The Eastern Kunlun Orogenic Belt(EKOB)has a complex geological structure and diverse magmatic activities,which are closely related to the Qaidam Basin and the Tethys tectonic evolution.There are at least 3 stages mafi...The Eastern Kunlun Orogenic Belt(EKOB)has a complex geological structure and diverse magmatic activities,which are closely related to the Qaidam Basin and the Tethys tectonic evolution.There are at least 3 stages mafic-ultramafic rocks occurred in the Early Paleozoic in EKOB.The first stage is the Later-Silurian to Early Devonian,represented by the giant Xiarihamu super large magmatic Cu-Ni deposit,containing about 1.18 million metric tons(Mt)of nickel with average grades of 0.65%Ni,and its age of ore-forming pyroxene peridotite is 411 Ma;The second stage is the Early Carboniferous,represented by the large Shitoukengde magmatic Cu-Ni sulfide deposit,and its ore-forming age of the olivine websterite is 334 Ma;The third stage of mafic-ultramafic rocks occurred mainly during the Middle-Late Triassic,represented by Xiaojianshan,Lalinggaoli,and Kaimuqi complexes,and no economical ore bodies have been found in this period.The authors summarized the difference between the ore-bearing and the nonmineralized mafic-ultramafic rocks in the EKOB.The olivine of the ore-bearing complexes contains higher MgO and SiO2 content but lower FeO and CaO contents,and the clinopyroxene of ore-bearing complexes contains lower FeO and CaO contents.Crustal sulfur contamination is key to the formation of the giant Xiarihamu Ni deposit,and crustal sulfur contamination degree of the giant magmatic Ni deposit is higher than that of large Ni deposit.The above indicators could guide the exploration and evaluation of similar deposits in the EKOB.展开更多
The West Kunlun orogenic belt(WKOB) along the northern margin of the Tibetan Plateau is important for understanding the evolution of the Proto-and Paleo-Tethys oceans. Previous investigations have focused on the igneo...The West Kunlun orogenic belt(WKOB) along the northern margin of the Tibetan Plateau is important for understanding the evolution of the Proto-and Paleo-Tethys oceans. Previous investigations have focused on the igneous rocks and ophiolites distributed mostly along the Xinjiang-Tibet road and the China-Pakistan road, and have constructed a preliminary tectonic model for this orogenic belt. However, few studies have focused on the so-called Precambrian basement in this area. As a result, the tectonic affinity of the individual terranes of the WKOB and their detailed evolution process are uncertain. Here we report new field observations, zircon and monazite U-Pb ages of the "Precambrian basement" of the South Kunlun terrane(SKT) and the Tianshuihai terrane(TSHT), two major terranes in the WKOB. Based on new zircon U-Pb age data, the amphibolite-facies metamorphosed volcanosedimentary sequence within SKT was deposited during the late Neoproterozoic to Cambrian(600-500 Ma), and the flysch-affinity Tianshuihai Group, as the basement of the TSHT, was deposited during the late Neoproterozoic rather than Mesoproterozoic. The rock association of the volcano-sedimentary sequence within SKT suggests a large early Paleozoic accretionary wedge formed by the long-term lowangle southward subduction of the Proto-Tethys Ocean between Tarim and TSHT. The amphibolitefacies metamorphism in SKT occurred at ca. 440 Ma. This ca. 440 Ma metamorphism is genetically related to the closure of the Proto-Tethys Ocean between Tarim and the Tianshuihai terrane, which led to the assembly of Tarim to Eastern Gondwana and the final formation of the Gondwana. Since the late Paleozoic to early Mesozoic, the northward subduction of the Paleo-Tethys Ocean along the HongshihuQiaoertianshan belt produced the voluminous early Mesozoic arc-signature granites along the southern part of NKT-TSHT. The Paleo-Tethys ocean between TSHT and Karakorum closed at ca. 200 Ma, as demonstrated by the monazite age of the paragneiss in the Kangxiwa Group. Our study does not favor the existence of a Precambrian basement in SKT.展开更多
The Mailong gold deposit is located in the eastern section of the East Kunlun orogenic belt and is one of the recently discovered important gold polymetallic deposits in the Qinhai Gouli region.The primary host rocks ...The Mailong gold deposit is located in the eastern section of the East Kunlun orogenic belt and is one of the recently discovered important gold polymetallic deposits in the Qinhai Gouli region.The primary host rocks of the Mailong gold deposit consist of intermediate-acid intrusive rocks from the Varisian and Indosinian periods,as well as the Precambrian Jinshuikou Group,with mineralization controlled by northeast and northwest faults.The alteration of the host rocks is mainly characterized by silicification,sericitization,chloritization,and carbonatization.Based on the cross-cutting relationships of the veins,the hydrothermal mineralization of the gold deposit can be categorized into three stages:the quartz-pyrite stage,the quartzpolymetallic sulfide stage,and the quartz-carbonate stage.Microthermometry of fluid inclusions indicates that the Mailong gold deposit belongs to a low-density(0.73–0.86 g/cm3),medium-temperature(240–340℃),and medium-salinity(4.01–10.74 wt%NaCl)NaCl-CO2-H2O fluid system.The C-H-O isotopic analysis suggests that the mineralizing fluids is derived from magmatic water,with later contributions from atmospheric precipitation.In-situ S isotopic results indicate that the mineralizing materials mainly derive from igneous rocks.A comprehensive analysis concludes that the Mailong gold deposit is a mesothermal hydrothermal vein-type gold deposit controlled by structural factors.展开更多
Based on field investigation in 1999, two deformational domains with d ifferent dynamics have been distinguished from the Jurassic geological outcrops in the Mohe area of NE China, i.e. northern ductile and southern p...Based on field investigation in 1999, two deformational domains with d ifferent dynamics have been distinguished from the Jurassic geological outcrops in the Mohe area of NE China, i.e. northern ductile and southern plastic-brittl e ones. Their deformational features are stated in this paper. And then, three st ages of structural deformation of the area relative to the late Mesozoic orogeni c processes of Mongolian-Okhotsk orogen are reconstructed as follows, (1) south w ards thrusting in the middle-late Jurassic, (2) eastwards thrusting and strike -s lipping parallel to the orogen in the late Jurassic, and (3) southeastwards thru sting in the early Cretaceous.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
Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an ...Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andeantype active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two-mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U-Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two-mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean(PAO) and represents a suture between the North China craton(NCC) and Central Asian Orogenic Belt(CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400–420 Ma. Magmatism of the second stage in 380–390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes-type active continental margin of the CAOB has been proposed, including a development of the subduction-free PAO before 446 Ma, a subduction of the PAO and arc-related magmatism during 446–380 Ma, and formation of a molasse basin during 380–360 Ma.展开更多
Ludong orogenic belt in China is an importantal continent collision orogenic belt in eastern Asia, between Sino Korean landmass and Yangtze landmass. The host rock of the orogenic belt is metamorphosed medium acidic i...Ludong orogenic belt in China is an importantal continent collision orogenic belt in eastern Asia, between Sino Korean landmass and Yangtze landmass. The host rock of the orogenic belt is metamorphosed medium acidic intrusive complexes, which can be divided into four types, that’s, quartz dioritz, granite dioritz, monzonitic granite and undertint monzonitic granite, principal minerals are plagioclases, potassium feldspars and quartzs, minor minerals are hornblendes, biotites, clinopyxenes and garnets, accessory mineral types and assemblages are very similar, specially, various rocks are mainly fine grained textures. They have the history of regional amphibolite facies metamorphism and deep middle shallow structural layer deformation, and are changed into various gneiss and tectonic system. There are many xenolithes of middle Proterozoic eclogite host rock extrahigh high pressure metamorphic complexes, a small xenolithes of early Proterozoic layered metamorphite system and granulites, and ultrabasic basic rocks of various epoches in the metamorphosed medium acidic intrusive complexes.展开更多
The Chinese Altai in northwestern Xinjiang has numerous outcrops of granitoids which provide critical information on accretionary orogenic processes and crustal growth of the Central Asian Orogenic Belt.Zircon U-Pb ag...The Chinese Altai in northwestern Xinjiang has numerous outcrops of granitoids which provide critical information on accretionary orogenic processes and crustal growth of the Central Asian Orogenic Belt.Zircon U-Pb ages, Hf-isotopic compositions and whole-rock geochemistry of monzogranite and granodiorites in the Qinghe County are employed to elucidate Paleozoic tectonics of the Chinese Altai. Granodiorites have crystallization ages of 424.6 ± 3.1 Ma(MSWD = 0.23) and 404.0 ± 3.4 Ma(MSWD = 0.18);monzogranite was emplaced in the early Permian with a crystallization age of 293.7 ± 4.6 Ma(MSWD = 1.06). Both granodiorites and monzogranite are I-type granites with A/CNK ratios of 0.92 -0.97 and 1.03 -1.06, respectively. They also show similar geochemical features of high HREE and Y contents, low Sr contents and Sr/Y ratios, as well as enrichment of Cs, Rb, Th and U, and depletion of Nb, Ta, P and Ti.These geochemical features indicate that the monzogranite and granodiorites were formed in an arc setting related to subduction. The gneissic monzogranites display high SiO_2 and K_2 O contents, and belong to the high-K calc-alkaline series. In the chondrite normalized REE distribution pattern, the monzogranite samples exhibit enrichment of LREE with strong negative Eu anomalies(σE u =0.44 -0.53), zircon εHf(t) values from +7.24 to +12.63 and two-stage Hf model ages of 463 -740 Ma. This suggests that the monzogranite was generated from the mixing of pelitic and mantle material. The granodiorite samples are calc-alkaline granites with lower contents of Si O_2 and Na_2 O + K_2 O, higher contents of TiO_2, Fe_2O_3~t, MgO and CaO compared to the monzogranite samples. They also show enrichment of LREE and moderate negative Eu anomalies(σE u= 0.54 =0.81), as well as slightly higher differentiation of LREE than that of HREE. The425 Ma granodiorite has zircon εHf(t) values from -0.51 to +1.98 and two-stage Hf model ages of 1133 -1240 Ma, whereas the 404 Ma granodiorite displays those of +2.52 to +7.50 and 816 -1071 Ma.Geochemistry and zircon Hf isotopic compositions indicate that granodiorites were formed by partial melting of juvenile lower crust. Together with regional geology and previous data, the geochemical and geochronological data of the monzogranite and granodiorites from this study suggest long-lived subduction and accretion along the Altai Orogen during ca. 425 -294 Ma.展开更多
Age calibrated deformation histories established by detailed mapping and dating of key magmatic time markers are correlated across all tectono-metamorphic provinces in the Damara Orogenic System.Correlations across st...Age calibrated deformation histories established by detailed mapping and dating of key magmatic time markers are correlated across all tectono-metamorphic provinces in the Damara Orogenic System.Correlations across structural belts result in an internally consistent deformation framework with evidence of stress field rotations with similar timing,and switches between different deformation events.Horizontal principle compressive stress rotated clockwise ~180°in total during Kaoko Belt evolution,and^135° during Damara Belt evolution.At most stages,stress field variation is progressive and can be attributed to events within the Damara Orogenic System,caused by changes in relative trajectories of the interacting Rio De La Plata,Congo,and Kalahari Cratons.Kaokoan orogenesis occurred earliest and evolved from collision and obduction at ~590 Ma,involving E-W directed shortening,progressing through different transpressional states with ~45° rotation of the stress field to strike-slip shear under NW-SE shortening at ~550-530 Ma.Damaran orogenesis evolved from collision at ~555-550 Ma with NW-SE directed shortening in common with the Kaoko Belt,and subsequently evolved through ~90°rotation of the stress field to NE-SW shortening at ~512-508 Ma.Both Kaoko and Damara orogenic fronts were operating at the same time,with all three cratons being coaxially convergent during the 550-530 Ma period;Rio De La Plata directed SE against the Congo Craton margin,and both together over-riding the Kalahari Craton margin also towards the SE.Progressive stress field rotation was punctuated by rapid and significant switches at ~530-525 Ma,~508 Ma and ~505 Ma.These three events included:(1)Culmination of main phase orogenesis in the Damara Belt,coinciding with maximum burial and peak metamorphism at 530-525 Ma.This occurred at the same time as termination of transpression and initiation of transtensional reactivation of shear zones in the Kaoko Belt.Principle compressive stress switched from NW-SE to NNW-SSE shortening in both Kaoko and Damara Belts at this time.This marks the start of Congo-Kalahari stress field overwhelming the waning Rio De La Plata-Congo stress field,and from this time forward contraction across the Damara Belt generated the stress field governing subsequent low-strain events in the Kaoko Belt.(2)A sudden switch to E-W directed shortening at ~508 Ma is interpreted as a far-field effect imposed on the Damara Orogenic System,most plausibly from arc obduction along the orogenic margin of Gondwana(Ross-Delamerian Orogen).(3)This imposed stress field established a N-S extension direction exploited by decompression melts,switch to vertical shortening,and triggered gravitational collapse and extension of the thermally weakened hot orogen core at ~505 Ma,producing an extensional metamorphic core complex across the Central Zone.展开更多
The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogen...The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogenic gold-bearing fault.This study investigated the major and trace-element compositions,zircon U-Pb dates and zircon Hf isotopic compositions of the Huanglonggou granodiorite.One Huanglonggou granodiorite sample yielded a weighted mean U-Pb zircon age of^221 Ma(Carnian).The Carnian granodiorite is metaluminous,with high alkalis contents of 6.37%--8.86%,high Al_2O_3contents of 15.41%--16.19%,high Sr contents of(426--475)×10^(-6),relatively high Sr/Y ratios,high(La/Yb)_Nvalues and low HREE,suggesting an adakite type high-Si O_2granite.The Huanglonggou granodiorite sample has zirconε_(Hf)(t)values ranging from-4.4 to+1.1.These Hf isotopic data suggest that the Carnian granodiorite was likely derived from the partial melting of subducted Paleo-Tethys oceanic slab.It is suggested that the Late Triassic granodiorite was emplaced during the northward subduction of Paleo-Tethys oceanic slab.Orogenic gold mineralization in the Wulonggou area formed after the emplacement of the Late Triassic intrusive rocks.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 East Kunlun terrain is located on the northern Qinghai—Tibet plateau, composed of the East Kunlun Mountain and the Qaidam Basin and bounded by the Qilian terrain on the north and Bayanhar—Songpan Ganze terrain o...The East Kunlun terrain is located on the northern Qinghai—Tibet plateau, composed of the East Kunlun Mountain and the Qaidam Basin and bounded by the Qilian terrain on the north and Bayanhar—Songpan Ganze terrain on the south. It is regarded as a composite orogenic belt characterized by having developed superimposed ductile tectonic regimes reflecting the collision orogeny during Early Paleozoic and Triassic periods. It has also experienced transformation from ductile to brittle deformation caused by the post orogeny, since Jurassic after the formation of the East Kunlun Mountain and the Qaidam Basin. A Paleozoic subduction complex zone was recently recognized along the north border of the East Kunlun terrain from Da Qaidam to Dulan (Xu,et al, 1 999). It is composed of ophiolite (of Early Paleozoic age?), tectonic melange and very high\|pressure metamorphic rocks with eclogite (\%p\%=2 2GPa, \%t\%=720℃) (Yang,et al.,1998) and garnet\|peridotite (\%p\%=2 5GPa, t =837℃). The Anyemaqin Triassic subduction complex zone trending in NWW\|SEE was developed along the eastern segment of the south border of the East Kunlun terrain. It is mainly composed of ultramafic and mafic rocks, pillow basalt, radiolaria\|bearing clastic rocks, tectonic melange and mylonite. The subduction complex zone contains a series of the southward overthrusting imbricated slices. Instead of this subduction complex zone, a 2 km\|wide sinistral strike\|slip ductile shear zone trending in E\|W was developed along the western segment. On the basis of macroscopic and microscopic studies on a series of structural sections, we divide the East Kunlun Mountain into four tectonic units as follows: (1) North Proterozoic Metamorphic Basement Zone; (2) South Early Paleozoic—Triassic Superimposed Fold Zone; (3) South Triassic Transpression Zone; (4) Anyemaqin Back\|Arc Decollement\|Thrust Zone.展开更多
To reveal the petrological characteristics, metamorphic evolution histon and tectonic setting of the pelitic granulites from Ailaoshan Orogen, Uest Yunnan, China, a comprehensive study in mineral chemistry, petrogeoch...To reveal the petrological characteristics, metamorphic evolution histon and tectonic setting of the pelitic granulites from Ailaoshan Orogen, Uest Yunnan, China, a comprehensive study in mineral chemistry, petrogeochemistry and geochronology studies is presented in this paper. Two metamorphic stages of the granulites can be established:(1) the peak metamorphism recorded by the mineral assemblage of garnet, kyanite, K-feidspar and rutile, and the initial retrograde metamorphism shown by the mineral assemblage of garnet, sillimanite, sapphirine, spinel, K-feldspar, plagioclase and biotite;(2) the superim-posed metamorphism recorded by the mineral assemblage of biotite, muscovite, plagioclase, quartz and ilmenite. Zircon LA-ICP-MS U-Pb dating indicates that the protolith of the granulite was deposited after 337 Ma. The initial retrograde metamorphism occurred at P-T conditions of 8.6-12 kbar at 850-920℃ estimated by mineral assemblages, the low pressure limit of kyanite stability and GBPQ geothermobarometer in Indosinian (about 235 Ma), and the late superimposed metamorphism occurred at the P-T condition of 3.5-3.9 kbar at 572-576℃ estimated by GBPQ geothermobarometer since 33Ma. The first stage was related to the amalgamation of the South China and Indochina blocks during the Triassic, and the second stage was possibly related with the large scale sinistral slip-shearing since the Oligocene. It is inferred that the upper continental crust was suhducted/underthrusted to the lower continental crust (deeper than 30 km) and underwent granulite-facies metamorphism and then quickly exhumed to the middle-upper crust (10-12 km) and initial retrograde metamorphism occurred due to the collision of the Indochina and South China blocks during Indosinian, which was followed by superimposition of the second stage of metamorphism since the Oligocene.展开更多
Basin and orogenic belt belong to the same tectonic system which has close connections in spatial distribution and dynamic mechanism.Structural styles analysis of basin－ range system， not only may rebuild basin－ ra...Basin and orogenic belt belong to the same tectonic system which has close connections in spatial distribution and dynamic mechanism.Structural styles analysis of basin－ range system， not only may rebuild basin－ range coupling process and landscape evolution of orogenic belt and its adjacent basin， but also become the foundation in exploring how orogenesis controls landform,climate,resources,energy and environment etc.In the light of geodynamic mechanism,three main types of basin－ range system may be classified,namely,stretch,compression and strike－ slip.In combination with their geotectonic settings and plate movement phases, a comprehensive classification scheme may be educed for structural styles of basin－ range system.Natural disasters and geo－ ecological environment in the Yangtze Valley have been restricted and impressed by crustal movement and Qinling－ Dabie etc.orogenesis since the Mesozoic and Cenozoic.In terms of collocating relation and contacting basin prototype and orogenic belt around the basin for cause of formation, typical structural styles of basin－ range system on the central orogenic chain within the Yangtze Valley consist of coupling Tongbo－ Dabie orogenic belt and Jianghan－ Dongtin fault basin on the northern margin of the central Yangtze landmass， and coupling Qinling－ Daba mountain margin thrust－ faulted orogenic belt and Sichuan foreland basin on the northern margin of upper－ Yangtze landmass.The paper analyzes evolutionary features of two typical structural styles of basin－ range system during syn－ orogenic, late－ orogenic and post－ orogenic stages,and probes into their dynamic mechanism.It is emphasized that,in different stages of basin－ range system of different properties and basin－ mountain transformation process,different structural styles may be formed;and different associations of structural styles can form different types of natural disasters complex and eco－ environment systems.展开更多
The Narooma-Batemans Bay(NBB)area along the southeast coast of Australia is a part of the eastern zone of the Early Paleozoic Lachlan Orogen.In the NBB,a set of rock association consisting of turbidites,siliceous rock...The Narooma-Batemans Bay(NBB)area along the southeast coast of Australia is a part of the eastern zone of the Early Paleozoic Lachlan Orogen.In the NBB,a set of rock association consisting of turbidites,siliceous rock,basic lava,and argillaceous melange zone is mainly developed.According to systematic field geological survey,the deformation of 3 stages(D1,D2,and D3)was identified in the NBB.At stage D1,with the original bedding S0 in a nearly east-west trending as the deformation plane,tight folds,isoclinal folds,and other structures formed in the NBB accompanied by structural transposition.As a result,crenulation cleavage developed along the axial plane of the folds and schistosity S1 formed.At stage D2,with north-south-trending schistosity S1 as the deformation plane,a large number of asymmetrical folds and rotated porphyroclasts formed owing to thrusting and shear.At stage D3,leftlateral strike-slip occurred along the main north-south-trending schistosity.Based on the analysis of the characteristics of tectonic deformation in the NBB and summary of previous research results,it is determined that the early-stage(D1)deformation is related to Ordovician Macquarie arc-continent collision and the deformation at stages D2 and D3 is the result of the westward subduction of Paleo-Pacific Plate.That is,it is not the continuous westward subduction of the Paleo-Pacific Plate that constitutes the evolution model of the NBB as previously considered.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
The end-Permian to Early–Middle Triassic magmatic rocks in Inner Mongolia can provide valuable insights into the relationships between the collisional processes and the magmatic responses during the final orogenic ev...The end-Permian to Early–Middle Triassic magmatic rocks in Inner Mongolia can provide valuable insights into the relationships between the collisional processes and the magmatic responses during the final orogenic evolution of Xing-Meng orogenic belt(XMOB). This paper presents zircon U-Pb ages and Hf isotopes, whole rock geochemical and Sr-Nd-Pb isotopic data for the Early–Middle Triassic diabases and monzogranites from the Langshan area, southwestern XMOB. Our results suggest that the studied diabases and monzogranites were respectively formed during Early Triassic and Middle Triassic. The Early Triassic diabases are characterized by "arc-like" geochemical signatures, including enrichment in Rb, U and K, and depletion in Nb, Ta, P and Ti. They have negative to weak positive εNd(t) values(-3.1 to +1.5) and relatively high initial ratios of 208 Pb/204 Pb(35.968–37.346), 207 Pb/204 Pb(15.448–15.508) and 206 Pb/204 Pb(16.280–17.492), indicating a subduction-metasomatized enriched lithospheric mantle source. Their low Ba/Rb(2.72–6.56), Ce/Y(0.97–1.39) and(Tb/Yb)N ratios(1.31–1.45) suggest that the parental magma was likely originated from low degree partial melting of the phlogopite-bearing lherzolite in a spinel-stability field. The Middle Triassic monzogranites show high Sr/Y ratios, low Mg O, Cr and Ni contents, high Zr/Sm ratios(40–64), negative zircon εHf(t) values(-25.8 to-8.8), as well as relatively flat heavy rare earth element patterns. They were likely derived from low degree partial melting of a moderately thickened ancient lower crust. The diabases and the slightly postdated high Sr/Y granites in this study represent the magmatic responses to the final orogenic evolution in the southwestern XMOB. Together with regional works, we propose that the slab break-off of the Paleo-Asian oceanic lithosphere following the terminal collision between the North China Craton and the South Mongolia terranes triggered asthenospheric upwelling, and the ongoing convergence further initiated moderately crustal thickening and uplift in the XMOB.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
A 3D model of deep crustal structure of the Archaean Karelia Craton and late Palaeoproterozoic Svecofennian Accretionary Orogen including the boundary zone is presented.The model is based on the combination of data fr...A 3D model of deep crustal structure of the Archaean Karelia Craton and late Palaeoproterozoic Svecofennian Accretionary Orogen including the boundary zone is presented.The model is based on the combination of data from geological mapping and reflection seismic studies,along profiles 1-EU,4 B,FIRE-1-2 a-2 and FIRE-3-3 a,and uses results of magnetotelluric soundings in southern Finland and northern Karelia.A seismogeological model of the crust and crust-mantle boundary is compared with a model of subhorizontal velocity-density layering of the crust.The TTG-type crust of the Palaeoarchaean and Mesoarchaean microcontinents within the Karelia Craton and the Belomorian Province are separated by gently dipping greenstone belts,at least some of which are palaeosutures.The structure of the crust was determined mainly by Palaeoproterozoic tectonism in the intracontinental settings modified by a strong collisional compression at the end of the Palaeoproterozoic.New insights into structure,origin and evolution of the Svecofennian Orogen are provided.The accretionary complex is characterized by inclined tectonic layering:the tectonic sheets,~15 km thick,are composed of volcanic-sedimentary rocks,including electro-conductive graphite-bearing sedimentary rocks,and electro-resistive granitoids,which plunge monotonously and consecutively eastward.Upon reaching the level of the lower crust,the tectonic sheets of the accretionary complex lose their distinct outlines.In the seismic reflection pattern they are replaced by a uniform acoustically translucent medium,where separate sheets can only be traced fragmentarily.The crust-mantle boundary bears a diffuse character:the transition from crust to mantle is recorded by the disappearance of the vaguely drawn boundaries of the tectonic sheets and in the gradual transition of acoustically homogeneous and translucent lower crust into transparent mantle.Under the effect of endogenic heat flow,the accretionary complex underwent high-temperature metamorphism and partial melting.Blurring of the rock contacts,which in the initial state created contrasts of acoustic impedance,was caused by partial melting and mixing of melts.The 3 D model is used as a starting point for the evolutionary model of the Svecofennian Accretionary Orogen and for determination of its place in the history of the Palaeoproterozoic Lauro-Russian intracontinental orogeny,which encompassed a predominant part of the territory of Lauroscandia,a palaeocontinent combining North American and East European cratons.The model includes three stages in the evolution of the Lauro-Russian Orogen(-2.5,2.2-2.1 and 1.95-1.87 Ga).The main feature of the Palaeoproterozoic evolution of the accretionary Svecofennian Orogen and Lauroscandia as a whole lay in the causal link with evolution of a superplume,which initiated plate-tectonic events.The Svecofennian-Pre-Labradorian palaeo-ocean originated in the superplume axial zone;the accretionary orogens were formed along both continental margins due to closure of the palaeo-ocean.展开更多
基金This study was financially supported by the Special Fund for Land and Resources Scientific Research of Public Interest(201511020)the Natural Science Foundation of Shaanxi Province(2017JM4002)Natural Science Foundation of China(41873053).
文摘The Eastern Kunlun Orogenic Belt(EKOB)has a complex geological structure and diverse magmatic activities,which are closely related to the Qaidam Basin and the Tethys tectonic evolution.There are at least 3 stages mafic-ultramafic rocks occurred in the Early Paleozoic in EKOB.The first stage is the Later-Silurian to Early Devonian,represented by the giant Xiarihamu super large magmatic Cu-Ni deposit,containing about 1.18 million metric tons(Mt)of nickel with average grades of 0.65%Ni,and its age of ore-forming pyroxene peridotite is 411 Ma;The second stage is the Early Carboniferous,represented by the large Shitoukengde magmatic Cu-Ni sulfide deposit,and its ore-forming age of the olivine websterite is 334 Ma;The third stage of mafic-ultramafic rocks occurred mainly during the Middle-Late Triassic,represented by Xiaojianshan,Lalinggaoli,and Kaimuqi complexes,and no economical ore bodies have been found in this period.The authors summarized the difference between the ore-bearing and the nonmineralized mafic-ultramafic rocks in the EKOB.The olivine of the ore-bearing complexes contains higher MgO and SiO2 content but lower FeO and CaO contents,and the clinopyroxene of ore-bearing complexes contains lower FeO and CaO contents.Crustal sulfur contamination is key to the formation of the giant Xiarihamu Ni deposit,and crustal sulfur contamination degree of the giant magmatic Ni deposit is higher than that of large Ni deposit.The above indicators could guide the exploration and evaluation of similar deposits in the EKOB.
基金funded by the National 305 Project of China (2018A03004-1, 2015BAB05B01-02)the Fundamental Research Fund for Central Universities(B16020127)
文摘The West Kunlun orogenic belt(WKOB) along the northern margin of the Tibetan Plateau is important for understanding the evolution of the Proto-and Paleo-Tethys oceans. Previous investigations have focused on the igneous rocks and ophiolites distributed mostly along the Xinjiang-Tibet road and the China-Pakistan road, and have constructed a preliminary tectonic model for this orogenic belt. However, few studies have focused on the so-called Precambrian basement in this area. As a result, the tectonic affinity of the individual terranes of the WKOB and their detailed evolution process are uncertain. Here we report new field observations, zircon and monazite U-Pb ages of the "Precambrian basement" of the South Kunlun terrane(SKT) and the Tianshuihai terrane(TSHT), two major terranes in the WKOB. Based on new zircon U-Pb age data, the amphibolite-facies metamorphosed volcanosedimentary sequence within SKT was deposited during the late Neoproterozoic to Cambrian(600-500 Ma), and the flysch-affinity Tianshuihai Group, as the basement of the TSHT, was deposited during the late Neoproterozoic rather than Mesoproterozoic. The rock association of the volcano-sedimentary sequence within SKT suggests a large early Paleozoic accretionary wedge formed by the long-term lowangle southward subduction of the Proto-Tethys Ocean between Tarim and TSHT. The amphibolitefacies metamorphism in SKT occurred at ca. 440 Ma. This ca. 440 Ma metamorphism is genetically related to the closure of the Proto-Tethys Ocean between Tarim and the Tianshuihai terrane, which led to the assembly of Tarim to Eastern Gondwana and the final formation of the Gondwana. Since the late Paleozoic to early Mesozoic, the northward subduction of the Paleo-Tethys Ocean along the HongshihuQiaoertianshan belt produced the voluminous early Mesozoic arc-signature granites along the southern part of NKT-TSHT. The Paleo-Tethys ocean between TSHT and Karakorum closed at ca. 200 Ma, as demonstrated by the monazite age of the paragneiss in the Kangxiwa Group. Our study does not favor the existence of a Precambrian basement in SKT.
基金Supported by Qinghai Provincial Geological Exploration Special Fund Project(No.2023085029KY004).
文摘The Mailong gold deposit is located in the eastern section of the East Kunlun orogenic belt and is one of the recently discovered important gold polymetallic deposits in the Qinhai Gouli region.The primary host rocks of the Mailong gold deposit consist of intermediate-acid intrusive rocks from the Varisian and Indosinian periods,as well as the Precambrian Jinshuikou Group,with mineralization controlled by northeast and northwest faults.The alteration of the host rocks is mainly characterized by silicification,sericitization,chloritization,and carbonatization.Based on the cross-cutting relationships of the veins,the hydrothermal mineralization of the gold deposit can be categorized into three stages:the quartz-pyrite stage,the quartzpolymetallic sulfide stage,and the quartz-carbonate stage.Microthermometry of fluid inclusions indicates that the Mailong gold deposit belongs to a low-density(0.73–0.86 g/cm3),medium-temperature(240–340℃),and medium-salinity(4.01–10.74 wt%NaCl)NaCl-CO2-H2O fluid system.The C-H-O isotopic analysis suggests that the mineralizing fluids is derived from magmatic water,with later contributions from atmospheric precipitation.In-situ S isotopic results indicate that the mineralizing materials mainly derive from igneous rocks.A comprehensive analysis concludes that the Mailong gold deposit is a mesothermal hydrothermal vein-type gold deposit controlled by structural factors.
文摘Based on field investigation in 1999, two deformational domains with d ifferent dynamics have been distinguished from the Jurassic geological outcrops in the Mohe area of NE China, i.e. northern ductile and southern plastic-brittl e ones. Their deformational features are stated in this paper. And then, three st ages of structural deformation of the area relative to the late Mesozoic orogeni c processes of Mongolian-Okhotsk orogen are reconstructed as follows, (1) south w ards thrusting in the middle-late Jurassic, (2) eastwards thrusting and strike -s lipping parallel to the orogen in the late Jurassic, and (3) southeastwards thru sting in the early Cretaceous.
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supported by grants from National Key R&D Program of China (2017YFC0601302)the NSF of China (41672214)Geological Survey Project of China Geological Survey (DD20189612, DD20190004).
文摘Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andeantype active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two-mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U-Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two-mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean(PAO) and represents a suture between the North China craton(NCC) and Central Asian Orogenic Belt(CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400–420 Ma. Magmatism of the second stage in 380–390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes-type active continental margin of the CAOB has been proposed, including a development of the subduction-free PAO before 446 Ma, a subduction of the PAO and arc-related magmatism during 446–380 Ma, and formation of a molasse basin during 380–360 Ma.
文摘Ludong orogenic belt in China is an importantal continent collision orogenic belt in eastern Asia, between Sino Korean landmass and Yangtze landmass. The host rock of the orogenic belt is metamorphosed medium acidic intrusive complexes, which can be divided into four types, that’s, quartz dioritz, granite dioritz, monzonitic granite and undertint monzonitic granite, principal minerals are plagioclases, potassium feldspars and quartzs, minor minerals are hornblendes, biotites, clinopyxenes and garnets, accessory mineral types and assemblages are very similar, specially, various rocks are mainly fine grained textures. They have the history of regional amphibolite facies metamorphism and deep middle shallow structural layer deformation, and are changed into various gneiss and tectonic system. There are many xenolithes of middle Proterozoic eclogite host rock extrahigh high pressure metamorphic complexes, a small xenolithes of early Proterozoic layered metamorphite system and granulites, and ultrabasic basic rocks of various epoches in the metamorphosed medium acidic intrusive complexes.
基金Financial support for this study was jointly provided by the National Natural Science Foundation of China (Grant Nos. 41421002, 41225008, 41702231)Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT1281)MOST Special Fund from the State Key Laboratory of Continental Dynamics, Northwest University, China
文摘The Chinese Altai in northwestern Xinjiang has numerous outcrops of granitoids which provide critical information on accretionary orogenic processes and crustal growth of the Central Asian Orogenic Belt.Zircon U-Pb ages, Hf-isotopic compositions and whole-rock geochemistry of monzogranite and granodiorites in the Qinghe County are employed to elucidate Paleozoic tectonics of the Chinese Altai. Granodiorites have crystallization ages of 424.6 ± 3.1 Ma(MSWD = 0.23) and 404.0 ± 3.4 Ma(MSWD = 0.18);monzogranite was emplaced in the early Permian with a crystallization age of 293.7 ± 4.6 Ma(MSWD = 1.06). Both granodiorites and monzogranite are I-type granites with A/CNK ratios of 0.92 -0.97 and 1.03 -1.06, respectively. They also show similar geochemical features of high HREE and Y contents, low Sr contents and Sr/Y ratios, as well as enrichment of Cs, Rb, Th and U, and depletion of Nb, Ta, P and Ti.These geochemical features indicate that the monzogranite and granodiorites were formed in an arc setting related to subduction. The gneissic monzogranites display high SiO_2 and K_2 O contents, and belong to the high-K calc-alkaline series. In the chondrite normalized REE distribution pattern, the monzogranite samples exhibit enrichment of LREE with strong negative Eu anomalies(σE u =0.44 -0.53), zircon εHf(t) values from +7.24 to +12.63 and two-stage Hf model ages of 463 -740 Ma. This suggests that the monzogranite was generated from the mixing of pelitic and mantle material. The granodiorite samples are calc-alkaline granites with lower contents of Si O_2 and Na_2 O + K_2 O, higher contents of TiO_2, Fe_2O_3~t, MgO and CaO compared to the monzogranite samples. They also show enrichment of LREE and moderate negative Eu anomalies(σE u= 0.54 =0.81), as well as slightly higher differentiation of LREE than that of HREE. The425 Ma granodiorite has zircon εHf(t) values from -0.51 to +1.98 and two-stage Hf model ages of 1133 -1240 Ma, whereas the 404 Ma granodiorite displays those of +2.52 to +7.50 and 816 -1071 Ma.Geochemistry and zircon Hf isotopic compositions indicate that granodiorites were formed by partial melting of juvenile lower crust. Together with regional geology and previous data, the geochemical and geochronological data of the monzogranite and granodiorites from this study suggest long-lived subduction and accretion along the Altai Orogen during ca. 425 -294 Ma.
基金a largely self-funded 1TAR projectsupported by ARC grants A00103456+1 种基金DP0210178 to Prof.David GrayNSF grants EAR0440188 and EAR0738874 to Prof.David Foster
文摘Age calibrated deformation histories established by detailed mapping and dating of key magmatic time markers are correlated across all tectono-metamorphic provinces in the Damara Orogenic System.Correlations across structural belts result in an internally consistent deformation framework with evidence of stress field rotations with similar timing,and switches between different deformation events.Horizontal principle compressive stress rotated clockwise ~180°in total during Kaoko Belt evolution,and^135° during Damara Belt evolution.At most stages,stress field variation is progressive and can be attributed to events within the Damara Orogenic System,caused by changes in relative trajectories of the interacting Rio De La Plata,Congo,and Kalahari Cratons.Kaokoan orogenesis occurred earliest and evolved from collision and obduction at ~590 Ma,involving E-W directed shortening,progressing through different transpressional states with ~45° rotation of the stress field to strike-slip shear under NW-SE shortening at ~550-530 Ma.Damaran orogenesis evolved from collision at ~555-550 Ma with NW-SE directed shortening in common with the Kaoko Belt,and subsequently evolved through ~90°rotation of the stress field to NE-SW shortening at ~512-508 Ma.Both Kaoko and Damara orogenic fronts were operating at the same time,with all three cratons being coaxially convergent during the 550-530 Ma period;Rio De La Plata directed SE against the Congo Craton margin,and both together over-riding the Kalahari Craton margin also towards the SE.Progressive stress field rotation was punctuated by rapid and significant switches at ~530-525 Ma,~508 Ma and ~505 Ma.These three events included:(1)Culmination of main phase orogenesis in the Damara Belt,coinciding with maximum burial and peak metamorphism at 530-525 Ma.This occurred at the same time as termination of transpression and initiation of transtensional reactivation of shear zones in the Kaoko Belt.Principle compressive stress switched from NW-SE to NNW-SSE shortening in both Kaoko and Damara Belts at this time.This marks the start of Congo-Kalahari stress field overwhelming the waning Rio De La Plata-Congo stress field,and from this time forward contraction across the Damara Belt generated the stress field governing subsequent low-strain events in the Kaoko Belt.(2)A sudden switch to E-W directed shortening at ~508 Ma is interpreted as a far-field effect imposed on the Damara Orogenic System,most plausibly from arc obduction along the orogenic margin of Gondwana(Ross-Delamerian Orogen).(3)This imposed stress field established a N-S extension direction exploited by decompression melts,switch to vertical shortening,and triggered gravitational collapse and extension of the thermally weakened hot orogen core at ~505 Ma,producing an extensional metamorphic core complex across the Central Zone.
基金Supported by Project of National Natural Science Foundation of China(No.41572056)
文摘The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogenic gold-bearing fault.This study investigated the major and trace-element compositions,zircon U-Pb dates and zircon Hf isotopic compositions of the Huanglonggou granodiorite.One Huanglonggou granodiorite sample yielded a weighted mean U-Pb zircon age of^221 Ma(Carnian).The Carnian granodiorite is metaluminous,with high alkalis contents of 6.37%--8.86%,high Al_2O_3contents of 15.41%--16.19%,high Sr contents of(426--475)×10^(-6),relatively high Sr/Y ratios,high(La/Yb)_Nvalues and low HREE,suggesting an adakite type high-Si O_2granite.The Huanglonggou granodiorite sample has zirconε_(Hf)(t)values ranging from-4.4 to+1.1.These Hf isotopic data suggest that the Carnian granodiorite was likely derived from the partial melting of subducted Paleo-Tethys oceanic slab.It is suggested that the Late Triassic granodiorite was emplaced during the northward subduction of Paleo-Tethys oceanic slab.Orogenic gold mineralization in the Wulonggou area formed after the emplacement of the Late Triassic intrusive rocks.
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).
文摘The East Kunlun terrain is located on the northern Qinghai—Tibet plateau, composed of the East Kunlun Mountain and the Qaidam Basin and bounded by the Qilian terrain on the north and Bayanhar—Songpan Ganze terrain on the south. It is regarded as a composite orogenic belt characterized by having developed superimposed ductile tectonic regimes reflecting the collision orogeny during Early Paleozoic and Triassic periods. It has also experienced transformation from ductile to brittle deformation caused by the post orogeny, since Jurassic after the formation of the East Kunlun Mountain and the Qaidam Basin. A Paleozoic subduction complex zone was recently recognized along the north border of the East Kunlun terrain from Da Qaidam to Dulan (Xu,et al, 1 999). It is composed of ophiolite (of Early Paleozoic age?), tectonic melange and very high\|pressure metamorphic rocks with eclogite (\%p\%=2 2GPa, \%t\%=720℃) (Yang,et al.,1998) and garnet\|peridotite (\%p\%=2 5GPa, t =837℃). The Anyemaqin Triassic subduction complex zone trending in NWW\|SEE was developed along the eastern segment of the south border of the East Kunlun terrain. It is mainly composed of ultramafic and mafic rocks, pillow basalt, radiolaria\|bearing clastic rocks, tectonic melange and mylonite. The subduction complex zone contains a series of the southward overthrusting imbricated slices. Instead of this subduction complex zone, a 2 km\|wide sinistral strike\|slip ductile shear zone trending in E\|W was developed along the western segment. On the basis of macroscopic and microscopic studies on a series of structural sections, we divide the East Kunlun Mountain into four tectonic units as follows: (1) North Proterozoic Metamorphic Basement Zone; (2) South Early Paleozoic—Triassic Superimposed Fold Zone; (3) South Triassic Transpression Zone; (4) Anyemaqin Back\|Arc Decollement\|Thrust Zone.
基金supported by the National Natural Science Foundation of China (Nos. 91755101, 41272219)the Chinese Ministry of Science and Technology (No. Sinoprobe-05-03)the China Geological Survey (No. DD20160022-07)
文摘To reveal the petrological characteristics, metamorphic evolution histon and tectonic setting of the pelitic granulites from Ailaoshan Orogen, Uest Yunnan, China, a comprehensive study in mineral chemistry, petrogeochemistry and geochronology studies is presented in this paper. Two metamorphic stages of the granulites can be established:(1) the peak metamorphism recorded by the mineral assemblage of garnet, kyanite, K-feidspar and rutile, and the initial retrograde metamorphism shown by the mineral assemblage of garnet, sillimanite, sapphirine, spinel, K-feldspar, plagioclase and biotite;(2) the superim-posed metamorphism recorded by the mineral assemblage of biotite, muscovite, plagioclase, quartz and ilmenite. Zircon LA-ICP-MS U-Pb dating indicates that the protolith of the granulite was deposited after 337 Ma. The initial retrograde metamorphism occurred at P-T conditions of 8.6-12 kbar at 850-920℃ estimated by mineral assemblages, the low pressure limit of kyanite stability and GBPQ geothermobarometer in Indosinian (about 235 Ma), and the late superimposed metamorphism occurred at the P-T condition of 3.5-3.9 kbar at 572-576℃ estimated by GBPQ geothermobarometer since 33Ma. The first stage was related to the amalgamation of the South China and Indochina blocks during the Triassic, and the second stage was possibly related with the large scale sinistral slip-shearing since the Oligocene. It is inferred that the upper continental crust was suhducted/underthrusted to the lower continental crust (deeper than 30 km) and underwent granulite-facies metamorphism and then quickly exhumed to the middle-upper crust (10-12 km) and initial retrograde metamorphism occurred due to the collision of the Indochina and South China blocks during Indosinian, which was followed by superimposition of the second stage of metamorphism since the Oligocene.
基金This paper is one of achievements of the Chinese Academy of Sciences " Knowledge Innovation Project" item(KZCX2- 113).
文摘Basin and orogenic belt belong to the same tectonic system which has close connections in spatial distribution and dynamic mechanism.Structural styles analysis of basin－ range system， not only may rebuild basin－ range coupling process and landscape evolution of orogenic belt and its adjacent basin， but also become the foundation in exploring how orogenesis controls landform,climate,resources,energy and environment etc.In the light of geodynamic mechanism,three main types of basin－ range system may be classified,namely,stretch,compression and strike－ slip.In combination with their geotectonic settings and plate movement phases, a comprehensive classification scheme may be educed for structural styles of basin－ range system.Natural disasters and geo－ ecological environment in the Yangtze Valley have been restricted and impressed by crustal movement and Qinling－ Dabie etc.orogenesis since the Mesozoic and Cenozoic.In terms of collocating relation and contacting basin prototype and orogenic belt around the basin for cause of formation, typical structural styles of basin－ range system on the central orogenic chain within the Yangtze Valley consist of coupling Tongbo－ Dabie orogenic belt and Jianghan－ Dongtin fault basin on the northern margin of the central Yangtze landmass， and coupling Qinling－ Daba mountain margin thrust－ faulted orogenic belt and Sichuan foreland basin on the northern margin of upper－ Yangtze landmass.The paper analyzes evolutionary features of two typical structural styles of basin－ range system during syn－ orogenic, late－ orogenic and post－ orogenic stages,and probes into their dynamic mechanism.It is emphasized that,in different stages of basin－ range system of different properties and basin－ mountain transformation process,different structural styles may be formed;and different associations of structural styles can form different types of natural disasters complex and eco－ environment systems.
基金This research was supported financially by the National Natural Science(41702213)Fundamental Research Funds of the Chinese Academy of Geological Sciences(K1614,YYWF201709).
文摘The Narooma-Batemans Bay(NBB)area along the southeast coast of Australia is a part of the eastern zone of the Early Paleozoic Lachlan Orogen.In the NBB,a set of rock association consisting of turbidites,siliceous rock,basic lava,and argillaceous melange zone is mainly developed.According to systematic field geological survey,the deformation of 3 stages(D1,D2,and D3)was identified in the NBB.At stage D1,with the original bedding S0 in a nearly east-west trending as the deformation plane,tight folds,isoclinal folds,and other structures formed in the NBB accompanied by structural transposition.As a result,crenulation cleavage developed along the axial plane of the folds and schistosity S1 formed.At stage D2,with north-south-trending schistosity S1 as the deformation plane,a large number of asymmetrical folds and rotated porphyroclasts formed owing to thrusting and shear.At stage D3,leftlateral strike-slip occurred along the main north-south-trending schistosity.Based on the analysis of the characteristics of tectonic deformation in the NBB and summary of previous research results,it is determined that the early-stage(D1)deformation is related to Ordovician Macquarie arc-continent collision and the deformation at stages D2 and D3 is the result of the westward subduction of Paleo-Pacific Plate.That is,it is not the continuous westward subduction of the Paleo-Pacific Plate that constitutes the evolution model of the NBB as previously considered.
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 Geological Survey of China (No. 1212011085490)the National Natural Science Foundation of China (No. 41421002)
文摘The end-Permian to Early–Middle Triassic magmatic rocks in Inner Mongolia can provide valuable insights into the relationships between the collisional processes and the magmatic responses during the final orogenic evolution of Xing-Meng orogenic belt(XMOB). This paper presents zircon U-Pb ages and Hf isotopes, whole rock geochemical and Sr-Nd-Pb isotopic data for the Early–Middle Triassic diabases and monzogranites from the Langshan area, southwestern XMOB. Our results suggest that the studied diabases and monzogranites were respectively formed during Early Triassic and Middle Triassic. The Early Triassic diabases are characterized by "arc-like" geochemical signatures, including enrichment in Rb, U and K, and depletion in Nb, Ta, P and Ti. They have negative to weak positive εNd(t) values(-3.1 to +1.5) and relatively high initial ratios of 208 Pb/204 Pb(35.968–37.346), 207 Pb/204 Pb(15.448–15.508) and 206 Pb/204 Pb(16.280–17.492), indicating a subduction-metasomatized enriched lithospheric mantle source. Their low Ba/Rb(2.72–6.56), Ce/Y(0.97–1.39) and(Tb/Yb)N ratios(1.31–1.45) suggest that the parental magma was likely originated from low degree partial melting of the phlogopite-bearing lherzolite in a spinel-stability field. The Middle Triassic monzogranites show high Sr/Y ratios, low Mg O, Cr and Ni contents, high Zr/Sm ratios(40–64), negative zircon εHf(t) values(-25.8 to-8.8), as well as relatively flat heavy rare earth element patterns. They were likely derived from low degree partial melting of a moderately thickened ancient lower crust. The diabases and the slightly postdated high Sr/Y granites in this study represent the magmatic responses to the final orogenic evolution in the southwestern XMOB. Together with regional works, we propose that the slab break-off of the Paleo-Asian oceanic lithosphere following the terminal collision between the North China Craton and the South Mongolia terranes triggered asthenospheric upwelling, and the ongoing convergence further initiated moderately crustal thickening and uplift in the XMOB.
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the RF state project(No.0135-2019-0036)partly supported by the project(No.0135-20180039)of the Program of the Presidium of the RAS“Fundamental problems of geological and geophysical study of lithospheric processes”the Russian Foundation for Basic Research for supporting project(No.19-05-00336)。
文摘A 3D model of deep crustal structure of the Archaean Karelia Craton and late Palaeoproterozoic Svecofennian Accretionary Orogen including the boundary zone is presented.The model is based on the combination of data from geological mapping and reflection seismic studies,along profiles 1-EU,4 B,FIRE-1-2 a-2 and FIRE-3-3 a,and uses results of magnetotelluric soundings in southern Finland and northern Karelia.A seismogeological model of the crust and crust-mantle boundary is compared with a model of subhorizontal velocity-density layering of the crust.The TTG-type crust of the Palaeoarchaean and Mesoarchaean microcontinents within the Karelia Craton and the Belomorian Province are separated by gently dipping greenstone belts,at least some of which are palaeosutures.The structure of the crust was determined mainly by Palaeoproterozoic tectonism in the intracontinental settings modified by a strong collisional compression at the end of the Palaeoproterozoic.New insights into structure,origin and evolution of the Svecofennian Orogen are provided.The accretionary complex is characterized by inclined tectonic layering:the tectonic sheets,~15 km thick,are composed of volcanic-sedimentary rocks,including electro-conductive graphite-bearing sedimentary rocks,and electro-resistive granitoids,which plunge monotonously and consecutively eastward.Upon reaching the level of the lower crust,the tectonic sheets of the accretionary complex lose their distinct outlines.In the seismic reflection pattern they are replaced by a uniform acoustically translucent medium,where separate sheets can only be traced fragmentarily.The crust-mantle boundary bears a diffuse character:the transition from crust to mantle is recorded by the disappearance of the vaguely drawn boundaries of the tectonic sheets and in the gradual transition of acoustically homogeneous and translucent lower crust into transparent mantle.Under the effect of endogenic heat flow,the accretionary complex underwent high-temperature metamorphism and partial melting.Blurring of the rock contacts,which in the initial state created contrasts of acoustic impedance,was caused by partial melting and mixing of melts.The 3 D model is used as a starting point for the evolutionary model of the Svecofennian Accretionary Orogen and for determination of its place in the history of the Palaeoproterozoic Lauro-Russian intracontinental orogeny,which encompassed a predominant part of the territory of Lauroscandia,a palaeocontinent combining North American and East European cratons.The model includes three stages in the evolution of the Lauro-Russian Orogen(-2.5,2.2-2.1 and 1.95-1.87 Ga).The main feature of the Palaeoproterozoic evolution of the accretionary Svecofennian Orogen and Lauroscandia as a whole lay in the causal link with evolution of a superplume,which initiated plate-tectonic events.The Svecofennian-Pre-Labradorian palaeo-ocean originated in the superplume axial zone;the accretionary orogens were formed along both continental margins due to closure of the palaeo-ocean.
