Detrital zircon and apatite U-Pb-Hf isotope and trace element analyses of the late Mesoproterozoic to early Neoproterozoic strata in southern Jilin provide detailed information on the sediment provenance and tectonic ...Detrital zircon and apatite U-Pb-Hf isotope and trace element analyses of the late Mesoproterozoic to early Neoproterozoic strata in southern Jilin provide detailed information on the sediment provenance and tectonic setting of the northeastern margin of the North China Craton(NCC).Here,we present U-Pb and Lu-Hf analyses of 712 detrital zircons,and U-Pb analyses of 347 detrital apatites from the Baifangzi,Diaoyutai and Qiaotou formations.The Baifangzi and Diaoyutai formations are dominated by Neoarchean(2.5-2.6 Ga)and Paleoproterozoic(1.8-1.9 Ga)zircons,indicating a predominant NCC provenance.The Qiaotou Formation is dominated by Mesoproterozoic(1.5-1.7 Ga and 1.1-1.3 Ga)zircons with mainly positiveεHf(t)values,which are similar to those from eastern Laurentia,implying a significant provenance transition.The detrital apatite age spectra of the Baifangzi and Diaoyutai Formations show major populations at 1.8-1.9 Ga and 1.1-1.3 Ga.Based on their trace element compositions,the Mesoproterozoic apatites were mainly sourced from metamorphic rocks,indicating regional metamorphism occurred in the NCC during 1.1-1.3 Ga.Combining these data with regional studies,we propose that the NCC was adjacent to eastern Laurentia during the assembly of the Rodinia supercontinent.展开更多
A comprehensive examination of detrital sandstone modes from the Sylhet Trough reveals a diverse range of sub-lithic to sub-feldspathic quartz arenites.Soil samples were gathered from Dupi Gaon(Jaintiapur)in Banglades...A comprehensive examination of detrital sandstone modes from the Sylhet Trough reveals a diverse range of sub-lithic to sub-feldspathic quartz arenites.Soil samples were gathered from Dupi Gaon(Jaintiapur)in Bangladesh,followed by a thorough analysis using field examination,X-ray diffraction(XRD),X-ray fluorescence(XRF),petrography,and heavy mineral concentration analyses.Field observations revealed the soil sample varying from white to yellowish to variegated,with thicknesses ranging from 15 cm to about 4 m,and exhibiting moderate softness.XRF analysis revealed significant SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)levels in the samples,with zirconium(Zr)and copper(Cu)showing consistently high concentrations.XRD analysis identified quartz as predominant,along with muscovite,biotite,and accessory minerals like rutile and magnetite.Petrographic analysis highlighted quartz as dominant,with fractures suggesting tectonic influences,while heavy mineral separation techniques identified zircon,garnet,goethite,rutile,and magnetite.These findings provide insights into sediment provenance,depositional processes,and environ-mental conditions during the formation of the Dupi Tila Formation.The comprehensive geochemical data of the entire rock indicates that most of the sediments originated from felsic igneous sources,and also suggests a moderate to high level of weathering in the source region.Overall,the analyses suggested an in situ origin of the Dupi Tila Formation,with parent materials being predominantly detrital rather than authigenic,supported by the presence of detrital quartz and an assessment of the depositional environment,providing insights into the geological conditions of the era and potential modes of sediment transportation.展开更多
Detrital zircon geochronology is reported from the c.1200 m thick Cambro-Ordovician sedimentary succession recovered in core from the COSC-2 continental drilling project in the Scandinavian Caledonides.Above a regolit...Detrital zircon geochronology is reported from the c.1200 m thick Cambro-Ordovician sedimentary succession recovered in core from the COSC-2 continental drilling project in the Scandinavian Caledonides.Above a regolith marking the sub-Cambrian peneplain,a lower to middle Cambrian(?)succession comprises conglomerate,sandstone and shale overlain by gravity flows fining upwards into the Alum Shale Formation.First results of detrital zircon geochronology from the Cambrian(?)succession show that the basal section of the autochthonous cover is characterized by mainly late Paleoproterozoic–early Mesoproterozoic detrital grains.The middle part of the succession is dominated by late Paleoproterozoic detritus with minor Mesoproterozoic and Archean input.The upper part of lower Cambrian(?)succession is characterized by Archean to Cambrian detritus.The maximum depositional age is calculated to 530.5±4 Ma for the upper part of the lower Cambrian succession.Two samples from the Lower Ordovician(?)succession above the Alum Shale Formation show predominantly Mesoproterozoic to early Neoproterozoic(1.5–0.9 Ga)ages.The autochthonous lower Cambrian(?)passive margin succession in the lower section is dominated by local detritus,sourced exclusively from the Eastern Segment of the Sveconorwegian Orogen,which includes the basement studied in COSC-2.Up-section,the provenance shifts towards the Transscandinavian Igneous Belt and Svecofennian Orogen sources,with the youngest part of the succession showing a notable input of Neoproterozoic–Cambrian active margin detritus.The Ordovician(?)succession is characterized by populations,likely derived from the Sveconorwegian Orogen,and a minor cratonic contribution.Statistical analysis of detrital zircon datasets across Baltica suggests that the Southern Baltica/Sandomirian Arc,rather than the Timanian Orogen,was a significant source of detrital material across the paleocontinent.The influence of Timanian Orogen grains is limited to northernmost Scandinavia,whereas Sandomirian detritus reached central Scandinavia in the lower to middle Cambrian and remained prevalent in southern Scandinavia into the Lower Ordovician.展开更多
When interpreting results,it is imperative to have some understanding of the degree to which the results are replicable.If the results cannot be replicated with independent data,then interpretations from the results b...When interpreting results,it is imperative to have some understanding of the degree to which the results are replicable.If the results cannot be replicated with independent data,then interpretations from the results become questionable.To minimize the potential for misinterpretations,the current study analyzes six time-series derived from globally sampled U-Pb zircon databases–of which,two are independent igneous databases,one being a quasi-independent igneous database,and three being independent detrital databases.These time-series are then analyzed with standard statistical methods to evaluate replicability.The methods include bandpass filtering to transform the raw time-series into stationary sequences,Student’s t-test,Monte Carlo simulations,periodograms from spectral analysis,correlation studies,and correlograms.Each test is designed to determine the replicability of a specific time-series,as well as the replicability of periodicities found from the time-series.The results show at least three key components to assessing replicability:(a)U-Pb igneous and detrital zircon age distributions are highly replicable,(b)time-series replicability gradually deteriorates with age,and(c)replicability is scale dependent,with low frequency cycles being more replicable than high frequency cycles.From the tests,we conclude that four harmonic cycles are highly replicable and statistically significant,these being periodicities of 810,270,90,and 67.5-myr.展开更多
Lower Carboniferous clastic sedimentary rocks(i.e.,the Nanduan Formation)in the Changning-Menglian belt of the southeastern Tibetan Plateau may provide new insights into the tectonic evolution of the Paleo-Tethys Ocea...Lower Carboniferous clastic sedimentary rocks(i.e.,the Nanduan Formation)in the Changning-Menglian belt of the southeastern Tibetan Plateau may provide new insights into the tectonic evolution of the Paleo-Tethys Ocean.This paper presents new petrographic,geochemical,and detrital zircon U-Pb age data to constrain the provenance and depositional setting of these rocks.Sandstone samples of the Nanduan Formation are all quartz arenites(Q_(92-99)F_(1-7)L_(0-2))with high SiO_(2)contents(85.1 wt.%-95.2 wt.%;average=90.9 wt.%),indicating high compositional maturity.They exhibit fractionated rare earth element(REE)patterns,with light REE enrichment[(La/Yb)_(N)=6.48-12.1]and negative Eu anomalies(Eu/Eu^(*)=0.53-0.74),and marked negative Sr-Cs-V-Cr-Ni anomalies in upper continental crust-normalised multi-element diagrams.The geochemical features and heavy mineral assemblages suggest that sediments were mainly derived from ancient sedimentary rocks in cratonic interiors or stable continental areas,and were probably deposited in a passive continental margin setting.Detrital zircon U-Pb dating(n=256)of the Nanduan Formation sandstones defines three distinct age peaks in the Pan-African(600-500 Ma),younger Grenvillian(950-850 Ma),and older Grenvillian(1250-1000 Ma).Their zircon age spectra are similar to those of Lower Paleozoic sedimentary rocks(i.e.,the Mengtong and Mengdingjie groups)in the BaoshanSibumasu Block,but significantly different from those of older rocks in the Simao-Indochina and other surrounding blocks(i.e.,the western Yangtze,western Cathaysia,western Qiangtang,Tethyan Himalaya,and Lhasa blocks).This suggests that the Nanduan Formation was deposited at the margin of the Baoshan-Sibumasu Block.Combining the new data presented in this study with published data,we suggest that the Nanduan Formation and underlying Lancang Group were deposited in the same setting during the Early and Late Paleozoic,respectively.展开更多
The tectonic evolution of Borneo and the affiliation between Southern and Northern Borneo remains unclear.The Rajang and Crocker Fan sediments,as one of the largest ancient submarine fans in Southeast Asia have witnes...The tectonic evolution of Borneo and the affiliation between Southern and Northern Borneo remains unclear.The Rajang and Crocker Fan sediments,as one of the largest ancient submarine fans in Southeast Asia have witnessed the tectonic evolution of Borneo since at least the late Mesozoic.In this study,we present laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)U-Pb dating and Hf isotopic results of detrital zircons from the Trusmadi and Crocker formations within the Crocker Fan of Sabah,Northern Borneo.Our results,coupled with previous data,show that the Crocker Fan sediments in Sabah of Northern Borneo display similar age spectra to the Rajang Fan sediments in Sarawak of Central Borneo,with two major age clusters at 130-80 and 280-200 Ma.Further provenance analysis based on mineral shape with a prismatic characteristic and similar detrital zircon Hf isotopes of the two formations illustrates that the Jurassic-Cretaceous and partly Triassic detrital zircons of the Crocker and Rajang Fan sediments were derived from the erosion of contemporaneous magmatic rocks;part of Permian-Triassic ones could be the recycling of the Jurassic deposits in SW Borneo.The initial provenance of these Permian-Triassic detritus could be synchronous magmatic rocks in the Tin belt of the Malay Peninsula.Combining with previous data,we propose that the entire Borneo continent,including both Southern and Northern Borneo,developed a common Mesozoic continental magmatic arc.Moreover,we postulate that the Rajang and Crocker fans formed in a fore-arc extensional rift basin related to the retreat of the subducted Paleo-Pacific Plate beneath the Northern Borneo margin.展开更多
The Southwest Tianshan is the suture zone between the Central Tianshan and the Tarim Craton.To better illustrate the subduction polarity of the Southwest Tianshan Ocean,a systematic detrital zircon LA-ICP-MS U-Pb geoc...The Southwest Tianshan is the suture zone between the Central Tianshan and the Tarim Craton.To better illustrate the subduction polarity of the Southwest Tianshan Ocean,a systematic detrital zircon LA-ICP-MS U-Pb geochronology of sedimentary rocks of the Devonian Apadaerkang Formation and the Carboniferous Akeqiayi Group of the Biedieli area in the Wushi region is the focus.Detrital zircon ages indicate that the youngest grains of the targeted quartz sandstones are Late Devonian and Early Carboniferous in age,respectively.These ages also have relatively similar age spectra,indicating a similar tectonic setting and source in the Biedieli area during the Devonian to Carboniferous.The main spectrum peaks occur at 2360,1960,810,640 and 440 Ma,with a principal age peak in the early Paleozoic(474-430 Ma),and the Central Tianshan Terrane is indicated as the main source.The detrital zircon geochronology and sedimentary characteristics of the Biedieli rocks indicate that the Paleozoic sedimentary rocks in the northern Wushi region were formed at an active continental margin,associated mainly with the early Paleozoic subduction of the South Tianshan Ocean.展开更多
The ocean crust remnants of the Proto-Tethys were preserved as the Kudi ophiolites in the West Kunlun Orogenic Belt(WKOB),and its evolutionary history was mainly constructed by research on igneous or metamorphic rocks...The ocean crust remnants of the Proto-Tethys were preserved as the Kudi ophiolites in the West Kunlun Orogenic Belt(WKOB),and its evolutionary history was mainly constructed by research on igneous or metamorphic rocks in the WKOB.Sedimentary rocks in the WKOB received little attention in the past;however,they could provide important constraints on the evolution of the oceanic lithosphere.Here,a series of shales and greywackes found in the Kudi area of WKOB were studied to constrain their deposition ages and explore their significance in the evolution of the ProtoTethys oceanic crust.The U-Pb dating and europium anomaly(Eu/Eu^(*))were analyzed for detrital zircons from greywackes interlayers,while bulk rare earth elements and yttrium(REY)of the shales were measured.Detrital zircons U-Pb ages yield a maximum deposition age of 436 Ma for the greywackes and black shales,while the REY distribution patterns of the black shales are similar to those of the Tarim Ordovician Saergan shales.Accordingly,the studied WKOB black shales were deposited in the Proto-Tethys Ocean during the Late Ordovician-Early Silurian period.The maximum deposition age at 436 Ma may represent a minimum closure time of the Proto-Tethys Ocean,which is also supported by the absence of increases in Eu/Eu^(*)values during the Late Ordovician-Early Silurian.Besides,our Eu/Eu^(*)values in detrital zircons indicate diminished orogenesis during the Archean to Meso-Proterozoic,subduction-related accretion at the margins of the supercontinent Rodinia during the Neoproterozoic.展开更多
The Central Yunnan Basin(CYB)that tectonically located on the southwest margin of the Yangtze Block and to the eastern segment of the Paleo-Tethys tectonic domain,is a typical‘red bed'sedimentary basin formed sin...The Central Yunnan Basin(CYB)that tectonically located on the southwest margin of the Yangtze Block and to the eastern segment of the Paleo-Tethys tectonic domain,is a typical‘red bed'sedimentary basin formed since Late Triassic.The CYB is composed of mega-thick fluvial and lacustrine facies successions.However,the tectonic evolution and sedimentary provenance studies on this basin are scarce.In this study,we report new detrital zircon ages of four sandstones from the Lower Jurassic Fengjiahe Formation(FJF),including four major clusters of 2060-1810,870-760,485-430,and 280-254 Ma,with sporadic Archean,Cambrian,and Triassic ages.We interpret that the Archaean and Proterozoic zircons were mainly derived from the western Yangtze Block,which may recycle from the Jiangnan Orogen,the Cathaysia Block and the Proterozoic igneous rocks.Ordovician and Silurian zircons were probably from the Ailaoshan orogenic belt,and the Lancang Group in western Yunnan,as well as the Yangtze,Cathaysia and Indosinian blocks.Permian zircons probably came from the Ailaoshan orogenic belt and the Emeishan basalt.The youngest zircon age of~212.9 Ma indicates that the depositional age of the FJF is younger than the Norian stage.We also proposed a geodynamic model of the CYB and the Ailaoshan orogenic belt during the Mesozoic.The Simao Block to the west of the CYB constituted the Ailaoshan orogenic belt and collaged with the Yangtze Block during the Early Triassic,provided sedimentary provenance to the CYB.The Changning-Menglian zone that composed of the Baoshan and the Simao Blocks,uplifted in the Late Triassic and provided provenance to the CYB.Collapse of the Ailaoshan orogenic belt in Late Triassic probably provided channel for source materials that transported from the Lincang granites to the CYB.We propose a transtensional tectonic setting of the central Yunnan during the Early Jurassic,after a short collision during the Indosinian Movement in the Late Triassic.展开更多
Arc-continent collision zones are critical areas where uplift,accretion,and erosion processes significantly influence the growth,elimination,or recycling of the continental crust.The Zagros–Makran Transition Zone,loc...Arc-continent collision zones are critical areas where uplift,accretion,and erosion processes significantly influence the growth,elimination,or recycling of the continental crust.The Zagros–Makran Transition Zone,located along the Minab-Zendan Fault,represents a convergence boundary between the Zagros continental domain and the Makran accretionary prism in southern Iran from the Cretaceous onwards.Several tectonic slices,including Neotethys ophiolitic remnants and the Ganj and Bajgan-Durkan complexes,have accreted along the southern margin of the Eurasian Plate during subduction in the western Makran wedge.To clarify the growth steps of the Makran Prism and the internal deformation associated with arc-continent collision,we used a provenance study of sandstones from the western Makran accretionary prism involving petrography of the main detrital components and U–Pb dating,Hf isotopic values,and trace elements of detrital zircon grains.Our findings reveal a progressive scenario in which oceanic arc-related rocks of the∼99 Ma Ganj Complex with Hf values ranging from+10 to+16 were uplifted during the Early to Late Eocene.The Eocene fore-arc sediments were sourced from the∼49–47 Ma Urumieh-Dokhtar Magmatic Arc with Hf values between−5 and+12,as well as from the Ganj Complex.The Jurassic–Cretaceous Bajgan-Durkan Complex was uplifted due to the Late Eocene to Oligocene collision of various terranes along the southern margin of the Eurasian Plate.This led to a major sediment influx into the Makran trench with a detrital signal in the range∼175–160 Ma with Hf isotopic values from−3 to+4 and alongside the Urumieh-Dokhtar Magmatic Arc with detrital ages ranging∼46–37 Ma and ca.80 Ma.Notably,metamorphic lithic grains began to appear in the sediments in the Late Eocene.The initial arrival of sediments from the Arabian margin to the arc-continent suture zone along the Minab-Zendan Fault indicates the onset of initial collision.During the Late Oligocene–Early Miocene,detrital zircon ages in the range of∼610–520 Ma,sourced from the Arabian basement,were deposited in the trench basin together with components from the Eocene Urumieh-Dokhtar Magmatic Arc and Cretaceous ophiolitic clasts of∼93 Ma with Hf isotopic values of+12 to+16.Following the development and uplift of the orogen from the Middle Miocene onward,detrital zircon grains from the Cretaceous–Miocene Urumieh-Dokhtar Magmatic Arc,Jurassic–Cretaceous Bajgan-Durkan Complex,and Cretaceous ophiolites are present in both the Makran and Zagros sedimentary domains.展开更多
The Erlian Basin is one of the most important multi-energy basins in China.The Baiyanhua area of the Chuanjing depression in the western Erlian Basin has recently become a favorable area for new progress in sandstone-...The Erlian Basin is one of the most important multi-energy basins in China.The Baiyanhua area of the Chuanjing depression in the western Erlian Basin has recently become a favorable area for new progress in sandstone-type uranium prospecting.However,the Cretaceous source-to-sink evolution of the Chuanjing depression in the Erlian Basin is poorly known.This paper presents the systematic geochemical and zircon U-Pb studies on the Saihantala Formation and Erlian Formation in the Baiyanhua area.The data obtained are functionally important for revealing the provenance and tectonic setting of the source rocks.The results show that the upper part of the Saihantala Formation and the lower part of the Erlian Formation are mainly composed of felsic sedimentary rocks.The source rocks originated from a continental margin arc environment in terms of tectonic setting.The detrital zircons ages have the dominant populations at ca.250-270 Ma,with two subdominant age groups at ca.1400-1800 and 1900-2100 Ma,respectively.Combined with the tectono-sedimentary evolution of the Chuanjing depression,we conclude that:(1)the provenance of the Cretaceous strata was mostly sourced from the Baiyanhua uplift;(2)the water depth became shallow in the Southern Sangendalai sag during the middle period of Saihantala,further preventing the formation of coal beds;(3)the formation of Baiyanhua uplift might provide the beneficial tectonic condition for uranium mineralization in the upper Saihantala Formation in southern Sangendalai sag.This is significant for us to understand the space allocation of coal and uranium in Chuanjing depression and evaluate the uranium metallogenic prospects in southern Sangendalai sag.展开更多
The Late Paleozoic-Early Mesozoic sedimentary system of the Luang Prabang Paleotethyan back-arc basin in northern Laos is important for investigating sedimentary provenance,paleogeographic patterns,and the tectonic ev...The Late Paleozoic-Early Mesozoic sedimentary system of the Luang Prabang Paleotethyan back-arc basin in northern Laos is important for investigating sedimentary provenance,paleogeographic patterns,and the tectonic evolution of the eastern Paleotethyan Ocean.This study presents systematic stratigraphy,petrology,geochemistry,and detrital zircon U-Pb-Hf isotopic analyses for the Late Carboniferous-Jurassic sedimentary strata on both sides of the Luang Prabang Basin.Based on distinct stratigraphic ages and provenance characteristics,the clastic rock samples can be divided into four groups.The Group 1 Late Carboniferous-Early Permian samples from the western part of the basin yield detrital zircon age-peaks of~348 and~1425 Ma,with correspondingεHf(t)values ranging from-2.0 to+15.5 and+1.5 to+14,respectively.The age spectrum of Group 2 Late Carboniferous-Early Permian samples from the eastern part of the basin shows major age-peaks of~287 and~1860 Ma,withεHf(t)values of-5.9--0.9 and-3.6-+4.2,respectively.Group 3 Late Permian-Triassic samples exhibit age-peaks of~242 and~1853 Ma,along withεHf(t)values of-0.7-+14.4 and-5.4--1.8,respectively.Group 4 Middle-Late Jurassic samples yield agepeaks of~237,~431,~813,~1833,and~2460 Ma,lacking Late Devonian(413-345 Ma)detrital zircons.All these data collectively suggest that the Group 1 sample primarily originated from the Sukhothai arc in western Indochina,Group 2 was from the Kontum and Truong Son in eastern Indochina,and Group 3 has a combined provenance of the Sukhothai,Kontum,and Truong Son.Regional comparisons suggest that the Jurassic provenance was mainly derived from South China,which was imported through the northern river system.Our data,combined with the regional angular unconformities between the Jurassic continental strata and pre-Jurassic marine strata,suggest that the Luang Prabang Basin transformed into a superimposed collisional retroforeland basin during the Jurassic,and the closure of the Luang Prabang BAB occurred before the Late Triassic.展开更多
The Qinling orogenic belt in central China underwent long-term tectonic evolution during an amalgamation between the North China and South China cratons.However,intense compressional deformation and uplift erosion res...The Qinling orogenic belt in central China underwent long-term tectonic evolution during an amalgamation between the North China and South China cratons.However,intense compressional deformation and uplift erosion resulted in the transformation and disappearance of much geological record from the Qinling orogenic belt,and the tectonic evolution of this belt remains poorly constrained during the Triassic.Located in the northernmost margin of the South China Craton,the Sichuan Basin preserves the complete Triassic sedimentary succession,and can provide significant information for understanding the Triassic tectonic evolution of the Qinling orogenic belt.We present detrital zircon U-Pb dating,trace element and in situ Lu-Hf isotope data for the Middle Triassic Leikoupo Formation and the Late Triassic Xujiahe Formation samples from the eastern Sichuan Basin,South China.The detrital zircon U-Pb ages of the Leikoupo Formation show seven age clusters of 280-242,350-300,500-400,1000-800,2000-1750,2100-2000 and 2600-2400 Ma,while those of the Xujiahe Formation show five age clusters of 300-200,500-350,1050-950,2000-1750 and 2600-2400 Ma.Combined with published paleocurrent and paleogeographic data,the sediments of the Leikoupo Formation are interpreted to be sourced from the North China Craton,Yangtze Craton and North Qinling orogenic belt,and the potential main source regions of the Xujiahe Formation included the South and North Qinling orogenic belts.Provenance analysis indicates that the North Qinling orogenic belt was in inherited uplift and coeval denudation in the Middle Triassic.The proportion of the detritus formed in the South Qinling orogenic belt increases gradually from the Leikoupo to Xujiahe formations.This significant provenance change indicates that rapid tectonic uplift and extensive denudation of the South Qinling orogenic belt occurred in the early Late Triassic,which is related to the collision between the North China and South China cratons during the Triassic.展开更多
During Early Cretaceous,NNE-trending extensional basins filling with various volcanic-sedimentary formations developed in the northeastern Da Hinggan Ling(Mts.),northeastern China.This study investigates the formation...During Early Cretaceous,NNE-trending extensional basins filling with various volcanic-sedimentary formations developed in the northeastern Da Hinggan Ling(Mts.),northeastern China.This study investigates the formation age and geological background of Jiufengshan Formation,providing insights into its tectonic setting and formation mechanisms.Detrital zircons from four sandstone samples of Jiufengshan Formation in Nenjiang area indicate a maximum depositional age of 116±1 Ma,corresponding to late Early Cretaceous.Petrographic analysis and zircon age peak comparisons suggest these sandstones originated from proximal deposits with nearby provenances of earlier and contemporaneous volcanic rocks.Further research on the sandstone framework and trace elements in detrital zircons indicates that the formation process of Jiufengshan Formation was likely related to the low-angle subduction of the Paleo-Pacific plate.展开更多
The Upper Triassic flysch sediments(Nieru Formation and Langjiexue Group)exposed in the Eastern Tethyan Himalayan Sequence are crucial for unraveling the controversial paleogeography and paleotectonics of the Himalaya...The Upper Triassic flysch sediments(Nieru Formation and Langjiexue Group)exposed in the Eastern Tethyan Himalayan Sequence are crucial for unraveling the controversial paleogeography and paleotectonics of the Himalayan orogen.This work reports new detrital zircon U-Pb ages and whole-rock geochemical data for clastic rocks from flysch strata in the Shannan area.The mineral modal composition data suggest that these units were mainly sourced from recycled orogen provenances.The chemical compositions of the sandstones in the strata are similar to the chemical composition of upper continental crust.These rocks have relatively low Chemical Index of Alteration values(with an average of 62)and Index of Compositional Variability values(0.69),indicating that they experienced weak weathering and were mainly derived from a mature source.The geochemical compositions of the Upper Triassic strata are similar to those of graywackes from continental island arcs and are indicative of an acidicintermediate igneous source.Furthermore,hornblende and feldspar experienced decomposition in the provenance,and the sediment became enriched in zircon and monazite during sediment transport.The detrital zircons in the strata feature two main age peaks at 225-275 Ma and 500-600 Ma,nearly continuous Paleoproterozoic to Neoproterozoic ages,and a broad inconspicuous cluster in the Tonian-Stenian(800-1200 Ma).The detrital zircons from the Upper Triassic sandstones in the study area lack peaks at 300-325 Ma(characteristic of the Lhasa block)and 1150-1200 Ma(characteristic of the Lhasa and West Australia blocks).Therefore,neither the Lhasa block nor the West Australia blocks likely acted as the main provenance of the Upper Triassic strata.Newly discovered Permian-Triassic basalt and mafic dikes in the Himalayas could have provided the 225-275 Ma detrital zircons.Therefore,Indian and Himalayan units were the main provenances of the flysch strata.The Tethyan Himalaya was part of the northern passive margin and was not an exotic terrane separated from India during the Permian to Early Cretaceous.This evidence suggests that the Neo-Tethyan ocean opened prior to the Late Triassic and that the Upper Triassic deposits were derived from continental crustal fragments adjacent to the northern passive continental margin of Greater India.展开更多
The calculation of a maximum depositional age(MDA)from a detrital zircon sample can provide insight into a variety of geological problems.However,the impact of sample size and calculation method on the accuracy of a r...The calculation of a maximum depositional age(MDA)from a detrital zircon sample can provide insight into a variety of geological problems.However,the impact of sample size and calculation method on the accuracy of a resulting MDA has not been evaluated.We use large populations of synthetic zircon dates(N≈25,000)to analyze the impact of varying sample size(n),measurement uncertainty,and the abundance of neardepositional-age zircons on the accuracy and uncertainty of 9 commonly used MDA calculation methods.Furthermore,a new method,the youngest statistical population is tested.For each method,500 samples of n synthetic dates were drawn from the parent population and MDAs were calculated.The mean and standard deviation of each method ove r the 500 trials at each n-value(50-1000,in increments of 50)were compa red to the known depositional age of the synthetic population and used to compare the methods quantitatively in two simulation scenarios.The first simulation scenario varied the proportion of near-depositional-age grains in the synthetic population.The second scenario varied the uncertainty of the dates used to calculate the MDAs.Increasing sample size initially decreased the mean residual error and standard deviation calculated by each method.At higher n-values(>~300 grains),calculated MDAs changed more slowly and the mean resid ual error increased or decreased depending on the method used.Increasing the p roportion of near-depositional-age grains and lowering measurement uncertainty decreased the number of measurements required for the calculated MDAs to stabilize and decreased the standard deviation in calculated MDAs of the 500 samples.Results of the two simulation scenarios show that the most successful way to increase the accuracy of a calculated M DA is by acquiring a large number of low-uncertainty measurements(300300)approach is used if the calculation of accurate MDAs are key to research goals.Other acquisition method s,such as high-to moderate-precision measurement methods(e.g.,1%-5%,2σ)acquiring low-to moderate-n datasets(50300).Additionally,they are most susceptible to producing erroneous MDAs due to contamination in the field or laboratory,or through disturbances of the youngest zircon’s U-Pb systematics(e.g.,lead loss).More conservative methods that still produce accurate MDAs and are less susceptible to contamination or lead loss include:youngest grain cluster at 1σunce rtainty(YGC 1σ),youngest grain clusterat 2σuncertainty(YGC 2σ),and youngest statistical population(YSP).The ages calculated by these methods may be more useful and appealing when fitting calculated MDAs in to pre-existing chronostratigraphic frameworks,as they are less likely to be younger than the true depositional age.From the results of our numerical models we illustrate what geologic processes(i.e.,tectonic or sedimentary)can be resolved using MDAs derived from strata of different ages.展开更多
In our study,the U-Pb age spectrum of detrital zircons from terrigenous sediments is used to determine the sources.The Middle and Upper Reaches of the Yangtze River drain the western Yangtze craton and eastern Tibetan...In our study,the U-Pb age spectrum of detrital zircons from terrigenous sediments is used to determine the sources.The Middle and Upper Reaches of the Yangtze River drain the western Yangtze craton and eastern Tibetan plateau,and take lots of sediments to the Jianghan （江汉） plain.Detrital zircons collected from Zhoulao （周老） core provide an ideal sample for the provenance studies.Here we report LA-ICP-MS U-Pb ages of 125 detrital zircons from one sand sample in the core sediments,which is recovered from a depth of 86.76-88.58 m and the paleomagnetic age is about 800 kaBP,in Zhoulao Town.The 125 zircons reveal nine major age peaks of 3.0,2.5-2.3,2.0-1.7 Ga,838-723,453-415,257,212,166 and 17 Ma.Only two zircons have ages of 14.8 and 16.5 Ma,their appearance indicates that the headwater of the Yangtze River had reached the Tibetan plateau about 800 ka ago.Our results also show that the Hanjiang （汉江） River did not influence the sediments of the Zhoulao core obviously at that time.展开更多
The Neoproterozoic Tonian strata (ca.870-725 Ma) in the western Jiangnan Orogen archive the records of sedimentary provenance and tectonic setting which can be used to understand the geological evolution of the South ...The Neoproterozoic Tonian strata (ca.870-725 Ma) in the western Jiangnan Orogen archive the records of sedimentary provenance and tectonic setting which can be used to understand the geological evolution of the South China Continent.These strata are separated into the basement and cover sequences by a regional angular unconformity.The basement sequence can be subdivided into the lower and the upper parts by the widespread interbedded ca.840 Ma basalt with pillow structure.In the present work,234 concordant detrital zircon analyses are obtained from three Tonian sandstone samples in the Fanjingshan district,Guizhou Province.Combined with previous results,a total of 1736 analyses of detrital zircon U-Pb ages derived from 12 formations of Tonian strata in the western Jiangnan Orogen are used to decipher the integrated sedimentary and tectonic histories.The zircons from the lowermost part of the basement sequence (the Yujiagou Formation) show oval morphology and display two Paleoproterozoic age peaks at 2325 Ma and 1845 Ma which are similar with the detrital zircon age peaks from the Late Paleoproterozoic to Early Mesoproterozoic Dongchuan/Dahongshan/Hekou groups,suggesting a passive margin basin in which the sediments were mainly sourced from the southwestern Yangtze Block.However,the zircon age population of the lower part of the basement sequence (the Xiaojiahe,Huixiangping formations and their equivalents) indicates the sedimentary derivation from bidirectional sources (the ca.870 Ma arc materials in the south and the old detritus from the southwestern Yangtze Block) which is consistent with a back arc setting for the deposition of the sediments.Zircons from the upper part of the basement sequence (the Duyantang Formation and its equivalent) show euhedral and subangular morphology and display a unimodal age peak at ca.835 Ma.This sequence was possibly deposited in a convergent setting and the detritus were came from the locally distributed syn-collisional igneous rocks.The lower part of the cover sequence (the Xinzhai and Wuye formations and their equivalents) shows a distinct zircon age peak at 815-809 Ma and two subordinate peaks at 2485 Ma and 2018 Ma,suggesting that the basin had gradually transformed into a continental rift basin and received the detritus from the ca.815 Ma post-collisional magmatic rocks as well as from different Paleoproterozoic source rocks in the northern Yangtze Block.We propose a tectonic evolution model that envisages eruption of ca.840 Ma basalt in a back arc basin that existed during ca.870-835 Ma,an angular unconformity was formed during amalgamation of the Yangtze Block and the Cathaysia Block at ca.835-820 Ma and the rifting of the South China Continent was initiated at ca.800 Ma.Our study concludes that the South China Continent was formed on the periphery of the Rodinia supercontinent.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.41902224,41602209).
文摘Detrital zircon and apatite U-Pb-Hf isotope and trace element analyses of the late Mesoproterozoic to early Neoproterozoic strata in southern Jilin provide detailed information on the sediment provenance and tectonic setting of the northeastern margin of the North China Craton(NCC).Here,we present U-Pb and Lu-Hf analyses of 712 detrital zircons,and U-Pb analyses of 347 detrital apatites from the Baifangzi,Diaoyutai and Qiaotou formations.The Baifangzi and Diaoyutai formations are dominated by Neoarchean(2.5-2.6 Ga)and Paleoproterozoic(1.8-1.9 Ga)zircons,indicating a predominant NCC provenance.The Qiaotou Formation is dominated by Mesoproterozoic(1.5-1.7 Ga and 1.1-1.3 Ga)zircons with mainly positiveεHf(t)values,which are similar to those from eastern Laurentia,implying a significant provenance transition.The detrital apatite age spectra of the Baifangzi and Diaoyutai Formations show major populations at 1.8-1.9 Ga and 1.1-1.3 Ga.Based on their trace element compositions,the Mesoproterozoic apatites were mainly sourced from metamorphic rocks,indicating regional metamorphism occurred in the NCC during 1.1-1.3 Ga.Combining these data with regional studies,we propose that the NCC was adjacent to eastern Laurentia during the assembly of the Rodinia supercontinent.
文摘A comprehensive examination of detrital sandstone modes from the Sylhet Trough reveals a diverse range of sub-lithic to sub-feldspathic quartz arenites.Soil samples were gathered from Dupi Gaon(Jaintiapur)in Bangladesh,followed by a thorough analysis using field examination,X-ray diffraction(XRD),X-ray fluorescence(XRF),petrography,and heavy mineral concentration analyses.Field observations revealed the soil sample varying from white to yellowish to variegated,with thicknesses ranging from 15 cm to about 4 m,and exhibiting moderate softness.XRF analysis revealed significant SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)levels in the samples,with zirconium(Zr)and copper(Cu)showing consistently high concentrations.XRD analysis identified quartz as predominant,along with muscovite,biotite,and accessory minerals like rutile and magnetite.Petrographic analysis highlighted quartz as dominant,with fractures suggesting tectonic influences,while heavy mineral separation techniques identified zircon,garnet,goethite,rutile,and magnetite.These findings provide insights into sediment provenance,depositional processes,and environ-mental conditions during the formation of the Dupi Tila Formation.The comprehensive geochemical data of the entire rock indicates that most of the sediments originated from felsic igneous sources,and also suggests a moderate to high level of weathering in the source region.Overall,the analyses suggested an in situ origin of the Dupi Tila Formation,with parent materials being predominantly detrital rather than authigenic,supported by the presence of detrital quartz and an assessment of the depositional environment,providing insights into the geological conditions of the era and potential modes of sediment transportation.
基金funded by the National Science Centre(NCN,Poland)project nos.2018/29/B/ST10/02315 and 2019/33/B/ST10/01728 and the Swedish Research Council(Vetenskapsrådet)grant no.2019-03688.OL is grateful to the Deutsche Forschunggemeinschaft for the support of his COSC-2 research(DFG 867/12-1,13-1,and 13-2)supported by a National Science Foundation(USA)grant EAR2050246.
文摘Detrital zircon geochronology is reported from the c.1200 m thick Cambro-Ordovician sedimentary succession recovered in core from the COSC-2 continental drilling project in the Scandinavian Caledonides.Above a regolith marking the sub-Cambrian peneplain,a lower to middle Cambrian(?)succession comprises conglomerate,sandstone and shale overlain by gravity flows fining upwards into the Alum Shale Formation.First results of detrital zircon geochronology from the Cambrian(?)succession show that the basal section of the autochthonous cover is characterized by mainly late Paleoproterozoic–early Mesoproterozoic detrital grains.The middle part of the succession is dominated by late Paleoproterozoic detritus with minor Mesoproterozoic and Archean input.The upper part of lower Cambrian(?)succession is characterized by Archean to Cambrian detritus.The maximum depositional age is calculated to 530.5±4 Ma for the upper part of the lower Cambrian succession.Two samples from the Lower Ordovician(?)succession above the Alum Shale Formation show predominantly Mesoproterozoic to early Neoproterozoic(1.5–0.9 Ga)ages.The autochthonous lower Cambrian(?)passive margin succession in the lower section is dominated by local detritus,sourced exclusively from the Eastern Segment of the Sveconorwegian Orogen,which includes the basement studied in COSC-2.Up-section,the provenance shifts towards the Transscandinavian Igneous Belt and Svecofennian Orogen sources,with the youngest part of the succession showing a notable input of Neoproterozoic–Cambrian active margin detritus.The Ordovician(?)succession is characterized by populations,likely derived from the Sveconorwegian Orogen,and a minor cratonic contribution.Statistical analysis of detrital zircon datasets across Baltica suggests that the Southern Baltica/Sandomirian Arc,rather than the Timanian Orogen,was a significant source of detrital material across the paleocontinent.The influence of Timanian Orogen grains is limited to northernmost Scandinavia,whereas Sandomirian detritus reached central Scandinavia in the lower to middle Cambrian and remained prevalent in southern Scandinavia into the Lower Ordovician.
基金supported by the French Agence Nationale de la Recherche(19-CE31-0002 AstroMeso)the European Research Council under the European Union’s Horizon 2020 Research and Innovation Program(Advanced Grant AstroGeo-885250).
文摘When interpreting results,it is imperative to have some understanding of the degree to which the results are replicable.If the results cannot be replicated with independent data,then interpretations from the results become questionable.To minimize the potential for misinterpretations,the current study analyzes six time-series derived from globally sampled U-Pb zircon databases–of which,two are independent igneous databases,one being a quasi-independent igneous database,and three being independent detrital databases.These time-series are then analyzed with standard statistical methods to evaluate replicability.The methods include bandpass filtering to transform the raw time-series into stationary sequences,Student’s t-test,Monte Carlo simulations,periodograms from spectral analysis,correlation studies,and correlograms.Each test is designed to determine the replicability of a specific time-series,as well as the replicability of periodicities found from the time-series.The results show at least three key components to assessing replicability:(a)U-Pb igneous and detrital zircon age distributions are highly replicable,(b)time-series replicability gradually deteriorates with age,and(c)replicability is scale dependent,with low frequency cycles being more replicable than high frequency cycles.From the tests,we conclude that four harmonic cycles are highly replicable and statistically significant,these being periodicities of 810,270,90,and 67.5-myr.
基金financially supported by the Yunnan Fundamental Research Projects(No.202201AT070077)the Ministry-Province Cooperation Pilot Projects(No.2023ZRBSHZ059)+1 种基金the Major Science and Technology Special Plan of Yunnan Province(No.202202AG050006)the National Natural Science Foundation of China(No.41603032)。
文摘Lower Carboniferous clastic sedimentary rocks(i.e.,the Nanduan Formation)in the Changning-Menglian belt of the southeastern Tibetan Plateau may provide new insights into the tectonic evolution of the Paleo-Tethys Ocean.This paper presents new petrographic,geochemical,and detrital zircon U-Pb age data to constrain the provenance and depositional setting of these rocks.Sandstone samples of the Nanduan Formation are all quartz arenites(Q_(92-99)F_(1-7)L_(0-2))with high SiO_(2)contents(85.1 wt.%-95.2 wt.%;average=90.9 wt.%),indicating high compositional maturity.They exhibit fractionated rare earth element(REE)patterns,with light REE enrichment[(La/Yb)_(N)=6.48-12.1]and negative Eu anomalies(Eu/Eu^(*)=0.53-0.74),and marked negative Sr-Cs-V-Cr-Ni anomalies in upper continental crust-normalised multi-element diagrams.The geochemical features and heavy mineral assemblages suggest that sediments were mainly derived from ancient sedimentary rocks in cratonic interiors or stable continental areas,and were probably deposited in a passive continental margin setting.Detrital zircon U-Pb dating(n=256)of the Nanduan Formation sandstones defines three distinct age peaks in the Pan-African(600-500 Ma),younger Grenvillian(950-850 Ma),and older Grenvillian(1250-1000 Ma).Their zircon age spectra are similar to those of Lower Paleozoic sedimentary rocks(i.e.,the Mengtong and Mengdingjie groups)in the BaoshanSibumasu Block,but significantly different from those of older rocks in the Simao-Indochina and other surrounding blocks(i.e.,the western Yangtze,western Cathaysia,western Qiangtang,Tethyan Himalaya,and Lhasa blocks).This suggests that the Nanduan Formation was deposited at the margin of the Baoshan-Sibumasu Block.Combining the new data presented in this study with published data,we suggest that the Nanduan Formation and underlying Lancang Group were deposited in the same setting during the Early and Late Paleozoic,respectively.
基金jointly supported by the Scientific Research Foundation of Third Institute of Oceanography,Ministry of Natural Resources,Xiamen(No.2018002)the Guangxi Natural Science Fundation(No.2022GXNSFBA035588)+1 种基金the National Natural Science Foundation of China(Nos.41506050,41402193)the Scientific Research Foundation of Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration(No.19-185-17-09)。
文摘The tectonic evolution of Borneo and the affiliation between Southern and Northern Borneo remains unclear.The Rajang and Crocker Fan sediments,as one of the largest ancient submarine fans in Southeast Asia have witnessed the tectonic evolution of Borneo since at least the late Mesozoic.In this study,we present laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)U-Pb dating and Hf isotopic results of detrital zircons from the Trusmadi and Crocker formations within the Crocker Fan of Sabah,Northern Borneo.Our results,coupled with previous data,show that the Crocker Fan sediments in Sabah of Northern Borneo display similar age spectra to the Rajang Fan sediments in Sarawak of Central Borneo,with two major age clusters at 130-80 and 280-200 Ma.Further provenance analysis based on mineral shape with a prismatic characteristic and similar detrital zircon Hf isotopes of the two formations illustrates that the Jurassic-Cretaceous and partly Triassic detrital zircons of the Crocker and Rajang Fan sediments were derived from the erosion of contemporaneous magmatic rocks;part of Permian-Triassic ones could be the recycling of the Jurassic deposits in SW Borneo.The initial provenance of these Permian-Triassic detritus could be synchronous magmatic rocks in the Tin belt of the Malay Peninsula.Combining with previous data,we propose that the entire Borneo continent,including both Southern and Northern Borneo,developed a common Mesozoic continental magmatic arc.Moreover,we postulate that the Rajang and Crocker fans formed in a fore-arc extensional rift basin related to the retreat of the subducted Paleo-Pacific Plate beneath the Northern Borneo margin.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.42172258,42072227,U2244205)the Science and Technology Major Project of Xinjiang Uygur Autonomous Region,China(2023A03002)+2 种基金the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(Grant No.2015BAB05B04)the Joint Innovation Fund of China National Uranium Co.,Ltd.,and State Key Laboratory of Nuclear Resources and Environment(Grant No.NRE2021-01)the China Geological Survey(Grant Nos.DD20242868,DZLXJK202206)。
文摘The Southwest Tianshan is the suture zone between the Central Tianshan and the Tarim Craton.To better illustrate the subduction polarity of the Southwest Tianshan Ocean,a systematic detrital zircon LA-ICP-MS U-Pb geochronology of sedimentary rocks of the Devonian Apadaerkang Formation and the Carboniferous Akeqiayi Group of the Biedieli area in the Wushi region is the focus.Detrital zircon ages indicate that the youngest grains of the targeted quartz sandstones are Late Devonian and Early Carboniferous in age,respectively.These ages also have relatively similar age spectra,indicating a similar tectonic setting and source in the Biedieli area during the Devonian to Carboniferous.The main spectrum peaks occur at 2360,1960,810,640 and 440 Ma,with a principal age peak in the early Paleozoic(474-430 Ma),and the Central Tianshan Terrane is indicated as the main source.The detrital zircon geochronology and sedimentary characteristics of the Biedieli rocks indicate that the Paleozoic sedimentary rocks in the northern Wushi region were formed at an active continental margin,associated mainly with the early Paleozoic subduction of the South Tianshan Ocean.
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supported by the Open Foundation of the State Key Laboratory of Continental Dynamics,Northwest University,China(No.16LCD06)the Basic Research Program from Department of Science and Technology Yunnan Province(No.202101AU070132)+1 种基金Jun Wang was also supported by the‘Double Top’Construction Projects(No.C176220100135)at Yunnan Universitysupported by the open fund from the Key Laboratory of Deep-Earth Dynamics of the Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing,10037,China(No.J1901)。
文摘The Central Yunnan Basin(CYB)that tectonically located on the southwest margin of the Yangtze Block and to the eastern segment of the Paleo-Tethys tectonic domain,is a typical‘red bed'sedimentary basin formed since Late Triassic.The CYB is composed of mega-thick fluvial and lacustrine facies successions.However,the tectonic evolution and sedimentary provenance studies on this basin are scarce.In this study,we report new detrital zircon ages of four sandstones from the Lower Jurassic Fengjiahe Formation(FJF),including four major clusters of 2060-1810,870-760,485-430,and 280-254 Ma,with sporadic Archean,Cambrian,and Triassic ages.We interpret that the Archaean and Proterozoic zircons were mainly derived from the western Yangtze Block,which may recycle from the Jiangnan Orogen,the Cathaysia Block and the Proterozoic igneous rocks.Ordovician and Silurian zircons were probably from the Ailaoshan orogenic belt,and the Lancang Group in western Yunnan,as well as the Yangtze,Cathaysia and Indosinian blocks.Permian zircons probably came from the Ailaoshan orogenic belt and the Emeishan basalt.The youngest zircon age of~212.9 Ma indicates that the depositional age of the FJF is younger than the Norian stage.We also proposed a geodynamic model of the CYB and the Ailaoshan orogenic belt during the Mesozoic.The Simao Block to the west of the CYB constituted the Ailaoshan orogenic belt and collaged with the Yangtze Block during the Early Triassic,provided sedimentary provenance to the CYB.The Changning-Menglian zone that composed of the Baoshan and the Simao Blocks,uplifted in the Late Triassic and provided provenance to the CYB.Collapse of the Ailaoshan orogenic belt in Late Triassic probably provided channel for source materials that transported from the Lincang granites to the CYB.We propose a transtensional tectonic setting of the central Yunnan during the Early Jurassic,after a short collision during the Indosinian Movement in the Late Triassic.
基金This research was supported by the NSFC grant(No.92255303)The first author is grateful for support from the IGGCAS postdoctoral program(2016IFPR01)under the guidance of Prof.Bo Wan.
文摘Arc-continent collision zones are critical areas where uplift,accretion,and erosion processes significantly influence the growth,elimination,or recycling of the continental crust.The Zagros–Makran Transition Zone,located along the Minab-Zendan Fault,represents a convergence boundary between the Zagros continental domain and the Makran accretionary prism in southern Iran from the Cretaceous onwards.Several tectonic slices,including Neotethys ophiolitic remnants and the Ganj and Bajgan-Durkan complexes,have accreted along the southern margin of the Eurasian Plate during subduction in the western Makran wedge.To clarify the growth steps of the Makran Prism and the internal deformation associated with arc-continent collision,we used a provenance study of sandstones from the western Makran accretionary prism involving petrography of the main detrital components and U–Pb dating,Hf isotopic values,and trace elements of detrital zircon grains.Our findings reveal a progressive scenario in which oceanic arc-related rocks of the∼99 Ma Ganj Complex with Hf values ranging from+10 to+16 were uplifted during the Early to Late Eocene.The Eocene fore-arc sediments were sourced from the∼49–47 Ma Urumieh-Dokhtar Magmatic Arc with Hf values between−5 and+12,as well as from the Ganj Complex.The Jurassic–Cretaceous Bajgan-Durkan Complex was uplifted due to the Late Eocene to Oligocene collision of various terranes along the southern margin of the Eurasian Plate.This led to a major sediment influx into the Makran trench with a detrital signal in the range∼175–160 Ma with Hf isotopic values from−3 to+4 and alongside the Urumieh-Dokhtar Magmatic Arc with detrital ages ranging∼46–37 Ma and ca.80 Ma.Notably,metamorphic lithic grains began to appear in the sediments in the Late Eocene.The initial arrival of sediments from the Arabian margin to the arc-continent suture zone along the Minab-Zendan Fault indicates the onset of initial collision.During the Late Oligocene–Early Miocene,detrital zircon ages in the range of∼610–520 Ma,sourced from the Arabian basement,were deposited in the trench basin together with components from the Eocene Urumieh-Dokhtar Magmatic Arc and Cretaceous ophiolitic clasts of∼93 Ma with Hf isotopic values of+12 to+16.Following the development and uplift of the orogen from the Middle Miocene onward,detrital zircon grains from the Cretaceous–Miocene Urumieh-Dokhtar Magmatic Arc,Jurassic–Cretaceous Bajgan-Durkan Complex,and Cretaceous ophiolites are present in both the Makran and Zagros sedimentary domains.
基金funded by the project initiated by the China Geological Survey“Investigation of sandstone-type uranium deposits in the Ordos and Qaidam Basins”(No.DD20190119)the National Key Research and Development Project(No.2018YFC0604200)from the Ministry of Science and Technology of the International Geoscience Programme(No.IGCP675),which is a joint endeavor of UNESCO and IUGS。
文摘The Erlian Basin is one of the most important multi-energy basins in China.The Baiyanhua area of the Chuanjing depression in the western Erlian Basin has recently become a favorable area for new progress in sandstone-type uranium prospecting.However,the Cretaceous source-to-sink evolution of the Chuanjing depression in the Erlian Basin is poorly known.This paper presents the systematic geochemical and zircon U-Pb studies on the Saihantala Formation and Erlian Formation in the Baiyanhua area.The data obtained are functionally important for revealing the provenance and tectonic setting of the source rocks.The results show that the upper part of the Saihantala Formation and the lower part of the Erlian Formation are mainly composed of felsic sedimentary rocks.The source rocks originated from a continental margin arc environment in terms of tectonic setting.The detrital zircons ages have the dominant populations at ca.250-270 Ma,with two subdominant age groups at ca.1400-1800 and 1900-2100 Ma,respectively.Combined with the tectono-sedimentary evolution of the Chuanjing depression,we conclude that:(1)the provenance of the Cretaceous strata was mostly sourced from the Baiyanhua uplift;(2)the water depth became shallow in the Southern Sangendalai sag during the middle period of Saihantala,further preventing the formation of coal beds;(3)the formation of Baiyanhua uplift might provide the beneficial tectonic condition for uranium mineralization in the upper Saihantala Formation in southern Sangendalai sag.This is significant for us to understand the space allocation of coal and uranium in Chuanjing depression and evaluate the uranium metallogenic prospects in southern Sangendalai sag.
基金supported by the National Key Research and Development Program of China(No.2023YFF0803701)the National Natural Science Foundation of China(Nos.42330302 and 42472265)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.SML2023SP239)。
文摘The Late Paleozoic-Early Mesozoic sedimentary system of the Luang Prabang Paleotethyan back-arc basin in northern Laos is important for investigating sedimentary provenance,paleogeographic patterns,and the tectonic evolution of the eastern Paleotethyan Ocean.This study presents systematic stratigraphy,petrology,geochemistry,and detrital zircon U-Pb-Hf isotopic analyses for the Late Carboniferous-Jurassic sedimentary strata on both sides of the Luang Prabang Basin.Based on distinct stratigraphic ages and provenance characteristics,the clastic rock samples can be divided into four groups.The Group 1 Late Carboniferous-Early Permian samples from the western part of the basin yield detrital zircon age-peaks of~348 and~1425 Ma,with correspondingεHf(t)values ranging from-2.0 to+15.5 and+1.5 to+14,respectively.The age spectrum of Group 2 Late Carboniferous-Early Permian samples from the eastern part of the basin shows major age-peaks of~287 and~1860 Ma,withεHf(t)values of-5.9--0.9 and-3.6-+4.2,respectively.Group 3 Late Permian-Triassic samples exhibit age-peaks of~242 and~1853 Ma,along withεHf(t)values of-0.7-+14.4 and-5.4--1.8,respectively.Group 4 Middle-Late Jurassic samples yield agepeaks of~237,~431,~813,~1833,and~2460 Ma,lacking Late Devonian(413-345 Ma)detrital zircons.All these data collectively suggest that the Group 1 sample primarily originated from the Sukhothai arc in western Indochina,Group 2 was from the Kontum and Truong Son in eastern Indochina,and Group 3 has a combined provenance of the Sukhothai,Kontum,and Truong Son.Regional comparisons suggest that the Jurassic provenance was mainly derived from South China,which was imported through the northern river system.Our data,combined with the regional angular unconformities between the Jurassic continental strata and pre-Jurassic marine strata,suggest that the Luang Prabang Basin transformed into a superimposed collisional retroforeland basin during the Jurassic,and the closure of the Luang Prabang BAB occurred before the Late Triassic.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC0602704)the National Natural Science Foundation of China(Grant No.U20B6001 and 91755211).
文摘The Qinling orogenic belt in central China underwent long-term tectonic evolution during an amalgamation between the North China and South China cratons.However,intense compressional deformation and uplift erosion resulted in the transformation and disappearance of much geological record from the Qinling orogenic belt,and the tectonic evolution of this belt remains poorly constrained during the Triassic.Located in the northernmost margin of the South China Craton,the Sichuan Basin preserves the complete Triassic sedimentary succession,and can provide significant information for understanding the Triassic tectonic evolution of the Qinling orogenic belt.We present detrital zircon U-Pb dating,trace element and in situ Lu-Hf isotope data for the Middle Triassic Leikoupo Formation and the Late Triassic Xujiahe Formation samples from the eastern Sichuan Basin,South China.The detrital zircon U-Pb ages of the Leikoupo Formation show seven age clusters of 280-242,350-300,500-400,1000-800,2000-1750,2100-2000 and 2600-2400 Ma,while those of the Xujiahe Formation show five age clusters of 300-200,500-350,1050-950,2000-1750 and 2600-2400 Ma.Combined with published paleocurrent and paleogeographic data,the sediments of the Leikoupo Formation are interpreted to be sourced from the North China Craton,Yangtze Craton and North Qinling orogenic belt,and the potential main source regions of the Xujiahe Formation included the South and North Qinling orogenic belts.Provenance analysis indicates that the North Qinling orogenic belt was in inherited uplift and coeval denudation in the Middle Triassic.The proportion of the detritus formed in the South Qinling orogenic belt increases gradually from the Leikoupo to Xujiahe formations.This significant provenance change indicates that rapid tectonic uplift and extensive denudation of the South Qinling orogenic belt occurred in the early Late Triassic,which is related to the collision between the North China and South China cratons during the Triassic.
基金Supported by the National Key R&D Program(No.2017YFC0601401-03).
文摘During Early Cretaceous,NNE-trending extensional basins filling with various volcanic-sedimentary formations developed in the northeastern Da Hinggan Ling(Mts.),northeastern China.This study investigates the formation age and geological background of Jiufengshan Formation,providing insights into its tectonic setting and formation mechanisms.Detrital zircons from four sandstone samples of Jiufengshan Formation in Nenjiang area indicate a maximum depositional age of 116±1 Ma,corresponding to late Early Cretaceous.Petrographic analysis and zircon age peak comparisons suggest these sandstones originated from proximal deposits with nearby provenances of earlier and contemporaneous volcanic rocks.Further research on the sandstone framework and trace elements in detrital zircons indicates that the formation process of Jiufengshan Formation was likely related to the low-angle subduction of the Paleo-Pacific plate.
基金sponsored by National Program on Key Basic Research Project(973 Program, Grant No. 2016YFC0600308)the China Geological Survey(Grant No. DD20160015)
文摘The Upper Triassic flysch sediments(Nieru Formation and Langjiexue Group)exposed in the Eastern Tethyan Himalayan Sequence are crucial for unraveling the controversial paleogeography and paleotectonics of the Himalayan orogen.This work reports new detrital zircon U-Pb ages and whole-rock geochemical data for clastic rocks from flysch strata in the Shannan area.The mineral modal composition data suggest that these units were mainly sourced from recycled orogen provenances.The chemical compositions of the sandstones in the strata are similar to the chemical composition of upper continental crust.These rocks have relatively low Chemical Index of Alteration values(with an average of 62)and Index of Compositional Variability values(0.69),indicating that they experienced weak weathering and were mainly derived from a mature source.The geochemical compositions of the Upper Triassic strata are similar to those of graywackes from continental island arcs and are indicative of an acidicintermediate igneous source.Furthermore,hornblende and feldspar experienced decomposition in the provenance,and the sediment became enriched in zircon and monazite during sediment transport.The detrital zircons in the strata feature two main age peaks at 225-275 Ma and 500-600 Ma,nearly continuous Paleoproterozoic to Neoproterozoic ages,and a broad inconspicuous cluster in the Tonian-Stenian(800-1200 Ma).The detrital zircons from the Upper Triassic sandstones in the study area lack peaks at 300-325 Ma(characteristic of the Lhasa block)and 1150-1200 Ma(characteristic of the Lhasa and West Australia blocks).Therefore,neither the Lhasa block nor the West Australia blocks likely acted as the main provenance of the Upper Triassic strata.Newly discovered Permian-Triassic basalt and mafic dikes in the Himalayas could have provided the 225-275 Ma detrital zircons.Therefore,Indian and Himalayan units were the main provenances of the flysch strata.The Tethyan Himalaya was part of the northern passive margin and was not an exotic terrane separated from India during the Permian to Early Cretaceous.This evidence suggests that the Neo-Tethyan ocean opened prior to the Late Triassic and that the Upper Triassic deposits were derived from continental crustal fragments adjacent to the northern passive continental margin of Greater India.
基金Funding for this research was provided by a NSERC Discovery Grant(No.RGPIN/341715-2013)to S.Hubbard and a Queen Eliz-abethⅡscholarship from the University of Calgary to D.Coutts
文摘The calculation of a maximum depositional age(MDA)from a detrital zircon sample can provide insight into a variety of geological problems.However,the impact of sample size and calculation method on the accuracy of a resulting MDA has not been evaluated.We use large populations of synthetic zircon dates(N≈25,000)to analyze the impact of varying sample size(n),measurement uncertainty,and the abundance of neardepositional-age zircons on the accuracy and uncertainty of 9 commonly used MDA calculation methods.Furthermore,a new method,the youngest statistical population is tested.For each method,500 samples of n synthetic dates were drawn from the parent population and MDAs were calculated.The mean and standard deviation of each method ove r the 500 trials at each n-value(50-1000,in increments of 50)were compa red to the known depositional age of the synthetic population and used to compare the methods quantitatively in two simulation scenarios.The first simulation scenario varied the proportion of near-depositional-age grains in the synthetic population.The second scenario varied the uncertainty of the dates used to calculate the MDAs.Increasing sample size initially decreased the mean residual error and standard deviation calculated by each method.At higher n-values(>~300 grains),calculated MDAs changed more slowly and the mean resid ual error increased or decreased depending on the method used.Increasing the p roportion of near-depositional-age grains and lowering measurement uncertainty decreased the number of measurements required for the calculated MDAs to stabilize and decreased the standard deviation in calculated MDAs of the 500 samples.Results of the two simulation scenarios show that the most successful way to increase the accuracy of a calculated M DA is by acquiring a large number of low-uncertainty measurements(300300)approach is used if the calculation of accurate MDAs are key to research goals.Other acquisition method s,such as high-to moderate-precision measurement methods(e.g.,1%-5%,2σ)acquiring low-to moderate-n datasets(50300).Additionally,they are most susceptible to producing erroneous MDAs due to contamination in the field or laboratory,or through disturbances of the youngest zircon’s U-Pb systematics(e.g.,lead loss).More conservative methods that still produce accurate MDAs and are less susceptible to contamination or lead loss include:youngest grain cluster at 1σunce rtainty(YGC 1σ),youngest grain clusterat 2σuncertainty(YGC 2σ),and youngest statistical population(YSP).The ages calculated by these methods may be more useful and appealing when fitting calculated MDAs in to pre-existing chronostratigraphic frameworks,as they are less likely to be younger than the true depositional age.From the results of our numerical models we illustrate what geologic processes(i.e.,tectonic or sedimentary)can be resolved using MDAs derived from strata of different ages.
基金supported by the National Natural Science Foundation of China (Nos. 40771213,40672206)the National Basic Research Program of China (No.2004CB720204)
文摘In our study,the U-Pb age spectrum of detrital zircons from terrigenous sediments is used to determine the sources.The Middle and Upper Reaches of the Yangtze River drain the western Yangtze craton and eastern Tibetan plateau,and take lots of sediments to the Jianghan （江汉） plain.Detrital zircons collected from Zhoulao （周老） core provide an ideal sample for the provenance studies.Here we report LA-ICP-MS U-Pb ages of 125 detrital zircons from one sand sample in the core sediments,which is recovered from a depth of 86.76-88.58 m and the paleomagnetic age is about 800 kaBP,in Zhoulao Town.The 125 zircons reveal nine major age peaks of 3.0,2.5-2.3,2.0-1.7 Ga,838-723,453-415,257,212,166 and 17 Ma.Only two zircons have ages of 14.8 and 16.5 Ma,their appearance indicates that the headwater of the Yangtze River had reached the Tibetan plateau about 800 ka ago.Our results also show that the Hanjiang （汉江） River did not influence the sediments of the Zhoulao core obviously at that time.
基金supported by the National Natural Science Foundation of China (41603039)China Postdoctoral ScienceFoundation (2016M601092)+2 种基金Open Foundation of State Key Laboratory of Ore Deposit Geochemistry (201510)Geosciences Research Foundation of Bureau of Geology and Mineral Exploration and Development Guizhou Province (QDKKH[2016]34)Guizhou Scientific and Technology Planning Project (QKHPTRC[2018]5626, QKHPTRC[2017]5739, QKH[2016]PTRC5401)
文摘The Neoproterozoic Tonian strata (ca.870-725 Ma) in the western Jiangnan Orogen archive the records of sedimentary provenance and tectonic setting which can be used to understand the geological evolution of the South China Continent.These strata are separated into the basement and cover sequences by a regional angular unconformity.The basement sequence can be subdivided into the lower and the upper parts by the widespread interbedded ca.840 Ma basalt with pillow structure.In the present work,234 concordant detrital zircon analyses are obtained from three Tonian sandstone samples in the Fanjingshan district,Guizhou Province.Combined with previous results,a total of 1736 analyses of detrital zircon U-Pb ages derived from 12 formations of Tonian strata in the western Jiangnan Orogen are used to decipher the integrated sedimentary and tectonic histories.The zircons from the lowermost part of the basement sequence (the Yujiagou Formation) show oval morphology and display two Paleoproterozoic age peaks at 2325 Ma and 1845 Ma which are similar with the detrital zircon age peaks from the Late Paleoproterozoic to Early Mesoproterozoic Dongchuan/Dahongshan/Hekou groups,suggesting a passive margin basin in which the sediments were mainly sourced from the southwestern Yangtze Block.However,the zircon age population of the lower part of the basement sequence (the Xiaojiahe,Huixiangping formations and their equivalents) indicates the sedimentary derivation from bidirectional sources (the ca.870 Ma arc materials in the south and the old detritus from the southwestern Yangtze Block) which is consistent with a back arc setting for the deposition of the sediments.Zircons from the upper part of the basement sequence (the Duyantang Formation and its equivalent) show euhedral and subangular morphology and display a unimodal age peak at ca.835 Ma.This sequence was possibly deposited in a convergent setting and the detritus were came from the locally distributed syn-collisional igneous rocks.The lower part of the cover sequence (the Xinzhai and Wuye formations and their equivalents) shows a distinct zircon age peak at 815-809 Ma and two subordinate peaks at 2485 Ma and 2018 Ma,suggesting that the basin had gradually transformed into a continental rift basin and received the detritus from the ca.815 Ma post-collisional magmatic rocks as well as from different Paleoproterozoic source rocks in the northern Yangtze Block.We propose a tectonic evolution model that envisages eruption of ca.840 Ma basalt in a back arc basin that existed during ca.870-835 Ma,an angular unconformity was formed during amalgamation of the Yangtze Block and the Cathaysia Block at ca.835-820 Ma and the rifting of the South China Continent was initiated at ca.800 Ma.Our study concludes that the South China Continent was formed on the periphery of the Rodinia supercontinent.
