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 giant Jiama deposit is a post-collisional porphyry Cu-polymetallic system located in the Gangdese metallogenic belt of Xizang.It consists of three deposits:The Main deposit,the Zegulangbei deposit,and the South Pi...The giant Jiama deposit is a post-collisional porphyry Cu-polymetallic system located in the Gangdese metallogenic belt of Xizang.It consists of three deposits:The Main deposit,the Zegulangbei deposit,and the South Pit deposit according to exploration and research.The South Pit deposit is a high-grade Cu-Pb-Zn deposit,but its genesis is unclear.To investigate its genesis,a detailed study was conducted on the deposit geology,geochronology and amphibole geochemistry.The results indicate that the weighted average 206Pb/238U age of the zircons from the granite porphyry in the South Pit is 15.38±0.45 Ma,and the molybdenite from the mineralized skarn yield a ReOs isochron age of 15.23±0.22 Ma,in line with the age of the Main deposit(15.7-14.3 Ma).The amphiboles in the granite porphyry of the South Pit,magnesiohornblende and actinolite,are high in Mg and Ca and low in K.They crystallized at temperatures of 705-7490C,pressures of 0.44-0.67 kbar,oxygen fugacity of-14.31--13.69(NNO),and depths of 1.7-2.5 km.Mapping of structure and alteration indicates that the South Pit skarn developed due to the metasomatism of marble of hornfels or carbonate in fold hinge dilation and an interlayer detachment zone by magmatic hydrothermal fluids.According to the age of magmatism and geological features,the South Pit deposit and the Main deposit have originated from the same Miocene magmatism,but the South Pit deposit was affected by the gliding nappe tectonic system.The amphibole geochemistry indicates that the ore-related magma of the South Pit has a high oxygen fugacity and is rich in water.展开更多
The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive pha...The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive phases of the Suzhou granite,whole-rock geochemistry,geochemistry and U-Th-Pb dating of monazite was analyzed.The unique geochemical characteristics show that the Suzhou pluton can be discriminated as an A-type granite.LA-ICP-MS U-Th-Pb dating of monazite in both the medium-and coarse-grained biotite granite(MBG)and the fine-grained biotite granite(FBG)indicates that the granite formed between 124 and 127 Ma.Based on geochemical characteristics and mineral textures,the MBG(Mnz-Ia)and FBG(Mnz-Ib)monazites are classified as magmatic monazites;another monazite(Mnz-II)from the MBG formed during a magmatic-hydrothermal transitional stage.Nb-Ta in the Suzhou pluton gradually concentrated during fractional crystallization and alteration of Ti-rich minerals and biotite.Ultimately,with the involvement of F-Li-rich fluid,Nb-Ta mineralization occurred during the magmatic-hydrothermal transition.The Suzhou pluton is considered part of a 600-km-and NE-SW-trending Nb-rich A-type granite belt together with other Early Cretaceous A-type granites in the Jiangnan Orogen that offers prospects of a new target for Nb-Ta prospecting.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
Zircon crystals,which form directly from igneous melts,are invaluable for probing the deep crustal basement and provide crucial insights into its composition and evolution.Supercontinent cycles,including the formation...Zircon crystals,which form directly from igneous melts,are invaluable for probing the deep crustal basement and provide crucial insights into its composition and evolution.Supercontinent cycles,including the formation and breakup of Columbia,Rodinia,and Gondwana,play a pivotal role in shaping global magmatic and metamorphic records,and deciphering magmatic patterns is critical for unraveling the complex interplay between tectonics and magmatism.This study investigates U-Pb geochronology and trace/rare earth element(REE)compositions of zircons from the Early Cretaceous Tethyan Himalaya Igneous Province,revealing critical insights into Precambrian-Paleozoic magmatic and tectonic evolution.Dominant Paleoproterozoic(2498 Ma,1912 Ma)and Neoproterozoic(826-762 Ma)zircon populations confirm the existence of the Precambrian basement.Neoproterozoic magmatism shows decoupling between light and heavy REE(LREE/HREE)and europium anomalies(Eu/Eu^(*)=Eu_(N)/(Sm_(N)×Gd_(N))^(1/2))during the 826-762 Ma and 725-702 Ma intervals,indicating that the Rodinia margin evolved from Andean-style subduction to continental collision.Early Paleozoic magmatism correlates with Pan-African orogenesis and subsequent Proto-Tethyan Ocean subduction beneath the Indian Craton.Neo-Tethyan initiation(ca.273 Ma)is evidenced by 200-300 Ma zircons which exhibit(1)absence of LREE/HREE-Eu/Eu^(*)crustal thickness correlations,and(2)a thermal peak at 273 Ma.展开更多
We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and g...We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and geochemical data,the granitoids in the region can be divided into two age groups:ca.285 Ma and ca.269 Ma.The granitoids of the first group are mainly composed of calc-alkaline to high-K calc-alkaline,weakly peraluminous Ⅰ-type granodiorites with ε_(Hf)(t)values of-19.6 to-4.3,which demonstrates evidence of crustal reworking;the granitoids of the second group,however,mainly consist of A-type granites that are high-K calc-alkaline to shoshonite,metaluminous to weakly peraluminous,and have high 10,000×Ga/Al ratios(2.59-3.12)and ε_(Hf)(t)values ranging from-11.3 to-2.7,all of which demonstrates a mixed crust-mantle source.We interpret the granitoids of the first group to have formed during the subduction of Central Asian oceanic crust and the second group to have formed by the asthenospheric upwelling caused by the formation of slab windows during late ocean ridge subduction.展开更多
The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho...The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho-types from the quarries in Kabbaldurga reveal a complex geological history in the Archean and early Paleoprotero-zoic.Magmatic protoliths predominantly record Paleoar-chean ages between 3.4 and 3.2 Ga.Combined U-Pb and Lu-Hf signatures indicate a history of recurrent crustal anatexis,juvenile magmatic input,and felsic injections.Mesoarchaean magmatic charnockites were generated mainly from hornblende-dehydration melting of Paleoar-chaean mafic rocks.In addition,Peninsular Gneissic Com-plex of the Dharwar Craton,commonly described as TTG suites,are likely generated by melting of hydrated basalt.The new data are consistent with the idea of a convecting magmatic cycle and also support the proposal that the southern Dharwar Craton comprises a tilted cross-sec-tion through the Archaean crust.Paleoproterozoic high-temperature event is documented here as a complex unit involving juvenile mafic magmatism,granulite facies imprints and crustal anatexis as well as felsic injections,occurring within a short time period around 2.5 Ga.展开更多
1.Objective The Eastern Junggar Kalamaili region in Xinjiang constitutes a significant tin metallogenic belt in northwest China(Fig.1a).It hosts four independent tin deposits-Kamusite,Ganliangzi,Beilekuduke,and Saresh...1.Objective The Eastern Junggar Kalamaili region in Xinjiang constitutes a significant tin metallogenic belt in northwest China(Fig.1a).It hosts four independent tin deposits-Kamusite,Ganliangzi,Beilekuduke,and Sareshenke-from west to east,supplemented by two tin mineralized points,namely Hongtujingzi and Sujiquan(Figs.1b).according to the ore type and the composition of gangue minerals,the tin deposits in the region are classified into two groups:Quartz vein type and greisen type,with the Sareshenke deposit ascribed to the former and the remainder to the latter.展开更多
To determine the geological age,petrogenesis,and tectonic setting of Mesozoic volcanic rocks in the Ningyuancun Formation in Xunke area,Lesser Hinggan Range,the zircon U-Pb geochronology,petrographic observations,and ...To determine the geological age,petrogenesis,and tectonic setting of Mesozoic volcanic rocks in the Ningyuancun Formation in Xunke area,Lesser Hinggan Range,the zircon U-Pb geochronology,petrographic observations,and geochemical analyses of major and trace elements were conducted in this study.Zircon U-Pb dating showed that the volcanic rocks of the Ningyuancun Formation were formed in the Early Cretaceous(112.97±0.90 Ma).Major element analyses revealed that the content of SiO_(2)weighted from 74.14%to 76.54%,indicating the volcanic rocks to be high-silica and felsic.The content of Al_(2)O_(3)varies from 12.48%to 13.65%.A total alkali content of the volcanic rocks range between 8.46%and 9.56%,with Na_(2)O/K_(2)O ratios from 0.69 to 0.89.This indicated that the volcanic rocks belonged to a highly differentiated calc-alkaline series.Additionally,A/CNK values range from 0.950 to 1.015,and A/NK values vary between 0.999 and 1.127,suggesting a peraluminous characteristic.Trace element analysis showed a right-sloping“V-shaped”REE pattern,with the enrichment in light REEs and a prominent negative anomaly of Eu.The volcanic rocks are enriched in Rb,Th,U,La,and Ce,while Ba,Sr,and Ti are depleted.Rb/Sr ratio ranges from 10.01 to 12.46,Ti/Y ratio is from 51.14 to 95.72,and Ti/Zr ratio is from 5.78 to 6.41.It is suggested that the magma was derived from the partial melting of crustal rocks.This evidenced that the Early Cretaceous high-silica rhyolites were formed in an intracontinental extension in eastern Northeast China during the northwestward subduction of the Pacific Plate.The crustal extension,asthenospheric mantle upwelling and underplating of mantle-derived magmas resulted in the residual crystalline mush in Early Cretaceous mafic magma chambers to erupt.展开更多
Porphyry-skarn deposits are genetically associated with multistage intrusive complexes.However,their ore fertility varies markedly,as exemplified by the coexistence of mineralized and barren intrusions within a single...Porphyry-skarn deposits are genetically associated with multistage intrusive complexes.However,their ore fertility varies markedly,as exemplified by the coexistence of mineralized and barren intrusions within a single pluton.The factors controlling this disparity,particularly whether high oxygen fugacity(fO_(2))and volatile-rich magmas are essential,remain poorly constrained.This study investigates the Fengyan Zn-Pb-Mo deposit in the central Fujian region by comparing geochronological and geochemical features of ore-associated granite porphyry and barren monzogranite.SIMS zircon U-Pb dating reveals the mineralized intrusion crystallized at 142.5±1.6 Ma,significantly later than the barren monzogranite(150.3±1.3 Ma).The ore-associated porphyry exhibits higher magma temperatures and sulfur contents,yet lower fO_(2)and water content relative to the barren monzogranite.Hf-O isotopes reveal greater mantle input in the ore-related granite porphyry(ε_(Hf)(t)=-11.5 to-7.5;δ^(18)O=6.50‰to 7.11‰)than in the ore-barren monzogranite(ε_(Hf)(t)=-16.0 to-9.5;δ^(18)O=6.81‰to 8.00‰).Furthermore,elevated fO_(2)and volatile-rich conditions are not prerequisites for Zn-Pb-Mo mineralization,implying other factors are key.The barren rock formed during low-angle subduction of the Paleo-Pacific plate,whereas the mineralized porphyry originated during slab rollback and lithospheric extension.This study highlights that medium-low fO_(2)(meanΔFMQ+0.39 in granite porphyry vs.+1.80 in monzogranite),volatile-poor magmatic systems in extensional settings can form significant mineralization,offering new insights for exploration in central Fujian and analogous regions.展开更多
A W-Mo mineralized region is located along the northern margin of the South Qinling tectonic belt of China. WMo mineralization occurs mainly in Cambrian–Ordovician clastic and carbonate rocks, and the ore bodies are ...A W-Mo mineralized region is located along the northern margin of the South Qinling tectonic belt of China. WMo mineralization occurs mainly in Cambrian–Ordovician clastic and carbonate rocks, and the ore bodies are structurally controlled by NW–SE-and NNE–SSW-striking faults. Evidence for magmatism in the area is widespread and is dominated by intermediate–felsic intrusives or apophyses, such as the Dongjiangkou, Yanzhiba, Lanbandeng, and Sihaiping granitic bodies. Quartz-vein-type mineralization and fault-controlled skarn-type mineralization dominate the ore systems, with additional enrichment in residual deposits. At present, there are few or insufficient studies on(1) the age of mineralization,(2) the relationship between intermediate–felsic granite and W-Mo mineralization,(3) the source of ore-forming materials, and(4) the metallogenic and tectonic setting of the mineralized area. In this paper, we present geochronology results for numerous intrusive granitic bodies in the South Qinling tectonic belt. U-Pb zircon geochronology of the Lanbandeng monzogranite and Wangjiaping biotite monzogranite yields ages of 222.7 ± 2.3 and 201.9 ± 1.8 Ma, respectively. In contrast to the Late Triassic age of the Lanbandeng monzogranite, the age of the newly discovered Wangjiaping biotite monzogranite places it at the Triassic–Jurassic boundary. Re-Os molybdenite geochronology on the Qipangou W-Mo deposit yielded a model age of 199.7 ± 3.9 Ma, indicating the deposit formed in the early Yanshanian period of the Early Jurassic. Granitoid intrusions in the mineralized area are characterized by composite granite bodies that crystallized at ca. 240–190 Ma. While there were multiple stages of intrusion, most occurred at 210–220 Ma, with waning magmatic activity at 200–190 Ma. The Re-Os age of molybdenite in the region is ca. 200–190 Ma, which may represent a newly discovered period of W-Mo metallogenesis that occurred during the final stages of magmatism. The heat associated with this magmatism drove ore formation and might have provided additional ore-forming components for metallogenesis(represented by the Wangjiaping biotite monzogranite). Ore materials in the mineralized area were derived from mixed crustal and mantle sources. Enrichment of the region occurred during intracontinental orogenesis in the late Indosinian–Yanshanian, subsequent to the main Indosinian collision. At this time, the tectonic environment was dominated by extension and strike-slip motion.展开更多
During the Late Paleozoic-Early Mesozoic Era,the sediment transport system and tectonic regime in the southeastern margin of the South China Block(SESCB)all changed,significantly affected by the Paleo-Pacific subducti...During the Late Paleozoic-Early Mesozoic Era,the sediment transport system and tectonic regime in the southeastern margin of the South China Block(SESCB)all changed,significantly affected by the Paleo-Pacific subduction.However,controversy exists about the Paleo-Pacific subduction's initiation time.This study uses detrital zircon U-Pb ages to discuss the Late Triassic source-tosink system in the SESCB.It provides some references for the Paleo-Pacific subduction process based on crucial age information and zircons'trace elements.The paleogeography and similarity of detrital zircon age distribution indicate that three sinks were found in the SESCB during the Late Triassic:1.the Yangchun-Kaiping-Gaoming area,comprising major age ranges of 260-220,460-400,and 1200-800 Ma,which might be sourced from the Yunkai terrane;2.the Jiexi-Kanshi-Nanjing area,characterized by the significant age component of 2000-1800 Ma,which corresponded to the Wuyi terrane;3.the Xinan area,consisting of significant age groups of 290-250 and 380-320 Ma,which might be sourced from the magmatic rocks formed by the Huinan Movement and Paleo-Pacific subduction.Note that 290-250 Ma zircons were widely distributed in the Upper Triassic strata,and their trace elements suggested the existence of a magmatic arc near the SESCB during the 290-250 Ma.Thus,we propose that the Paleo-Pacific subduction might have begun in the Early Permian.展开更多
A zircon U-Pb geochronological study on the volcanic rocks reveals that both of the Zhangjiakou and Yixian Formations, northern Hebei Province, are of the Early Cretaceous, with ages of 135-130 Ma and 129-120 Ma, resp...A zircon U-Pb geochronological study on the volcanic rocks reveals that both of the Zhangjiakou and Yixian Formations, northern Hebei Province, are of the Early Cretaceous, with ages of 135-130 Ma and 129-120 Ma, respectively. It is pointed out that the ages of sedimentary basins and volcanism in the northern Hebei -western Liaoning area become younger from west to east, i. e. the volcanism of the Luanping Basin commenced at c. 135 Ma, the Luotuo Mount area of the Chengde Basin c. 130 Ma, and western Liaoning c. 128 Ma. With a correlation of geochronological stratigraphy and biostratigraphy, we deduce that the Xing'anling Group, which comprises the Great Hinggan Mountains volcanic rock belt in eastern China, is predominantly of the early-middle Early Cretaceous, while the Jiande and Shimaoshan Groups and their equivalents, which form the volcanic rock belt in the southeastern coast area of China, are of the mid-late Early Cretaceous, and both the Jehol and Jiande Biotas are of the Early Cretaceous, not Late Jurassic or Late Jurassic-Early Cretaceous. Combining the characteristics of the volcanic rocks and, in a large area, hiatus in the strata of the Late Jurassic or Late Jurassic-early Early Cretaceous between the formations mentioned above and the underlying sequences, we can make the conclusion that, in the Late Jurassic-early Early Cretaceous, the eastern China region was of high relief or plateau, where widespread post-orogenic volcanic series of the Early Cretaceous obviously became younger from inland in the west to continental margin in the east. This is not the result of an oceanward accretion of the subduction belt between the Paleo-Pacific ocean plate and the Asian continent, but rather reflects the extension feature, i.e. after the closure of the Paleo-Pacific ocean, the Paleo-Pacific ancient continent collided with the Asian continent and reached the peak of orogenesis, and then the compression waned and resulted in the retreating of the post-orogenic extension from outer orogenic zone to inner part (or collision zone). The determination of the eruption age of the volcanics of the Zhangjiakou Formation definitely constrains the switch period, which began in the Indosinian and finished in the Yanshanian, that is, 140-135 Ma. The switch is concretely the change from the approximate E-W Paleo-Asian tectonic system to the NE to NNE Pacific system, and the period is also the apex of a continent-continent collision and orogenesis of subduction, being consumed and eventually disappearing of the Paleo-Pacific ancient continent, and all the processes commenced in the Indosinian. While the following post-orogenic large-scale eruption in the Early Cretaceous marks the final completeness of the Paleo-Pacific structure dynamics system.展开更多
This paper reviews the basic principles of radiometric geochronology as implemented in a new software package called Isoplot R, which was designed to be free, flexible and future-proof. Isoplot R is free because it is...This paper reviews the basic principles of radiometric geochronology as implemented in a new software package called Isoplot R, which was designed to be free, flexible and future-proof. Isoplot R is free because it is written in non-proprietary languages(R, Javascript and HTML) and is released under the GPL license. The program is flexible because its graphical user interface(GUI) is separated from the command line functionality, and because its code is completely open for inspection and modification. To increase future-proofness, the software is built on free and platform-independent foundations that adhere to international standards, have existed for several decades, and continue to grow in popularity.Isoplot R currently includes functions for U-Pb, Pb-Pb,40 Ar/39 Ar, Rb-Sr, Sm-Nd, Lu-Hf, Re-Os, U-Th-He,fission track and U-series disequilibrium dating. It implements isochron regression in two and three dimensions, visualises multi-aliquot datasets as cumulative age distributions, kernel density estimates and radial plots, and calculates weighted mean ages using a modified Chauvenet outlier detection criterion that accounts for the analytical uncertainties in heteroscedastic datasets. Overdispersion of geochronological data with respect to these analytical uncertainties can be attributed to either a proportional underestimation of the analytical uncertainties, or to an additive geological scatter term.Isoplot R keeps track of error correlations of the isotopic ratio measurements within aliquots of the same samples. It uses a statistical framework that will allow it to handle error correlations between aliquots in the future. Other ongoing developments include the implementation of alternative user interfaces and the integration of Isoplot R with other data reduction software.展开更多
Zircon U-Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon （via laser ablati...Zircon U-Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon （via laser ablation and secondary ionization mass spectrometry） has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable （e.g. detrital zircons as a sedi- ment fingerprinting method）. The ease of acquisition, while bringing benefit to the Earth science com- munity, has also led to diverse interpretations of geochronological data. In this work we seek to refocus U -Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow. We discuss a range of data filtering approaches and their inherent limitations （e.g. discordance and the reduced chi-squared; MSWD）. We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both 238U/206pb and 207pb/206pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios. As our in situ analytical techniques become progressively more precise, appropriate statistical handing of U-Pb datasets will become increasingly pertinent.展开更多
The subduction of the Bangonghu-Nujiang Meso-Tethys and the collision between the Lhasa and Qiangtang blocks were important events in the growth of the Tibetan crust. However, the timing of collision initiation and cl...The subduction of the Bangonghu-Nujiang Meso-Tethys and the collision between the Lhasa and Qiangtang blocks were important events in the growth of the Tibetan crust. However, the timing of collision initiation and closure timing, as well as nature and structure of the Bangonghu ocean basin, are still poorly constrained. The Lagkor Tso ophiolite, located in the south of Gerze County, Tibet, is one of the most completed ophiolites preserved in the southern side of the Bangonghu- Nujiang suture zone. This study discussed the tectonic evolution of the Bangonghu-Nujiang suture zone as revealed by the Lagkor Tso ophiolite investigated by field investigations, petrology, geochemistry, geochronology and tectonic analysis methods. We present new LA-ICP-MS zircon U-Pb and 39Ar/4~Ar ages for the Lagkor Tso ophiolite, in addition to geochemical and platinum-group element （PGE） data presented for the Lagkor Tso ophiolite in Tibet. It is suggested that the ancient Lagkor Tso oceanic basin split in Middle Jurassic （161.2 ± 2.7 Ma - 165.4 ± 3.5 Ma）, and experienced a second tectonic emplacement during the Early Cretaceous （137.90 ± 6.39 Ma）. The Lagkor Tso ophiolite likely developed in an independent suture zone. The Bangonghu-Nujiang ocean subducted southwards, and the dehydration of the subducting oceanic crust materials caused partial melting of the continental mantle wedge, which formed the second-order expanding center of the obduction dish. This led to inter-arc expansion, followed by the formation of inter-arc and back-arc basins with island arc features, which are represented by ophiolites around the Shiquanhe-Lagkor Tso -Yongzhu region. The tectonic environment presently can be considered to be similar to that of the current Western Pacific, in which a large number of island arc-ocean basin systems are developed.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
The formation time of the Fengshuigouhe Group in the northwestern Lesser Xing＇an Range , NE China, remains controversial owing to the lake of the precise dating data. This article reports zircon U-Pb ages for the le...The formation time of the Fengshuigouhe Group in the northwestern Lesser Xing＇an Range , NE China, remains controversial owing to the lake of the precise dating data. This article reports zircon U-Pb ages for the leptynite and gneissic granitoids from the Fengshuigouhe Group in the northwestern Lesser Xing＇an Range. The aim is to constrain the formation time and prove- nance of Fengshuigouhe Group. Field observation indicates that the Fengshuigouhe Group consists of a suit of metamorphic rocks （leptynite） and gneissic granitoids intruding the leptynite, and that both of them are cut by late granitic pegmatite. Zircons from two leptynites are euhedral-subhedral in shape and display oscillatory zoning in CL （cathodeluminescence） images. These detrital zircons give weighted mean ages of 255, 291,321,361, 469, and 520 Ma. The youngest age of them is interpreted to maximum deposi- tional age of the protoliths of these leptynites. Zircons from gneissic granites are euhedral and subhedral in shape and exhibit typical oscillatory zoning in CL images. The dating results indicate that the gneissic granites were formed in the Early Jurassic （185~2 Ma）. Zircons from the late granitic pegmatite are sub- hedral in shape and exhibit two types in CL images： structureless and oscillatory zoning. The former gives a weighted mean age of 143~1 Ma, considered to represent the timing of crystallization of the pegmatite, the latter yield several groups of ages： 178, 273, 319, 482, 611, and 788 Ma, representing the crystallization age of inherited or captured zircons entrained by the pegmatite. Taken together, we conclude that the Fengshuigouhe Group in the northwestern Lesser Xing＇an Range formed between Late Paleozoic （255Ma） to Early Mesozoic （185 Ma）, rather than Neoproterozoic as previously believed, and that the sediments in the Fengshuigouhe Group were sourced directly from geological bodies in the study area and adjacent regions. KEY WORDS： the Lesser Xing＇an Range, Fengshuigouhe Group, formation time, leptynite, zircon U-Pb geochronology.展开更多
Zircon U-Pb ages, Hf isotope data and whole-rock major and trace element data for the Middle to Late Ordovician gabbros and granites in the Erguna Massif, NE China were presented in this paper. The petrogenesis of the...Zircon U-Pb ages, Hf isotope data and whole-rock major and trace element data for the Middle to Late Ordovician gabbros and granites in the Erguna Massif, NE China were presented in this paper. The petrogenesis of these rocks and the Early Paleozoic tectonic evolution of the massif were discussed. Zircons from the granites and gabbros are of magmatic origin based on their cathodoluminescence（CL） images. The 206Pb/238 U ages obtained from 20 spots on zircons from the granites range from 446±9 to 464±10 Ma, yielding a weighted mean age of 455±10 Ma; and 16 spots on zircons from the gabbros range from 465±10 to 466±7 Ma, yielding a weighted mean age of 465±2 Ma. Chemically, the Late Ordovician granites in the Erguna Massif are weakly peraluminous and similar to A-type granites. The granites and gabbros are all enriched in light rare earth elements and large ion lithophile elements（e.g., Rb, K）, and depleted in heavy rare earth elements and high field strength elements（e.g., Nb, Ta, and Ti）; they all exhibit marked negative Eu anomalies. Their zircon εHf（t） values range mainly from ＋1.86 to ＋6.21（for the granites） and ＋1.39 to ＋3.89（for the gabbros）, except for one spot with a value of-0.27（for a gabbro）. The TDM1 ages for the gabbros and TDM2 ages for the granites vary from 928 to 1 091 Ma and from 1 287 to 1 675 Ma, respectively. It is concluded that the primary magma of the granites could have been derived by partial melting of Mesoproterozoic newly accreted crustal material, whereas the primary magma of the gabbros originated by partial melting of a depleted mantle wedge that had been metasomatized by fluids derived from a subducted slab. These Middle-Late Ordovician granites and gabbros constitute a typical bimodal igneous rock association, implying an extensional environment that was probably related to the post-collisional development of the Erguna and Xing＇an massifs in the early Early Paleozoic.展开更多
An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesi...An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesitic tuff from the Muang-Nan Formation in the Xaignabouli area, which had been mapped as the Permian–Early Triassic on the 1 : 1 000 000 geological map or Late Carboniferous on the 1 : 200 000 geological maps. Zircon U-Pb dating of three samples yielded weighted mean ages of 235±2.6, 232±1.4 and 278±2.8 Ma, respectively, suggesting a Late Triassic origin for the Nam Hang Formation and an Early Permian origin for the Muang-Nan Formation. Geochemically, they are characterized by depletions in HFSEs(e.g., Nb, Ta, Ti) and high LILE/HFSE ratios, and they have positive zircon ε_(Hf)(t) values of 8.7–15.9, which exhibits the continental arc volcanic affinity and partial melting of subducting oceanic slab in the magma source. Combined with spatial occurrence of the volcanic rock and existing geochronological and geochemical data, we suggest that the Xaignabouli-Luang Prabang volcanic belt can be linked to the Loei-Phetchabun belt. The Permian–Triassic volcanic rocks in this belt might be a product of the Nan back-arc basin eastward subduction.展开更多
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supported by the National Key Research and Development Program of China(No.2022YFC2905004)Open Fund from Sino Probe Laboratory(No.SL202405)+4 种基金the Basic Research Fund of Institute of mineral Resource,Chinese Academy of Geological Sciences(No.JKYZD202316)the National Natural Science Foundation of China(Nos.42272093,42230813)China Scholarship Council Project,and the Geological Survey Project(No.DD20230054)Science and Technology Support Project in a new round of prospecting breakthrough strategic action(No.ZKKJ202429)the Central Government Guided Local Scientific and Technological Development Funding Project(No.XZ202401YD0006)。
文摘The giant Jiama deposit is a post-collisional porphyry Cu-polymetallic system located in the Gangdese metallogenic belt of Xizang.It consists of three deposits:The Main deposit,the Zegulangbei deposit,and the South Pit deposit according to exploration and research.The South Pit deposit is a high-grade Cu-Pb-Zn deposit,but its genesis is unclear.To investigate its genesis,a detailed study was conducted on the deposit geology,geochronology and amphibole geochemistry.The results indicate that the weighted average 206Pb/238U age of the zircons from the granite porphyry in the South Pit is 15.38±0.45 Ma,and the molybdenite from the mineralized skarn yield a ReOs isochron age of 15.23±0.22 Ma,in line with the age of the Main deposit(15.7-14.3 Ma).The amphiboles in the granite porphyry of the South Pit,magnesiohornblende and actinolite,are high in Mg and Ca and low in K.They crystallized at temperatures of 705-7490C,pressures of 0.44-0.67 kbar,oxygen fugacity of-14.31--13.69(NNO),and depths of 1.7-2.5 km.Mapping of structure and alteration indicates that the South Pit skarn developed due to the metasomatism of marble of hornfels or carbonate in fold hinge dilation and an interlayer detachment zone by magmatic hydrothermal fluids.According to the age of magmatism and geological features,the South Pit deposit and the Main deposit have originated from the same Miocene magmatism,but the South Pit deposit was affected by the gliding nappe tectonic system.The amphibole geochemistry indicates that the ore-related magma of the South Pit has a high oxygen fugacity and is rich in water.
基金supported by the National Natural Science Foundation of China(Grant Nos.41903025 and 41803048)the National Nonprofit Institute Research Grant of IGGE(Grant Nos.AS2024J03,JY202106 and AS2022P03)+2 种基金the Hebei Key Science and Technology Program(Grant No.19057411Z)the National Science and Technology Major Project(Grant No.2024ZD1002402)the China Geological Survey Project(Grant No.DD20221807).
文摘The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive phases of the Suzhou granite,whole-rock geochemistry,geochemistry and U-Th-Pb dating of monazite was analyzed.The unique geochemical characteristics show that the Suzhou pluton can be discriminated as an A-type granite.LA-ICP-MS U-Th-Pb dating of monazite in both the medium-and coarse-grained biotite granite(MBG)and the fine-grained biotite granite(FBG)indicates that the granite formed between 124 and 127 Ma.Based on geochemical characteristics and mineral textures,the MBG(Mnz-Ia)and FBG(Mnz-Ib)monazites are classified as magmatic monazites;another monazite(Mnz-II)from the MBG formed during a magmatic-hydrothermal transitional stage.Nb-Ta in the Suzhou pluton gradually concentrated during fractional crystallization and alteration of Ti-rich minerals and biotite.Ultimately,with the involvement of F-Li-rich fluid,Nb-Ta mineralization occurred during the magmatic-hydrothermal transition.The Suzhou pluton is considered part of a 600-km-and NE-SW-trending Nb-rich A-type granite belt together with other Early Cretaceous A-type granites in the Jiangnan Orogen that offers prospects of a new target for Nb-Ta prospecting.
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funded by the National Natural Science Foundation of China(42172055)。
文摘Zircon crystals,which form directly from igneous melts,are invaluable for probing the deep crustal basement and provide crucial insights into its composition and evolution.Supercontinent cycles,including the formation and breakup of Columbia,Rodinia,and Gondwana,play a pivotal role in shaping global magmatic and metamorphic records,and deciphering magmatic patterns is critical for unraveling the complex interplay between tectonics and magmatism.This study investigates U-Pb geochronology and trace/rare earth element(REE)compositions of zircons from the Early Cretaceous Tethyan Himalaya Igneous Province,revealing critical insights into Precambrian-Paleozoic magmatic and tectonic evolution.Dominant Paleoproterozoic(2498 Ma,1912 Ma)and Neoproterozoic(826-762 Ma)zircon populations confirm the existence of the Precambrian basement.Neoproterozoic magmatism shows decoupling between light and heavy REE(LREE/HREE)and europium anomalies(Eu/Eu^(*)=Eu_(N)/(Sm_(N)×Gd_(N))^(1/2))during the 826-762 Ma and 725-702 Ma intervals,indicating that the Rodinia margin evolved from Andean-style subduction to continental collision.Early Paleozoic magmatism correlates with Pan-African orogenesis and subsequent Proto-Tethyan Ocean subduction beneath the Indian Craton.Neo-Tethyan initiation(ca.273 Ma)is evidenced by 200-300 Ma zircons which exhibit(1)absence of LREE/HREE-Eu/Eu^(*)crustal thickness correlations,and(2)a thermal peak at 273 Ma.
基金financially supported by the Geological Survey of China(Grant Nos.DD20240075,and DD20243516)the National Natural Science Foundation of China(Grant No.41872209)Basic Scientific Research Fund of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J2314)。
文摘We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and geochemical data,the granitoids in the region can be divided into two age groups:ca.285 Ma and ca.269 Ma.The granitoids of the first group are mainly composed of calc-alkaline to high-K calc-alkaline,weakly peraluminous Ⅰ-type granodiorites with ε_(Hf)(t)values of-19.6 to-4.3,which demonstrates evidence of crustal reworking;the granitoids of the second group,however,mainly consist of A-type granites that are high-K calc-alkaline to shoshonite,metaluminous to weakly peraluminous,and have high 10,000×Ga/Al ratios(2.59-3.12)and ε_(Hf)(t)values ranging from-11.3 to-2.7,all of which demonstrates a mixed crust-mantle source.We interpret the granitoids of the first group to have formed during the subduction of Central Asian oceanic crust and the second group to have formed by the asthenospheric upwelling caused by the formation of slab windows during late ocean ridge subduction.
基金funded by the India-Brazil bilateral co-operation Project:INT/BRAZIL/P-02/2013by Indian Statistical Institute,Geoscience Institute of São Paulo University,Brazil and Department of Geology,University of Calcutta.M.Hueck thanks FAPESP for a post-doctoral fellowship(grant 2019/06838-2).
文摘The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho-types from the quarries in Kabbaldurga reveal a complex geological history in the Archean and early Paleoprotero-zoic.Magmatic protoliths predominantly record Paleoar-chean ages between 3.4 and 3.2 Ga.Combined U-Pb and Lu-Hf signatures indicate a history of recurrent crustal anatexis,juvenile magmatic input,and felsic injections.Mesoarchaean magmatic charnockites were generated mainly from hornblende-dehydration melting of Paleoar-chaean mafic rocks.In addition,Peninsular Gneissic Com-plex of the Dharwar Craton,commonly described as TTG suites,are likely generated by melting of hydrated basalt.The new data are consistent with the idea of a convecting magmatic cycle and also support the proposal that the southern Dharwar Craton comprises a tilted cross-sec-tion through the Archaean crust.Paleoproterozoic high-temperature event is documented here as a complex unit involving juvenile mafic magmatism,granulite facies imprints and crustal anatexis as well as felsic injections,occurring within a short time period around 2.5 Ga.
基金supported by the National Key R&D Program of China(No.2021YFC2901802)project of the China Geological Survey(No.DD20240073)Key R&D Program of Shaanxi Province(No.2024GH-ZDXM-26).
文摘1.Objective The Eastern Junggar Kalamaili region in Xinjiang constitutes a significant tin metallogenic belt in northwest China(Fig.1a).It hosts four independent tin deposits-Kamusite,Ganliangzi,Beilekuduke,and Sareshenke-from west to east,supplemented by two tin mineralized points,namely Hongtujingzi and Sujiquan(Figs.1b).according to the ore type and the composition of gangue minerals,the tin deposits in the region are classified into two groups:Quartz vein type and greisen type,with the Sareshenke deposit ascribed to the former and the remainder to the latter.
基金Supported by Finance Project of heilongjiang Province(No.HLJKD2015-11)Ministry of Natural Resources Scientific and Technological Achievements(No.20220654)National Natural Science Foundation of China(No.42261134535).
文摘To determine the geological age,petrogenesis,and tectonic setting of Mesozoic volcanic rocks in the Ningyuancun Formation in Xunke area,Lesser Hinggan Range,the zircon U-Pb geochronology,petrographic observations,and geochemical analyses of major and trace elements were conducted in this study.Zircon U-Pb dating showed that the volcanic rocks of the Ningyuancun Formation were formed in the Early Cretaceous(112.97±0.90 Ma).Major element analyses revealed that the content of SiO_(2)weighted from 74.14%to 76.54%,indicating the volcanic rocks to be high-silica and felsic.The content of Al_(2)O_(3)varies from 12.48%to 13.65%.A total alkali content of the volcanic rocks range between 8.46%and 9.56%,with Na_(2)O/K_(2)O ratios from 0.69 to 0.89.This indicated that the volcanic rocks belonged to a highly differentiated calc-alkaline series.Additionally,A/CNK values range from 0.950 to 1.015,and A/NK values vary between 0.999 and 1.127,suggesting a peraluminous characteristic.Trace element analysis showed a right-sloping“V-shaped”REE pattern,with the enrichment in light REEs and a prominent negative anomaly of Eu.The volcanic rocks are enriched in Rb,Th,U,La,and Ce,while Ba,Sr,and Ti are depleted.Rb/Sr ratio ranges from 10.01 to 12.46,Ti/Y ratio is from 51.14 to 95.72,and Ti/Zr ratio is from 5.78 to 6.41.It is suggested that the magma was derived from the partial melting of crustal rocks.This evidenced that the Early Cretaceous high-silica rhyolites were formed in an intracontinental extension in eastern Northeast China during the northwestward subduction of the Pacific Plate.The crustal extension,asthenospheric mantle upwelling and underplating of mantle-derived magmas resulted in the residual crystalline mush in Early Cretaceous mafic magma chambers to erupt.
基金jointly funded by Innovation Youth Project of Natural Science Foundation of Fujian Province(No.2024J08144)the Open Fund Project of the Key Laboratory of Ionic Rare Earth Resources and Environment,Ministry of Natural Resources(Grant no.2022IRERE101)+2 种基金the National Natural Science Foundation of China(No.41820104010)Basic Scientific Research Fund of Chinese Academy of Geological Sciences(No.JYYWF20180601)China Scholarship Council(CSC,201908110163)。
文摘Porphyry-skarn deposits are genetically associated with multistage intrusive complexes.However,their ore fertility varies markedly,as exemplified by the coexistence of mineralized and barren intrusions within a single pluton.The factors controlling this disparity,particularly whether high oxygen fugacity(fO_(2))and volatile-rich magmas are essential,remain poorly constrained.This study investigates the Fengyan Zn-Pb-Mo deposit in the central Fujian region by comparing geochronological and geochemical features of ore-associated granite porphyry and barren monzogranite.SIMS zircon U-Pb dating reveals the mineralized intrusion crystallized at 142.5±1.6 Ma,significantly later than the barren monzogranite(150.3±1.3 Ma).The ore-associated porphyry exhibits higher magma temperatures and sulfur contents,yet lower fO_(2)and water content relative to the barren monzogranite.Hf-O isotopes reveal greater mantle input in the ore-related granite porphyry(ε_(Hf)(t)=-11.5 to-7.5;δ^(18)O=6.50‰to 7.11‰)than in the ore-barren monzogranite(ε_(Hf)(t)=-16.0 to-9.5;δ^(18)O=6.81‰to 8.00‰).Furthermore,elevated fO_(2)and volatile-rich conditions are not prerequisites for Zn-Pb-Mo mineralization,implying other factors are key.The barren rock formed during low-angle subduction of the Paleo-Pacific plate,whereas the mineralized porphyry originated during slab rollback and lithospheric extension.This study highlights that medium-low fO_(2)(meanΔFMQ+0.39 in granite porphyry vs.+1.80 in monzogranite),volatile-poor magmatic systems in extensional settings can form significant mineralization,offering new insights for exploration in central Fujian and analogous regions.
基金Shaanxi Mineral Resources and Geological Survey (Grant no. 214027160195)a project on magmatism and W-Mo mineralization in the mineralized areas of western Zhen’anShaanxi Mineral Resources and Geological Survey (Grant no. 61201506280)a project that combined exploration and technical approaches in the mineralized areas of the Qinling mineralized belt。
文摘A W-Mo mineralized region is located along the northern margin of the South Qinling tectonic belt of China. WMo mineralization occurs mainly in Cambrian–Ordovician clastic and carbonate rocks, and the ore bodies are structurally controlled by NW–SE-and NNE–SSW-striking faults. Evidence for magmatism in the area is widespread and is dominated by intermediate–felsic intrusives or apophyses, such as the Dongjiangkou, Yanzhiba, Lanbandeng, and Sihaiping granitic bodies. Quartz-vein-type mineralization and fault-controlled skarn-type mineralization dominate the ore systems, with additional enrichment in residual deposits. At present, there are few or insufficient studies on(1) the age of mineralization,(2) the relationship between intermediate–felsic granite and W-Mo mineralization,(3) the source of ore-forming materials, and(4) the metallogenic and tectonic setting of the mineralized area. In this paper, we present geochronology results for numerous intrusive granitic bodies in the South Qinling tectonic belt. U-Pb zircon geochronology of the Lanbandeng monzogranite and Wangjiaping biotite monzogranite yields ages of 222.7 ± 2.3 and 201.9 ± 1.8 Ma, respectively. In contrast to the Late Triassic age of the Lanbandeng monzogranite, the age of the newly discovered Wangjiaping biotite monzogranite places it at the Triassic–Jurassic boundary. Re-Os molybdenite geochronology on the Qipangou W-Mo deposit yielded a model age of 199.7 ± 3.9 Ma, indicating the deposit formed in the early Yanshanian period of the Early Jurassic. Granitoid intrusions in the mineralized area are characterized by composite granite bodies that crystallized at ca. 240–190 Ma. While there were multiple stages of intrusion, most occurred at 210–220 Ma, with waning magmatic activity at 200–190 Ma. The Re-Os age of molybdenite in the region is ca. 200–190 Ma, which may represent a newly discovered period of W-Mo metallogenesis that occurred during the final stages of magmatism. The heat associated with this magmatism drove ore formation and might have provided additional ore-forming components for metallogenesis(represented by the Wangjiaping biotite monzogranite). Ore materials in the mineralized area were derived from mixed crustal and mantle sources. Enrichment of the region occurred during intracontinental orogenesis in the late Indosinian–Yanshanian, subsequent to the main Indosinian collision. At this time, the tectonic environment was dominated by extension and strike-slip motion.
基金supported by the National Natural Science Foundation of China(No.41872101)the Graduate Innovation Fund of Jilin University(No.2022046)。
文摘During the Late Paleozoic-Early Mesozoic Era,the sediment transport system and tectonic regime in the southeastern margin of the South China Block(SESCB)all changed,significantly affected by the Paleo-Pacific subduction.However,controversy exists about the Paleo-Pacific subduction's initiation time.This study uses detrital zircon U-Pb ages to discuss the Late Triassic source-tosink system in the SESCB.It provides some references for the Paleo-Pacific subduction process based on crucial age information and zircons'trace elements.The paleogeography and similarity of detrital zircon age distribution indicate that three sinks were found in the SESCB during the Late Triassic:1.the Yangchun-Kaiping-Gaoming area,comprising major age ranges of 260-220,460-400,and 1200-800 Ma,which might be sourced from the Yunkai terrane;2.the Jiexi-Kanshi-Nanjing area,characterized by the significant age component of 2000-1800 Ma,which corresponded to the Wuyi terrane;3.the Xinan area,consisting of significant age groups of 290-250 and 380-320 Ma,which might be sourced from the magmatic rocks formed by the Huinan Movement and Paleo-Pacific subduction.Note that 290-250 Ma zircons were widely distributed in the Upper Triassic strata,and their trace elements suggested the existence of a magmatic arc near the SESCB during the 290-250 Ma.Thus,we propose that the Paleo-Pacific subduction might have begun in the Early Permian.
文摘A zircon U-Pb geochronological study on the volcanic rocks reveals that both of the Zhangjiakou and Yixian Formations, northern Hebei Province, are of the Early Cretaceous, with ages of 135-130 Ma and 129-120 Ma, respectively. It is pointed out that the ages of sedimentary basins and volcanism in the northern Hebei -western Liaoning area become younger from west to east, i. e. the volcanism of the Luanping Basin commenced at c. 135 Ma, the Luotuo Mount area of the Chengde Basin c. 130 Ma, and western Liaoning c. 128 Ma. With a correlation of geochronological stratigraphy and biostratigraphy, we deduce that the Xing'anling Group, which comprises the Great Hinggan Mountains volcanic rock belt in eastern China, is predominantly of the early-middle Early Cretaceous, while the Jiande and Shimaoshan Groups and their equivalents, which form the volcanic rock belt in the southeastern coast area of China, are of the mid-late Early Cretaceous, and both the Jehol and Jiande Biotas are of the Early Cretaceous, not Late Jurassic or Late Jurassic-Early Cretaceous. Combining the characteristics of the volcanic rocks and, in a large area, hiatus in the strata of the Late Jurassic or Late Jurassic-early Early Cretaceous between the formations mentioned above and the underlying sequences, we can make the conclusion that, in the Late Jurassic-early Early Cretaceous, the eastern China region was of high relief or plateau, where widespread post-orogenic volcanic series of the Early Cretaceous obviously became younger from inland in the west to continental margin in the east. This is not the result of an oceanward accretion of the subduction belt between the Paleo-Pacific ocean plate and the Asian continent, but rather reflects the extension feature, i.e. after the closure of the Paleo-Pacific ocean, the Paleo-Pacific ancient continent collided with the Asian continent and reached the peak of orogenesis, and then the compression waned and resulted in the retreating of the post-orogenic extension from outer orogenic zone to inner part (or collision zone). The determination of the eruption age of the volcanics of the Zhangjiakou Formation definitely constrains the switch period, which began in the Indosinian and finished in the Yanshanian, that is, 140-135 Ma. The switch is concretely the change from the approximate E-W Paleo-Asian tectonic system to the NE to NNE Pacific system, and the period is also the apex of a continent-continent collision and orogenesis of subduction, being consumed and eventually disappearing of the Paleo-Pacific ancient continent, and all the processes commenced in the Indosinian. While the following post-orogenic large-scale eruption in the Early Cretaceous marks the final completeness of the Paleo-Pacific structure dynamics system.
文摘This paper reviews the basic principles of radiometric geochronology as implemented in a new software package called Isoplot R, which was designed to be free, flexible and future-proof. Isoplot R is free because it is written in non-proprietary languages(R, Javascript and HTML) and is released under the GPL license. The program is flexible because its graphical user interface(GUI) is separated from the command line functionality, and because its code is completely open for inspection and modification. To increase future-proofness, the software is built on free and platform-independent foundations that adhere to international standards, have existed for several decades, and continue to grow in popularity.Isoplot R currently includes functions for U-Pb, Pb-Pb,40 Ar/39 Ar, Rb-Sr, Sm-Nd, Lu-Hf, Re-Os, U-Th-He,fission track and U-series disequilibrium dating. It implements isochron regression in two and three dimensions, visualises multi-aliquot datasets as cumulative age distributions, kernel density estimates and radial plots, and calculates weighted mean ages using a modified Chauvenet outlier detection criterion that accounts for the analytical uncertainties in heteroscedastic datasets. Overdispersion of geochronological data with respect to these analytical uncertainties can be attributed to either a proportional underestimation of the analytical uncertainties, or to an additive geological scatter term.Isoplot R keeps track of error correlations of the isotopic ratio measurements within aliquots of the same samples. It uses a statistical framework that will allow it to handle error correlations between aliquots in the future. Other ongoing developments include the implementation of alternative user interfaces and the integration of Isoplot R with other data reduction software.
文摘Zircon U-Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon （via laser ablation and secondary ionization mass spectrometry） has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable （e.g. detrital zircons as a sedi- ment fingerprinting method）. The ease of acquisition, while bringing benefit to the Earth science com- munity, has also led to diverse interpretations of geochronological data. In this work we seek to refocus U -Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow. We discuss a range of data filtering approaches and their inherent limitations （e.g. discordance and the reduced chi-squared; MSWD）. We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both 238U/206pb and 207pb/206pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios. As our in situ analytical techniques become progressively more precise, appropriate statistical handing of U-Pb datasets will become increasingly pertinent.
基金supported by the National Nature Science Foundation of China (grant No.41372208)China Geological Survey (grant No.1212011221105 and 1212011121259)
文摘The subduction of the Bangonghu-Nujiang Meso-Tethys and the collision between the Lhasa and Qiangtang blocks were important events in the growth of the Tibetan crust. However, the timing of collision initiation and closure timing, as well as nature and structure of the Bangonghu ocean basin, are still poorly constrained. The Lagkor Tso ophiolite, located in the south of Gerze County, Tibet, is one of the most completed ophiolites preserved in the southern side of the Bangonghu- Nujiang suture zone. This study discussed the tectonic evolution of the Bangonghu-Nujiang suture zone as revealed by the Lagkor Tso ophiolite investigated by field investigations, petrology, geochemistry, geochronology and tectonic analysis methods. We present new LA-ICP-MS zircon U-Pb and 39Ar/4~Ar ages for the Lagkor Tso ophiolite, in addition to geochemical and platinum-group element （PGE） data presented for the Lagkor Tso ophiolite in Tibet. It is suggested that the ancient Lagkor Tso oceanic basin split in Middle Jurassic （161.2 ± 2.7 Ma - 165.4 ± 3.5 Ma）, and experienced a second tectonic emplacement during the Early Cretaceous （137.90 ± 6.39 Ma）. The Lagkor Tso ophiolite likely developed in an independent suture zone. The Bangonghu-Nujiang ocean subducted southwards, and the dehydration of the subducting oceanic crust materials caused partial melting of the continental mantle wedge, which formed the second-order expanding center of the obduction dish. This led to inter-arc expansion, followed by the formation of inter-arc and back-arc basins with island arc features, which are represented by ophiolites around the Shiquanhe-Lagkor Tso -Yongzhu region. The tectonic environment presently can be considered to be similar to that of the current Western Pacific, in which a large number of island arc-ocean basin systems are developed.
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.
基金supported by the National Natural Science Foundation of China(No.41072038)China Geological Survey(No.1212010070301)the Opening Foundation of the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan
文摘The formation time of the Fengshuigouhe Group in the northwestern Lesser Xing＇an Range , NE China, remains controversial owing to the lake of the precise dating data. This article reports zircon U-Pb ages for the leptynite and gneissic granitoids from the Fengshuigouhe Group in the northwestern Lesser Xing＇an Range. The aim is to constrain the formation time and prove- nance of Fengshuigouhe Group. Field observation indicates that the Fengshuigouhe Group consists of a suit of metamorphic rocks （leptynite） and gneissic granitoids intruding the leptynite, and that both of them are cut by late granitic pegmatite. Zircons from two leptynites are euhedral-subhedral in shape and display oscillatory zoning in CL （cathodeluminescence） images. These detrital zircons give weighted mean ages of 255, 291,321,361, 469, and 520 Ma. The youngest age of them is interpreted to maximum deposi- tional age of the protoliths of these leptynites. Zircons from gneissic granites are euhedral and subhedral in shape and exhibit typical oscillatory zoning in CL images. The dating results indicate that the gneissic granites were formed in the Early Jurassic （185~2 Ma）. Zircons from the late granitic pegmatite are sub- hedral in shape and exhibit two types in CL images： structureless and oscillatory zoning. The former gives a weighted mean age of 143~1 Ma, considered to represent the timing of crystallization of the pegmatite, the latter yield several groups of ages： 178, 273, 319, 482, 611, and 788 Ma, representing the crystallization age of inherited or captured zircons entrained by the pegmatite. Taken together, we conclude that the Fengshuigouhe Group in the northwestern Lesser Xing＇an Range formed between Late Paleozoic （255Ma） to Early Mesozoic （185 Ma）, rather than Neoproterozoic as previously believed, and that the sediments in the Fengshuigouhe Group were sourced directly from geological bodies in the study area and adjacent regions. KEY WORDS： the Lesser Xing＇an Range, Fengshuigouhe Group, formation time, leptynite, zircon U-Pb geochronology.
基金financially supported by the National Key Basic Research Program of China (Nos. 2013CB429802 and 2013CB429803)the National Natural Science Foundation of China (No. 41272077)by the Opening Foundation of the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan (No. GPMR201104)
文摘Zircon U-Pb ages, Hf isotope data and whole-rock major and trace element data for the Middle to Late Ordovician gabbros and granites in the Erguna Massif, NE China were presented in this paper. The petrogenesis of these rocks and the Early Paleozoic tectonic evolution of the massif were discussed. Zircons from the granites and gabbros are of magmatic origin based on their cathodoluminescence（CL） images. The 206Pb/238 U ages obtained from 20 spots on zircons from the granites range from 446±9 to 464±10 Ma, yielding a weighted mean age of 455±10 Ma; and 16 spots on zircons from the gabbros range from 465±10 to 466±7 Ma, yielding a weighted mean age of 465±2 Ma. Chemically, the Late Ordovician granites in the Erguna Massif are weakly peraluminous and similar to A-type granites. The granites and gabbros are all enriched in light rare earth elements and large ion lithophile elements（e.g., Rb, K）, and depleted in heavy rare earth elements and high field strength elements（e.g., Nb, Ta, and Ti）; they all exhibit marked negative Eu anomalies. Their zircon εHf（t） values range mainly from ＋1.86 to ＋6.21（for the granites） and ＋1.39 to ＋3.89（for the gabbros）, except for one spot with a value of-0.27（for a gabbro）. The TDM1 ages for the gabbros and TDM2 ages for the granites vary from 928 to 1 091 Ma and from 1 287 to 1 675 Ma, respectively. It is concluded that the primary magma of the granites could have been derived by partial melting of Mesoproterozoic newly accreted crustal material, whereas the primary magma of the gabbros originated by partial melting of a depleted mantle wedge that had been metasomatized by fluids derived from a subducted slab. These Middle-Late Ordovician granites and gabbros constitute a typical bimodal igneous rock association, implying an extensional environment that was probably related to the post-collisional development of the Erguna and Xing＇an massifs in the early Early Paleozoic.
基金financially supported by the China Geological Survey (No. 121201010000150013)
文摘An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesitic tuff from the Muang-Nan Formation in the Xaignabouli area, which had been mapped as the Permian–Early Triassic on the 1 : 1 000 000 geological map or Late Carboniferous on the 1 : 200 000 geological maps. Zircon U-Pb dating of three samples yielded weighted mean ages of 235±2.6, 232±1.4 and 278±2.8 Ma, respectively, suggesting a Late Triassic origin for the Nam Hang Formation and an Early Permian origin for the Muang-Nan Formation. Geochemically, they are characterized by depletions in HFSEs(e.g., Nb, Ta, Ti) and high LILE/HFSE ratios, and they have positive zircon ε_(Hf)(t) values of 8.7–15.9, which exhibits the continental arc volcanic affinity and partial melting of subducting oceanic slab in the magma source. Combined with spatial occurrence of the volcanic rock and existing geochronological and geochemical data, we suggest that the Xaignabouli-Luang Prabang volcanic belt can be linked to the Loei-Phetchabun belt. The Permian–Triassic volcanic rocks in this belt might be a product of the Nan back-arc basin eastward subduction.
