The construction of geochemical disciplines has brought new vitality to the development of traditional geology.In the new round of“Double First-Class”discipline construction at Central South University,the course of...The construction of geochemical disciplines has brought new vitality to the development of traditional geology.In the new round of“Double First-Class”discipline construction at Central South University,the course of Advanced Geochemistry has effectively stimulated students’interest in learning and further improved their scientific thinking and research innovation skills through the implementation of“Guiding Interactive”teaching reform measures,which has important theoretical significance and practical value.展开更多
Geochemistry, zircon U–Pb geochronology, and Hf isotope data for the Early Paleozoic granites in the Baoshan Block reveal the Early Paleozoic tectonic evolution of the Proto-Tethys. The samples are high-K, calcalkali...Geochemistry, zircon U–Pb geochronology, and Hf isotope data for the Early Paleozoic granites in the Baoshan Block reveal the Early Paleozoic tectonic evolution of the Proto-Tethys. The samples are high-K, calcalkaline, strongly peraluminous rocks with A/CNK values of 1.37–1.46, are enriched in SiO2, K2O, and Rb, and are depleted in Nb, P, Ti, Eu, and heavy rare earth elements,which indicates the crystallization fractionation of the granitic magma. Zircon U–Pb dating indicates that they formed in ca. 480 Ma. The Nansa granites have εHf(t) values ranging from-16.04 to 4.36 with corresponding TC DMages of 2.10–0.81 Ga, which suggests the magmas derived from the partial melting of ancient metasedimentary with minor involvement of mantle-derived components. A synthesis of data for the Early Paleozoic igneous rocks in the Baoshan block and adjacent(Tengchong,Qiangtang, Sibumasu, Himalaya, etc.) blocks indicates that these blocks were all aligned along the proto-Tethyan margin of East Gondwana in the Early Paleozoic. The Early Paleozoic S-type granites from Nansa were generated in a high-temperature and low-pressure(HTLP) extensional tectonic setting, which resulted from Andean-type orogeny instead of the final assembly of Gondwana or crustal extension in a non-arc environment. In certain places, an expanding environment may exist in opposition to the tectonic backdrop of the lithosphere’s thickening and shortening, leading the crust to melt and decompress,mantle-derived materials to mix, and a small quantity of peraluminous granite to emerge.展开更多
Rubidium(Rb)deposits mostly occur in the South China and Central Asia orogenic belts and are often closely associated with highly differentiated granites.This study investigates a newly-discovered giant Rb deposit at ...Rubidium(Rb)deposits mostly occur in the South China and Central Asia orogenic belts and are often closely associated with highly differentiated granites.This study investigates a newly-discovered giant Rb deposit at Gariatong in the Central Lhasa terrane in Tibet.Detailed field studies and logging data revealed that the Rb mineralization mainly occurs in monzogranite and is related to greisenization.LA-ICP-MS U-Pb dating of zircon yielded ages of 19.1±0.2 Ma and 19.0±0.2 Ma for greisenized monzogranite and fresh monzogranite,respectively.The monzogranites are characterized as strongly peraluminous,with high contents of SiO2,Al2O3,K2O and Na2O as well as a high differentiation index.They are enriched in light rare earth and large ion lithophile elements with significant negative Eu anomalies and depleted high fieldstrength elements.Petrological and geochemical features of these ore-related monzogranites suggest that they are highly fractionated S-type granites,derived from remelting of crustal materials in a post-collisional setting.The geochemistry of zircon and apatite points to a low oxygen fugacity of the ore-related monzogranite during the magma’s evolution.The discovery of the Gariatong Rb deposit suggests that the Central Lhasa terrane may be an important region for rare metal mineralization.展开更多
The Ain El Bey abandoned mine,in North-West Tunisia,fits into the geodynamic context of the European and African plate boundary.Ore deposit corresponds to veins and breccia of multiphase Cu–Fe-rich mineralization rel...The Ain El Bey abandoned mine,in North-West Tunisia,fits into the geodynamic context of the European and African plate boundary.Ore deposit corresponds to veins and breccia of multiphase Cu–Fe-rich mineralization related to various hydrothermal fluid circulations.Petromineralogical studies indicate a rich mineral paragenesis with a minimum of seven mineralization phases and,at least,six pyrite generations.As is also the case for galena and native silver,native gold is observed for the first time as inclusion in quartz which opens up,thus,new perspectives for prospecting and evaluating the potential for noble metals associated with the mineralization.Scanning Electron Microscope—Energy Dispersive Spectroscopy and Transmission electron microscopy analyses show,in addition,a large incorporation of trace elements,including Ag and Au,in mineral structures such as fahlores(tetrahedrite-tennantite)and chalcopyrite ones.The mineral/mineral associations,used as geothermometers,gave estimated temperatures for the mineralizing fluids varying from 254 to 330 C for phase III,from 254 to 350 ℃ for phase IV,and from 200 to 300 ℃ for phases V and VI.The seventh and last identified mineralization phase,marked by a deposit of native gold,reflects a drop in the mineralizing fluid’s temperature(<200 ℃)compatible with boiling conditions.Such results open up perspectives for the development of precious metal research and the revaluation of the Cu–Fe ore deposit at the Ain El Bey abandoned mine,as well as at the surrounding areas fitting in the geodynamic framework of the Africa-Europe plate boundary.展开更多
The Late Paleozoic and Mesozoic tectonic framework of the Nanpanjiang Basin has much been disputed.Herein,the middle-acid volcanic rock,dacite,exposed to the Zhesang gold district,southeast Yunnan Province,has been an...The Late Paleozoic and Mesozoic tectonic framework of the Nanpanjiang Basin has much been disputed.Herein,the middle-acid volcanic rock,dacite,exposed to the Zhesang gold district,southeast Yunnan Province,has been analyzed.The results show that the dacite belongs to a calc-alkaline series,SiO_(2)contents range from 62.79 to 76.66 wt%.Zircon SHRIMP U–Pb dating of dacite demonstrates that they were formed in the Early Triassic(247.8±1.7 Ma,MSWD=1.2).All samples exhibit enrichment in LILE(e.g.Rb,K,Th,and U),and depletion in HFSE(e.g.Nb,Ta,and Ti),which has the geochemical affinity of I-type granite.La–La/Sm and La–La/Yb discrimination diagrams show that the partial melting,mainly of the mafic lower crust,of rocks,plays a major role in the formation process.The dacite has low initial ^(87)Sr/^(86)Sr ratios(0.706954 to 0.708589)and negative ε_(Nd)(t)values(-11.77 to-10.88).Zircons in dacite have ε_(Hf)(t)values of-16.2 to-8.3,and the two-stage Hf model ages are 1799–2301 Ma,mostly concentrated between 1800 and 1900 Ma,indicating that the magma source area is the reconstructed ancient lower crust mixed with some mantle materials,and crystal fractionation process underwent in the late stage of magma migration.This study reveals that the arc-volcanic rocks of the Early Triassic in the southern margin of the Nanpanjiang Basin were formed by the subduction of the Late Paleozoic ocean basin within the border region between China and Vietnam.展开更多
Six outcrop sections in Fenghe River,Northwestern China,were sampled and analyzed.This study aims to determine provenance,tectonic setting,and source-area paleoweathering of the sediments of Fenghe River in combinatio...Six outcrop sections in Fenghe River,Northwestern China,were sampled and analyzed.This study aims to determine provenance,tectonic setting,and source-area paleoweathering of the sediments of Fenghe River in combination of lithofacies analysis and bulk-rock geochemical data.The lithofacies in the studied area were classified as gravel,sand,and fine-grained clastic lithofacies,reflecting generally channel fill deposits,channel bar deposits,and over-bank deposits,respectively.The Chemical Index of Alteration(CIA),Plagioclase Index of Alteration(PIA),and Chemical Index of Weathering(CIW)values ranged 50.10–62.29,50.13–66.35,56.52–71.12,respectively,together with element ratios such as Rb/Sr,K/Na,Rb/K,Th/K,Rb/Ti,and Cs/Ti indicate that the source area was under a low to moderate chemical weathering condition probably in cold and semi-arid climates.Moreover,plot of SiO_(2)vs.(Al_(2)O_(3)+K_(2)O+Na_(2)O)suggests that the sediments were deposited in a semi-arid climate.Plots of Cr/Th vs.Th/Sc,TiO_(2)vs.Zr,La/Yb vs.rare earth element(REE),and La-Th-Sc ternary diagrams,along with the lithology,indicate that the sediments in Fenghe River were mainly originated from felsic igneous rocks.Major elements-based discrimination diagrams and Th-Sc-Zr/10 and La-Th-Sc ternary diagram of the samples indicates that the source rocks of Fenghe River developed in a composite active continental margin and continental island arc field.展开更多
Aptian is characterized by widespread deposition of organic-rich sediment.The Aptian bitumen limestone horizon,which is thin decimetre-thick sequences,locally crops out in the Kircaova area,Eastern Black Sea Region(Ea...Aptian is characterized by widespread deposition of organic-rich sediment.The Aptian bitumen limestone horizon,which is thin decimetre-thick sequences,locally crops out in the Kircaova area,Eastern Black Sea Region(Eastern Pontides).They are well correlated with Aptian bitumen limestone in the other Tethys Reams.They are proposed as episodes of increased organic matter.However,background factors controlling organic matter enrichment are poorly known.In this study,we present new inorganic geochemistry,including trace elements,rare earth elements(REE),redox-sensitive elements(RSE),stable-isotopes(δ~(18)O andδ~(13)C),and total organic carbon(TOC).We integrated new geochemical data with existing stratigraphy,paleontology,and organic chemistry data to provide new insight into the depositional environment and paleoclimate conditions during Aptian.The lacustrine bitumen limestone(LBL)samples have variedδ~(13)C(ave.-1.45‰)andδ~(18)O(ave.-4.50‰).They possess distinct REE patterns,with an average of REE(ave.14.45 ppm)and Y/Ho(ave.35)ratios.In addition,they have variable Nd/YbN(0.28-0.81;ave.0.56)and Ce/Ce*(0.68-0.97;ave.0.86),and relatively high Eu^(*)/Eu(1.23-1.53;ave.1.35).They display seawater signatures with reduced oxygen conditions.The enrichment in RSE(Mo,Cu,Ni,and Zn)and the low Mo/TOC(0.70-3.69;ave.2.41)support a certain degree of water restriction.The high Sr/Ba,Sr/Cu,Ga/Rb,and K/Al records of the LBL facies suggest hot house climatic conditions.The sedimentary environment was probably an isolated basin that is transformed from the marine basin.In addition to depositional conditions,the regional parameters such as the climate,increased run-off period,nutrient levels,alkalinity level,and dominant carbonate producers favored the enrichment in organic matter of LBL facies.Thus,extreme greenhouse palaeoclimate conditions have an important role in organic matter enrichment in the isolated basin.Our results are conformable with the published data from marine,semi-restricted basin,and lacustrine settings in the different parts of the Tethys margin.Thus,this approach provides the first insight into the Aptian greenhouse paleo-climate conditions of the Eastern Black Sea Region,NE Turkey.展开更多
Jiama is a giant,high-grade porphyry copper system in the Gangdese metallogenic belt,Tibet.Multistage intermediate-felsic porphyries intruded in this deposit,some of which are strongly associated with copper-polymetal...Jiama is a giant,high-grade porphyry copper system in the Gangdese metallogenic belt,Tibet.Multistage intermediate-felsic porphyries intruded in this deposit,some of which are strongly associated with copper-polymetallic mineralization.These ore-bearing porphyries include monzogranite,granodiorite,and quartz diorite porphyries.A new granite aplite dyke was found in the south of Jiama.Its age,genesis,and relationship with ore-related magmatism are obscure.Here,its emplacement age and petrogenesis were determined using mineralogy,zircon U-Pb dating,geochemistry,and Sr-Nd-Pb isotope studies.The zircon LA-ICP-MS U-Pb age of the aplite dyke is 16.66±0.21 Ma(n=14,MSWD=0.66),earlier than that of the ore-bearing porphyries(~15 Ma)in Jiama.Furthermore,the aplite exhibits high amounts of silicon(SiO_(2)=73.39%-74.74%),potassium(K_(2)O=5.12%-6.61%),aluminum(Al_(2)O_(3)=14.25%-14.69%),and light/heavy rare earth elements(LREE/HREE=12.12-16.19)as well as negative europium(δEu=0.47-0.72)and weak negative cerium anomalies(δCe=0.84-0.93).The aplite dyke is characteristic of metaluminous-peraluminous I-type granite,which is rich in large-ion lithophile elements(Rb,Ba,Th and U)and depleted in high-field-strength elements(Nb,P and Ti).The aplite dyke and ore-bearing porphyries in the Jiama deposit are the results of a partial melting of the juvenile lower crust,according to whole-rock geochemistry and Sr-Nd-Pb isotope data,but the dyke and ore-bearing porphyries were emplaced from the same magma chamber at different times.Thus,the aplite dyke shows the composition of the early evolution stage of shallow magma in the Jiama deposit and is the product of rapid condensation and crystallization.展开更多
The Dunde iron-zinc polymetallic deposit is one of large iron deposits occurred in the Awulale Metallogenetic Belt,Western Tianshan(NW-China).This study reports new geochronology and geochemistry for granite in the Du...The Dunde iron-zinc polymetallic deposit is one of large iron deposits occurred in the Awulale Metallogenetic Belt,Western Tianshan(NW-China).This study reports new geochronology and geochemistry for granite in the Dunde mining area in order to constrain the tectonicmagmatic activities and metallogenesis of this region.Granites in the southwest of Dunde mining area are mainly syenogranites intruded into volcanics of the Dahalajunshan Formation in the Early Carboniferous,and they are far from the area where ore bodies and mineralized altered rocks are widely developed.LA-ICP-MS U–Pb zircon dating indicates that Dunde syenogranite was at 306.8±1.0 Ma,which could constrain the upper limit of metallogenic age for this deposit.The Dunde granites are high SiO_(2)(73.41–80.07 wt%),high differentiation index(D.I.=89.7–95.0),weakly peraluminous to metaluminous(A/CNK=0.94–1.08),and they are enriched in LILE and LREE and depleted in Eu,Ba,Sr and P_(2)O_(5),indicating that they belong to highly fractionated Ⅰ-type granite.Based on εHf values(+9.2 to+10.5)for zircon and high εNd(-t)values(+4.7 to+5.8)for whole-rock,and the two-stage model ages for 601–735 Ma,suggest that the magma source could be the juvenile lower crust.Combined with regional geological setting,the 306.8 Ma Dunde granites are formed in post-collision extensional tectonic setting.展开更多
Numerous studies have focused on modern hydroclimate and the modulated mechanisms in the Tianshan Mountains(TMs),arid central Asia.However,the detailed information of hydroclimatic processes beyond the instrumental pe...Numerous studies have focused on modern hydroclimate and the modulated mechanisms in the Tianshan Mountains(TMs),arid central Asia.However,the detailed information of hydroclimatic processes beyond the instrumental period is still scarce.This paper reconstructed a hydrology history from core sediments of the Dalongchi Lake in the Tianshan Mountains.The comparability between endmembers(EMs)of grain size and ICP-AES based geochemical elements in the lake sediments highlighted their availability for hydrological reconstructions.Hydrodynamic forces(EM1,EM4,Ti/Al and Li/Al),chemical weathering intensity[(Mg+Ca+K)/Al],salinity proxy(Mg/Ca)and redoxsensitive proxy(Fe/Mn)highly correlated with the first principal component(P<0.01),whereas paleoproductivity proxies(TN,TOC,Ba/Al,Zn/Al and Cu/Al)and C/N showed high loadings on the second principal component(P<0.05).The inferred hydrology progress was nonlinearly responded to temperature,precipitation and climate-dictated glaciers.Specifically,the water level didn’t always covary with the humidity because of glaciers.The maximum water level was the comprehensive result of glaciers melting and high humidity around 1830 CE.Thereafter,water level continually decreased with declining moisture at high temperature,implying a limited buffering capacity of glaciers in the Dalongchi Lake basin.EM3-indicated eolian activity intensity was caused by the behaviors of Siberian High because the latter intensified surface wind and the dust transportation.The hydrothermal patterns were characterized by warm/dry and cold/wet alternations in a long run although warm/wet pattern was identified from a short-term view.展开更多
The effect of various depositional parameters including paleoclimate,paleosalinity and provenance,on the depositional mechanism of lacustrine shale is very important in reconstructing the depositional environment.The ...The effect of various depositional parameters including paleoclimate,paleosalinity and provenance,on the depositional mechanism of lacustrine shale is very important in reconstructing the depositional environment.The classification of shale lithofacies and the interpretation of shale depositional environment are key features used in shale oil and gas exploration and development activity.The lower 3rd member of the Eocene Shahejie Formation(Es_(3)^(x)shale)was selected for this study,as one of the main prospective intervals for shale oil exploration and development in the intracratonic Bohai Bay Basin.Mineralogically,it is composed of quartz(avg.9.6%),calcite(avg.58.5%),dolomite(avg.7%),pyrite(avg.3.3%)and clay minerals(avg.20%).An advanced methodology(thin-section petrography,total organic carbon and total organic sulfur contents analysis,X-ray diffraction(XRD),X-ray fluorescence(XRF),field-emission scanning electron microscopy(FE-SEM))was adopted to establish shale lithofacies and to interpret the depositional environment in the lacustrine basin.Six different types of lithofacies were recognized,based on mineral composition,total organic carbon(TOC)content and sedimentary structures.Various inorganic geochemical proxies(Rb/Sr,Ca/(Ca+Fe),Ti/Al,Al/Ca,Al/Ti,Zr/Rb)have been used to interpret and screen variations in depositional environmental parameters during the deposition of the Es_(3)^(x)shale.The experimental results indicate that the environment during the deposition of the Es_(3)^(x)shale was warm and humid with heightened salinities,moderate to limited detrital input,higher paleohydrodynamic settings and strong oxygen deficient(reducing)conditions.A comprehensive depositional model of the lacustrine shale was developed.The interpretations deduced from this research work are expected to not only expand the knowledge of shale lithofacies classification for lacustrine fine-grained rocks,but can also offer a theoretical foundation for lacustrine shale oil exploration and development.展开更多
The Goshgarchay Cu-Au deposit is located in the central part of the northwest flank of the Murovdagh region in the Lesser Caucasus.The Goshgarchay Cu-Au deposit is associated with Middle Jurassic volcanic and Late Jur...The Goshgarchay Cu-Au deposit is located in the central part of the northwest flank of the Murovdagh region in the Lesser Caucasus.The Goshgarchay Cu-Au deposit is associated with Middle Jurassic volcanic and Late Jurassic-Early Cretaceous high-K calc-alkaline intrusive rocks.The Cu-Au mineralization is commonly related to quartz-sericite-chlorite alteration dominantly composed of chalcopyrite,gold,sphalerite,pyrite,bornite,hematite,covellite,chalcocite,malachite,and azurite.The Goshgarchay copper-gold deposit,which is 600 m wide and approximately 1.2 km long,is seen as a faultcontrolled and vein-,stockwork-and disseminated type deposit.The Goshgarchay Cu-Au deposit predominantly comprises Cu(max.64500 ppm)and Au(max.11.3 ppm),while it comprises relatively less amounts Zn(max.437 ppm),Mo(max.47.5 ppm),Pb(max.134 ppm),and Ag(max.21 ppm).The homogenization temperatures and salinities of fluid inclusions in quartz for stage Ⅰ range from 380℃ to 327℃,and 6.9 wt% to 2.6 wt% NaCl eq.,respectively.Thand salinities in quartz for stage Ⅱ range from 304℃ to 253℃,and 7.6 wt% to 3.2 wt% NaCl eq.,respectively.The calculated δ^(34)S_(h2s)values(-1.5‰ to 5.5‰)of sulfides and especially the narrow range of δ^(34)S_(h2s) values of chalcopyrite and bornite(between -0.07‰ and +0.7‰)indicate that the source of the Goshgarchay Cu-Au mineralization is magmatic.Based on the mineralogical,geochemical,fluid inclusion,and sulfur isotopic data,the Goshgarchay Cu-Au deposit represents a late stage peripheral magmatic-hydrothermal mineralization probably underlain by a concealed porphyry deposit.展开更多
Tonstein layers are found worldwide in the Permo-Carboniferous coal-bearing strata.This study investigates the geochronology,mineralogy,and geochemistry of four tonstein samples from the Permo-Carboniferous Benxi Form...Tonstein layers are found worldwide in the Permo-Carboniferous coal-bearing strata.This study investigates the geochronology,mineralogy,and geochemistry of four tonstein samples from the Permo-Carboniferous Benxi Formation,Ordos Basin,North China Craton(NCC).The typical features of the studied tonsteins include thin beds,lateral continuity,angular quartz grains,and euhedral zircons with similar U-Pb ages,indicating a significant pyroclastic origin.In addition,the tonstein samples have low TiO_(2)/Al_(2)O_(3)ratios(<0.02)and rare earth elements and yttrium(REY)concentrations with obvious negative Eu anomalies,indicating that the tonsteins have a felsic magma origin.Moreover,compared with the mean composition of clay shale,the studied tonsteins are characterized by high concentrations of the elements Nb and Ta,which may affect the concentration of the corresponding elements in surrounding coal seams.The zircon U-Pb ages of the tonsteins(293.9-298.8 Ma)provide a precise chronological framework on the Benxi Formation in the Ordos Basin,constraining the Gzhelian-Aselian stages.The tonsteins were probably sourced from arc volcanism along the western margin of the NCC during the early Permian,implying that the Alxa Terrane had not amalgamated with the NCC at that time.展开更多
Studies in the northern South China Sea(SCS)basement remain important for understanding the evolution of the Southeast Asian continental margin.Due to a thick cover of sediments and scarce borehole penetration,little ...Studies in the northern South China Sea(SCS)basement remain important for understanding the evolution of the Southeast Asian continental margin.Due to a thick cover of sediments and scarce borehole penetration,little is known about the age and tectonic affinity of this basement.In this study,an integrated study of zircon U-Pb geochronology,Hf isotopes,and whole-rock major and trace elements on seven basement granitoids from seven boreholes of Qiongdongnan Basin has been carried out.New zircon U-Pb results for these granitoids present middle-late Permian((270.0±1.2)Ma;(253±3.4)Ma),middle to late Triassic((246.2±3.4)Ma;(239.3±0.96)Ma;(237.9±0.99)Ma;(228.9±1.0)Ma)and Late Cretaceous ages((120.6±0.6)Ma).New data from this study,in combination with the previous dataset,indicates that granitoid ages in northern SCS basement vary from 270 Ma to 70.5 Ma,with three age groups of 270–196 Ma,162–142 Ma,and 137–71 Ma,respectively.Except for the late Paleozoic-Mesozoic rocks in the basement of the northern SCS,a few old zircon grains with the age of(2708.1±17)Ma to(2166.6±19)Ma provide clues to the existence of the pre-Proterozoic components.The geochemical signatures indicate that the middle Permian-early Cretaceous granitoids from the Qiongdongnan Basin are I-type granites formed in a volcanic arc environment,which were probably related to the subduction of the Paleo-Pacific Plate.展开更多
We report the mineralogy and geochemistry of hydrothermal sulphide from the crater of a volcanic high near 18°36.4′S of the Central Lau Spreading Center.During 1990s,that volcanic structure was reported active a...We report the mineralogy and geochemistry of hydrothermal sulphide from the crater of a volcanic high near 18°36.4′S of the Central Lau Spreading Center.During 1990s,that volcanic structure was reported active and sulphide samples were collected by MIR submersible.A section of a chimney-like structure from the crater-floor was studied here.The Fe-depleted sphalerites,and Co-depleted pyrites in that chimney were similar to those commonly found in low to moderate temperature(<300℃)sulphides from sediment-starved hydrothermal systems.Bulk analyses of three parts of that chimney section showed substantial enrichment of Zn(18%–20%)and Fe(14%–27%)but depletion of Cu(0.8%–1.3%).In chondrite-normalized rare earth element-patterns,the significant negative Ce-anomalies(Ce/Ce*=0.27–0.39)and weakly positive Eu-anomalies(Eu/Eu*=1.60–1.68)suggested sulphide mineralisation took place from reduced low-temperature fluid.The depleted concentration of lithophiles in this sulphide indicates restricted contribution of sub-ducting plate in genesis of source fluid as compared to those from other parts of Lau Spreading Centre.Uniform mineralogy and bulk composition of subsamples across the chimney section suggests barely any alteration of fluid composition and/or mode of mineralisation occurred during its growth.展开更多
The Merguechoum fluorite-barite mineralization,located in the Eastern Meseta of Morocco,is hosted in the Late Hercynian granite.The ore consists of fine crystals of fluorite 1,massive barite 1,euhedral crystals of flu...The Merguechoum fluorite-barite mineralization,located in the Eastern Meseta of Morocco,is hosted in the Late Hercynian granite.The ore consists of fine crystals of fluorite 1,massive barite 1,euhedral crystals of fluorite 2,and barite 2 with calcite and minor quartz and sulfides.The Merguechoum ore deposits have never been investigated.This study was the first contribution that studied the genesis of fluorite and barite.The ore occurs as dissemination within granite intrusion and also fills the NE-SWtrending meter-sized fractures and faults.The values of the total Rare Earth Elements and Yttrium(REY)and the ratios of LREY/HREY,Y/Ho,Tb/Ca,and Tb/La indicate that the Merguechoum fluorite precipitated from hydrothermal fluids,likely basinal brines,which interacted with the Hercynian granite.The REY data indicate that the ore-forming fluids of the early stage have intensely interacted with the Hercynian granite compared to those of the late ore stage.The gradual decrease in the europium(Eu/Eu^(*)),yttrium(Y/Y^(*)),and cerium(Ce/Ce^(*))anomalies and a low concentration ofΣREY observed in the second ore stage compared to the first ore stage suggest an increase in p H and fO_(2)and by inference a decrease in temperature during the evolution of the hydrothermal system.This evolution could be explained by fluid mixing between the ascending basinal hydrothermal fluids and the diluted sulfate-rich meteoric water barite separates from selected samples reveal that the dissolved sulfates(SO_(4)^(2-))were derived from Permian–Triassic sulfates and/or coeval poreseawater sulfates.The proposed fluid mixing triggered the precipitation of an early-stage F-Ba assemblage followed by the second-stage F-Ba mineralization.Geologic fieldwork,REY inventories,and isotope data point to the ore genesis during the Permian–Triassic extensional tectonic activity concerning the Pangea rifting.This extensional tectonic environment is likely the driving force that mobilized a large amount of the ore-forming basinal brines along the available faults and fractures to the loci of ore deposition.展开更多
Nyiragongo volcanic eruptions of 1977 and 2002 emitted silica-undersaturated lavas named melilite-nephelinites with microlithic to sub-porphyritic textures, and consisted of olivine, clinopyroxene (augite), phlogopite...Nyiragongo volcanic eruptions of 1977 and 2002 emitted silica-undersaturated lavas named melilite-nephelinites with microlithic to sub-porphyritic textures, and consisted of olivine, clinopyroxene (augite), phlogopite, melilite, magnetite, and rare plagioclases. This melilite-nephelinite as an evolved rock, shows low SiO<sub>2</sub> (38.40 - 39.52 wt%) and MgO (3.10 - 4.01 wt%), and relatively high FeOt (13.76 - 14.10 wt%), Al<sub>2</sub>O<sub>3</sub> (15.01 - 16.48 wt%), CaO (11.00 - 12.29 wt%) and Na<sub>2</sub>O + K<sub>2</sub>O (10.34 - 11.85 wt%). Unlike LA-ICP-MS on silicate melt inclusions (SMIs) hosted in augite show a pristine melt of picrobasaltic (low Ti-picrite) rock poor in SiO<sub>2</sub> (31.14 - 32.26 wt%), FeOt (2.19 - 2.79 wt%), Al<sub>2</sub>O<sub>3</sub> (8.01 - 9.57 wt%), and Na<sub>2</sub>O + K<sub>2</sub>O (2.34 - 3.05 wt%), while enriched in MgO (20.27 - 28.63 wt%), and CaO (24.95 - 33.17 wt%). The sums (∑REEs) for lavas and SMIs are ranging 712 - 799 and 43 - 119 ppm respectively. REE contracted multi-element patterns showed a W-feature for most lavas except for SMIs. High Rb/Sr, and low Ba/Rb, Zr/Nb, and Sm/Hf ratios of lavas suggest a phlogopite-rich source of materials. .展开更多
Zircon U-Pb isotope dating and whole-rock geochemical analyses were undertaken for the rhyolite,rhyolitic lithic crystal tuff and dacitic tuff from the Manketouebo Formation in the Keyihe area,in order to constrain th...Zircon U-Pb isotope dating and whole-rock geochemical analyses were undertaken for the rhyolite,rhyolitic lithic crystal tuff and dacitic tuff from the Manketouebo Formation in the Keyihe area,in order to constrain their genesis and tectonic significance.Zircon LA-ICP-MS U-Pb data indicate that the rhyolite and rhyolitic lithic crystal tuff were formed during 137±5 Ma and 143±1 Ma,respectively.These volcanic rocks have high SiO2(70.03%–76.46%)and K2O+Na2O(8.10%–9.52%)contents,but low CaO(0.03%–0.95%)and MgO(0.07%–0.67%)contents,which belong to the peraluminous and high-K calc-alkaline rocks.They are enriched in light rare earth elements(REEs),and exhibit fractionation of light over heavy REEs,withδEu values of 0.37–0.83.The volcanic rocks are enriched in LILEs(e.g.,Rb,U and K)and depleted in HFSEs(e.g.,Nb,Ti,P and Ta).The chemical composition suggests that these volcanic rocks formed by partial melting of crust material.Combined with previous regional research results,the authors consider that the volcanic rocks of the Manketouebo Formation in the Keyihe area were formed under an extensional environment related to the closure of the Mongolia–Okhotsk Ocean.展开更多
The Mokama granites are located in the Kibara belt (KIB) and hosts tin oxide group minerals (TOGM: Sn-W), and sulfide group minerals (SGM: Cu-Zn-Fe-As). The essential of Cu mineralization (non-economic deposit) is dis...The Mokama granites are located in the Kibara belt (KIB) and hosts tin oxide group minerals (TOGM: Sn-W), and sulfide group minerals (SGM: Cu-Zn-Fe-As). The essential of Cu mineralization (non-economic deposit) is disseminated inside the rock and consists of minerals (Raman, EPMA and metallographic microscopy) including chalcopyrite and bornite that are replaced by chalcocite and covellite, and the last also replaced later by malachite. The chemistry (XRF, LA-ICP-MS) of these peraluminous S-type leucogranites show SiO<sub>2</sub> (71 wt% - 79 wt%), ASI (1.4 - 3.1 molar), and are enriched in Rb (681 - 1000 ppm), Ta (12–151 ppm), Sn (43 - 142 ppm), Cu (10 - 4300 ppm), Zn (60 - 740 ppm), U (2.2 - 20.7 ppm) while depleted in Zr (20 - 31 ppm), Sr (20 - 69 ppm), Hf (1.3 - 2.0 ppm), Th (2.2 - 18.9 ppm), W (9 - 113 ppm), Pb (5 - 50 ppm), Ge (5 - 10 ppm), Cs (21 - 53 ppm) and Bi (0.6 - 17.4 ppm) and low ratios of (La/Yb) N, (Gd/Yb) N, (La/Sm) N). Fluid inclusion assemblages (FIAs) hosted in quartz in the Mokama granites show ranges of salinities of 4 - 23 wt% (NaCl equivalent) and homogenization temperatures (Th) of 190°C - 550°C. A boiling assemblage in the granite suggests a fluid phase separation occurred at about 380 - 610 bars, and this corresponds to apparent paleodepths of approximately 1 - 2 km (lithostatic model) or 3 - 5 km (hydrostatic model). FIAs hosted in TOGM such as cassiterite (salinities of 2 wt% - 10 wt% and Th of 220°C - 340°C) helped set up the possible temperature limit of SGM (Cu sulfide) precipitations that are estimated below 200°C.展开更多
The Sohnari Member of the Early Eocene Laki Formation is massively deposited in the Southern Indus Basin of Pakistan and is considered a potential source rock to generate hydrocarbons.However,the detailed paleoclimati...The Sohnari Member of the Early Eocene Laki Formation is massively deposited in the Southern Indus Basin of Pakistan and is considered a potential source rock to generate hydrocarbons.However,the detailed paleoclimatic,paleoweathering,and depositional conditions of the Sohnari Member have not been studied earlier.This research mainly discusses the detailed mineralogical(bulk and clay)and elemental geochemistry of the Laki Formation from two outcrop sections(Jhimpir and Lakhra)in the Southern Indus Basin,Pakistan.The bulk minerals,including quartz(low),hematite,calcite,halite,gypsum,and clay minerals such as kaolinite,chlorite,smectite and illite have been discussed here.These results demonstrate the paleo-environment of studied area was arid with enhanced saline and weak to strong oxidizing depositional conditions.The chemical index of alteration(CIA)values in Jhimpir and Lakhra sections are in the ranges of 41.30-97.93 and 22.30-96.19,respectively,indicating that the Sohnari sediments experienced weak to intense chemical weathering in the source area.The interpretation of the A-CN-K ternary diagram is consistent with the clay mineral contents in the studied sediments,which is characterized by the predominance of kaolinite,gibbsite and chlorite,demonstrating the weak to strong weathering state under warm and humid climatic conditions.The chemical indices such as Sr/Ba,δU,V/Cr,Ni/Co,and Cu/Zn,U/Th and Ba/Ga show that Sohnari rocks of Early Eocene Laki Formation underwent strong evaporation,oxic water column with warm to humid and minor contact of cold climatic conditions.Based on our present data,it can be concluded that the sediments of Sohnari Member of Laki Formation from Jhimpir and Lakhra areas of Southern Indus Basin in Pakistan are related to Indio-Eurasian collision and came from the Indian shield rocks that were deposited in a brackish water body with a minor contact of the freshwater oxidizing paleo-environment depositional conditions.展开更多
基金This article is the research result of the Education and Teaching Reform Research Project(No.2022JGB038)of Central South University and supported by the Scientific Research Fund of Hunan Provincial Education Department(No.23B0953).
文摘The construction of geochemical disciplines has brought new vitality to the development of traditional geology.In the new round of“Double First-Class”discipline construction at Central South University,the course of Advanced Geochemistry has effectively stimulated students’interest in learning and further improved their scientific thinking and research innovation skills through the implementation of“Guiding Interactive”teaching reform measures,which has important theoretical significance and practical value.
基金funded by the National Natural Science Foundation of China (2019M653840XB)the National Natural Science Foundation of China (41972043 and 42062006)。
文摘Geochemistry, zircon U–Pb geochronology, and Hf isotope data for the Early Paleozoic granites in the Baoshan Block reveal the Early Paleozoic tectonic evolution of the Proto-Tethys. The samples are high-K, calcalkaline, strongly peraluminous rocks with A/CNK values of 1.37–1.46, are enriched in SiO2, K2O, and Rb, and are depleted in Nb, P, Ti, Eu, and heavy rare earth elements,which indicates the crystallization fractionation of the granitic magma. Zircon U–Pb dating indicates that they formed in ca. 480 Ma. The Nansa granites have εHf(t) values ranging from-16.04 to 4.36 with corresponding TC DMages of 2.10–0.81 Ga, which suggests the magmas derived from the partial melting of ancient metasedimentary with minor involvement of mantle-derived components. A synthesis of data for the Early Paleozoic igneous rocks in the Baoshan block and adjacent(Tengchong,Qiangtang, Sibumasu, Himalaya, etc.) blocks indicates that these blocks were all aligned along the proto-Tethyan margin of East Gondwana in the Early Paleozoic. The Early Paleozoic S-type granites from Nansa were generated in a high-temperature and low-pressure(HTLP) extensional tectonic setting, which resulted from Andean-type orogeny instead of the final assembly of Gondwana or crustal extension in a non-arc environment. In certain places, an expanding environment may exist in opposition to the tectonic backdrop of the lithosphere’s thickening and shortening, leading the crust to melt and decompress,mantle-derived materials to mix, and a small quantity of peraluminous granite to emerge.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC2905001)the National Natural Science Foundation of China(Grant Nos.42272093,42230813)+1 种基金the Basic Research Fund of the Chinese Academy of Geological Sciences(Grant Nos.JKYZD202316,KK2116)the China Scholarship Council project and the Geological Survey project(Grant No.DD20230054).
文摘Rubidium(Rb)deposits mostly occur in the South China and Central Asia orogenic belts and are often closely associated with highly differentiated granites.This study investigates a newly-discovered giant Rb deposit at Gariatong in the Central Lhasa terrane in Tibet.Detailed field studies and logging data revealed that the Rb mineralization mainly occurs in monzogranite and is related to greisenization.LA-ICP-MS U-Pb dating of zircon yielded ages of 19.1±0.2 Ma and 19.0±0.2 Ma for greisenized monzogranite and fresh monzogranite,respectively.The monzogranites are characterized as strongly peraluminous,with high contents of SiO2,Al2O3,K2O and Na2O as well as a high differentiation index.They are enriched in light rare earth and large ion lithophile elements with significant negative Eu anomalies and depleted high fieldstrength elements.Petrological and geochemical features of these ore-related monzogranites suggest that they are highly fractionated S-type granites,derived from remelting of crustal materials in a post-collisional setting.The geochemistry of zircon and apatite points to a low oxygen fugacity of the ore-related monzogranite during the magma’s evolution.The discovery of the Gariatong Rb deposit suggests that the Central Lhasa terrane may be an important region for rare metal mineralization.
基金funded by the‘‘Laboratoire de Recherche Ressources,Mate´riaux et Ecosyste´mes’’,University of Carthage 7021 Zarzouna,Bizerte,Tunisia.
文摘The Ain El Bey abandoned mine,in North-West Tunisia,fits into the geodynamic context of the European and African plate boundary.Ore deposit corresponds to veins and breccia of multiphase Cu–Fe-rich mineralization related to various hydrothermal fluid circulations.Petromineralogical studies indicate a rich mineral paragenesis with a minimum of seven mineralization phases and,at least,six pyrite generations.As is also the case for galena and native silver,native gold is observed for the first time as inclusion in quartz which opens up,thus,new perspectives for prospecting and evaluating the potential for noble metals associated with the mineralization.Scanning Electron Microscope—Energy Dispersive Spectroscopy and Transmission electron microscopy analyses show,in addition,a large incorporation of trace elements,including Ag and Au,in mineral structures such as fahlores(tetrahedrite-tennantite)and chalcopyrite ones.The mineral/mineral associations,used as geothermometers,gave estimated temperatures for the mineralizing fluids varying from 254 to 330 C for phase III,from 254 to 350 ℃ for phase IV,and from 200 to 300 ℃ for phases V and VI.The seventh and last identified mineralization phase,marked by a deposit of native gold,reflects a drop in the mineralizing fluid’s temperature(<200 ℃)compatible with boiling conditions.Such results open up perspectives for the development of precious metal research and the revaluation of the Cu–Fe ore deposit at the Ain El Bey abandoned mine,as well as at the surrounding areas fitting in the geodynamic framework of the Africa-Europe plate boundary.
基金supported by the Open Fund for Sanjiang Key Laboratory of Mineralization and Resource Exploration and Utilization,Ministry of Natural Resources(ZRZYBSJSYS2021002)Yunnan Major Scientific and Technological Projects(Grant No.202202AG050006)+2 种基金the National Natural Science Foundation of China(No.41772070)supported by the National Research Center of Geoanalysis(NRCG)Chinese Academy of Geological Sciences(CAGS)。
文摘The Late Paleozoic and Mesozoic tectonic framework of the Nanpanjiang Basin has much been disputed.Herein,the middle-acid volcanic rock,dacite,exposed to the Zhesang gold district,southeast Yunnan Province,has been analyzed.The results show that the dacite belongs to a calc-alkaline series,SiO_(2)contents range from 62.79 to 76.66 wt%.Zircon SHRIMP U–Pb dating of dacite demonstrates that they were formed in the Early Triassic(247.8±1.7 Ma,MSWD=1.2).All samples exhibit enrichment in LILE(e.g.Rb,K,Th,and U),and depletion in HFSE(e.g.Nb,Ta,and Ti),which has the geochemical affinity of I-type granite.La–La/Sm and La–La/Yb discrimination diagrams show that the partial melting,mainly of the mafic lower crust,of rocks,plays a major role in the formation process.The dacite has low initial ^(87)Sr/^(86)Sr ratios(0.706954 to 0.708589)and negative ε_(Nd)(t)values(-11.77 to-10.88).Zircons in dacite have ε_(Hf)(t)values of-16.2 to-8.3,and the two-stage Hf model ages are 1799–2301 Ma,mostly concentrated between 1800 and 1900 Ma,indicating that the magma source area is the reconstructed ancient lower crust mixed with some mantle materials,and crystal fractionation process underwent in the late stage of magma migration.This study reveals that the arc-volcanic rocks of the Early Triassic in the southern margin of the Nanpanjiang Basin were formed by the subduction of the Late Paleozoic ocean basin within the border region between China and Vietnam.
基金Supported by the National Natural Science Foundation of China (Nos.42130206,41302076)the MOST Special Fund awarded by the State Key Laboratory of Continental Dynamics,Northwest University (No.201210128)the Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Mineral,Shandong University of Science and Technology (No.DMSM2017033)。
文摘Six outcrop sections in Fenghe River,Northwestern China,were sampled and analyzed.This study aims to determine provenance,tectonic setting,and source-area paleoweathering of the sediments of Fenghe River in combination of lithofacies analysis and bulk-rock geochemical data.The lithofacies in the studied area were classified as gravel,sand,and fine-grained clastic lithofacies,reflecting generally channel fill deposits,channel bar deposits,and over-bank deposits,respectively.The Chemical Index of Alteration(CIA),Plagioclase Index of Alteration(PIA),and Chemical Index of Weathering(CIW)values ranged 50.10–62.29,50.13–66.35,56.52–71.12,respectively,together with element ratios such as Rb/Sr,K/Na,Rb/K,Th/K,Rb/Ti,and Cs/Ti indicate that the source area was under a low to moderate chemical weathering condition probably in cold and semi-arid climates.Moreover,plot of SiO_(2)vs.(Al_(2)O_(3)+K_(2)O+Na_(2)O)suggests that the sediments were deposited in a semi-arid climate.Plots of Cr/Th vs.Th/Sc,TiO_(2)vs.Zr,La/Yb vs.rare earth element(REE),and La-Th-Sc ternary diagrams,along with the lithology,indicate that the sediments in Fenghe River were mainly originated from felsic igneous rocks.Major elements-based discrimination diagrams and Th-Sc-Zr/10 and La-Th-Sc ternary diagram of the samples indicates that the source rocks of Fenghe River developed in a composite active continental margin and continental island arc field.
文摘Aptian is characterized by widespread deposition of organic-rich sediment.The Aptian bitumen limestone horizon,which is thin decimetre-thick sequences,locally crops out in the Kircaova area,Eastern Black Sea Region(Eastern Pontides).They are well correlated with Aptian bitumen limestone in the other Tethys Reams.They are proposed as episodes of increased organic matter.However,background factors controlling organic matter enrichment are poorly known.In this study,we present new inorganic geochemistry,including trace elements,rare earth elements(REE),redox-sensitive elements(RSE),stable-isotopes(δ~(18)O andδ~(13)C),and total organic carbon(TOC).We integrated new geochemical data with existing stratigraphy,paleontology,and organic chemistry data to provide new insight into the depositional environment and paleoclimate conditions during Aptian.The lacustrine bitumen limestone(LBL)samples have variedδ~(13)C(ave.-1.45‰)andδ~(18)O(ave.-4.50‰).They possess distinct REE patterns,with an average of REE(ave.14.45 ppm)and Y/Ho(ave.35)ratios.In addition,they have variable Nd/YbN(0.28-0.81;ave.0.56)and Ce/Ce*(0.68-0.97;ave.0.86),and relatively high Eu^(*)/Eu(1.23-1.53;ave.1.35).They display seawater signatures with reduced oxygen conditions.The enrichment in RSE(Mo,Cu,Ni,and Zn)and the low Mo/TOC(0.70-3.69;ave.2.41)support a certain degree of water restriction.The high Sr/Ba,Sr/Cu,Ga/Rb,and K/Al records of the LBL facies suggest hot house climatic conditions.The sedimentary environment was probably an isolated basin that is transformed from the marine basin.In addition to depositional conditions,the regional parameters such as the climate,increased run-off period,nutrient levels,alkalinity level,and dominant carbonate producers favored the enrichment in organic matter of LBL facies.Thus,extreme greenhouse palaeoclimate conditions have an important role in organic matter enrichment in the isolated basin.Our results are conformable with the published data from marine,semi-restricted basin,and lacustrine settings in the different parts of the Tethys margin.Thus,this approach provides the first insight into the Aptian greenhouse paleo-climate conditions of the Eastern Black Sea Region,NE Turkey.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC2905001)National Natural Science Foundation of China(Grant Nos.42272093 and 42230813)+2 种基金Basic Research Fund of Chinese Academy of Geological Sciences(Grant Nos.JKYZD202316,KJ2102,KK2116,and JKY202208)Geological Survey Project(Grant No.DD20221684)China Scholarship Council(Grant No.CSC202206400059)。
文摘Jiama is a giant,high-grade porphyry copper system in the Gangdese metallogenic belt,Tibet.Multistage intermediate-felsic porphyries intruded in this deposit,some of which are strongly associated with copper-polymetallic mineralization.These ore-bearing porphyries include monzogranite,granodiorite,and quartz diorite porphyries.A new granite aplite dyke was found in the south of Jiama.Its age,genesis,and relationship with ore-related magmatism are obscure.Here,its emplacement age and petrogenesis were determined using mineralogy,zircon U-Pb dating,geochemistry,and Sr-Nd-Pb isotope studies.The zircon LA-ICP-MS U-Pb age of the aplite dyke is 16.66±0.21 Ma(n=14,MSWD=0.66),earlier than that of the ore-bearing porphyries(~15 Ma)in Jiama.Furthermore,the aplite exhibits high amounts of silicon(SiO_(2)=73.39%-74.74%),potassium(K_(2)O=5.12%-6.61%),aluminum(Al_(2)O_(3)=14.25%-14.69%),and light/heavy rare earth elements(LREE/HREE=12.12-16.19)as well as negative europium(δEu=0.47-0.72)and weak negative cerium anomalies(δCe=0.84-0.93).The aplite dyke is characteristic of metaluminous-peraluminous I-type granite,which is rich in large-ion lithophile elements(Rb,Ba,Th and U)and depleted in high-field-strength elements(Nb,P and Ti).The aplite dyke and ore-bearing porphyries in the Jiama deposit are the results of a partial melting of the juvenile lower crust,according to whole-rock geochemistry and Sr-Nd-Pb isotope data,but the dyke and ore-bearing porphyries were emplaced from the same magma chamber at different times.Thus,the aplite dyke shows the composition of the early evolution stage of shallow magma in the Jiama deposit and is the product of rapid condensation and crystallization.
基金supported by Special Fund for Basic Scientific Research of Central Colleges,Chang’an University(Grant No.:300102279210)the Natural Science Foundation of Shaanxi Province(Grant No.:2019JQ-690)the geological and mineral survey evaluation project of China Geological Survey(Grant No.:DD20190065).
文摘The Dunde iron-zinc polymetallic deposit is one of large iron deposits occurred in the Awulale Metallogenetic Belt,Western Tianshan(NW-China).This study reports new geochronology and geochemistry for granite in the Dunde mining area in order to constrain the tectonicmagmatic activities and metallogenesis of this region.Granites in the southwest of Dunde mining area are mainly syenogranites intruded into volcanics of the Dahalajunshan Formation in the Early Carboniferous,and they are far from the area where ore bodies and mineralized altered rocks are widely developed.LA-ICP-MS U–Pb zircon dating indicates that Dunde syenogranite was at 306.8±1.0 Ma,which could constrain the upper limit of metallogenic age for this deposit.The Dunde granites are high SiO_(2)(73.41–80.07 wt%),high differentiation index(D.I.=89.7–95.0),weakly peraluminous to metaluminous(A/CNK=0.94–1.08),and they are enriched in LILE and LREE and depleted in Eu,Ba,Sr and P_(2)O_(5),indicating that they belong to highly fractionated Ⅰ-type granite.Based on εHf values(+9.2 to+10.5)for zircon and high εNd(-t)values(+4.7 to+5.8)for whole-rock,and the two-stage model ages for 601–735 Ma,suggest that the magma source could be the juvenile lower crust.Combined with regional geological setting,the 306.8 Ma Dunde granites are formed in post-collision extensional tectonic setting.
基金financially supported by the National Natural Science Foundation of China(No.41902024U1203821L08)+3 种基金the Chongqing Science and Technology Commission(cstc2019jcyjmsxmX0656)the Talent Introduction Program of Chongqing Three Gorges University(17RC08)the Research Center for Sustainable Development of the Three Gorges Reservoir Area(18sxxyjd12)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2022447)。
文摘Numerous studies have focused on modern hydroclimate and the modulated mechanisms in the Tianshan Mountains(TMs),arid central Asia.However,the detailed information of hydroclimatic processes beyond the instrumental period is still scarce.This paper reconstructed a hydrology history from core sediments of the Dalongchi Lake in the Tianshan Mountains.The comparability between endmembers(EMs)of grain size and ICP-AES based geochemical elements in the lake sediments highlighted their availability for hydrological reconstructions.Hydrodynamic forces(EM1,EM4,Ti/Al and Li/Al),chemical weathering intensity[(Mg+Ca+K)/Al],salinity proxy(Mg/Ca)and redoxsensitive proxy(Fe/Mn)highly correlated with the first principal component(P<0.01),whereas paleoproductivity proxies(TN,TOC,Ba/Al,Zn/Al and Cu/Al)and C/N showed high loadings on the second principal component(P<0.05).The inferred hydrology progress was nonlinearly responded to temperature,precipitation and climate-dictated glaciers.Specifically,the water level didn’t always covary with the humidity because of glaciers.The maximum water level was the comprehensive result of glaciers melting and high humidity around 1830 CE.Thereafter,water level continually decreased with declining moisture at high temperature,implying a limited buffering capacity of glaciers in the Dalongchi Lake basin.EM3-indicated eolian activity intensity was caused by the behaviors of Siberian High because the latter intensified surface wind and the dust transportation.The hydrothermal patterns were characterized by warm/dry and cold/wet alternations in a long run although warm/wet pattern was identified from a short-term view.
基金supported by the National Science and Technology Major Project of China(Grant No.2017ZX05009-002)the National Natural Science Foundation of China(Nos.U1762217,41702139,42072164 and 41821002)+2 种基金Taishan Scholars Program(No.TSQN201812030)the Fundamental Research Funds for the Central Universities(19CX07003A)the School of Geosciences,China University of Petroleum,East China,for analytical support and financial support。
文摘The effect of various depositional parameters including paleoclimate,paleosalinity and provenance,on the depositional mechanism of lacustrine shale is very important in reconstructing the depositional environment.The classification of shale lithofacies and the interpretation of shale depositional environment are key features used in shale oil and gas exploration and development activity.The lower 3rd member of the Eocene Shahejie Formation(Es_(3)^(x)shale)was selected for this study,as one of the main prospective intervals for shale oil exploration and development in the intracratonic Bohai Bay Basin.Mineralogically,it is composed of quartz(avg.9.6%),calcite(avg.58.5%),dolomite(avg.7%),pyrite(avg.3.3%)and clay minerals(avg.20%).An advanced methodology(thin-section petrography,total organic carbon and total organic sulfur contents analysis,X-ray diffraction(XRD),X-ray fluorescence(XRF),field-emission scanning electron microscopy(FE-SEM))was adopted to establish shale lithofacies and to interpret the depositional environment in the lacustrine basin.Six different types of lithofacies were recognized,based on mineral composition,total organic carbon(TOC)content and sedimentary structures.Various inorganic geochemical proxies(Rb/Sr,Ca/(Ca+Fe),Ti/Al,Al/Ca,Al/Ti,Zr/Rb)have been used to interpret and screen variations in depositional environmental parameters during the deposition of the Es_(3)^(x)shale.The experimental results indicate that the environment during the deposition of the Es_(3)^(x)shale was warm and humid with heightened salinities,moderate to limited detrital input,higher paleohydrodynamic settings and strong oxygen deficient(reducing)conditions.A comprehensive depositional model of the lacustrine shale was developed.The interpretations deduced from this research work are expected to not only expand the knowledge of shale lithofacies classification for lacustrine fine-grained rocks,but can also offer a theoretical foundation for lacustrine shale oil exploration and development.
基金financially supported by the Scientific Research Project Coordination of Konya Technical University(Grant No.211007014)。
文摘The Goshgarchay Cu-Au deposit is located in the central part of the northwest flank of the Murovdagh region in the Lesser Caucasus.The Goshgarchay Cu-Au deposit is associated with Middle Jurassic volcanic and Late Jurassic-Early Cretaceous high-K calc-alkaline intrusive rocks.The Cu-Au mineralization is commonly related to quartz-sericite-chlorite alteration dominantly composed of chalcopyrite,gold,sphalerite,pyrite,bornite,hematite,covellite,chalcocite,malachite,and azurite.The Goshgarchay copper-gold deposit,which is 600 m wide and approximately 1.2 km long,is seen as a faultcontrolled and vein-,stockwork-and disseminated type deposit.The Goshgarchay Cu-Au deposit predominantly comprises Cu(max.64500 ppm)and Au(max.11.3 ppm),while it comprises relatively less amounts Zn(max.437 ppm),Mo(max.47.5 ppm),Pb(max.134 ppm),and Ag(max.21 ppm).The homogenization temperatures and salinities of fluid inclusions in quartz for stage Ⅰ range from 380℃ to 327℃,and 6.9 wt% to 2.6 wt% NaCl eq.,respectively.Thand salinities in quartz for stage Ⅱ range from 304℃ to 253℃,and 7.6 wt% to 3.2 wt% NaCl eq.,respectively.The calculated δ^(34)S_(h2s)values(-1.5‰ to 5.5‰)of sulfides and especially the narrow range of δ^(34)S_(h2s) values of chalcopyrite and bornite(between -0.07‰ and +0.7‰)indicate that the source of the Goshgarchay Cu-Au mineralization is magmatic.Based on the mineralogical,geochemical,fluid inclusion,and sulfur isotopic data,the Goshgarchay Cu-Au deposit represents a late stage peripheral magmatic-hydrothermal mineralization probably underlain by a concealed porphyry deposit.
基金supported by the National Natural Science Foundation of China(Grant Nos.41972170,42102127)Shandong Provincial Natural Science Foundation(Grant No.ZR2021QD087)+1 种基金Chinese Postdoctoral Science Foundation(Grant No.2021M702019)SDUST Research Fund(Grant No.2018TDJH101)。
文摘Tonstein layers are found worldwide in the Permo-Carboniferous coal-bearing strata.This study investigates the geochronology,mineralogy,and geochemistry of four tonstein samples from the Permo-Carboniferous Benxi Formation,Ordos Basin,North China Craton(NCC).The typical features of the studied tonsteins include thin beds,lateral continuity,angular quartz grains,and euhedral zircons with similar U-Pb ages,indicating a significant pyroclastic origin.In addition,the tonstein samples have low TiO_(2)/Al_(2)O_(3)ratios(<0.02)and rare earth elements and yttrium(REY)concentrations with obvious negative Eu anomalies,indicating that the tonsteins have a felsic magma origin.Moreover,compared with the mean composition of clay shale,the studied tonsteins are characterized by high concentrations of the elements Nb and Ta,which may affect the concentration of the corresponding elements in surrounding coal seams.The zircon U-Pb ages of the tonsteins(293.9-298.8 Ma)provide a precise chronological framework on the Benxi Formation in the Ordos Basin,constraining the Gzhelian-Aselian stages.The tonsteins were probably sourced from arc volcanism along the western margin of the NCC during the early Permian,implying that the Alxa Terrane had not amalgamated with the NCC at that time.
基金The National Natural Science Foundation of China under contract No.42072181。
文摘Studies in the northern South China Sea(SCS)basement remain important for understanding the evolution of the Southeast Asian continental margin.Due to a thick cover of sediments and scarce borehole penetration,little is known about the age and tectonic affinity of this basement.In this study,an integrated study of zircon U-Pb geochronology,Hf isotopes,and whole-rock major and trace elements on seven basement granitoids from seven boreholes of Qiongdongnan Basin has been carried out.New zircon U-Pb results for these granitoids present middle-late Permian((270.0±1.2)Ma;(253±3.4)Ma),middle to late Triassic((246.2±3.4)Ma;(239.3±0.96)Ma;(237.9±0.99)Ma;(228.9±1.0)Ma)and Late Cretaceous ages((120.6±0.6)Ma).New data from this study,in combination with the previous dataset,indicates that granitoid ages in northern SCS basement vary from 270 Ma to 70.5 Ma,with three age groups of 270–196 Ma,162–142 Ma,and 137–71 Ma,respectively.Except for the late Paleozoic-Mesozoic rocks in the basement of the northern SCS,a few old zircon grains with the age of(2708.1±17)Ma to(2166.6±19)Ma provide clues to the existence of the pre-Proterozoic components.The geochemical signatures indicate that the middle Permian-early Cretaceous granitoids from the Qiongdongnan Basin are I-type granites formed in a volcanic arc environment,which were probably related to the subduction of the Paleo-Pacific Plate.
文摘We report the mineralogy and geochemistry of hydrothermal sulphide from the crater of a volcanic high near 18°36.4′S of the Central Lau Spreading Center.During 1990s,that volcanic structure was reported active and sulphide samples were collected by MIR submersible.A section of a chimney-like structure from the crater-floor was studied here.The Fe-depleted sphalerites,and Co-depleted pyrites in that chimney were similar to those commonly found in low to moderate temperature(<300℃)sulphides from sediment-starved hydrothermal systems.Bulk analyses of three parts of that chimney section showed substantial enrichment of Zn(18%–20%)and Fe(14%–27%)but depletion of Cu(0.8%–1.3%).In chondrite-normalized rare earth element-patterns,the significant negative Ce-anomalies(Ce/Ce*=0.27–0.39)and weakly positive Eu-anomalies(Eu/Eu*=1.60–1.68)suggested sulphide mineralisation took place from reduced low-temperature fluid.The depleted concentration of lithophiles in this sulphide indicates restricted contribution of sub-ducting plate in genesis of source fluid as compared to those from other parts of Lau Spreading Centre.Uniform mineralogy and bulk composition of subsamples across the chimney section suggests barely any alteration of fluid composition and/or mode of mineralisation occurred during its growth.
文摘The Merguechoum fluorite-barite mineralization,located in the Eastern Meseta of Morocco,is hosted in the Late Hercynian granite.The ore consists of fine crystals of fluorite 1,massive barite 1,euhedral crystals of fluorite 2,and barite 2 with calcite and minor quartz and sulfides.The Merguechoum ore deposits have never been investigated.This study was the first contribution that studied the genesis of fluorite and barite.The ore occurs as dissemination within granite intrusion and also fills the NE-SWtrending meter-sized fractures and faults.The values of the total Rare Earth Elements and Yttrium(REY)and the ratios of LREY/HREY,Y/Ho,Tb/Ca,and Tb/La indicate that the Merguechoum fluorite precipitated from hydrothermal fluids,likely basinal brines,which interacted with the Hercynian granite.The REY data indicate that the ore-forming fluids of the early stage have intensely interacted with the Hercynian granite compared to those of the late ore stage.The gradual decrease in the europium(Eu/Eu^(*)),yttrium(Y/Y^(*)),and cerium(Ce/Ce^(*))anomalies and a low concentration ofΣREY observed in the second ore stage compared to the first ore stage suggest an increase in p H and fO_(2)and by inference a decrease in temperature during the evolution of the hydrothermal system.This evolution could be explained by fluid mixing between the ascending basinal hydrothermal fluids and the diluted sulfate-rich meteoric water barite separates from selected samples reveal that the dissolved sulfates(SO_(4)^(2-))were derived from Permian–Triassic sulfates and/or coeval poreseawater sulfates.The proposed fluid mixing triggered the precipitation of an early-stage F-Ba assemblage followed by the second-stage F-Ba mineralization.Geologic fieldwork,REY inventories,and isotope data point to the ore genesis during the Permian–Triassic extensional tectonic activity concerning the Pangea rifting.This extensional tectonic environment is likely the driving force that mobilized a large amount of the ore-forming basinal brines along the available faults and fractures to the loci of ore deposition.
文摘Nyiragongo volcanic eruptions of 1977 and 2002 emitted silica-undersaturated lavas named melilite-nephelinites with microlithic to sub-porphyritic textures, and consisted of olivine, clinopyroxene (augite), phlogopite, melilite, magnetite, and rare plagioclases. This melilite-nephelinite as an evolved rock, shows low SiO<sub>2</sub> (38.40 - 39.52 wt%) and MgO (3.10 - 4.01 wt%), and relatively high FeOt (13.76 - 14.10 wt%), Al<sub>2</sub>O<sub>3</sub> (15.01 - 16.48 wt%), CaO (11.00 - 12.29 wt%) and Na<sub>2</sub>O + K<sub>2</sub>O (10.34 - 11.85 wt%). Unlike LA-ICP-MS on silicate melt inclusions (SMIs) hosted in augite show a pristine melt of picrobasaltic (low Ti-picrite) rock poor in SiO<sub>2</sub> (31.14 - 32.26 wt%), FeOt (2.19 - 2.79 wt%), Al<sub>2</sub>O<sub>3</sub> (8.01 - 9.57 wt%), and Na<sub>2</sub>O + K<sub>2</sub>O (2.34 - 3.05 wt%), while enriched in MgO (20.27 - 28.63 wt%), and CaO (24.95 - 33.17 wt%). The sums (∑REEs) for lavas and SMIs are ranging 712 - 799 and 43 - 119 ppm respectively. REE contracted multi-element patterns showed a W-feature for most lavas except for SMIs. High Rb/Sr, and low Ba/Rb, Zr/Nb, and Sm/Hf ratios of lavas suggest a phlogopite-rich source of materials. .
基金Supported by Project of National Natural Science Foundation of China(No.41872234)。
文摘Zircon U-Pb isotope dating and whole-rock geochemical analyses were undertaken for the rhyolite,rhyolitic lithic crystal tuff and dacitic tuff from the Manketouebo Formation in the Keyihe area,in order to constrain their genesis and tectonic significance.Zircon LA-ICP-MS U-Pb data indicate that the rhyolite and rhyolitic lithic crystal tuff were formed during 137±5 Ma and 143±1 Ma,respectively.These volcanic rocks have high SiO2(70.03%–76.46%)and K2O+Na2O(8.10%–9.52%)contents,but low CaO(0.03%–0.95%)and MgO(0.07%–0.67%)contents,which belong to the peraluminous and high-K calc-alkaline rocks.They are enriched in light rare earth elements(REEs),and exhibit fractionation of light over heavy REEs,withδEu values of 0.37–0.83.The volcanic rocks are enriched in LILEs(e.g.,Rb,U and K)and depleted in HFSEs(e.g.,Nb,Ti,P and Ta).The chemical composition suggests that these volcanic rocks formed by partial melting of crust material.Combined with previous regional research results,the authors consider that the volcanic rocks of the Manketouebo Formation in the Keyihe area were formed under an extensional environment related to the closure of the Mongolia–Okhotsk Ocean.
文摘The Mokama granites are located in the Kibara belt (KIB) and hosts tin oxide group minerals (TOGM: Sn-W), and sulfide group minerals (SGM: Cu-Zn-Fe-As). The essential of Cu mineralization (non-economic deposit) is disseminated inside the rock and consists of minerals (Raman, EPMA and metallographic microscopy) including chalcopyrite and bornite that are replaced by chalcocite and covellite, and the last also replaced later by malachite. The chemistry (XRF, LA-ICP-MS) of these peraluminous S-type leucogranites show SiO<sub>2</sub> (71 wt% - 79 wt%), ASI (1.4 - 3.1 molar), and are enriched in Rb (681 - 1000 ppm), Ta (12–151 ppm), Sn (43 - 142 ppm), Cu (10 - 4300 ppm), Zn (60 - 740 ppm), U (2.2 - 20.7 ppm) while depleted in Zr (20 - 31 ppm), Sr (20 - 69 ppm), Hf (1.3 - 2.0 ppm), Th (2.2 - 18.9 ppm), W (9 - 113 ppm), Pb (5 - 50 ppm), Ge (5 - 10 ppm), Cs (21 - 53 ppm) and Bi (0.6 - 17.4 ppm) and low ratios of (La/Yb) N, (Gd/Yb) N, (La/Sm) N). Fluid inclusion assemblages (FIAs) hosted in quartz in the Mokama granites show ranges of salinities of 4 - 23 wt% (NaCl equivalent) and homogenization temperatures (Th) of 190°C - 550°C. A boiling assemblage in the granite suggests a fluid phase separation occurred at about 380 - 610 bars, and this corresponds to apparent paleodepths of approximately 1 - 2 km (lithostatic model) or 3 - 5 km (hydrostatic model). FIAs hosted in TOGM such as cassiterite (salinities of 2 wt% - 10 wt% and Th of 220°C - 340°C) helped set up the possible temperature limit of SGM (Cu sulfide) precipitations that are estimated below 200°C.
文摘The Sohnari Member of the Early Eocene Laki Formation is massively deposited in the Southern Indus Basin of Pakistan and is considered a potential source rock to generate hydrocarbons.However,the detailed paleoclimatic,paleoweathering,and depositional conditions of the Sohnari Member have not been studied earlier.This research mainly discusses the detailed mineralogical(bulk and clay)and elemental geochemistry of the Laki Formation from two outcrop sections(Jhimpir and Lakhra)in the Southern Indus Basin,Pakistan.The bulk minerals,including quartz(low),hematite,calcite,halite,gypsum,and clay minerals such as kaolinite,chlorite,smectite and illite have been discussed here.These results demonstrate the paleo-environment of studied area was arid with enhanced saline and weak to strong oxidizing depositional conditions.The chemical index of alteration(CIA)values in Jhimpir and Lakhra sections are in the ranges of 41.30-97.93 and 22.30-96.19,respectively,indicating that the Sohnari sediments experienced weak to intense chemical weathering in the source area.The interpretation of the A-CN-K ternary diagram is consistent with the clay mineral contents in the studied sediments,which is characterized by the predominance of kaolinite,gibbsite and chlorite,demonstrating the weak to strong weathering state under warm and humid climatic conditions.The chemical indices such as Sr/Ba,δU,V/Cr,Ni/Co,and Cu/Zn,U/Th and Ba/Ga show that Sohnari rocks of Early Eocene Laki Formation underwent strong evaporation,oxic water column with warm to humid and minor contact of cold climatic conditions.Based on our present data,it can be concluded that the sediments of Sohnari Member of Laki Formation from Jhimpir and Lakhra areas of Southern Indus Basin in Pakistan are related to Indio-Eurasian collision and came from the Indian shield rocks that were deposited in a brackish water body with a minor contact of the freshwater oxidizing paleo-environment depositional conditions.
