The Jiama deposit,a significant porphyry-skarn-type copper polymetallic deposit located within the Gangdese metallogenic belt in Tibet,China,exemplifies a typical porphyry metallogenic system.However,the mineral chemi...The Jiama deposit,a significant porphyry-skarn-type copper polymetallic deposit located within the Gangdese metallogenic belt in Tibet,China,exemplifies a typical porphyry metallogenic system.However,the mineral chemistry of its accessory minerals remains under-examined,posing challenges for resource assessment and ore prospecting.Utilizing electron microprobe analysis and LA-ICP-MS analysis,this study investigated the geochemical characteristics of apatite in ore-bearing granite and monzogranite porphyries,as well as granodiorite,quartz diorite,and dark diorite porphyries in the deposit.It also delved into the diagenetic and metallogenic information from these geochemical signatures.Key findings include:(1)The SiO_(2) content,rare earth element(REE)contents,and REE partition coefficients of apatite indicate that the dark diorite porphyry possibly does not share a cogenetic magma source with the other four types of porphyries;(2)the volatile F and Cl contents in apatite,along with their ratio,indicate the Jiama deposit,formed in a collisional setting,demonstrates lower Cl/F ratios in apatite than the same type of deposits formed in a subduction environment;(3)compared to non-ore-bearing rock bodies in other deposits formed in a collisional setting,apatite in the Jiama deposit exhibits lower Ce and Ga contents.This might indicate that rock bodies in the Jiama deposit have higher oxygen fugacity.Nevertheless,the marginal variation in oxygen fugacity between ore-bearing and non-ore-bearing rock bodies within the deposit suggests oxygen fugacity may not serve as the decisive factor in the ore-hosting potential of rock bodies in the Jiama deposit.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
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
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 ...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 ℃ 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 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
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
In this paper,we build a remote-sensing satellite imagery priori-information data set,and propose an approach to evaluate the robustness of remote-sensing image feature detectors.The building TH Priori-Information(TPI...In this paper,we build a remote-sensing satellite imagery priori-information data set,and propose an approach to evaluate the robustness of remote-sensing image feature detectors.The building TH Priori-Information(TPI)data set with 2297 remote sensing images serves as a standardized high-resolution data set for studies related to remote-sensing image features.The TPI contains 1)raw and calibrated remote-sensing images with high spatial and temporal resolutions(up to 2 m and 7 days,respectively),and 2)a built-in 3-D target area model that supports view position,view angle,lighting,shadowing,and other transformations.Based on TPI,we further present a quantized approach,including the feature recurrence rate,the feature match score,and the weighted feature robustness score,to evaluate the robustness of remote-sensing image feature detectors.The quantized approach gives general and objective assessments of the robustness of feature detectors under complex remote-sensing circumstances.Three remote-sensing image feature detectors,including scale-invariant feature transform(SIFT),speeded up robust features(SURF),and priori information based robust features(PIRF),are evaluated using the proposed approach on the TPI data set.Experimental results show that the robustness of PIRF outperforms others by over 6.2%.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
Shadow detection is a crucial task in high-resolution remote-sensing image processing. Various shadow detection methods have been explored during the last decades. These methods did improve the detection accuracy but ...Shadow detection is a crucial task in high-resolution remote-sensing image processing. Various shadow detection methods have been explored during the last decades. These methods did improve the detection accuracy but are still not robust enough to get satisfactory results for failing to extract enough information from the original images. To take full advantage of various features of shadows, a new method combining edges information with the spectral and spatial information is proposed in this paper. As known, edge is one of the most important characteristics in the high-resolution remote-sensing images. Unfortunately, in shadow detection, it is a high-risk strategy to determine whether a pixel is the edge or not strictly because intensity values on shadow boundaries are always between those in shadow and non-shadow areas. Therefore, a soft edge description model is developed to describe the degree of each pixel belonging to the edges or not. Sequentially, the soft edge description is incorporating to a fuzzy clustering procedure based on HMRF (Hidden Markov Random Fields), in which more appropriate spatial contextual information can be used. More concretely, it consists of two components: the soft edge description model and an iterative shadow detection algorithm. Experiments on several remote sensing images have shown that the proposed method can obtain more accurate shadow detection results.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
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
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
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
This article expounds the vital role undertaken by telemetry in monitoring and assessment in flood control in China. By analyzing the data from their surveys, the authors give an all-round exposition of problems in th...This article expounds the vital role undertaken by telemetry in monitoring and assessment in flood control in China. By analyzing the data from their surveys, the authors give an all-round exposition of problems in the country’s drive for disaster reduction and propose countermeasures in the fight against the possible flood problems in the future.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 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
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
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)a geological survey project(Grant No.DD20230054).
文摘The Jiama deposit,a significant porphyry-skarn-type copper polymetallic deposit located within the Gangdese metallogenic belt in Tibet,China,exemplifies a typical porphyry metallogenic system.However,the mineral chemistry of its accessory minerals remains under-examined,posing challenges for resource assessment and ore prospecting.Utilizing electron microprobe analysis and LA-ICP-MS analysis,this study investigated the geochemical characteristics of apatite in ore-bearing granite and monzogranite porphyries,as well as granodiorite,quartz diorite,and dark diorite porphyries in the deposit.It also delved into the diagenetic and metallogenic information from these geochemical signatures.Key findings include:(1)The SiO_(2) content,rare earth element(REE)contents,and REE partition coefficients of apatite indicate that the dark diorite porphyry possibly does not share a cogenetic magma source with the other four types of porphyries;(2)the volatile F and Cl contents in apatite,along with their ratio,indicate the Jiama deposit,formed in a collisional setting,demonstrates lower Cl/F ratios in apatite than the same type of deposits formed in a subduction environment;(3)compared to non-ore-bearing rock bodies in other deposits formed in a collisional setting,apatite in the Jiama deposit exhibits lower Ce and Ga contents.This might indicate that rock bodies in the Jiama deposit have higher oxygen fugacity.Nevertheless,the marginal variation in oxygen fugacity between ore-bearing and non-ore-bearing rock bodies within the deposit suggests oxygen fugacity may not serve as the decisive factor in the ore-hosting potential of rock bodies in the Jiama deposit.
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 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funded by the “Laboratoire de Recherche Ressources, Matériaux et Ecosystémes”, 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 ℃ 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the National Key Research and Development Program of China under Grant 2018YFF0301205in part by the National Natural Science Foundation of China under Grant NSFC 61925105 and Grant 61801260.
文摘In this paper,we build a remote-sensing satellite imagery priori-information data set,and propose an approach to evaluate the robustness of remote-sensing image feature detectors.The building TH Priori-Information(TPI)data set with 2297 remote sensing images serves as a standardized high-resolution data set for studies related to remote-sensing image features.The TPI contains 1)raw and calibrated remote-sensing images with high spatial and temporal resolutions(up to 2 m and 7 days,respectively),and 2)a built-in 3-D target area model that supports view position,view angle,lighting,shadowing,and other transformations.Based on TPI,we further present a quantized approach,including the feature recurrence rate,the feature match score,and the weighted feature robustness score,to evaluate the robustness of remote-sensing image feature detectors.The quantized approach gives general and objective assessments of the robustness of feature detectors under complex remote-sensing circumstances.Three remote-sensing image feature detectors,including scale-invariant feature transform(SIFT),speeded up robust features(SURF),and priori information based robust features(PIRF),are evaluated using the proposed approach on the TPI data set.Experimental results show that the robustness of PIRF outperforms others by over 6.2%.
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Shadow detection is a crucial task in high-resolution remote-sensing image processing. Various shadow detection methods have been explored during the last decades. These methods did improve the detection accuracy but are still not robust enough to get satisfactory results for failing to extract enough information from the original images. To take full advantage of various features of shadows, a new method combining edges information with the spectral and spatial information is proposed in this paper. As known, edge is one of the most important characteristics in the high-resolution remote-sensing images. Unfortunately, in shadow detection, it is a high-risk strategy to determine whether a pixel is the edge or not strictly because intensity values on shadow boundaries are always between those in shadow and non-shadow areas. Therefore, a soft edge description model is developed to describe the degree of each pixel belonging to the edges or not. Sequentially, the soft edge description is incorporating to a fuzzy clustering procedure based on HMRF (Hidden Markov Random Fields), in which more appropriate spatial contextual information can be used. More concretely, it consists of two components: the soft edge description model and an iterative shadow detection algorithm. Experiments on several remote sensing images have shown that the proposed method can obtain more accurate shadow detection results.
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.
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.
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. .
文摘This article expounds the vital role undertaken by telemetry in monitoring and assessment in flood control in China. By analyzing the data from their surveys, the authors give an all-round exposition of problems in the country’s drive for disaster reduction and propose countermeasures in the fight against the possible flood problems in the future.
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.
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 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.