Deep-time Earth research plays a pivotal role in deciphering the rates,patterns,and mechanisms of Earth's evolutionary processes throughout geological history,providing essential scientific foundations for climate...Deep-time Earth research plays a pivotal role in deciphering the rates,patterns,and mechanisms of Earth's evolutionary processes throughout geological history,providing essential scientific foundations for climate prediction,natural resource exploration,and sustainable planetary stewardship.To advance Deep-time Earth research in the era of big data and artificial intelligence,the International Union of Geological Sciences initiated the“Deeptime Digital Earth International Big Science Program”(DDE)in 2019.At the core of this ambitious program lies the development of geoscience knowledge graphs,serving as a transformative knowledge infrastructure that enables the integration,sharing,mining,and analysis of heterogeneous geoscience big data.The DDE knowledge graph initiative has made significant strides in three critical dimensions:(1)establishing a unified knowledge structure across geoscience disciplines that ensures consistent representation of geological entities and their interrelationships through standardized ontologies and semantic frameworks;(2)developing a robust and scalable software infrastructure capable of supporting both expert-driven and machine-assisted knowledge engineering for large-scale graph construction and management;(3)implementing a comprehensive three-tiered architecture encompassing basic,discipline-specific,and application-oriented knowledge graphs,spanning approximately 20 geoscience disciplines.Through its open knowledge framework and international collaborative network,this initiative has fostered multinational research collaborations,establishing a robust foundation for next-generation geoscience research while propelling the discipline toward FAIR(Findable,Accessible,Interoperable,Reusable)data practices in deep-time Earth systems research.展开更多
This study investigates the facies development and sedimentology of the Late Permian Chhidru Formation,a mixed carbonate-siliciclastic unit exposed in the Western Salt Range,Potwar Basin,Pakistan.The formation is subd...This study investigates the facies development and sedimentology of the Late Permian Chhidru Formation,a mixed carbonate-siliciclastic unit exposed in the Western Salt Range,Potwar Basin,Pakistan.The formation is subdivided into four lithological units reflecting lateral variability,with thicknesses and lithologies ranging from fossiliferous sandy limestone to interbedded limestone and sandstone.These successions record a depositional shift from a carbonate platform to mixed carbonate-clastic,and ultimately,clastic-dominated environments.Lithostratigraphy suggests deposition on the underlying Wargal Limestone carbonates during a Late Permian sea-level fall on the northwest Indian margin of Gondwana.Similar Permian successions with identical lithological characteristics are documented in the Persian Gulf(Dalan Formation),Arabian Platform(Khuff Formation),and Iran(Nesen and Hambust formations).Petrographic analysis reveals deposition in the distal middle to proximal inner shelf settings of a carbonate-siliciclastic mixed,unrimmed platform.Based on identified foraminiferal assemblages,the Chhidru Formation's age is estimated to range from the late Wuchiapingian to Changhsingian stages of the Lopingian epoch.展开更多
The dominant geodynamic processes that underpin the formation and evolution of Earth’s early crust remain enigmatic calling for new information from less studied ancient cratonic nuclei.Here,we present U-Pb ages and ...The dominant geodynamic processes that underpin the formation and evolution of Earth’s early crust remain enigmatic calling for new information from less studied ancient cratonic nuclei.Here,we present U-Pb ages and Hf isotopic compositions of detrital zircon grains from^2.9 Ga old quartzites and magmatic zircon from a 3.505 Ga old dacite from the Iron Ore Group of the Singhbhum craton,eastern India.The detrital zircon grains range in age between 3.95 Ga and 2.91 Ga.Together with the recently reported Hadean,Eoarchean xenocrystic(up to 4.24 Ga)and modem detritus zircon grains from the Singhbhum craton,our results suggest that the Eoarchean detrital zircons represent crust generated by recycling of Hadean felsic crust formed at^4.3-4.2 Ga and^3.95 Ga.We observe a prominent shift in Hf isotope compositions at^3.6-3.5 Ga towards super-chondritic values,which signify an increased role for depleted mantle and the relevance of plate tectonics.The Paleo-,Mesoarchean zircon Hf isotopic record in the craton indicates crust generation involving the role of both depleted and enriched mantle sources.We infer a short-lived suprasubduction setting around^3.6-3.5 Ga followed by mantle plume activity during the Paleo-,Mesoarchean crust formation in the Singhbhum craton.The Singhbhum craton provides an additional repository for Earth’s oldest materials.展开更多
Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing ...Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing pyrite is as higher as 171.664 ppm on average,with relatively higher light rare earth elements（LREE;159.556 ppm） and lower HREE（12.108 ppm）.TheΣLREE/ΣHREE ratio is 12.612 and（La/Yb）_N is 11.765.These indicate that pyrite is rich in LREE.The（La/Sm）_N ratio is 3.758 and that of（Gd/Yb）_N is 1.695.These are obvious LREE fractionations.The rare earth element（REE） distribution patterns show obvious Eu anomaly with averageδEu values of 0.664,andδCe anomalies of 1.044.REE characteristics are similar to those of wall rocks（regional metamorphic rocks）,but different from those of the Dexing granodiorite porphyry and Damaoshan biotite granite.These features indicate that the ore-forming materials in the Jinshan gold deposit derived from the wall rocks, and the ore-forming fluids derived from metamorphic water.The Co/Ni ratio（average value 0.38） of pyrite suggests that the Jinshan gold deposit formed under a medium-low temperature.It is inferred from the values of high-field strength elements,LREE,Hf/Sm,Nb/La,and Th/La of the pyrite that the ore-forming fluids of the Jinshan gold deposit derived from metamorphic water with Cl〉F.展开更多
Liquid-liquid immiscibility has crucial influences on geological processes,such as magma degassing and formation of ore deposits.Sulfate,as an important component,associates with many kinds of deposits.Two types of im...Liquid-liquid immiscibility has crucial influences on geological processes,such as magma degassing and formation of ore deposits.Sulfate,as an important component,associates with many kinds of deposits.Two types of immiscibility,including(i)fluid-melt immiscibility between an aqueous solution and a sulfate melt,and(ii)fluid-fluid immiscibility between two aqueous fluids with different sulfate concentrations,have been identified for sulfate-water systems.In this study,we investigated the immiscibility behaviors of a sulfate-and quartz-saturated Na_(2)SO_(4)-SiO_(2)-H_(2)O system at elevated temperature,to explore the phase relationships involving both types of immiscibility.The fluid-melt immiscibility appeared first when the Na_(2)SO_(4)-SiO_(2)-H_(2)O sample was heated to~270℃,and then fluid-fluid immiscibility emerged while the sample was further heated to~450℃.At this stage,the coexistence of one water-saturated sulfate melt and two aqueous fluids with distinct sulfate concentrations was observed.The three immiscible phases remain stable over a wide pressure-temperature range,and the appearance temperature of the fluid-fluid immiscibility increases with the increased pressure.Considering that sulfate components occur extensively in carbonatite-related deposits,the fluid-fluid immiscibility can result in significant sulfate fractionation and provides implications for understanding the formation of carbonatite-related rare earth deposits.展开更多
1 Introduction Sedimentary rocks archive important information for understanding how the earth system operates and how life and environments have evolved through earth history.Properly identifying characteristics of s...1 Introduction Sedimentary rocks archive important information for understanding how the earth system operates and how life and environments have evolved through earth history.Properly identifying characteristics of sedimentary rocks,along with the subsequent interpretation of depositional processes and sedimentary environments in a basin or locality.展开更多
We seek to understand lithospheric rheology by mapping continental earthquake depths relative to Moho depth,across the entire India/Asia convergent orogen,and eventually worldwide.Such mapping has particular value in ...We seek to understand lithospheric rheology by mapping continental earthquake depths relative to Moho depth,across the entire India/Asia convergent orogen,and eventually worldwide.Such mapping has particular value in geothermometry,and potentially in identifying regions of delamination.How:We are extending our Sn/Lg method beyond amplitude ratios of regional seismic phases measured on arrays(array Sn/Lg method,Wang and Klemperer,2021)to include frequency proxies for earthquake depth relative to Moho(Wang&Klemperer,2024a,b;Harris et al.,2024).展开更多
Eoarchean(3.6–4.0 Ga)tonalite–trondhjemite–granodiorite(TTG)are the major component of Earth’s oldest persevered continental crust,thereby holding the key to understanding how continental crust originated and when...Eoarchean(3.6–4.0 Ga)tonalite–trondhjemite–granodiorite(TTG)are the major component of Earth’s oldest persevered continental crust,thereby holding the key to understanding how continental crust originated and when plate tectonics started in the early Earth.TTGs are mostly generated by partial melting of hydrated mafic rocks at different depths(e.g.,Moyen and Martin,2012),but whether this requires subduction remains enigmatic(e.g.,Palin et al.,2016).Recent studies show that most early Archean TTGs formed at relatively low pressures(≤1.5 GPa)and do not require subduction(e.g.,Johnson et al.,2017).We have identified a suite of Eoarchean tonalitic gneisses dated at^3.7 Ga from the Tarim Craton,northwestern China(Ge et al.,2018).These rocks are probably the oldest high-pressure TTGs so far documented worldwide.Thermodynamic and trace element modelling demonstrates that the parent magma may have been generated by water-fluxed partial melting of moderately enriched arc-like basalts at 1.8–1.9 GPa and 800–830℃,indicating an apparent geothermal gradient(400–450℃GPa-1)typical for hot subduction zones.They also locally record geochemical evidence for magma interaction with a mantle wedge.Accordingly,we propose that these highpressure TTGs were generated by partial melting of a subducted proto-arc during arc accretion.Our model implies that modernstyle plate tectonics was operative,at least locally,at^3.7 Ga and was responsible for generating some of the oldest continental nuclei.展开更多
The petrogenesis and genetic link to polymetallic mineralization of the granites in the Dayishan complex,southern Hunan province remain debated.Here,we present an integrated study on the petrology,zircon U-Pb ages and...The petrogenesis and genetic link to polymetallic mineralization of the granites in the Dayishan complex,southern Hunan province remain debated.Here,we present an integrated study on the petrology,zircon U-Pb ages and whole-rock geochemistry for this complex.Our findings indicate that the southern complex consists of(amphibole-bearing)biotite granites and muscovite granites emplaced at 153-151 Ma,and the central and northern complex consists of two-mica granites and tourmaline-bearing muscovite granites,respectively with the former emplaced at 164 Ma and the latter at 150 Ma.The(amphibole-bearing)biotite granites have SiO_(2) contents of 68.0-73.8 wt% and are enriched in alkalis and rare earth elements and depleted in Sr and Ba.They display Zr+Y+Ce+Nb>350 ppm and 10000×Ga/Al>2.6 along with high zircon saturation temperatures(821-883oC).The two-mica granites and(tourmaline-bearing)muscovite granites have high SiO_(2)(74.4-77.3 wt%)and low Ga/Al,Zr+Nb+Ce+Y,K/Rb,Zr/Hf,and Nb/Ta along with low zircon saturation temperatures(709-817℃).Geochemical characteristics suggest that the(amphibole-bearing)biotite granites are A-type granites generated through shallow dehydration melting of early Paleozoic granitoids,and that the two-mica granites and(tourmaline-bearing)muscovite granites are fractionated A-type granites produced through fractionation crystallization from the(amphibole-bearing)biotite granites accompanied by fluid fractionation.展开更多
Durable aggregates are essential for the stability and longevity of construction projects,and the Los Angeles Abrasion(LAA)value is a widely used indicator of aggregate durability.However,direct LAA testing is time-co...Durable aggregates are essential for the stability and longevity of construction projects,and the Los Angeles Abrasion(LAA)value is a widely used indicator of aggregate durability.However,direct LAA testing is time-consuming,costly,and requires specialized facilities.This study introduces a novel and efficient alternative by developing two hybrid machine learning models Artificial Neural Network integrated with Particle Swarm Optimization(ANN-PSO)and Artificial Neural Network combined with Teaching-Learning-Based Optimization(ANN-TLBO)for the first time to predict LAA values from petrographic characteristics of carbonate rocks.A total of 160 rock samples from 10 geological formations in Pakistan’s Salt Range were analyzed through petrographic examination and LAA testing.The predictive performance of the proposed models was compared with established techniques,including Multiple Linear Regression,Random Forest,Adaptive Boosting,Gradient Boosting,K-Nearest Neighbors,and Multilayer Perceptron.Results demonstrate that ANN-PSO significantly outperformed all other approaches,achieving an R^(2)of 0.9982,RMSE of 0.209,MAE of 0.159,and MAPE of 0.009.Model robustness was validated using Taylor plots,REC curves,and an external dataset.Sensitivity analysis identified quartz,calcite,and feldspar as the most influential factors affecting LAA prediction.The findings confirm that the ANN-PSO and ANN-TLBO models provide highly accurate,cost-effective,and practical alternatives to traditional LAA testing.This innovative approach advances rock mechanics and material assessment,offering engineers and geologists enhanced tools for aggregate selection and durability evaluation in infrastructure projects.展开更多
The paper reports SHRIMP U-Pb zircon data of a dark eclogite and a post-eclogite garnet-bearing gneissic granitic rock from the Bixiling area, Yuexi County, Anhui Province, in the eastern Dabie Mountains. The eclogite...The paper reports SHRIMP U-Pb zircon data of a dark eclogite and a post-eclogite garnet-bearing gneissic granitic rock from the Bixiling area, Yuexi County, Anhui Province, in the eastern Dabie Mountains. The eclogite, which is metamorphosed basic tuff, contains very scarce zircons in omphacite or garnet, but more zircons in quartz. They usually exhibit a double-layered texture, as shown clearly in cathodoluminescence images. Their inner main parts give a 206Pb/238U age of 757±7 Ma, representing the approximate age of the high-pressure (HP)- ultrahigh-pressure (UHP) metamorphic event during which the eclogite was formed. The outer peripheral parts of the zircons, which have been modified by late-stage fluids, give an age of 223±3 Ma. The granitic rock contains more zircons of anatectic origin found mostly in feldspar and quartz and usually also showing a similar composite texture. The inner main parts of the anatectic zircons with oscillatory zoning give a 206Pb/238U age of 727±15 Ma for the approximate age of the emplacement of the granitic rock, and their outer parts, an age of 219±3 Ma for a similar or even the same fluid event. It is thus suggested that the HP-UHP metamorphism of the Bixiling eclogite facies rocks took place during the Neoproterozoic Jinningian, and the Indosinian age values may only represent a late event in the nature of fluid activity.展开更多
A new type of shale oil in alkaline lacustrine sediments has been discovered in the Late Paleozoic Fengcheng Formation,Mahu Sag,Junggar Basin,China.The fine-grained sedimentary rocks deposited in this alkaline lacustr...A new type of shale oil in alkaline lacustrine sediments has been discovered in the Late Paleozoic Fengcheng Formation,Mahu Sag,Junggar Basin,China.The fine-grained sedimentary rocks deposited in this alkaline lacustrine environment can be divided into four types and eight sub-types:mudstone(with no alkali minerals),including massive dolomitic mudstone,and massive and laminated calcareous mudstone;dolomite,including massive argillaceous dolomite(with alkali minerals),and massive and laminated argillaceous dolomite(with no alkali minerals);evaporites;and pyroclastic rocks.The massive argillaceous dolomite(with alkali minerals)and pyroclastic rocks have the highest shale oil potential,with average oil saturation index(OSI)values of 344.67 and 124.65 mg HC/g TOC,respectively.Shale oil exploration in the representative well MY1 indicates that the Fengcheng Formation is thick and contains abundant natural fractures,brittle minerals,and mobile oil.The entire Fengcheng Formation is oilbearing and contains three concentrated stratigraphic intervals of shale oil(i.e.,sweet spots).Well MY1 indicates that,compared with source rocks developed in marine and sulfate-type saline basins,the fine-grained sedimentary rocks deposited in alkaline lacustrine environments can also have high shale oil potential.The co-existence and regular distribution of conventional and unconventional reservoirs in the Fengcheng Formation indicate that it is an ideal exploration target for multiple resource types.展开更多
Objective The Dajishan W-Ta-Nb deposit is located in the junction of southern Jiangxi and Guangdong Provinces(Fig. 1a). This deposit contains about 190, 000 tons of WO3 reserves,belonging to a super-large W deposit. M...Objective The Dajishan W-Ta-Nb deposit is located in the junction of southern Jiangxi and Guangdong Provinces(Fig. 1a). This deposit contains about 190, 000 tons of WO3 reserves,belonging to a super-large W deposit. Most W mineralization (mainly wolframite) at Dajishan occurred in quartz veins, with also some disseminated wolframite in the No. 69 granite.展开更多
The Changjiang（Yangtze）is one of the largest rivers in the world.It formed a huge incised valley at its mouth during the Last Glacial Maximum;the incised-valley fill,approximately 80–110 m thick,supplies an importa...The Changjiang（Yangtze）is one of the largest rivers in the world.It formed a huge incised valley at its mouth during the Last Glacial Maximum;the incised-valley fill,approximately 80–110 m thick,supplies an important foundation for the generation of shallow biogenic-gas reservoirs.Two cores and 13 cone penetration tests were used to elaborate the characteristics,formation mechanism,and distribution of the shallow biogenic-gas reservoirs in the study area.The natural gas is mainly composed of CH4（generally[95%）with a δ^13CCH4 and δ^13CCO2 of-75.8 to-67.7% and -34.5 to-6.6%,respectively,and a δDCH4 of-215 to-185%,indicating a biogenic origin by the carbon dioxide reduction pathway.Commercial biogenic gas occurs primarily in the sand bodies of fluvial-channel,floodplain,and paleo-estuary facies with a burial depth of 50–80 m.Gas sources as well as cap beds are gray to yellowish-gray mud of floodplain,paleoestuary,and offshore shallow marine facies.The organic matter in gas sources is dominated by immature type Ⅲ kerogen（gas prone）.The difference in permeability（about4–6 orders of magnitude）between cap beds and reservoirs makes the cap beds effectively prevent the upward escape of gas in the reservoirs.This formation mechanism is consistent with that for the shallow biogenic gas in the late Quaternary Qiantang River incised valley to the south.Therefore,this study should provide further insight into understanding the formation and distribution of shallow biogenic gas in other similar postglacial incised-valley systems.展开更多
The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in th...The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in the Variscan blocks incorporated in the Ligurian Alps because they experienced low temperature Alpine metamorphism. During the Paleozoic, these blocks, together with the other Alpine basements, were placed between the Corsica-Sardinia and the Bohemian Massif along the northern margin of Gondwana. In this framework, they host several a variegated lithostratigraphy forming two main complexes(Complexs I and II) that can be distinguished by both the protoliths and their crosscutting relationships, which indicate that the acidic and mafic intrusives of Complex II cut an already folded sequence made of sediments, basalts and granitoids of Complex I. Both complexes were involved in the Variscan orogenic phases as highlighted by the pervasive eclogite-amphibolite facies schistosity(foliation II). However, rare relicts of a metamorphic foliation at amphibolite facies conditions(foliation I)is locally preserved only in the rocks of Complex I. It is debatable if this schistosity was produced during the early folding event e occurred between the emplacement of Complex I and II e rather than during an early stage of the Variscan metamorphic cycle.New SHRIMP and LA ICP-MS Ue Pb zircon dating integrated with literature data, provide emplacement ages of the several volcanic or intrusive bodies of both complexes. The igneous activity of Complex I is dated between 507 ± 15 Ma and 494 ± 5 Ma, while Complex II between 467 ± 12 Ma and 445.5 ± 12 Ma.The folding event recorded only by the Complex I should therefore have occurred between 494 ± 5 Ma and 467 ± 12 Ma. The Variscan eclogite-amphibolite facies metamorphism is instead constrained between ~420 Ma and ~300 Ma. These ages and the geochemical signature of these rocks allow constraining the Early Paleozoic tectono-magmatic evolution of the Ligurian blocks, from a middleeupper Cambrian rifting stage, through the formation of an Early Ordovician volcanic arc during the Rheic Ocean subduction, until a Late Ordovician extension related to the arc collapse and subsequent rifting of the PaleoThetys. Furthermore, the ~420-350 Ma ages from zircon rims testify to thermal perturbations that may be associated with the Silurian rifting-related magmatism, followed by the subduction-collisional phases of the Variscan orogeny.展开更多
We performed a systematic trace and rare earth element analysis for the bedded Fe-Mn carbonate rocks related to the stratiform Ag-Pb-Zn mineralization in the Lengshuikeng ore district, Jiangxi Province, South China. T...We performed a systematic trace and rare earth element analysis for the bedded Fe-Mn carbonate rocks related to the stratiform Ag-Pb-Zn mineralization in the Lengshuikeng ore district, Jiangxi Province, South China. Three types of Fe-Mn carbonates are distinguished, namely, the massive, breccia, and vein types. Both carbonate and silicate fractions in the samples are analyzed for their trace and rare earth element concentrations using a step acid-leaching technique. Our results show that the carbonate fractions in the massive type samples have the lowest REE concentrations but pronounced positive Eu and Y anomalies with Eu/Eu＊ value from 1.3 to 6.2 and Y/Ho value from 40.1 to 59.5, and similar characteristics are also shown for the silicate fractions in the massive type samples（Eu/Eu＊=1.0-6.7, Y/Ho=20.7-55.1）. These REE characteristics are similar to those of Sedex type massive sulfide deposits worldwide, and we suggest that the massive type Fe-Mn carbonate rocks were likely formed from an exhalative volcanic-hydrothermal fluid feeding the depression basin of a volcanic lake. The high concentrations of redox-sensitive elements and ratios such as U/Th, V/Cr and V/（V＋Ni） indicate a dysoxic environment for the Fe-Mn carbonate deposition. In contrast, the breccia type and vein type Fe-Mn carbonate samples show different trace and rare earth element features from those of massive type samples, and they are more similar to the volcanic rocks and magmatic-hydrothermal fluids in the Lengshuikeng ore district and may reflect strong overprinting from volcanic and sub-volcanic magmatism related to the porphyry type mineralization in the district.展开更多
As the southernmost segment of the Central Asian Orogenic Belt(CAOB),the northern Alxa orogenic belt(NAOB)connects the southeastern and southwestern segments of the CAOB.The NAOB amalgamated with the closure of the Pa...As the southernmost segment of the Central Asian Orogenic Belt(CAOB),the northern Alxa orogenic belt(NAOB)connects the southeastern and southwestern segments of the CAOB.The NAOB amalgamated with the closure of the Paleo-Asian Ocean;however,the closure time of the Paleo-Asian Ocean is still on great debate.In this study,we reported new detrital zircon U-Pb geochronology and Hf-O isotopes for the Permo-Carboniferous sediments in the northern Alxa to constrain the provenance and its tectonic implications.The Permo-Carbonifereous Amushan Formation is composed of volcanic-carbonite-clastic rocks and was deposited in a shallow marine environment.Based on the zircon U-Pb geochronology,the Amushan Formation was deposited in the late Carboniferous to early Permian,but some outcrops of volcanic and clastic rocks in the Quaganqulu area were likely formed in the middle to late Permian.The integrated zircon age spectrum for the clastic rocks shows a wide range from late Archean to Paleoproterozoic,Mesoproterozoic(with a peak age at 1458 Ma),early Neoproterozoic(with peak ages of 988 Ma and 929 Ma),early Paleozoic(with a peak age at 447 Ma) and late Paleozoic(with a peak age at 294 Ma).Combined with the zircon Hf-O isotopes,the provenance was considered to be the Alxa Block,the Shalazhashan terrane and the Zhusileng-Hangwula block(and the southern Beishan orogenic belt).The multiple source regions to the south and north of the Paleo-Asian Ocean indicate the closure of this ocean before the late Carboniferous.The absence or small proportion of depositional age-approximated zircons in most samples makes their age spectra similar to extensional basins.Combined with the intra-plate volcanism,the deposits were considered to be formed in extensional settings.Accordingly,after the closure of the Paleo-Asian Ocean,the NAOB stepped into an extensional stage.展开更多
In this study, we carried out petrography, zircon U-Pb geochronology and Hf isotopic analyses on a granitic pegmatite dyke in the Xiaoqinling area in southern margin of the North China Craton（NCC）. Our study suggest...In this study, we carried out petrography, zircon U-Pb geochronology and Hf isotopic analyses on a granitic pegmatite dyke in the Xiaoqinling area in southern margin of the North China Craton（NCC）. Our study suggests that the pegmatite dyke likely crystallized from a volatile-rich pegmatitic magma. Different from most other pegmatite elsewhere, zircon from this pegmatite dyke does not contain unusually high U and Th concentrations and suffered no evident radioactive damage, therefore we successfully obtained a zircon U-Pb dating using laser ablation-inductively coupled plasma-mass spectrometry（LA-ICP-MS）, which yields an average 207Pb/206 Pb age of 1 814±6 Ma, representing the intrusive age of the granitic pegmatite dyke. Zircon εHf（t） values are between-8.3 and-3.0, corresponding to Hf depleted mantle model ages from 2 649 to 2 991 Ma with an average of 2 881 Ma. These data indicate that this granitic pegmatite dyke may have been derived from partial melting of Meso-Neoarchean metamorphic rocks from the Xiaoqinling basement. Granitic pegmatite magma may have emplaced within the Taihua Group wall rocks during the last stage of the middle to high grade metamorphism. Furthermore, according to the petrographic observation, the 1.81 Ga pegmatite dyke and the 1 800–1 750 Ma Xiong’er Group rocks were not undergone middle to high grade metamorphism, indicating 1.81 Ga as the termination of the latest regional metamorphism in the southern margin of the NCC.展开更多
Shales are a major sink for K into seawater delivered from continental weathering,and are potential recorders of K cycling.High precision K isotope analyses reveal a[0.6%variation in δ^41K values(41K/39K relative to ...Shales are a major sink for K into seawater delivered from continental weathering,and are potential recorders of K cycling.High precision K isotope analyses reveal a[0.6%variation in δ^41K values(41K/39K relative to NIST SRM 3141a)from a set of well characterized postArchean Australian shale(PAAS)samples.By contrast,loess samples have relatively homogenous δ^41K values(-0.5±0.1%),which may represent the average K composition of upper continental crust.Most of the shales analyzed in this study have experienced K enrichment relative to average continental crust,and the majority of them define a trend of decreasing δ^41K value(from-0.5to-0.7%)with increasing K content and K/Na ratio,indicating cation exchange in clays minerals is accompanied by K isotope fractionation.Several shale samples do not follow the trend and have elevated δ^41K values up to-0.1%,and these samples are characterized by variable Fe isotope compositions,which reflect post-depositional processes.The K isotope variability observed in shales,in combination with recent findings about K isotope fractionation during continental weathering,indicates that K isotopes fractionate during cycling of K between different reservoirs,and K isotopes in sediments may be used to trace geological cycling of K.展开更多
The study of fluid inclusions can help constrain the conditions at which diagenetic minerals precipitated,leading to a better understanding of the geologic controls and relative timing of changes in porosity and/or mi...The study of fluid inclusions can help constrain the conditions at which diagenetic minerals precipitated,leading to a better understanding of the geologic controls and relative timing of changes in porosity and/or mineralising events.Many of the diagenetic minerals are easily deformed and it is important to check for any post-entrapment changes to the inclusions.Possible post-entrapment changes include reaction with the host crystal,necking down,nucleation metastability and thermal reequilibration.The recommended method of detecting these problems is to examine individual fluid inclusion assemblages（FIAs） and report data for each individual FIA.These studies have been enhanced by the development of new micro-analytical techniques such as micro-fluorescence spectroscopy,micro-infrared spectroscopy,nuclear magnetic resonance,various mass spectrometry techniques and the analysis of individual fluid inclusions using laser ablation/decrepitation methods.Special techniques have been developed for hydrocarbon-bearing inclusions such as the Grains containing Oil Inclusions（GOI）,Fluid Inclusion Stratigraphy（FIS）,and the Molecular Composition of Inclusions（MCI） techniques.The fluid inclusions that form in some minerals during diagenesis provide the only direct means of examining the fluids present in these systems.They provide useful temperature,pressure,and fluid composition data that cannot be obtained by other means.展开更多
基金Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDB0740000National Key Research and Development Program of China,No.2022YFB3904200,No.2022YFF0711601+1 种基金Key Project of Innovation LREIS,No.PI009National Natural Science Foundation of China,No.42471503。
文摘Deep-time Earth research plays a pivotal role in deciphering the rates,patterns,and mechanisms of Earth's evolutionary processes throughout geological history,providing essential scientific foundations for climate prediction,natural resource exploration,and sustainable planetary stewardship.To advance Deep-time Earth research in the era of big data and artificial intelligence,the International Union of Geological Sciences initiated the“Deeptime Digital Earth International Big Science Program”(DDE)in 2019.At the core of this ambitious program lies the development of geoscience knowledge graphs,serving as a transformative knowledge infrastructure that enables the integration,sharing,mining,and analysis of heterogeneous geoscience big data.The DDE knowledge graph initiative has made significant strides in three critical dimensions:(1)establishing a unified knowledge structure across geoscience disciplines that ensures consistent representation of geological entities and their interrelationships through standardized ontologies and semantic frameworks;(2)developing a robust and scalable software infrastructure capable of supporting both expert-driven and machine-assisted knowledge engineering for large-scale graph construction and management;(3)implementing a comprehensive three-tiered architecture encompassing basic,discipline-specific,and application-oriented knowledge graphs,spanning approximately 20 geoscience disciplines.Through its open knowledge framework and international collaborative network,this initiative has fostered multinational research collaborations,establishing a robust foundation for next-generation geoscience research while propelling the discipline toward FAIR(Findable,Accessible,Interoperable,Reusable)data practices in deep-time Earth systems research.
基金Dr.Stergios D.Zarkogiannis would like to acknowledge UK Research and Innovation Grant(SODIOM)EP/Y004221/1 in supporting the research reported here.
文摘This study investigates the facies development and sedimentology of the Late Permian Chhidru Formation,a mixed carbonate-siliciclastic unit exposed in the Western Salt Range,Potwar Basin,Pakistan.The formation is subdivided into four lithological units reflecting lateral variability,with thicknesses and lithologies ranging from fossiliferous sandy limestone to interbedded limestone and sandstone.These successions record a depositional shift from a carbonate platform to mixed carbonate-clastic,and ultimately,clastic-dominated environments.Lithostratigraphy suggests deposition on the underlying Wargal Limestone carbonates during a Late Permian sea-level fall on the northwest Indian margin of Gondwana.Similar Permian successions with identical lithological characteristics are documented in the Persian Gulf(Dalan Formation),Arabian Platform(Khuff Formation),and Iran(Nesen and Hambust formations).Petrographic analysis reveals deposition in the distal middle to proximal inner shelf settings of a carbonate-siliciclastic mixed,unrimmed platform.Based on identified foraminiferal assemblages,the Chhidru Formation's age is estimated to range from the late Wuchiapingian to Changhsingian stages of the Lopingian epoch.
基金Financial support from the Ministry of Earth Sci-ences,New Delhi for Excimer 193 nm LA system at CSIR-NGRI MoES/P.O.(Seismo)/1(245)/2014for the project on Singhbhum craton to S.D.,E.V.S.S.K.B.,B.S.and T.V.K(No.MoES/P.O.(Geosci)45/2015+1 种基金GAP-738-28EVB)part of the CSIR-NGRI projects INDEX(PSC0204) and GEOMET
文摘The dominant geodynamic processes that underpin the formation and evolution of Earth’s early crust remain enigmatic calling for new information from less studied ancient cratonic nuclei.Here,we present U-Pb ages and Hf isotopic compositions of detrital zircon grains from^2.9 Ga old quartzites and magmatic zircon from a 3.505 Ga old dacite from the Iron Ore Group of the Singhbhum craton,eastern India.The detrital zircon grains range in age between 3.95 Ga and 2.91 Ga.Together with the recently reported Hadean,Eoarchean xenocrystic(up to 4.24 Ga)and modem detritus zircon grains from the Singhbhum craton,our results suggest that the Eoarchean detrital zircons represent crust generated by recycling of Hadean felsic crust formed at^4.3-4.2 Ga and^3.95 Ga.We observe a prominent shift in Hf isotope compositions at^3.6-3.5 Ga towards super-chondritic values,which signify an increased role for depleted mantle and the relevance of plate tectonics.The Paleo-,Mesoarchean zircon Hf isotopic record in the craton indicates crust generation involving the role of both depleted and enriched mantle sources.We infer a short-lived suprasubduction setting around^3.6-3.5 Ga followed by mantle plume activity during the Paleo-,Mesoarchean crust formation in the Singhbhum craton.The Singhbhum craton provides an additional repository for Earth’s oldest materials.
基金supported by the National Natural Science Foundation of China(No. 40373025)
文摘Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing pyrite is as higher as 171.664 ppm on average,with relatively higher light rare earth elements（LREE;159.556 ppm） and lower HREE（12.108 ppm）.TheΣLREE/ΣHREE ratio is 12.612 and（La/Yb）_N is 11.765.These indicate that pyrite is rich in LREE.The（La/Sm）_N ratio is 3.758 and that of（Gd/Yb）_N is 1.695.These are obvious LREE fractionations.The rare earth element（REE） distribution patterns show obvious Eu anomaly with averageδEu values of 0.664,andδCe anomalies of 1.044.REE characteristics are similar to those of wall rocks（regional metamorphic rocks）,but different from those of the Dexing granodiorite porphyry and Damaoshan biotite granite.These features indicate that the ore-forming materials in the Jinshan gold deposit derived from the wall rocks, and the ore-forming fluids derived from metamorphic water.The Co/Ni ratio（average value 0.38） of pyrite suggests that the Jinshan gold deposit formed under a medium-low temperature.It is inferred from the values of high-field strength elements,LREE,Hf/Sm,Nb/La,and Th/La of the pyrite that the ore-forming fluids of the Jinshan gold deposit derived from metamorphic water with Cl〉F.
基金funded by the National Natural Science Foundation of China(Grant nos.41930427,41872078,and 41502069)the Young Elite Scientists Sponsorship Program by CAST(Grant no.YESS20180143)the Fundamental Research Funds for the Central Universities(Grant nos.FRF-TP-18-017A3 and FRF-IDRY-19-001)。
文摘Liquid-liquid immiscibility has crucial influences on geological processes,such as magma degassing and formation of ore deposits.Sulfate,as an important component,associates with many kinds of deposits.Two types of immiscibility,including(i)fluid-melt immiscibility between an aqueous solution and a sulfate melt,and(ii)fluid-fluid immiscibility between two aqueous fluids with different sulfate concentrations,have been identified for sulfate-water systems.In this study,we investigated the immiscibility behaviors of a sulfate-and quartz-saturated Na_(2)SO_(4)-SiO_(2)-H_(2)O system at elevated temperature,to explore the phase relationships involving both types of immiscibility.The fluid-melt immiscibility appeared first when the Na_(2)SO_(4)-SiO_(2)-H_(2)O sample was heated to~270℃,and then fluid-fluid immiscibility emerged while the sample was further heated to~450℃.At this stage,the coexistence of one water-saturated sulfate melt and two aqueous fluids with distinct sulfate concentrations was observed.The three immiscible phases remain stable over a wide pressure-temperature range,and the appearance temperature of the fluid-fluid immiscibility increases with the increased pressure.Considering that sulfate components occur extensively in carbonatite-related deposits,the fluid-fluid immiscibility can result in significant sulfate fractionation and provides implications for understanding the formation of carbonatite-related rare earth deposits.
文摘1 Introduction Sedimentary rocks archive important information for understanding how the earth system operates and how life and environments have evolved through earth history.Properly identifying characteristics of sedimentary rocks,along with the subsequent interpretation of depositional processes and sedimentary environments in a basin or locality.
基金supported by Stanford University and by NSF-EAR-1627930CAS participation by CAS(XDB0710000)NSFC(92355301,42074067)。
文摘We seek to understand lithospheric rheology by mapping continental earthquake depths relative to Moho depth,across the entire India/Asia convergent orogen,and eventually worldwide.Such mapping has particular value in geothermometry,and potentially in identifying regions of delamination.How:We are extending our Sn/Lg method beyond amplitude ratios of regional seismic phases measured on arrays(array Sn/Lg method,Wang and Klemperer,2021)to include frequency proxies for earthquake depth relative to Moho(Wang&Klemperer,2024a,b;Harris et al.,2024).
基金supported by grants from the Natural Science Foundation of China(41672186 and 41502178)Jiangsu Province(BK20150577)the China Postdoctoral Science Foundation(2015M570432)
文摘Eoarchean(3.6–4.0 Ga)tonalite–trondhjemite–granodiorite(TTG)are the major component of Earth’s oldest persevered continental crust,thereby holding the key to understanding how continental crust originated and when plate tectonics started in the early Earth.TTGs are mostly generated by partial melting of hydrated mafic rocks at different depths(e.g.,Moyen and Martin,2012),but whether this requires subduction remains enigmatic(e.g.,Palin et al.,2016).Recent studies show that most early Archean TTGs formed at relatively low pressures(≤1.5 GPa)and do not require subduction(e.g.,Johnson et al.,2017).We have identified a suite of Eoarchean tonalitic gneisses dated at^3.7 Ga from the Tarim Craton,northwestern China(Ge et al.,2018).These rocks are probably the oldest high-pressure TTGs so far documented worldwide.Thermodynamic and trace element modelling demonstrates that the parent magma may have been generated by water-fluxed partial melting of moderately enriched arc-like basalts at 1.8–1.9 GPa and 800–830℃,indicating an apparent geothermal gradient(400–450℃GPa-1)typical for hot subduction zones.They also locally record geochemical evidence for magma interaction with a mantle wedge.Accordingly,we propose that these highpressure TTGs were generated by partial melting of a subducted proto-arc during arc accretion.Our model implies that modernstyle plate tectonics was operative,at least locally,at^3.7 Ga and was responsible for generating some of the oldest continental nuclei.
基金supported financially by the National Natural Science Foundation of China(Grant Nos.41872054 and 41272083)。
文摘The petrogenesis and genetic link to polymetallic mineralization of the granites in the Dayishan complex,southern Hunan province remain debated.Here,we present an integrated study on the petrology,zircon U-Pb ages and whole-rock geochemistry for this complex.Our findings indicate that the southern complex consists of(amphibole-bearing)biotite granites and muscovite granites emplaced at 153-151 Ma,and the central and northern complex consists of two-mica granites and tourmaline-bearing muscovite granites,respectively with the former emplaced at 164 Ma and the latter at 150 Ma.The(amphibole-bearing)biotite granites have SiO_(2) contents of 68.0-73.8 wt% and are enriched in alkalis and rare earth elements and depleted in Sr and Ba.They display Zr+Y+Ce+Nb>350 ppm and 10000×Ga/Al>2.6 along with high zircon saturation temperatures(821-883oC).The two-mica granites and(tourmaline-bearing)muscovite granites have high SiO_(2)(74.4-77.3 wt%)and low Ga/Al,Zr+Nb+Ce+Y,K/Rb,Zr/Hf,and Nb/Ta along with low zircon saturation temperatures(709-817℃).Geochemical characteristics suggest that the(amphibole-bearing)biotite granites are A-type granites generated through shallow dehydration melting of early Paleozoic granitoids,and that the two-mica granites and(tourmaline-bearing)muscovite granites are fractionated A-type granites produced through fractionation crystallization from the(amphibole-bearing)biotite granites accompanied by fluid fractionation.
文摘Durable aggregates are essential for the stability and longevity of construction projects,and the Los Angeles Abrasion(LAA)value is a widely used indicator of aggregate durability.However,direct LAA testing is time-consuming,costly,and requires specialized facilities.This study introduces a novel and efficient alternative by developing two hybrid machine learning models Artificial Neural Network integrated with Particle Swarm Optimization(ANN-PSO)and Artificial Neural Network combined with Teaching-Learning-Based Optimization(ANN-TLBO)for the first time to predict LAA values from petrographic characteristics of carbonate rocks.A total of 160 rock samples from 10 geological formations in Pakistan’s Salt Range were analyzed through petrographic examination and LAA testing.The predictive performance of the proposed models was compared with established techniques,including Multiple Linear Regression,Random Forest,Adaptive Boosting,Gradient Boosting,K-Nearest Neighbors,and Multilayer Perceptron.Results demonstrate that ANN-PSO significantly outperformed all other approaches,achieving an R^(2)of 0.9982,RMSE of 0.209,MAE of 0.159,and MAPE of 0.009.Model robustness was validated using Taylor plots,REC curves,and an external dataset.Sensitivity analysis identified quartz,calcite,and feldspar as the most influential factors affecting LAA prediction.The findings confirm that the ANN-PSO and ANN-TLBO models provide highly accurate,cost-effective,and practical alternatives to traditional LAA testing.This innovative approach advances rock mechanics and material assessment,offering engineers and geologists enhanced tools for aggregate selection and durability evaluation in infrastructure projects.
文摘The paper reports SHRIMP U-Pb zircon data of a dark eclogite and a post-eclogite garnet-bearing gneissic granitic rock from the Bixiling area, Yuexi County, Anhui Province, in the eastern Dabie Mountains. The eclogite, which is metamorphosed basic tuff, contains very scarce zircons in omphacite or garnet, but more zircons in quartz. They usually exhibit a double-layered texture, as shown clearly in cathodoluminescence images. Their inner main parts give a 206Pb/238U age of 757±7 Ma, representing the approximate age of the high-pressure (HP)- ultrahigh-pressure (UHP) metamorphic event during which the eclogite was formed. The outer peripheral parts of the zircons, which have been modified by late-stage fluids, give an age of 223±3 Ma. The granitic rock contains more zircons of anatectic origin found mostly in feldspar and quartz and usually also showing a similar composite texture. The inner main parts of the anatectic zircons with oscillatory zoning give a 206Pb/238U age of 727±15 Ma for the approximate age of the emplacement of the granitic rock, and their outer parts, an age of 219±3 Ma for a similar or even the same fluid event. It is thus suggested that the HP-UHP metamorphism of the Bixiling eclogite facies rocks took place during the Neoproterozoic Jinningian, and the Indosinian age values may only represent a late event in the nature of fluid activity.
基金funded by PetroChina Science and Technology Major Project(Grant No.2019E-2602)。
文摘A new type of shale oil in alkaline lacustrine sediments has been discovered in the Late Paleozoic Fengcheng Formation,Mahu Sag,Junggar Basin,China.The fine-grained sedimentary rocks deposited in this alkaline lacustrine environment can be divided into four types and eight sub-types:mudstone(with no alkali minerals),including massive dolomitic mudstone,and massive and laminated calcareous mudstone;dolomite,including massive argillaceous dolomite(with alkali minerals),and massive and laminated argillaceous dolomite(with no alkali minerals);evaporites;and pyroclastic rocks.The massive argillaceous dolomite(with alkali minerals)and pyroclastic rocks have the highest shale oil potential,with average oil saturation index(OSI)values of 344.67 and 124.65 mg HC/g TOC,respectively.Shale oil exploration in the representative well MY1 indicates that the Fengcheng Formation is thick and contains abundant natural fractures,brittle minerals,and mobile oil.The entire Fengcheng Formation is oilbearing and contains three concentrated stratigraphic intervals of shale oil(i.e.,sweet spots).Well MY1 indicates that,compared with source rocks developed in marine and sulfate-type saline basins,the fine-grained sedimentary rocks deposited in alkaline lacustrine environments can also have high shale oil potential.The co-existence and regular distribution of conventional and unconventional reservoirs in the Fengcheng Formation indicate that it is an ideal exploration target for multiple resource types.
基金supported by the National Key Research and Development Program of China (grant No. 2016YFC0600203)the Natural Science Foundation of China (grants No. 41672065, 41830428,41472032)
文摘Objective The Dajishan W-Ta-Nb deposit is located in the junction of southern Jiangxi and Guangdong Provinces(Fig. 1a). This deposit contains about 190, 000 tons of WO3 reserves,belonging to a super-large W deposit. Most W mineralization (mainly wolframite) at Dajishan occurred in quartz veins, with also some disseminated wolframite in the No. 69 granite.
基金supported by the National Natural Science Foundation of China under Grant Numbers 41402092 and 41572112the Natural Science Foundation (Youth Science Fund Project) of Jiangsu Province (BK20140604)the Scholarship under State Scholarship Fund sponsored by the China Scholarship Council (File No. 201506195035)
文摘The Changjiang（Yangtze）is one of the largest rivers in the world.It formed a huge incised valley at its mouth during the Last Glacial Maximum;the incised-valley fill,approximately 80–110 m thick,supplies an important foundation for the generation of shallow biogenic-gas reservoirs.Two cores and 13 cone penetration tests were used to elaborate the characteristics,formation mechanism,and distribution of the shallow biogenic-gas reservoirs in the study area.The natural gas is mainly composed of CH4（generally[95%）with a δ^13CCH4 and δ^13CCO2 of-75.8 to-67.7% and -34.5 to-6.6%,respectively,and a δDCH4 of-215 to-185%,indicating a biogenic origin by the carbon dioxide reduction pathway.Commercial biogenic gas occurs primarily in the sand bodies of fluvial-channel,floodplain,and paleo-estuary facies with a burial depth of 50–80 m.Gas sources as well as cap beds are gray to yellowish-gray mud of floodplain,paleoestuary,and offshore shallow marine facies.The organic matter in gas sources is dominated by immature type Ⅲ kerogen（gas prone）.The difference in permeability（about4–6 orders of magnitude）between cap beds and reservoirs makes the cap beds effectively prevent the upward escape of gas in the reservoirs.This formation mechanism is consistent with that for the shallow biogenic gas in the late Quaternary Qiantang River incised valley to the south.Therefore,this study should provide further insight into understanding the formation and distribution of shallow biogenic gas in other similar postglacial incised-valley systems.
基金supported by Italian 1:50,000 Geological Mapping (CARGdR egione Liguria Project, University of Pavia grants)
文摘The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in the Variscan blocks incorporated in the Ligurian Alps because they experienced low temperature Alpine metamorphism. During the Paleozoic, these blocks, together with the other Alpine basements, were placed between the Corsica-Sardinia and the Bohemian Massif along the northern margin of Gondwana. In this framework, they host several a variegated lithostratigraphy forming two main complexes(Complexs I and II) that can be distinguished by both the protoliths and their crosscutting relationships, which indicate that the acidic and mafic intrusives of Complex II cut an already folded sequence made of sediments, basalts and granitoids of Complex I. Both complexes were involved in the Variscan orogenic phases as highlighted by the pervasive eclogite-amphibolite facies schistosity(foliation II). However, rare relicts of a metamorphic foliation at amphibolite facies conditions(foliation I)is locally preserved only in the rocks of Complex I. It is debatable if this schistosity was produced during the early folding event e occurred between the emplacement of Complex I and II e rather than during an early stage of the Variscan metamorphic cycle.New SHRIMP and LA ICP-MS Ue Pb zircon dating integrated with literature data, provide emplacement ages of the several volcanic or intrusive bodies of both complexes. The igneous activity of Complex I is dated between 507 ± 15 Ma and 494 ± 5 Ma, while Complex II between 467 ± 12 Ma and 445.5 ± 12 Ma.The folding event recorded only by the Complex I should therefore have occurred between 494 ± 5 Ma and 467 ± 12 Ma. The Variscan eclogite-amphibolite facies metamorphism is instead constrained between ~420 Ma and ~300 Ma. These ages and the geochemical signature of these rocks allow constraining the Early Paleozoic tectono-magmatic evolution of the Ligurian blocks, from a middleeupper Cambrian rifting stage, through the formation of an Early Ordovician volcanic arc during the Rheic Ocean subduction, until a Late Ordovician extension related to the arc collapse and subsequent rifting of the PaleoThetys. Furthermore, the ~420-350 Ma ages from zircon rims testify to thermal perturbations that may be associated with the Silurian rifting-related magmatism, followed by the subduction-collisional phases of the Variscan orogeny.
基金supported by the National 973 Program of China (No. 2012CB416706)
文摘We performed a systematic trace and rare earth element analysis for the bedded Fe-Mn carbonate rocks related to the stratiform Ag-Pb-Zn mineralization in the Lengshuikeng ore district, Jiangxi Province, South China. Three types of Fe-Mn carbonates are distinguished, namely, the massive, breccia, and vein types. Both carbonate and silicate fractions in the samples are analyzed for their trace and rare earth element concentrations using a step acid-leaching technique. Our results show that the carbonate fractions in the massive type samples have the lowest REE concentrations but pronounced positive Eu and Y anomalies with Eu/Eu＊ value from 1.3 to 6.2 and Y/Ho value from 40.1 to 59.5, and similar characteristics are also shown for the silicate fractions in the massive type samples（Eu/Eu＊=1.0-6.7, Y/Ho=20.7-55.1）. These REE characteristics are similar to those of Sedex type massive sulfide deposits worldwide, and we suggest that the massive type Fe-Mn carbonate rocks were likely formed from an exhalative volcanic-hydrothermal fluid feeding the depression basin of a volcanic lake. The high concentrations of redox-sensitive elements and ratios such as U/Th, V/Cr and V/（V＋Ni） indicate a dysoxic environment for the Fe-Mn carbonate deposition. In contrast, the breccia type and vein type Fe-Mn carbonate samples show different trace and rare earth element features from those of massive type samples, and they are more similar to the volcanic rocks and magmatic-hydrothermal fluids in the Lengshuikeng ore district and may reflect strong overprinting from volcanic and sub-volcanic magmatism related to the porphyry type mineralization in the district.
基金We thank the National Natural Science Foundation of China(Grant Nos.41902224,41372225)China Postdoctoral Science Foundation(Grant No.2018M640275)+1 种基金Fundamental Research Funds for the Central Universities(Grant No.2412019QD002)National Key Research and Development Project of China(Grant No.2017YFC0601302)for their financial support.
文摘As the southernmost segment of the Central Asian Orogenic Belt(CAOB),the northern Alxa orogenic belt(NAOB)connects the southeastern and southwestern segments of the CAOB.The NAOB amalgamated with the closure of the Paleo-Asian Ocean;however,the closure time of the Paleo-Asian Ocean is still on great debate.In this study,we reported new detrital zircon U-Pb geochronology and Hf-O isotopes for the Permo-Carboniferous sediments in the northern Alxa to constrain the provenance and its tectonic implications.The Permo-Carbonifereous Amushan Formation is composed of volcanic-carbonite-clastic rocks and was deposited in a shallow marine environment.Based on the zircon U-Pb geochronology,the Amushan Formation was deposited in the late Carboniferous to early Permian,but some outcrops of volcanic and clastic rocks in the Quaganqulu area were likely formed in the middle to late Permian.The integrated zircon age spectrum for the clastic rocks shows a wide range from late Archean to Paleoproterozoic,Mesoproterozoic(with a peak age at 1458 Ma),early Neoproterozoic(with peak ages of 988 Ma and 929 Ma),early Paleozoic(with a peak age at 447 Ma) and late Paleozoic(with a peak age at 294 Ma).Combined with the zircon Hf-O isotopes,the provenance was considered to be the Alxa Block,the Shalazhashan terrane and the Zhusileng-Hangwula block(and the southern Beishan orogenic belt).The multiple source regions to the south and north of the Paleo-Asian Ocean indicate the closure of this ocean before the late Carboniferous.The absence or small proportion of depositional age-approximated zircons in most samples makes their age spectra similar to extensional basins.Combined with the intra-plate volcanism,the deposits were considered to be formed in extensional settings.Accordingly,after the closure of the Paleo-Asian Ocean,the NAOB stepped into an extensional stage.
基金financially supported by the National Key Basic Research Program of China (No. 2006CB403506)the National Natural Science Foundation of China (No. 41203011)the Fundamental Research Funds for the Central Universities (No. 2013B03014)
文摘In this study, we carried out petrography, zircon U-Pb geochronology and Hf isotopic analyses on a granitic pegmatite dyke in the Xiaoqinling area in southern margin of the North China Craton（NCC）. Our study suggests that the pegmatite dyke likely crystallized from a volatile-rich pegmatitic magma. Different from most other pegmatite elsewhere, zircon from this pegmatite dyke does not contain unusually high U and Th concentrations and suffered no evident radioactive damage, therefore we successfully obtained a zircon U-Pb dating using laser ablation-inductively coupled plasma-mass spectrometry（LA-ICP-MS）, which yields an average 207Pb/206 Pb age of 1 814±6 Ma, representing the intrusive age of the granitic pegmatite dyke. Zircon εHf（t） values are between-8.3 and-3.0, corresponding to Hf depleted mantle model ages from 2 649 to 2 991 Ma with an average of 2 881 Ma. These data indicate that this granitic pegmatite dyke may have been derived from partial melting of Meso-Neoarchean metamorphic rocks from the Xiaoqinling basement. Granitic pegmatite magma may have emplaced within the Taihua Group wall rocks during the last stage of the middle to high grade metamorphism. Furthermore, according to the petrographic observation, the 1.81 Ga pegmatite dyke and the 1 800–1 750 Ma Xiong’er Group rocks were not undergone middle to high grade metamorphism, indicating 1.81 Ga as the termination of the latest regional metamorphism in the southern margin of the NCC.
基金supported by the National Key R&D Program of China (Project No. 2017YFC0602801)National Science Foundation of China (Grant Nos. 41622301, 41873004)+1 种基金supported by the NASA Astrobiology Institute (NNA13AA94A to BLB)the National Science Foundation (1741048-EAR to BLB)
文摘Shales are a major sink for K into seawater delivered from continental weathering,and are potential recorders of K cycling.High precision K isotope analyses reveal a[0.6%variation in δ^41K values(41K/39K relative to NIST SRM 3141a)from a set of well characterized postArchean Australian shale(PAAS)samples.By contrast,loess samples have relatively homogenous δ^41K values(-0.5±0.1%),which may represent the average K composition of upper continental crust.Most of the shales analyzed in this study have experienced K enrichment relative to average continental crust,and the majority of them define a trend of decreasing δ^41K value(from-0.5to-0.7%)with increasing K content and K/Na ratio,indicating cation exchange in clays minerals is accompanied by K isotope fractionation.Several shale samples do not follow the trend and have elevated δ^41K values up to-0.1%,and these samples are characterized by variable Fe isotope compositions,which reflect post-depositional processes.The K isotope variability observed in shales,in combination with recent findings about K isotope fractionation during continental weathering,indicates that K isotopes fractionate during cycling of K between different reservoirs,and K isotopes in sediments may be used to trace geological cycling of K.
文摘The study of fluid inclusions can help constrain the conditions at which diagenetic minerals precipitated,leading to a better understanding of the geologic controls and relative timing of changes in porosity and/or mineralising events.Many of the diagenetic minerals are easily deformed and it is important to check for any post-entrapment changes to the inclusions.Possible post-entrapment changes include reaction with the host crystal,necking down,nucleation metastability and thermal reequilibration.The recommended method of detecting these problems is to examine individual fluid inclusion assemblages（FIAs） and report data for each individual FIA.These studies have been enhanced by the development of new micro-analytical techniques such as micro-fluorescence spectroscopy,micro-infrared spectroscopy,nuclear magnetic resonance,various mass spectrometry techniques and the analysis of individual fluid inclusions using laser ablation/decrepitation methods.Special techniques have been developed for hydrocarbon-bearing inclusions such as the Grains containing Oil Inclusions（GOI）,Fluid Inclusion Stratigraphy（FIS）,and the Molecular Composition of Inclusions（MCI） techniques.The fluid inclusions that form in some minerals during diagenesis provide the only direct means of examining the fluids present in these systems.They provide useful temperature,pressure,and fluid composition data that cannot be obtained by other means.
