Determining the evolutionary history of the Permian-Triassic Kunlun-Qaidam Continental Arc is essential to understanding the subduction and closure processes of the South Kunlun Ocean.In this paper,we utilize(La/Yb)N ...Determining the evolutionary history of the Permian-Triassic Kunlun-Qaidam Continental Arc is essential to understanding the subduction and closure processes of the South Kunlun Ocean.In this paper,we utilize(La/Yb)N ratios collected from a fi ltered geochemical dataset on Permian to Triassic calc-alkaline rocks(55 wt%–68 wt%SiO_(2))and plutonic rocks within the Kunlun-Qaidam Continental Arc to reconstruct the spatiotemporal variation of the relative crustal thickness.Combined with known geologic observations,we discuss the subduction-accretionary tectonics of the South Kunlun Ocean and the topographic evolution of the Kunlun-Qaidam Continental Arc.Two episodes of crustal thickening and thinning were revealed.The reconstructed thickness reveals two crustal thickening and thinning events for the Kunlun-Qaidam Continental Arc from ca.270 to 210 Ma.The southern sector of the Kunlun-Qaidam Continental Arc is about 7 km thicker than the northern portion,with a maximum thickness of about 55 km at ca.270 and 230 Ma.The ca.270 and 230 Ma crustal thickening events coincide with renewed northward subduction of the South Kunlun Ocean plate and ocean closure,respectively,whereas the ca.270‒240 Ma and ca.230‒210 Ma crustal thinning events may refl ect slab break-off of the oceanic plate and lithospheric collapse during the post-collision extension,respectively.展开更多
In the western segment of the East Kunlun Orogen(WEKO),muscovite granite and garnet granite from the Hureguole intrusion exhibit zircon U-Pb ages of 435-442 Ma.Geochemically,these rocks contain high concentrations of ...In the western segment of the East Kunlun Orogen(WEKO),muscovite granite and garnet granite from the Hureguole intrusion exhibit zircon U-Pb ages of 435-442 Ma.Geochemically,these rocks contain high concentrations of SiO_(2),K_(2)O and Al_(2)O_(3),with low concentrations of TiO_(2)and MgO,indicating a peraluminous high-K calc-alkaline affinity.They are enriched in Rb,Th,U and LREE,depleted in Eu,Ba,Sr and Ti,being classified as S-type granites.Negative whole-rockε_(Nd)(t)values(-9.8 to-9.1)and zirconε_(Hf)(t)values(-11.6 to-8.2)for those granites indicate that they were derived from partial melting of pelitic rocks in the Paleoproterozoic Baishahe Formation of the Jinshuikou Group.Based on the collected zircon ages,Cambrian-Devonian magmatic activity in the WEKO was divided into three stages:early(446-520 Ma),middle(427-441 Ma)and late(372-424 Ma)stages.Statistically,whole-rock Nd and zircon Hf isotope data(ε_(Nd)(t)/T_(DM)^(Nd),ε_(Hf)(t)/T_(DMC)^(Hf))from Paleozoic igneous rocks in the WEKO reveal a magma source that was initially dominated by depleted mantle components in the northward subduction stage of the Proto-Tethy an Ocean plate(446-520 Ma),shifting to predominantly crustal sources during the closure period of the North Qimantagh back-arc basin(427-441 Ma),then to crust-mantle mixed sources in the post-collision stage(372-424 Ma).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
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
Coupled dissolution-precipitation is one of the critical processes influencing the mineralogical and geochemical evolution of pegmatites.This mechanism involves the simultaneous dissolution of primary mineral phases a...Coupled dissolution-precipitation is one of the critical processes influencing the mineralogical and geochemical evolution of pegmatites.This mechanism involves the simultaneous dissolution of primary mineral phases and the precipitation of secondary phases,driven by changes in the chemical environment,often mediated by hydrothermal fluids.The Bailongshan Li deposit,located in the West Kunlun region of northwest China,is a significant geological formation known for its rich lithium content and associated rare metals such as tantalum,niobium,and tin.This study investigates the coupled dissolution-precipitation processes that have played a crucial role in the mineralization of this deposit,focusing on key minerals,including cassiterite(Cst),columbite-group minerals(CGM),and elbaite(Elb).Using a combination of petrographic analysis,back-scattered electron(BSE)imaging,cathodoluminescence(CL)imaging,and micro X-ray fluorescence(XRF)mapping,we examined the textural and chemical characteristics of these minerals.Our findings reveal intricate patchy zoning patterns and element distributions(indicated by the Nb,Ta,W,Mn,Fe,Hf,Ti for CGM;Hf,Ti Rb,W,Nb,Ta for Cst;Ti,Zn,Fe,W,Hf,Mn,K for Elb)that indicate multiple stages of mineral alteration driven by fluid-mediated processes.The coupled dissolution-precipitation mechanisms observed in the Bailongshan deposit have resulted in significant redistribution and enrichment of economically valuable elements.The study highlights the importance of hydrothermal fluids in altering primary mineral phases and precipitating secondary phases with distinct compositions.These processes not only modified the mineralogical makeup of the pegmatite but also enhanced its economic potential by concentrating rare metals.Signatures of coupled dissolutionprecipitation processes can serve as an essential tool for mineral exploration,guiding the search for high-grade zones within similar pegmatitic formations.展开更多
The origin of magnesium and iron isotope variations in mafic–ultramafic rocks has long been debated.In particular,a substantial lack of understanding exists regarding how the variation in the Mg and Fe isotopic compo...The origin of magnesium and iron isotope variations in mafic–ultramafic rocks has long been debated.In particular,a substantial lack of understanding exists regarding how the variation in the Mg and Fe isotopic compositions of arc magmas relates to fractional crystallization.Here,we report new Mg and Fe isotopic analyses of mafic–ultramafic rocks formed by co-genetic magmatic evolution in the Eastern Kunlun orogenic belt.The ultramafic and gabbro samples present mantle-like Mg isotopic compositions,with δ^(26)Mg values ranging from−0.279‰to−0.266‰for wehrlite,−0.266‰to−0.243‰for clinopyroxenite,and−0.284‰to−0.253‰for gabbro.In contrast,the δ^(26)Mg values of the hornblende gabbro samples are significantly higher(−0.195‰to−0.176‰).These rocks have similar heavy Fe isotopic compositions,withδ56Fe values ranging from 0.020‰to 0.157‰.The high δ^(26)Mg values observed in the hornblende gabbro are interpreted as indicating a maximum of 6%olivine fractionation,whereas the slightly high δ^(26)Mg values in the clinopyroxenite are ascribed to the accumulation of titanomagnetite.The Fe isotopic signatures of these rocks are inherited from magmatic sources.A comparison of the studied rocks with other mafic-ultramafic rocks implies that partial melting of mantle wedges induced by metasomatism of marine sediment-derived melts could generate“dry”arc magmatism,which would necessitate a more comprehensive and detailed analysis in further investigations.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
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
As fundamental parameters of the Antarctic Ice Sheet,ice thickness and subglacial topography are critical factors for studying the basal conditions and mass balance in Antarctica.During CHINARE 24（the 24 th Chinese N...As fundamental parameters of the Antarctic Ice Sheet,ice thickness and subglacial topography are critical factors for studying the basal conditions and mass balance in Antarctica.During CHINARE 24（the 24 th Chinese National Antarctic Research Expedition,2007/08）,the research team used a deep ice-penetrating radar system to measure the ice thickness and subglacial topography of the ＂Chinese Wall＂ around Kunlun Station,East Antarctica.Preliminary results show that the ice thickness varies mostly from 1600 m to 2800 m along the ＂Chinese Wall＂,with the thickest ice being 3444 m,and the thinnest ice 1255 m.The average bedrock elevation is 1722 m,while the minimum is just 604 m.Compared with the northern side of the ice divide,the ice thickness is a little greater and the subglacial topography lower on the southern side,which is also characterized by four deep valleys.We found no basal freeze-on ice in the Gamburtsev Subglacial Mountains area,subglacial lakes,or water bodies along the ＂Chinese Wall＂.Ice thickness and subglacial topography data extracted from the Bedmap 2 database along the ＂Chinese Wall＂ are consistent with our results,but their resolution and accuracy are very limited in areas where the bedrock fluctuates intensely.The distribution of ice thickness and subglacial topography detected by ice-penetrating radar clarifies the features of the ice sheet in this ＂inaccessible＂ region.These results will help to advance the study of ice sheet dynamics and the determination of future locations of the GSM＇s geological and deep ice core drilling sites in the Dome A region.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 Helegangnaren feldspar granite exposed in the eastern part of East Kunlun, is characterized by high concentrations of SiO2 and alkaline, low abundances of Fe, Mg and Ca, metaluminous-weak peraluminous. Trace eleme...The Helegangnaren feldspar granite exposed in the eastern part of East Kunlun, is characterized by high concentrations of SiO2 and alkaline, low abundances of Fe, Mg and Ca, metaluminous-weak peraluminous. Trace elements analysis shows that the granite is depleted extremely in Ba, Sr and Eu, and rich in some large-ion lithophile elements and high field strength elements. Besides, the granite has high Ga contents, the values of 104（Ga/AI） vary from 2.50 to 2.77, which is mainly greater than the lower limit of A-type granites （2.6）, and is higher than the I- and S- type granites＇ average （2.1 and 2.28, respectively）. Rare earth element （REE） is characterized by relatively high fractionations of light REE （LREE） and heavy REE （HREE） （LREE/HREE=9.3-13.60, （La/Yb）N=10.92-18.02）, pronounced negative Eu anomalies （JEn=0.08-0.13）, and exhibits right- dipping gull pattern. Major elements, rare elements and trace elements features show the granite is ascribed to A-type granite and A2 subtype in tectonic genetic type. They are plotted into post-collision or within-plate area in a variety of tectonic discriminations. Geological and geochemical data comprehensively suggest that the granite is formed in a post-collision extensive tectonic setting. Laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） zircon U-Pb dating yields a weighted mean age of 425 Ma, belonging to Middle Silurian, which is similar to the age of the post- collision geological events in the region. The differences of magmatic rocks in formation age, rocks assemblage and rocks series systematically indicate that the regional tectonic stress regime in the East Kunlun orogenic belt experienced a major transformation from compress to extension in Middle Silurianin, and the Helegangnaren feldspar granite intruded in the early stage of tectonic transformation.展开更多
This study reports zircon U-Pb and Hf isotopes and whole-rock elemental data for granodiorites from the East Kunlun orogen. The zircon U-Pb dating defines their crystallization age of 235 Ma. The rocks are characteriz...This study reports zircon U-Pb and Hf isotopes and whole-rock elemental data for granodiorites from the East Kunlun orogen. The zircon U-Pb dating defines their crystallization age of 235 Ma. The rocks are characterized by high-K calc-alkaline, magnesian and metaluminous with（K2O＋Na2O）=6.38 wt.%–7.01 wt.%, Mg#=42–50 [Mg#=100×molar Mg/（Mg＋Fe OT）], A/CNK=0.92–0.98, coupled with high εHf（t） values from-0.65 to-1.80. The rocks were derived from partial melting of a juvenile mafic crustal source within normal crust thickness. The juvenile lower crust was generated by mixing lithospheric mantle-derived melt（55%–60%） and supracrustal melt（40%–45%） during the seafloor subduction. Together with available data from the East Kunlun, it is proposed that the studied Middle Triassic granodiorites were formed in post-collisional extension setting, in which melting of the juvenile lower crust in response to the basaltic magma underplating resulted in the production of high-K granodioritic melts.展开更多
Mesoproterozoic volcanic rocks occurring in the north of the western Kunlun Mountains can be divided into two groups. The first group (north belt) is an reversely-evolved bimodal series. Petrochemistry shows that the ...Mesoproterozoic volcanic rocks occurring in the north of the western Kunlun Mountains can be divided into two groups. The first group (north belt) is an reversely-evolved bimodal series. Petrochemistry shows that the alkalinity of the rocks decreases from early to late: alkaline→calc-alkaline→tholeiite, and geochemistry proves that the volcanic rocks were formed in rifting tectonic systems. The sedimentary facies shows characteristics of back-arc basins. The second (south belt) group, which occurs to the south of Yutian-Minfeng-Cele, is composed of calc-alkaline island arc (basaltic) andesite and minor rhyolite. The space distribution, age and geochemistry of the two volcanite groups indicate that they were formed in a back-arc basin (the first group) and an island arc (the second group) respectively and indicate the plate evolution during the Mesoproterozoic. The orogeny took place at -1.05 Ga, which was coeval with the Grenville orogeny. This study has provided important geological data for exploring the position of the Paleo-Tarim plate in the Rodinia super-continent.展开更多
The Kekekete mafic-ultramafic rocks are exposed in the Kekesha-Kekekete-Dawate area, which are in the eastern part of the East Kunlun Orogenic Belt. It outcrops as tectonic slices intruding tectonically in the Paleopr...The Kekekete mafic-ultramafic rocks are exposed in the Kekesha-Kekekete-Dawate area, which are in the eastern part of the East Kunlun Orogenic Belt. It outcrops as tectonic slices intruding tectonically in the Paleoproterozoic Baishahe Group and the Paleozoic Nachitai Group. The Kekekete mafic and ultramafic rocks is located near the central fault in East Kunlun and lithologically mainly consists of serpentinite, augite peridotite, and gabbro. The LA-ICP-MS zircon U-Pb age of the gabbro is 501±7 Ma, indicating that Kekekete mafic-ultramafic rocks formed in the Middle Cambrian. This rock assemblage is relatively poor in SiO2 and （Na20＋K20） but rich in MgO and SFeO. The chondrite-normalized REE patterns of the gabbro dip slightly to the right; the primitive mantle and MORB-normalized spidergrams of trace elements show enrichment of large-ion lithophile elements （Cs, Rb, Ba, etc.） and no differentiation of high field strength elements. The general dominance of E- MORB features and the geochemical characteristics of OIB suggest that the Kekekete mafic- ultramafic rocks formed in an initial oceanic basin with slightly enriched mantle being featured by varying degrees of mixing of N-MORB depleted mantle and a similar-OIB-type source. From a comprehensive study of the previous data, the author believes that the tectonic history of the East Kunlun region was controlled by a geodynamic system of rifting and extension in the late stages of the Neoproterozoic to early stages of the Early Paleozoic and this formed the paleo-oceanic basin or rift system now represented by the ophiolites along the central fault in East Kunlun, the Kekekete mafic- ultramafic rocks and Delisitan ophiolite.展开更多
A high-angle ductile thrusting deformation with top-to-the-north movement penetratively developed in the Proterozoic-Early Paleozoic metamorphic rocks along the Central East Kunlun belt. The deformed rocks suffered ep...A high-angle ductile thrusting deformation with top-to-the-north movement penetratively developed in the Proterozoic-Early Paleozoic metamorphic rocks along the Central East Kunlun belt. The deformed rocks suffered epidote-amphibolite facies metamorphism. On the basis of our previous study, we present more data in this paper to further support that the ducdle thrust deformation occurred in the later Caledonian and more detailed information about the deformation. A zircon U-Pb concordant age of 446±2.2 Ma of a deformed granodiorite in the ductile thrust zone was obtained and can be interpreted as the lower limit of the deformation. A syntectonically crystallized and also strongly deformed hornblende Ar/ Ar dating gives an Ar/Ar plateau age of 426.5±3.8 Ma, which represents the deformation age. A strongly orientated muscovite gives an Ar/Ar plateau age of 408±1.6Ma, representing the cooling age after the peak temperature, constraining the upper limit of the ductile thrust deformation. This ductile thrust deformation can be interpreted as the result of the closing of the Central East Kunlun archipelago ocean. To the north, Ar/Ar plateau ages of 382.9±0.2 Ma and 386.8±0.8 Ma of muscovite in the deformed Xiaomiao Group represent the uplift cooling ages of deeper rocks after the thrusting movement. The original thrusting foliation has a low angle. A rotation model was put forward to explain the development of the foliation from the original low-angle to present high-angle dipping.展开更多
The A＇nyemaqen （阿尼玛卿） ophiolite belt along the southern margin of the East Kunlun （昆仑） Mountains marks the suture formed by the closure of paleo-Tethys. The Dur＇ngoi ophiolite in the eastern part of this b...The A＇nyemaqen （阿尼玛卿） ophiolite belt along the southern margin of the East Kunlun （昆仑） Mountains marks the suture formed by the closure of paleo-Tethys. The Dur＇ngoi ophiolite in the eastern part of this belt consists of meta-peridotite, mafic-ultramafic cumulates, sheeted dikes and basaltic lavas. The meta-peridotites consist of dunite, harzburgite, lherzolite, feldspar-bearing lherzolite and garnet-bearing lherzolite and contain residual spinel with Cr# [100×Cr/（Cr＋Al）] ranging from 30 to 57 and Mg# [100×Mg/（Mg＋Fe2＋）] ranging from 50 to 75, indicating an Al- and Mg-rich series. The meta-peridotites have a relatively narrow range of composition with Mg# of 89.2-92.6, Al2O3 contents of （1-4） wt.% and slightly depleted chondrite normalized REE patterns, indicating that they represent relict mantle material that has undergone intermediate to low degrees of partial melting. Garnets in the lherzolite are andradite, enriched in Ca and Fe and depleted in Mg and AI （And=95-97, Pyr=0.3-5, Gro=0-3）, indicating a metamorphic origin. The cumulate rocks mainly consist of dunite, wehrlite, pyroxenite and gabbro. A well-layered gabbro-pyroxenite complex is defined by modal variations in plagioclase and pyroxene. Blocks of garnet-pyroxenite or rodingite are locally present in the meta-peridotites. Garnets in the cumulate rocks are grossular （Gro=69-90, And=9-19, Br=l-12）, also metamorphic origin. The diabase dikes are moderately depleted in LREE [（La/Sm）N=0.5-0.8] and HREE resulting in slightly convex chondrite-normalized patterns with slightly positive Eu anomalies （δEu=1.1-1.3）. The basaltic lavas have REE patterns similar to those of MORB with （La/Sm）N ratios of 0.5-1 and small negative Eu anomalies. They appear to have been derived from a depleted mantle source and to have undergone little or no differentiation during crystallization. SHRIMP U-Pb dating of zircons from the basalts yields 286pb/238U ages of 276-319 Ma （average 308.0±4.9 Ma）. The Dur＇ngoi ophiolite is interpreted as a dismembered fragment of paleo-oceanic crust emplaced during closure of the paleo-Tethyan Ocean basin. Three other suites of oceanic lavas are recognized in the area： island arc volcanic （IAV） rocks, possible back arc basin （BAB） basalts and possible post-collisional volcanic （PCV） and plutonic rocks. The distribution of these rocks suggests north-directed subduction. Opening of the A＇nyemaqen oceanic basin started at least as early as Late Carboniferous （308 Ma） and the basin probably closed during the Early Triassic. The IAV formed in Late Permian （260 Ma）, the BAB in Early-Middle Triassic, and the PCV in Late Triassic. Several large scale, ductile, sinistral strike-slip fault zones, extending hundreds to thousands kilometers, formed along or north of the suture during the Early-Late Triassic, e.g., they are the south margin fault zone of East Kunlun （200-220 Ma）, the Altyn Tagh fault （220-230 Ma）, and the North Qaidam fault zone （240-250 Ma）. These strike-slip faults were probably generated by oblique subduction and closure of the paleo-Tethyan Ocean basin, possibly during exhumation of the subducted plate or uplift of the overriding plate, coincident with post-collisional magmatism.展开更多
The East Kunlun Orogenic Belt(EKOB) provides an important link to reconstruct the evolution of the Proto-Tethys and Paleo-Tethys realm. The EKOB is marked by widespread Early Paleozoic magmatism.Here we report the pet...The East Kunlun Orogenic Belt(EKOB) provides an important link to reconstruct the evolution of the Proto-Tethys and Paleo-Tethys realm. The EKOB is marked by widespread Early Paleozoic magmatism.Here we report the petrology, bulk geochemistry, zircon Ue Pb dating and, Lue Hf and SreN d isotopic data of the Early Paleozoic granitic rocks in Zhiyu area of the southern EKOB. Based on the zircon U-Pb dating, these granitoids, consisting of diorite, granodiorite and monzogranite, were formed during 450 -430 Ma the Late Ordovician to Middle Silurian. The diorite and granodiorite are high Sr/Y ratio as adakitic affinities, and the monzogranite belongs to highly fractionated I-type. Their(^(87)Sr/^(86)Sr)ivalues range from 0.7059 to 0.7085, εNd(t) values from -1.6 to -6.0 and the zircon εHf(t) values show large variations from +9.1 to -8.6 with Hf model ages(T_(DM2)) about 848 Ma and 1970 Ma. The large variations of whole-rock Nd and zircon Hf isotopes demonstrate strong isotopic heterogeneity of the source regions which probably resulted from multi-phase underplating of mantle-derived magmas. Geochemical and isotopic studies proved that the diorite and granodiorite had been derived from partial melting of heterogeneous crustal source with variable contributions from ancient continental crust and juvenile components, and the monzogranites were representing fractional crystallization and crustal contamination for arc magma. The Early Paleozoic adakitic rocks and high-K calc-alkaline granitoids in the southern EKOB were likely emplaced in a continental marginal arc setting possibly linked to the southwards subduction of the Paleo Kunlun Ocean and the magma generation is linked to partial melting of thickened continental crust induced by underplating of mantle-derived magmas.展开更多
It is a puzzle to determine metallogenetic ages in the world. This article uses zircon fission track （FT） dating to probe the mineralizing epochs of Wulonggou （五龙沟） gold ore deposits in eastern Kunlun （昆仑） ...It is a puzzle to determine metallogenetic ages in the world. This article uses zircon fission track （FT） dating to probe the mineralizing epochs of Wulonggou （五龙沟） gold ore deposits in eastern Kunlun （昆仑） Mountains. Total of six zircon FT ages have been obtained and can be divided into groups of 235-216 and 197-181 Ma, as well as 162 and 124 Ma, revealing multiple epochs of metalloge- netic processes took place in Wulonggou area, mainly first two age groups. The mineralizing ages be- come lower from northeast Yanjingou （岩金沟） to southwest Hongqigon （红旗沟）. The second epoch of 197-181 Ma is first achieved by this work. It is shown that the FT ages consist with other isotopic data and reflect different regional thermotectonic events.展开更多
The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small u...The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian （426-422 Ma）, and their zircons have ~Hf（t） values of-9.4 to 5.9 with the older TDMm ages （0.80-1.42 Ga）. Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion iithophile elements （e.g., K, Rb, Th） and depleted in heavy rare earth elements and high field strength elements （e.g., Ta, Nb, Zr, Ti）. Sulfides from the deposit have the slightly higher ~34S values of 1.9-4.3%o than the mantle （0 ~ 2%o）. The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.展开更多
U–Pb analysis of zircons from igneous rocks in the Elashan Mountain,easternmost segment of the East Kunlun Orogen yielded 252–232 Ma.Geochemically,these rocks are mainly high in SiO_(2),K_2O and K_2O+Na_2O contents,...U–Pb analysis of zircons from igneous rocks in the Elashan Mountain,easternmost segment of the East Kunlun Orogen yielded 252–232 Ma.Geochemically,these rocks are mainly high in SiO_(2),K_2O and K_2O+Na_2O contents,low in P_2O_5 and TiO_(2) contents,depleted in Ba,Sr,P,Ti and enriched in U,Hf,Zr,showing features of I–type granite.The zirconεHf(t)values of the Early Triassic Jiamuge'er rhyolite porphyry(252±3 Ma)are positive(+1.6 to+12.1),suggesting a juvenile crustal source mixing with little old crustal component,and the zirconεHf(t)values of the Middle Triassic Manzhang'gang granodiorite(244±3 Ma)and Dehailong diorite(237±3 Ma)are predominately negative(-8.4 to+1.0),indicating an older crustal source.In comparison,the zirconεHf(t)values of the Late Triassic syenogranites from Suigen'ergang(234±2Ma),Ge'ermugang(233±2 Ma)and Yue'ergen(232±3 Ma)plutons vary from-3.8 to+5.0,suggesting a crust-mantle mixing source.From Early–Middle Triassic(252–237 Ma)to Late Triassic(234–232 Ma),the geochemical characteristics of these rocks show the change from a subduction–collision setting to a post-collision or within-plate setting.By comparing of these new age data with 77 zircon U–Pb ages of igneous rocks of the eastern part of East Kunlun orogen from published literatures,we conclude that the igneous rocks of Elashan Mountain and these of the eastern part of East Kunlun Orogen belong to one magmatic belt.All these data indicate that the Triassic magmatic events of the eastern part of East Kunlun Orogen can be divided into three stages:252–238 Ma,238–226 Ma and 226–212 Ma.Statistically,the averageεHf(t)values of the threestage igneous rocks show a tendency,from the old to young,from-0.75±0.25 to lower-2.65±0.52 and then to-1.22±0.25,respectively,which reveal the change of their sources.These characteristics can be explained as a crust-mantle mixing source generated in a subductional stage,mainly crust source in a syn–collisional stage and a crust-mantle mixing source(lower crust with mantle-derived underplating magma)in a post-collisional stage.The identification of these three magmatic events in the Elashan Mountain,including all the eastern part of East Kunlun Orogen,provides new evidence for better understanding of the tectonic evolution of the northward subduction and closure of the Paleo-Tethyan(252–238 Ma),the collision of the Songpan–Ganzi block with the southern margin of Qaidam block(238–226 Ma),and the post–collisional setting(226–212 Ma)during the Early Mesozoic period.展开更多
基金support for this study was jointly given by the NSFC(grants 41930217,42072260 and 42372253)the Youth Innovation Team of Shaanxi Universities.
文摘Determining the evolutionary history of the Permian-Triassic Kunlun-Qaidam Continental Arc is essential to understanding the subduction and closure processes of the South Kunlun Ocean.In this paper,we utilize(La/Yb)N ratios collected from a fi ltered geochemical dataset on Permian to Triassic calc-alkaline rocks(55 wt%–68 wt%SiO_(2))and plutonic rocks within the Kunlun-Qaidam Continental Arc to reconstruct the spatiotemporal variation of the relative crustal thickness.Combined with known geologic observations,we discuss the subduction-accretionary tectonics of the South Kunlun Ocean and the topographic evolution of the Kunlun-Qaidam Continental Arc.Two episodes of crustal thickening and thinning were revealed.The reconstructed thickness reveals two crustal thickening and thinning events for the Kunlun-Qaidam Continental Arc from ca.270 to 210 Ma.The southern sector of the Kunlun-Qaidam Continental Arc is about 7 km thicker than the northern portion,with a maximum thickness of about 55 km at ca.270 and 230 Ma.The ca.270 and 230 Ma crustal thickening events coincide with renewed northward subduction of the South Kunlun Ocean plate and ocean closure,respectively,whereas the ca.270‒240 Ma and ca.230‒210 Ma crustal thinning events may refl ect slab break-off of the oceanic plate and lithospheric collapse during the post-collision extension,respectively.
基金funded by the China Postdoctoral Science Foundation(Grant No.2019M663959XB)the Geological Survey and Development Bureau of Qinghai Province 2019 Geological Survey Project(2019[45])the Key Laboratory of Deep Dynamics of the Ministry of Natural Resources,Open Research Project 2019。
文摘In the western segment of the East Kunlun Orogen(WEKO),muscovite granite and garnet granite from the Hureguole intrusion exhibit zircon U-Pb ages of 435-442 Ma.Geochemically,these rocks contain high concentrations of SiO_(2),K_(2)O and Al_(2)O_(3),with low concentrations of TiO_(2)and MgO,indicating a peraluminous high-K calc-alkaline affinity.They are enriched in Rb,Th,U and LREE,depleted in Eu,Ba,Sr and Ti,being classified as S-type granites.Negative whole-rockε_(Nd)(t)values(-9.8 to-9.1)and zirconε_(Hf)(t)values(-11.6 to-8.2)for those granites indicate that they were derived from partial melting of pelitic rocks in the Paleoproterozoic Baishahe Formation of the Jinshuikou Group.Based on the collected zircon ages,Cambrian-Devonian magmatic activity in the WEKO was divided into three stages:early(446-520 Ma),middle(427-441 Ma)and late(372-424 Ma)stages.Statistically,whole-rock Nd and zircon Hf isotope data(ε_(Nd)(t)/T_(DM)^(Nd),ε_(Hf)(t)/T_(DMC)^(Hf))from Paleozoic igneous rocks in the WEKO reveal a magma source that was initially dominated by depleted mantle components in the northward subduction stage of the Proto-Tethy an Ocean plate(446-520 Ma),shifting to predominantly crustal sources during the closure period of the North Qimantagh back-arc basin(427-441 Ma),then to crust-mantle mixed sources in the post-collision stage(372-424 Ma).
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 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jointly supported by the National Natural Science Foundation of China(Nos.42250202,92162323,42272075)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.24lgqb001)+1 种基金the Natural Science Foundation Project of Guangdong Province(No.2022A1515010003)the Guangdong Province Introduced Innovative R&D Team of Big Data—Mathematical Earth Sciences and Extreme Geological Events Team(No.2021ZT09H399)。
文摘Coupled dissolution-precipitation is one of the critical processes influencing the mineralogical and geochemical evolution of pegmatites.This mechanism involves the simultaneous dissolution of primary mineral phases and the precipitation of secondary phases,driven by changes in the chemical environment,often mediated by hydrothermal fluids.The Bailongshan Li deposit,located in the West Kunlun region of northwest China,is a significant geological formation known for its rich lithium content and associated rare metals such as tantalum,niobium,and tin.This study investigates the coupled dissolution-precipitation processes that have played a crucial role in the mineralization of this deposit,focusing on key minerals,including cassiterite(Cst),columbite-group minerals(CGM),and elbaite(Elb).Using a combination of petrographic analysis,back-scattered electron(BSE)imaging,cathodoluminescence(CL)imaging,and micro X-ray fluorescence(XRF)mapping,we examined the textural and chemical characteristics of these minerals.Our findings reveal intricate patchy zoning patterns and element distributions(indicated by the Nb,Ta,W,Mn,Fe,Hf,Ti for CGM;Hf,Ti Rb,W,Nb,Ta for Cst;Ti,Zn,Fe,W,Hf,Mn,K for Elb)that indicate multiple stages of mineral alteration driven by fluid-mediated processes.The coupled dissolution-precipitation mechanisms observed in the Bailongshan deposit have resulted in significant redistribution and enrichment of economically valuable elements.The study highlights the importance of hydrothermal fluids in altering primary mineral phases and precipitating secondary phases with distinct compositions.These processes not only modified the mineralogical makeup of the pegmatite but also enhanced its economic potential by concentrating rare metals.Signatures of coupled dissolutionprecipitation processes can serve as an essential tool for mineral exploration,guiding the search for high-grade zones within similar pegmatitic formations.
基金This research was financially co-supported by the National Natural Science Foundation of China(Grant Nos.42121002 and 91755207).
文摘The origin of magnesium and iron isotope variations in mafic–ultramafic rocks has long been debated.In particular,a substantial lack of understanding exists regarding how the variation in the Mg and Fe isotopic compositions of arc magmas relates to fractional crystallization.Here,we report new Mg and Fe isotopic analyses of mafic–ultramafic rocks formed by co-genetic magmatic evolution in the Eastern Kunlun orogenic belt.The ultramafic and gabbro samples present mantle-like Mg isotopic compositions,with δ^(26)Mg values ranging from−0.279‰to−0.266‰for wehrlite,−0.266‰to−0.243‰for clinopyroxenite,and−0.284‰to−0.253‰for gabbro.In contrast,the δ^(26)Mg values of the hornblende gabbro samples are significantly higher(−0.195‰to−0.176‰).These rocks have similar heavy Fe isotopic compositions,withδ56Fe values ranging from 0.020‰to 0.157‰.The high δ^(26)Mg values observed in the hornblende gabbro are interpreted as indicating a maximum of 6%olivine fractionation,whereas the slightly high δ^(26)Mg values in the clinopyroxenite are ascribed to the accumulation of titanomagnetite.The Fe isotopic signatures of these rocks are inherited from magmatic sources.A comparison of the studied rocks with other mafic-ultramafic rocks implies that partial melting of mantle wedges induced by metasomatism of marine sediment-derived melts could generate“dry”arc magmatism,which would necessitate a more comprehensive and detailed analysis in further investigations.
基金supported by the National Key Research and Development Project(No.2022YFC2903302)the Second Tibet Plateau Scientific Expedition and Research Program(STEP),(No.2019QZKK0802)+2 种基金the National Natural Science Foundation of China(No.42361144841)the Chinese Academy of Geological Sciences Basal Research Fund(No.JKYZD202402)the Scientific Research Fund Project of BGRIMM Technology Group(No.JTKY202427822)。
文摘0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).
基金financially supported by 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 National Basic Research Program of China(Grant Nos.2013CBA01804 and 2012CB957702)the Chinese Polar Environmental Comprehensive Investigation and Assessment Programs(Grant No.CHINARE-02-02)the National Science Foundation of China(Grant No.41101071)
文摘As fundamental parameters of the Antarctic Ice Sheet,ice thickness and subglacial topography are critical factors for studying the basal conditions and mass balance in Antarctica.During CHINARE 24（the 24 th Chinese National Antarctic Research Expedition,2007/08）,the research team used a deep ice-penetrating radar system to measure the ice thickness and subglacial topography of the ＂Chinese Wall＂ around Kunlun Station,East Antarctica.Preliminary results show that the ice thickness varies mostly from 1600 m to 2800 m along the ＂Chinese Wall＂,with the thickest ice being 3444 m,and the thinnest ice 1255 m.The average bedrock elevation is 1722 m,while the minimum is just 604 m.Compared with the northern side of the ice divide,the ice thickness is a little greater and the subglacial topography lower on the southern side,which is also characterized by four deep valleys.We found no basal freeze-on ice in the Gamburtsev Subglacial Mountains area,subglacial lakes,or water bodies along the ＂Chinese Wall＂.Ice thickness and subglacial topography data extracted from the Bedmap 2 database along the ＂Chinese Wall＂ are consistent with our results,but their resolution and accuracy are very limited in areas where the bedrock fluctuates intensely.The distribution of ice thickness and subglacial topography detected by ice-penetrating radar clarifies the features of the ice sheet in this ＂inaccessible＂ region.These results will help to advance the study of ice sheet dynamics and the determination of future locations of the GSM＇s geological and deep ice core drilling sites in the Dome A region.
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financially supported by National Natural Science Foundation of China (Grant Nos. 41172186, 40972136 and 40572121)Special Fund for Basic Scientific Research of Central Colleges, Chang’an University, China (Grant Nos.CHD2011TD020, CHD2009JC070, CHD2009JC053 and CHD2009JC046)the Commonweal Geological Survey,the Aluminum Corporation of China and the Land-Resources Department of Qinghai Province (Grant No.200801)
文摘The Helegangnaren feldspar granite exposed in the eastern part of East Kunlun, is characterized by high concentrations of SiO2 and alkaline, low abundances of Fe, Mg and Ca, metaluminous-weak peraluminous. Trace elements analysis shows that the granite is depleted extremely in Ba, Sr and Eu, and rich in some large-ion lithophile elements and high field strength elements. Besides, the granite has high Ga contents, the values of 104（Ga/AI） vary from 2.50 to 2.77, which is mainly greater than the lower limit of A-type granites （2.6）, and is higher than the I- and S- type granites＇ average （2.1 and 2.28, respectively）. Rare earth element （REE） is characterized by relatively high fractionations of light REE （LREE） and heavy REE （HREE） （LREE/HREE=9.3-13.60, （La/Yb）N=10.92-18.02）, pronounced negative Eu anomalies （JEn=0.08-0.13）, and exhibits right- dipping gull pattern. Major elements, rare elements and trace elements features show the granite is ascribed to A-type granite and A2 subtype in tectonic genetic type. They are plotted into post-collision or within-plate area in a variety of tectonic discriminations. Geological and geochemical data comprehensively suggest that the granite is formed in a post-collision extensive tectonic setting. Laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） zircon U-Pb dating yields a weighted mean age of 425 Ma, belonging to Middle Silurian, which is similar to the age of the post- collision geological events in the region. The differences of magmatic rocks in formation age, rocks assemblage and rocks series systematically indicate that the regional tectonic stress regime in the East Kunlun orogenic belt experienced a major transformation from compress to extension in Middle Silurianin, and the Helegangnaren feldspar granite intruded in the early stage of tectonic transformation.
基金financially supported by the China Geological Survey(Nos.12120115069701,12120113095700 and 1212011220391)the National Natural Science Foundation of China(No.41272079)+2 种基金the China Postdoctoral Science Foundation-China(No.2015M582529)the State Key Laborato-ry of Continental Tectonics and Dynamics(No.K201508)the Special Financial Support Program of Central Government for Local Universities(No.80000-14Z019)
文摘This study reports zircon U-Pb and Hf isotopes and whole-rock elemental data for granodiorites from the East Kunlun orogen. The zircon U-Pb dating defines their crystallization age of 235 Ma. The rocks are characterized by high-K calc-alkaline, magnesian and metaluminous with（K2O＋Na2O）=6.38 wt.%–7.01 wt.%, Mg#=42–50 [Mg#=100×molar Mg/（Mg＋Fe OT）], A/CNK=0.92–0.98, coupled with high εHf（t） values from-0.65 to-1.80. The rocks were derived from partial melting of a juvenile mafic crustal source within normal crust thickness. The juvenile lower crust was generated by mixing lithospheric mantle-derived melt（55%–60%） and supracrustal melt（40%–45%） during the seafloor subduction. Together with available data from the East Kunlun, it is proposed that the studied Middle Triassic granodiorites were formed in post-collisional extension setting, in which melting of the juvenile lower crust in response to the basaltic magma underplating resulted in the production of high-K granodioritic melts.
文摘Mesoproterozoic volcanic rocks occurring in the north of the western Kunlun Mountains can be divided into two groups. The first group (north belt) is an reversely-evolved bimodal series. Petrochemistry shows that the alkalinity of the rocks decreases from early to late: alkaline→calc-alkaline→tholeiite, and geochemistry proves that the volcanic rocks were formed in rifting tectonic systems. The sedimentary facies shows characteristics of back-arc basins. The second (south belt) group, which occurs to the south of Yutian-Minfeng-Cele, is composed of calc-alkaline island arc (basaltic) andesite and minor rhyolite. The space distribution, age and geochemistry of the two volcanite groups indicate that they were formed in a back-arc basin (the first group) and an island arc (the second group) respectively and indicate the plate evolution during the Mesoproterozoic. The orogeny took place at -1.05 Ga, which was coeval with the Grenville orogeny. This study has provided important geological data for exploring the position of the Paleo-Tarim plate in the Rodinia super-continent.
基金supported by the National Science Foundation of China (Grant No., 41172186, 40972136, 40572121)the Special Fund for Basic Scientific Research of Central Colleges, Chang’an University (Grant Nos. CHD2011TD020, 2013G1271091, 2013G1271092)the Commonweal Geological Survey, the Aluminum Corporation of China and the Land-Resources Department of Qinghai Province (Grant No., 200801)
文摘The Kekekete mafic-ultramafic rocks are exposed in the Kekesha-Kekekete-Dawate area, which are in the eastern part of the East Kunlun Orogenic Belt. It outcrops as tectonic slices intruding tectonically in the Paleoproterozoic Baishahe Group and the Paleozoic Nachitai Group. The Kekekete mafic and ultramafic rocks is located near the central fault in East Kunlun and lithologically mainly consists of serpentinite, augite peridotite, and gabbro. The LA-ICP-MS zircon U-Pb age of the gabbro is 501±7 Ma, indicating that Kekekete mafic-ultramafic rocks formed in the Middle Cambrian. This rock assemblage is relatively poor in SiO2 and （Na20＋K20） but rich in MgO and SFeO. The chondrite-normalized REE patterns of the gabbro dip slightly to the right; the primitive mantle and MORB-normalized spidergrams of trace elements show enrichment of large-ion lithophile elements （Cs, Rb, Ba, etc.） and no differentiation of high field strength elements. The general dominance of E- MORB features and the geochemical characteristics of OIB suggest that the Kekekete mafic- ultramafic rocks formed in an initial oceanic basin with slightly enriched mantle being featured by varying degrees of mixing of N-MORB depleted mantle and a similar-OIB-type source. From a comprehensive study of the previous data, the author believes that the tectonic history of the East Kunlun region was controlled by a geodynamic system of rifting and extension in the late stages of the Neoproterozoic to early stages of the Early Paleozoic and this formed the paleo-oceanic basin or rift system now represented by the ophiolites along the central fault in East Kunlun, the Kekekete mafic- ultramafic rocks and Delisitan ophiolite.
文摘A high-angle ductile thrusting deformation with top-to-the-north movement penetratively developed in the Proterozoic-Early Paleozoic metamorphic rocks along the Central East Kunlun belt. The deformed rocks suffered epidote-amphibolite facies metamorphism. On the basis of our previous study, we present more data in this paper to further support that the ducdle thrust deformation occurred in the later Caledonian and more detailed information about the deformation. A zircon U-Pb concordant age of 446±2.2 Ma of a deformed granodiorite in the ductile thrust zone was obtained and can be interpreted as the lower limit of the deformation. A syntectonically crystallized and also strongly deformed hornblende Ar/ Ar dating gives an Ar/Ar plateau age of 426.5±3.8 Ma, which represents the deformation age. A strongly orientated muscovite gives an Ar/Ar plateau age of 408±1.6Ma, representing the cooling age after the peak temperature, constraining the upper limit of the ductile thrust deformation. This ductile thrust deformation can be interpreted as the result of the closing of the Central East Kunlun archipelago ocean. To the north, Ar/Ar plateau ages of 382.9±0.2 Ma and 386.8±0.8 Ma of muscovite in the deformed Xiaomiao Group represent the uplift cooling ages of deeper rocks after the thrusting movement. The original thrusting foliation has a low angle. A rotation model was put forward to explain the development of the foliation from the original low-angle to present high-angle dipping.
基金supported by China Geological Survey (Nos. 1212010918013 and 1212010610105)
文摘The A＇nyemaqen （阿尼玛卿） ophiolite belt along the southern margin of the East Kunlun （昆仑） Mountains marks the suture formed by the closure of paleo-Tethys. The Dur＇ngoi ophiolite in the eastern part of this belt consists of meta-peridotite, mafic-ultramafic cumulates, sheeted dikes and basaltic lavas. The meta-peridotites consist of dunite, harzburgite, lherzolite, feldspar-bearing lherzolite and garnet-bearing lherzolite and contain residual spinel with Cr# [100×Cr/（Cr＋Al）] ranging from 30 to 57 and Mg# [100×Mg/（Mg＋Fe2＋）] ranging from 50 to 75, indicating an Al- and Mg-rich series. The meta-peridotites have a relatively narrow range of composition with Mg# of 89.2-92.6, Al2O3 contents of （1-4） wt.% and slightly depleted chondrite normalized REE patterns, indicating that they represent relict mantle material that has undergone intermediate to low degrees of partial melting. Garnets in the lherzolite are andradite, enriched in Ca and Fe and depleted in Mg and AI （And=95-97, Pyr=0.3-5, Gro=0-3）, indicating a metamorphic origin. The cumulate rocks mainly consist of dunite, wehrlite, pyroxenite and gabbro. A well-layered gabbro-pyroxenite complex is defined by modal variations in plagioclase and pyroxene. Blocks of garnet-pyroxenite or rodingite are locally present in the meta-peridotites. Garnets in the cumulate rocks are grossular （Gro=69-90, And=9-19, Br=l-12）, also metamorphic origin. The diabase dikes are moderately depleted in LREE [（La/Sm）N=0.5-0.8] and HREE resulting in slightly convex chondrite-normalized patterns with slightly positive Eu anomalies （δEu=1.1-1.3）. The basaltic lavas have REE patterns similar to those of MORB with （La/Sm）N ratios of 0.5-1 and small negative Eu anomalies. They appear to have been derived from a depleted mantle source and to have undergone little or no differentiation during crystallization. SHRIMP U-Pb dating of zircons from the basalts yields 286pb/238U ages of 276-319 Ma （average 308.0±4.9 Ma）. The Dur＇ngoi ophiolite is interpreted as a dismembered fragment of paleo-oceanic crust emplaced during closure of the paleo-Tethyan Ocean basin. Three other suites of oceanic lavas are recognized in the area： island arc volcanic （IAV） rocks, possible back arc basin （BAB） basalts and possible post-collisional volcanic （PCV） and plutonic rocks. The distribution of these rocks suggests north-directed subduction. Opening of the A＇nyemaqen oceanic basin started at least as early as Late Carboniferous （308 Ma） and the basin probably closed during the Early Triassic. The IAV formed in Late Permian （260 Ma）, the BAB in Early-Middle Triassic, and the PCV in Late Triassic. Several large scale, ductile, sinistral strike-slip fault zones, extending hundreds to thousands kilometers, formed along or north of the suture during the Early-Late Triassic, e.g., they are the south margin fault zone of East Kunlun （200-220 Ma）, the Altyn Tagh fault （220-230 Ma）, and the North Qaidam fault zone （240-250 Ma）. These strike-slip faults were probably generated by oblique subduction and closure of the paleo-Tethyan Ocean basin, possibly during exhumation of the subducted plate or uplift of the overriding plate, coincident with post-collisional magmatism.
基金financially sponsored by The National Key Research and Development Program of China (Grant No. 2016YFC0600502)the Program of the China Geological Survey (Grant Nos. 1212011121260, 1212011220920)111 Project (B07011)
文摘The East Kunlun Orogenic Belt(EKOB) provides an important link to reconstruct the evolution of the Proto-Tethys and Paleo-Tethys realm. The EKOB is marked by widespread Early Paleozoic magmatism.Here we report the petrology, bulk geochemistry, zircon Ue Pb dating and, Lue Hf and SreN d isotopic data of the Early Paleozoic granitic rocks in Zhiyu area of the southern EKOB. Based on the zircon U-Pb dating, these granitoids, consisting of diorite, granodiorite and monzogranite, were formed during 450 -430 Ma the Late Ordovician to Middle Silurian. The diorite and granodiorite are high Sr/Y ratio as adakitic affinities, and the monzogranite belongs to highly fractionated I-type. Their(^(87)Sr/^(86)Sr)ivalues range from 0.7059 to 0.7085, εNd(t) values from -1.6 to -6.0 and the zircon εHf(t) values show large variations from +9.1 to -8.6 with Hf model ages(T_(DM2)) about 848 Ma and 1970 Ma. The large variations of whole-rock Nd and zircon Hf isotopes demonstrate strong isotopic heterogeneity of the source regions which probably resulted from multi-phase underplating of mantle-derived magmas. Geochemical and isotopic studies proved that the diorite and granodiorite had been derived from partial melting of heterogeneous crustal source with variable contributions from ancient continental crust and juvenile components, and the monzogranites were representing fractional crystallization and crustal contamination for arc magma. The Early Paleozoic adakitic rocks and high-K calc-alkaline granitoids in the southern EKOB were likely emplaced in a continental marginal arc setting possibly linked to the southwards subduction of the Paleo Kunlun Ocean and the magma generation is linked to partial melting of thickened continental crust induced by underplating of mantle-derived magmas.
基金supported by the China Geological Survey (No.2011-03-04-06)Found Project of the Geology & Mineral Ex-ploration Development Authority of Qinghai Provincethe National Natural Science Foundation of China (Nos. 41172088,40872141 and 41072160
文摘It is a puzzle to determine metallogenetic ages in the world. This article uses zircon fission track （FT） dating to probe the mineralizing epochs of Wulonggou （五龙沟） gold ore deposits in eastern Kunlun （昆仑） Mountains. Total of six zircon FT ages have been obtained and can be divided into groups of 235-216 and 197-181 Ma, as well as 162 and 124 Ma, revealing multiple epochs of metalloge- netic processes took place in Wulonggou area, mainly first two age groups. The mineralizing ages be- come lower from northeast Yanjingou （岩金沟） to southwest Hongqigon （红旗沟）. The second epoch of 197-181 Ma is first achieved by this work. It is shown that the FT ages consist with other isotopic data and reflect different regional thermotectonic events.
基金financially supported by the National Natural Science Foundation of China(No.41272093)China geological survey project(No.12120114080901)
文摘The Shitoukengde Ni-Cu deposit, located in the Eastern Kunlun Orogen, comprises three mafic-ultramafic complexes, with the No. I complex hosting six Ni-Cu orebodies found recently. The deposit is hosted in the small ultramafic bodies intruding Proterozoic metamorphic rocks. Complexes at Shitoukengde contain all kinds of mafic-ultramafic rocks, and olivine websterite and pyroxene peridotite are the most important Ni-Cu-hosted rocks. Zircon U-Pb dating suggests that the Shitoukengde Ni-Cu deposit formed in late Silurian （426-422 Ma）, and their zircons have ~Hf（t） values of-9.4 to 5.9 with the older TDMm ages （0.80-1.42 Ga）. Mafic-ultramafic rocks from the No. I complex show the similar rare earth and trace element patterns, which are enriched in light rare earth elements and large ion iithophile elements （e.g., K, Rb, Th） and depleted in heavy rare earth elements and high field strength elements （e.g., Ta, Nb, Zr, Ti）. Sulfides from the deposit have the slightly higher ~34S values of 1.9-4.3%o than the mantle （0 ~ 2%o）. The major and trace element characteristics, and Sr-Nd-Pb and Hf, S isotopes indicate that their parental magmas originated from a metasomatised, asthenospheric mantle source which had previously been modified by subduction-related fluids, and experienced significant crustal contamination both in the magma chamber and during ascent triggering S oversaturation by addition of S and Si, that resulted in the deposition and enrichment of sulfides. Combined with the tectonic evolution, we suggest that the Shitoukengde Ni-Cu deposit formed in the post-collisional, extensional regime related to the subducted oceanic slab break-off after the Wanbaogou oceanic basalt plateau collaged northward to the Qaidam Block in late Silurian.
基金supported by China Geological Survey(Nos.12120113094000,1212010811033 and 12120113093600)National Natural Science Foundation of China(Nos.41172062 and 41572052)
文摘U–Pb analysis of zircons from igneous rocks in the Elashan Mountain,easternmost segment of the East Kunlun Orogen yielded 252–232 Ma.Geochemically,these rocks are mainly high in SiO_(2),K_2O and K_2O+Na_2O contents,low in P_2O_5 and TiO_(2) contents,depleted in Ba,Sr,P,Ti and enriched in U,Hf,Zr,showing features of I–type granite.The zirconεHf(t)values of the Early Triassic Jiamuge'er rhyolite porphyry(252±3 Ma)are positive(+1.6 to+12.1),suggesting a juvenile crustal source mixing with little old crustal component,and the zirconεHf(t)values of the Middle Triassic Manzhang'gang granodiorite(244±3 Ma)and Dehailong diorite(237±3 Ma)are predominately negative(-8.4 to+1.0),indicating an older crustal source.In comparison,the zirconεHf(t)values of the Late Triassic syenogranites from Suigen'ergang(234±2Ma),Ge'ermugang(233±2 Ma)and Yue'ergen(232±3 Ma)plutons vary from-3.8 to+5.0,suggesting a crust-mantle mixing source.From Early–Middle Triassic(252–237 Ma)to Late Triassic(234–232 Ma),the geochemical characteristics of these rocks show the change from a subduction–collision setting to a post-collision or within-plate setting.By comparing of these new age data with 77 zircon U–Pb ages of igneous rocks of the eastern part of East Kunlun orogen from published literatures,we conclude that the igneous rocks of Elashan Mountain and these of the eastern part of East Kunlun Orogen belong to one magmatic belt.All these data indicate that the Triassic magmatic events of the eastern part of East Kunlun Orogen can be divided into three stages:252–238 Ma,238–226 Ma and 226–212 Ma.Statistically,the averageεHf(t)values of the threestage igneous rocks show a tendency,from the old to young,from-0.75±0.25 to lower-2.65±0.52 and then to-1.22±0.25,respectively,which reveal the change of their sources.These characteristics can be explained as a crust-mantle mixing source generated in a subductional stage,mainly crust source in a syn–collisional stage and a crust-mantle mixing source(lower crust with mantle-derived underplating magma)in a post-collisional stage.The identification of these three magmatic events in the Elashan Mountain,including all the eastern part of East Kunlun Orogen,provides new evidence for better understanding of the tectonic evolution of the northward subduction and closure of the Paleo-Tethyan(252–238 Ma),the collision of the Songpan–Ganzi block with the southern margin of Qaidam block(238–226 Ma),and the post–collisional setting(226–212 Ma)during the Early Mesozoic period.
