian orogenic belt include calc-alkaline granites, diabase dykes, kaligranites and alkaline granites. Investigation in field geology, petrology, mineralogy and geochemistry shows that the calc-alkaline granites belong to the syntexis-type (or I-type) and were formed in a pre-collisional magmatic arc environment. In consideration of the fact that kaligranites have many features of alkaline granites with higher consolidation temperatures than the calc-alkaline granites and show a discontinuity of minor element and REE evolution in respect to the calc-alkaline granites, they could not have been derived by differentiation of magmas for the calc-alkaline granites, but are likely to have been generated in an environment analogous to that for alkaline granites. The triplet of basic dyke swarms, kaligranites and alkaline granites could be regarded as a prominent indication of the initial stage of post-collisional delamination and extension. These rocks might have originated from underplating and intraplating of mantle-derived magmas at varying levels with varying degrees of partial melting, mixing, and interchange of crustal and mantle materials
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the National Natural Science Foundation of China and Shandong Province(Nos.ZR2018BD019,41572182,41803031,41272225)the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Wuhan)(No.MSFGPMR02-3)the Youth Innovation Team Development Plan of the Universities in Shandong Province。
文摘Lamprophyre dykes that crosscut different types of ultrahigh pressure(UHP)metamorphic rocks are widely distributed in the Triassic Sulu UHP orogenic belt.Although abundant studies have been performed on these dykes,their origin and petrogenesis remain topics of controversy.This study presents the results of a detailed field-based study of petrology,whole-rock geochemistry and zircon U-Pb and Lu-Hf isotopes on lamprophyre dykes exposed in the central Sulu UHP zone,aiming at shedding lights on their petrogenesis and providing clues on the geological evolution of eastern continental China during the Cretaceous.The lamprophyres are typically porphyritic,with phenocrysts dominantly composed of amphibole and clinopyroxene set in a lamprophyric matrix.The dykes have moderate Si O2(47.70 wt.%–60.44 wt.%),variably high Mg O(2.58 wt.%–8.28 wt.%)and Fe2 O3 T(4.88 wt.%–9.26 wt.%)contents with high Mg#of 49–66.Geochemically,they have enriched light rare earth element(REE)and flat heavy REE patterns((La/Gd)N=5.14–10.56;(Dy/Yb)N=1.43–1.54)with negligible Eu anomalies(Eu/Eu*=0.83–1.10),and they show enrichment in large ion lithophile elements(e.g.,Ba and K)but depletion in high-field strength elements(e.g.,Nb,Ti and P).In-situ zircon U-Pb geochronology reveals that the lamprophyres have concordant ages of 120–115 Ma,demonstrating that the dykes emplaced in the Early Cretaceous.These zircons have?Hf(t)values ranging from-26.0 to-11.0.Inherited zircons that occur in the dykes are dated to be Neoproterozoic,in line with the protolith ages of their host(i.e.,the UHP rocks).An integration of these data allows us to propose that the lamprophyres were generated during the Cretaceous,by melting of subcontinental lithospheric mantle-derived metasomatite with enriched chemical compositions underneath the North China Craton.The metasomatite was formed mainly by peridotite-fluid/melt reactions,with the fluids/melts mainly liberated from subducted Yangtze continental crust during the Triassic.Regional extension,lithospheric thinning and mantle upwelling caused by rollback of the subducted paleoPacific plate is considered to account for the generation of the lamprophyres as well as the extensive arc-like magmatic rocks in eastern continental China during the Early Cretaceous.
基金funded by the Regional Geological Survey Project of the China Geological Survey(DD20221646)the National Natural Science Foundation of China(42172218).
文摘The Indosinian and Yanshanian orogenic movements are both important Mesozoic orogenies in eastern China.The resulted tectonic belts are neither products of the third stage of crustal evolution,as proposed by Chen Guoda,nor intra-continental(or intraplate)orogenic belts generated by intraplate dynamics,as argued by some scholars-rather,they are superposed orogenic belts formed on the pre-existing continental crust in eastern China due to Mesozoic Paleo-Pacific dynamic system.In the past,these orogenic belts were called the marginal Pacific epicontinental activation belts of eastern China.In the Mesozoic,under the effect of Paleo-Pacific dynamic system,the East Asia margin orogenic system formed along Northeast Russia-Sikhote Alin(Russia)-Japan-Ryukyu-Taiwan(China)-Palawan(Philippines)regions,while simultaneously the Mesozoic superposed orogenic system formed in the pre-existing continental crust in eastern China adjacent to the East Asia continental margin.The two orogenic systems,both driven by Mesozoic Paleo-Pacific dynamic system,developed synchronously to form the giant Mesozoic orogenic system in the Pacific tectonic domain in eastern Asia,radically changing the pre-Indosian tectonic framework of the area.
文摘The alkali feldspar granite of Gabal El Atawi is post orogenic granite originated from subalkaline magma in extensional suite. It is developed within plate tectonic setting and has A2-type character which generated from apparent crustal source. The petrographic, geochemical and radioactive characteristics of El Atawi granite meet and fulfill the requirements of being fertile granite and it can be considered as promising uraniferous granite. Fluid inclusion studies of the altered granite elucidated two different solutions acting on the host granitic pluton. The first is NaCl-CaCl low temperature fluid with a wide range of salinity. The second is high temperature and salinity Fe-Mg-Na chloride solution. Different fractures in the granite acted as good channels for the hydrothermal fluids that leached uranium from its bearing minerals disseminated all over the host granite and redeposited it in the alteration zones.
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A wealth of retrogressive microstructures have been discovered from the UHP metamorphic rocks in Dabie orogenic belt, namely, the ultrahigh-pressure (URP) eclogites, jadeite quartzites and kyanite-zoisite-quartz vein. The most important are pseudomorphic replacements of UHP minerals like coesite, the corona reaction textures iuduced by solid-solid reactions as well as the corona and symplectites induced by reactions involving fluid. According to the textural relationships the sequence of mineral Paragenesis and the metamorphic stages in the UHP eclogites can be delineated; the mineral geobarothermometry of the various stages of retrograde metamorphism is studied and a clockwise, nearly isothermal decompressive metamorphic PT-trajectory for the UHP eclogites can be reconstructed. In terms of the PT-trajectory the two stage post collision uplirt and exhumation processes are reflected. When the UHP metumorphic rocks extruded to the lower-middle crust partial melting happened which bad in turn caused tke crustal extension and the further exhumation or the UHP metomorphic rocks. Based on the field strain analysis combined with geochronological data a scenario or post collision uplift aud exhumation model is presented.
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funded by the National Natural Science Foundation of China(42263006)Open Fund from the Jiangxi Province,China(Grant No.20224ACB203011 and 2020101003)East China University of Technology(DHYC-202401 and 1410000874).
文摘Subducting slabs transport carbon to deep mantle depths and release it into the overlying mantle wedge and lithospheric mantle through multiple mechanisms,including mechanical removal via diapirism,metamorphic decarbonization,carbonate dissolution and parting melting.Identifying the dominant carbon recycling mechanism responsible for carbonation of subcontinental lithospheric mantle(SCLM)remains challenging,yet it is critical for understanding the genesis of post-collisional carbonatites and associated rare earth element deposits.To address this issue,we investigate the Li isotopic systematics of typical post-collisional carbonatite-alkalic complexes from Mianning-Dechang(MD),Southeast Xizang.Our results show that the less-evolved magmas(lamprophyres)have mantle-like or slightly lowerδ^(7)Li values(0.3‰–3.6‰)with limited variability,contrasting sharply with the widerδ^(7)Li range observed in associated carbonatites and syenites.We interpret this dichotomy as reflecting distinct processes:while the variable and anomalousδ^(7)Li values in differentiated rocks(carbonatites and syenites)were caused by late-stage magmatic-hydrothermal processes(including biotite fractionation,fluid exsolution and hydrothermal alteration),the lamprophyres retain the primary Li isotopic signature of their mantle source.Together with their arc-like trace element and EM1-EM2-type Sr-Nd-Pb isotopic signatures,such mantle-like or slightly lowerδ^(7)Li values of the lamprophyres preclude carbon derivation from high-δ^(7)Li reservoirs(altered oceanic crust,serpentinites)and recycling of sedimentary carbon through metamorphic decarbonization or dissolution.Instead,these features indicate that the carbon was predominantly transported into the mantle source via partial melting of subducted carbonate-bearing sediments.This study demonstrates that Li isotopes can serve as a tracer for identifying the mechanism of carbon recycling in collision zones.
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 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 Natural Science Foundation of Shandong Province(Grant No.ZR2022QD055)the Taishan Scholars(Grant No.tstp 20231214)the National Natural Science Foundation of China(Grant No.42372247).
文摘Post-collisional magmatism contains important clues for understanding the reworking and growth of continental crust,as well as lithospheric delamination and orogenic collapse.Early Devonian magmatism has been identified in the North Qilian Orogenic Belt(NQOB).This paper reports an integrated study of petrology,whole-rock geochemistry,Sm-Nd isotope and zircon U-Pb dating,as well as Lu-Hf isotopic data,for two Early Devonian intrusive plutons.The Yongchang and Chijin granites yield zircon U-Pb ages of 394-407 Ma and 414 Ma,respectively.Both of them are characterized by weakly peraluminous to metaluminous without typical aluminium-rich minerals,LREE-enriched patterns with negative Eu anomalies and a negative correlation between P_(2)O_(5) and SiO_(2) contents,consistent with geochemical features of I-type granitoids.Zircons from the studied granites display negative to weak positive ε_(Hf)(t)values(−5.7 to 2.1),which agree well with those of negative ε_(Nd)(t)values(−6.4 to−2.9)for the whole-rock samples,indicating that they were derived from the partial melting of Mesoproterozoic crust.Furthermore,low Sr/Y ratios(1.13-21.28)and high zircon saturation temperatures(745℃ to 839℃,with the majority being>800℃)demonstrated a relatively shallow depth level below the garnet stability field and an additional heat source.Taken together,the Early Devonian granitic magmatism could have been produced by the partial melting of ancient crustal materials heated by mantle-derived magmas at high-temperature and low-pressure conditions during postcollisional extensional collapse.The data obtained in this study,when viewed in conjunction with previous studies,provides more information about the tectonic processes that followed the closure of the North Qilian Ocean.The tectonic transition from continental collision to post-collisional delamination could be constrained to~430 Ma,which is provided by the sudden decrease of Sr/Y and La/Yb ratios and an increase in zircon ε_(Hf)(t)values for granitoids.A two-stage tectonic evolution model from continental collision to post-collisional extensional collapse for the NQOB includes(a)continental collision and crustal thickening during ca.455-430 Ma,characterized by granulite-facies metamorphism and widespread low-Mg adakitic magmatism;(b)post-collisional delamination of thickened continental crust and extensional collapse of orogen during ca.430-390 Ma,provided by coeval high-Mg adakitic magmatism,A-type granites and I-type granitoids with low Sr-Y ratios.
文摘The Xikuangshan antimony deposit in central Hunan, South China, is the largest antimony deposit ever known in the world. The ore bodies are strictly confined to the footwalls of mafor high-angle normal faults which transect the inclined folds in the flank;away from the fault planes,both the homogenization temperatures of inclusions in gangue minerals and the intensity of antimony mineralization decrease.These characteristics strongly demonstrate that the faults are used as the conduit for the metal-bearing fluid in mineralization.The normal faults,striking the NE to NNE,are interpreted to be generated by the postmgenic extension in the time from Cretaceous to Paleogene.Crustal or lithospheric thinning, directly resulting from regional extension inevitably increase the geothermal gradient, Which is likely to cause large-scale convection of underground water that may leach out and transport valuablemetals such as Sb from source rocks.Focussed discharge along the fault zones contributes to the formation of the supergiant antimony deposit in Xikuangshan under the appropriate sedimentary barrier.
