The Dongfengnanshan Cu polymetallic deposit is one representative deposit of the Tianbaoshan ore district in the Yanbian area, northeast(NE) China. There occur two types of ore bodies in this deposit, the stratiform o...The Dongfengnanshan Cu polymetallic deposit is one representative deposit of the Tianbaoshan ore district in the Yanbian area, northeast(NE) China. There occur two types of ore bodies in this deposit, the stratiform ore bodies and veintype ones, controlled by the Early Permian strata and the Late Hercynian diorite intrusion, respectively. Due to the ambiguous genetic type of the stratiform ore bodies, there has been controversy on the relationship between them and veintype ore bodies. To determine the genetic type of stratiform ore bodies, laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) in situ trace elements and S–Pb isotope analysis have been carried on the sulfides in the stratiform ore bodies. Compared with that in skarn, Mississippi Valley-type(MVT), and epithermal deposits, sphalerite samples in the stratiform ore bodies of the Dongfengnanshan deposit are significantly enriched in Fe, Mn, and In, while depleted in Ga, Ge, and Cd, which is similar to the sphalerite in volcanic-associated massive sulfide(VMS) deposits. Co/Ni ratio of pyrrhotites in the stratiform ore bodies is similar to that in VMS-type deposits. The concentrations of Zn and Cd of chalcopyrites are similar to those of recrystallized VMS-type deposits. These characteristics also reflect the intermediate ore-forming temperature of the stratiform ore bodies in this deposit. Sulfur isotope compositions of sulfides are similar to those of VMS-type deposits, reflecting that sulfur originated from the Permian Miaoling Formation. Lead isotope compositions indicate mixed-source for lead. Moreover, the comparison of the Dongfengnanshan stratiform ore bodies with some VMStype deposits in China and abroad, on the trace elements and S–Pb isotope characteristics of the sulfides reveals that the stratiform ore bodies of the Dongfengnanshan deposit belong to the VMS-type, and have closely genetic relationship with the early Permian marine volcanic sedimentary rocks.展开更多
Epithermal gold deposits are typical precious metal deposits related to volcanic and subvolcanic magmatism.Due to the lack of direct geological and petrographic evidences,the origin of the ore-forming fluid is deduced...Epithermal gold deposits are typical precious metal deposits related to volcanic and subvolcanic magmatism.Due to the lack of direct geological and petrographic evidences,the origin of the ore-forming fluid is deduced from the spatial diagenesis-mineralization relationship,chronological data,physicochemical characteristics of mineral fluid inclusions,mineral or rock elements and isotopic geochemical characteristics.By objectively examining this scientific problem via a geological field survey and petrographic analysis of the Gaosongshan epithermal gold deposit,we recently discovered and verified the following points:(1) Pyrite-bearing spherical quartz aggregates (PSQA) occur in the rhyolitic porphyry;(2) the mineralization is structurally dominated by WNW- and ENE-trending systems and occurs mostly in hydrothermal breccias and pyrite-quartz veins,and the ore types are mainly hematite-crusted quartz,hydrothermal breccia,massive pyrite-quartz,etc.;(3) the alteration types consist of prevalent silicification,sericitization,propylitization and carbonation,with local adularization and illitization.The ore minerals are mainly pyrite,primary hematite,native gold,and electrum,with lesser amounts of chalcopyrite,magnetite,sphalerite,and galena,indicating a characteristic epithermal low-sulfidation deposit.The ore-forming fluid may have been primarily derived from magmatic fluid exsolved from a crystallizing rhyolitic porphyry magma.Further zircon U-Pb geochronology,fluid inclusion,physicochemical and isotopic geochemical analyses revealed that (1) rhyolitic porphyry magmatism occurred at 104.6 ± 1.0 Ma,whereas the crystallization of the PSQA occurred at 100.8 ± 2.1 Ma;(2) the hydrothermal fluid of the pre-ore stage was an exsolved CO2-bearing H2O-NaCl magmatic fluid that produced inclusions mainly composed of pure vapor (PV),vapor-rich (WV) and liquid-rich (WL) inclusions with a small number of melt-(M) and solid-bearing (S) inclusions;mineralization-stage quartz contains WL and rare PV,WV and pure liquid (PL) inclusions characterized by the H2O-NaCl system with low formation temperatures and low salinities;(3) the characteristics of hydrogen,oxygen,sulfur,and lead isotopes and those of rare earth elements (REEs) provide insight into the affinity between PSQA and orebodies resulting from juvenile crust or enriched mantle.Combined with previous research on the mineralogenetic epoch (99.32 ± 0.01 Ma),we further confirm that the mineralization of the deposit occurred in the late Early Cretaceous,which coincides with the extension of the continental margin induced by subduction of the Pacific Plate beneath the Eurasian Plate.The formation of the ore deposit was proceeded by a series of magmatic and hydrothermal events,including melting of enriched juvenile crust,upwelling,the eruption and emplacement of the rhyolitic magma,the exsolution and accumulation of magmatic hydrothermal fluid,decompression,the cooling and immiscibility/boiling of the fluid,and mixing of the magmatic fluid with meteoric water,in association with water-rock interaction.展开更多
The supergiant Shuangjianzishan(SJZ) Ag-Pb-Zn deposit is in the southern segment of the Great Hinggan Range(SGHR), northeast China. Previous studies suggest the ore-forming material and fluid originated from the magma...The supergiant Shuangjianzishan(SJZ) Ag-Pb-Zn deposit is in the southern segment of the Great Hinggan Range(SGHR), northeast China. Previous studies suggest the ore-forming material and fluid originated from the magmatic system, and the mineralization age was consistent with the diagenetic age. However,the relationship between granitic magmatism and mineralization is still unclear in the SJZ. In this study, CH-O-He-Ar and in-situ S-Pb isotope analyses were conducted to determine the sources of ore-forming fluids and metals, which were combined with geochemistry data of SJZ granitoids from previous studies to constrain the relationship between the magmatism and the mineralization. The C-H-O-He-Ar-S-Pb isotopic compositions suggested the SJZ ore-forming material and fluids were derived from a magmatic source, which has mixed a small amount of mantle-derived materials. In addition, the disseminated sulfide from the syenogranite has comparable S-Pb isotopic composition with the sulfide minerals from ore veins,suggesting that the generation of the SJZ ore-forming fluids has a close relationship with the syenogranite magmatism. Combining with the geochemical characters of the syenogranite, the authors proposed that the mantle-derived fingerprint of the SJZ ore-forming fluid might be caused by the parent magma of the syenogranite, which was derived from partial melting of the juvenile lower crust, and underwent the residual melts segregated from a crystal mush in the shallow magma reservoir. The extraction of the syenogranite parent magma further concentrated the fertilized fluids, which was crucial to mineralization of the SJZ Ag-Pb-Zn deposit.展开更多
The Sichuan-Yunnan-Guizhou(SYG)metallogenic province of southwest China is one of the most important Zn-Pb ore zones in China,with^200 Mt ZnPb ores at mean grades of 10 wt.%Zn and 5 wt.%Pb.The source and mechanism of ...The Sichuan-Yunnan-Guizhou(SYG)metallogenic province of southwest China is one of the most important Zn-Pb ore zones in China,with^200 Mt ZnPb ores at mean grades of 10 wt.%Zn and 5 wt.%Pb.The source and mechanism of the regional Zn-Pb mineralization remain controversial despite many investigations that have been conducted.The Wusihe Zn-Pb deposit is a representative large-scale Zn-Pb deposit in the northern SYG,which mainly occurs in the Dengying Formation and yields Zn-Pb resources of^3.7 Mt.In this paper,Zn and S isotopes,and Fe and Cd contents of sphalerite from the Wusihe deposit were investigated in an attempt to constrain the controls on Zn and S isotopic variations,the potential sources of ore-forming components,and the possible mineralization mechanisms.Both theδ66Zn andδ34S values in sphalerite from the Wusihe deposit increase systematically from the bottom to the top of the strata-bound orebodies.Such spatial evolution inδ66Zn andδ34S values of sphalerite can be attributed to isotopic Rayleigh fractionation during sphalerite precipitation with temperature variations.The strong correlations between the Zn-S isotopic compositions and Fe-Cd concentrations in sphalerite suggest that their variations were dominated by a similar mechanism.However,the Rayleigh fractionation mechanism cannot explain the spatial variations of Fe and Cd concentrations of sphalerite in this deposit.It is noted that the bottom and top sphalerites from the strata-bound orebodies document contrasting Zn and S isotopic compositions which correspond to the Zn and S isotopic characteristics of basement rocks and host rocks,respectively.Therefore,the mixing of two-source fluids with distinct Zn-S isotopic signatures was responsible for the spatial variations of Zn-S isotopic compositions of sphalerite from the Wusihe deposit.The fluids from basement rocks are characterized by relatively lighter Zn(~0.2‰)and S(~5‰)isotopic compositions while the fluids from host rocks are marked by relatively heavier Zn(~0.6‰)and S(~15‰)isotopic compositions.展开更多
The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbo...The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks,with a unique combination of barite and witherite.The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 ℃,whereas those from the witherite have two peaks of 165-175 ℃,and 215-225℃,respectively.Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H_2O,although some contains N_2,H_2S,and CH_4.The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members,one dominated by H_2O without other volatiles,and the other containing CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6 in addition to H_2O.CO_2,H_2S,and some CH_4 are interpreted as products of chemical reactions during mineralization.Organic gases(CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6) in the fluids were critical in the formation of barium sulfate versus carbonate.The δ^(34)S values of barite range from 38.26‰ to54.23‰(CDT),the δ^(34)S values of sulfides coexisting with barium minerals vary from 22.44‰ to25.11‰(CDT),and those in the wall rock from 11.60‰ to 19.06‰(CDT).We propose that the SO_4^(2-)generally experienced bacterial sulfate reduction in seawater before mineralization,and some SO_4^(2-)also experienced thermochemical sulfate reduction in hydrothermal system during mineralization.The δ^(13)C values of witherite range from-27.30‰ to-11.80‰(PDB),suggesting that carbon was sourced from organic substances(like CH_4,C_2H_4,and C_2H_6).The formation of witherite was possibly associated with thermochemical sulfate reduction,which caused the consumption of the organic gases and SO_4^(2-) in the hydrothermal solutions,consequently inhibiting barite formation.The important conditions for forming witherite include high fluid temperatures,high Ba^(2+) concentrations,CO_2 in the fluids,low HS^- concentrations,and the subsequent rapid diffusion of H_2S during thermochemical sulfate reduction of the fluids.展开更多
The Yinchanggou-Qiluogou Pb-Zn deposit,located in the western Yangtze Block,southwest China,is hosted by the Upper Sinian Dengying Formation dolostone.Ore bodies occur in the Qiluogou anticline and the NS-and NNW-tren...The Yinchanggou-Qiluogou Pb-Zn deposit,located in the western Yangtze Block,southwest China,is hosted by the Upper Sinian Dengying Formation dolostone.Ore bodies occur in the Qiluogou anticline and the NS-and NNW-trending faults.Sulfide ores mainly consist of sphalerite,pyrite,galena and calcite,with subordinate dolomite and quartz.Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt%Zn and 6.89wt%Pb.The δD(H2O-SMOW) and δ18O(H2O-SMOW) values of fluid inclusions in quartz and calcite samples range from-68.9‰ to-48.7‰ and 7.3‰ to 15.9‰,respectively,suggesting that H2O in the hydrothermal fluids sourced from metamorphic water.Calcite samples have δ13C(PDB) values ranging from-6.2‰ to-4.1‰ and δ18O(SMOW) values ranging from 15.1‰ to 17.4‰,indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates.The δ34S(CDT) values of sulfide minerals range from 5.5‰ to 20.3‰,suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids.The 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40,15.66 to 15.76 and 38.25 to 38.88,respectively.The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone.This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks.The ore geology and C-H-O-S-Pb isotopic data suggest that the YinchanggouQiluogou deposit is an unusual carbonate-hosted,strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.展开更多
The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb+Zn reserves of more than 5 million ton...The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb+Zn reserves of more than 5 million tons at Pb+Zn grade of higher than 25%and contains abundant associated metals,such as Ag,Ge,Cd,and Ga.The deposits are hosted in the Lower Carboniferous carbonate strata and the Permian Emeishan basalts which distributed in the northern and southwestern parts of the orefield.Calcite is the only gangue mineral in the primary ores of the deposits and can be classified into three types,namely lumpy,patch and vein calcites in accordance with their occurrence.There is not intercalated contact between calcite and ore minerals and among the three types of calcite,indicating that they are the same ore-forming age with different stages and its forming sequence is from lumpy to patch to vein calcites. This paper presents the rare earth element(REE) and C-O isotopic compositions of calcites in the Huize Pb-Zn deposits.From lumpy to patch to vein calcites,REE contents decrease as LREE/ HREE ratios increase.The chondrite-normalized REE patterns of the three types of calcites are characterized by LREE-rich shaped,in which the lumpy calcite shows(La)_N〈(Ce)_N〈(Pr)_N≈(Nd)_N with Eu/Eu~*〈1,the patch calcite has(La)_N〈(Ce)_N〈(Pr)_N≈(Nd)_N with Eu/Eu~*〉1,and the vein calcite displays(La)_N〉(Ce)_N〉(Pr)_N〉(Nd)_N with Eu/Eu~*〉1.The REE geochemistry of the three types of calcite is different from those of the strata of various age and Permian Emeishan basalt exposed in the orefield.Theδ^(13) C_(PDb) andδ^(18)O_(Smow) values of the three types of calcites vary from-3.5‰to-2.1‰and 16.7‰to 18.6‰,respectively,falling within a small field between primary mantle and marine carbonate in theδ^(13)C_(PDb) vsδ^(18)O_(Smow) diagram. Various lines of evidence demonstrate that the three types of calcites in the deposits are produced from the same source with different stages.The ore-forming fluids of the deposits resulted from crustal -mantle mixing processes,in which the mantle-derived fluid components might be formed from degassing of mantle or/and magmatism of the Permian Emeishan basalts,and the crustal fluid was mainly provided by carbonate strata in the orefield.The ore-forming fluids in the deposits were homogenized before mineralization,and the ore-forming environment varied from relatively reducing to oxidizing.展开更多
Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, w...Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, which are widely used to reconstruct the geological/geochemical conditions in paleoenvironments and the evolutionary trajectories of biogeochemical cycles, offer an opportunity to investigate power laws in ancient geological systems. In this study, I focus on the Phanerozoic sedimentary records of carbon, oxygen, sulfur, and strontium isotopes, which have well documented and extraordinarily comprehensive datasets. I perform statistical analyses on these datasets and show that the variations in the sedimentary records of the four isotopes exhibit power-law behaviors. The exponents of these power laws range between 2.2 and 2.9;this narrow interval indicates that the variations in carbon, oxygen, sulfur, and strontium isotopes likely belong to the same universality class, suggesting that these systematic power-law patterns are governed by universal, scale-free mechanisms. I then derive a general form for these power laws from a minimalistic model based on basic physical principles and geosystem-specific assumptions, which provides an interpretation for the power-law patterns from the perspective of thermodynamics. The fundamental mechanisms regulating such patterns might have been ubiquitous in paleoenvironments, implying that similar power-law behaviors may exist in the sedimentary records of other isotopes.展开更多
The Weiquan Ag-polymetallic deposit is located on the southern margin of the Central Asian Orogenic Belt and in the western segment of the Aqishan-Yamansu arc belt in East Tianshan,northwestern China. Its orebodies, c...The Weiquan Ag-polymetallic deposit is located on the southern margin of the Central Asian Orogenic Belt and in the western segment of the Aqishan-Yamansu arc belt in East Tianshan,northwestern China. Its orebodies, controlled by faults, occur in the lower Carboniferous volcanosedimentary rocks of the Yamansu Formation as irregular veins and lenses. Four stages of mineralization have been recognized on the basis of mineral assemblages, ore fabrics, and crosscutting relationships among the ore veins. Stage I is the skarn stage(garnet + pyroxene), Stage Ⅱ is the retrograde alteration stage(epidote + chlorite + magnetite ± hematite 士 actinolite ± quartz),Stage Ⅲ is the sulfide stage(Ag and Bi minerals + pyrite + chalcopyrite + galena + sphalerite + quartz ± calcite ± tetrahedrite),and Stage IV is the carbonate stage(quartz + calcite ± pyrite). Skarnization,silicification, carbonatization,epidotization,chloritization, sericitization, and actinolitization are the principal types of hydrothermal alteration. LAICP-MS U-Pb dating yielded ages of 326.5±4.5 and 298.5±1.5 Ma for zircons from the tuff and diorite porphyry, respectively. Given that the tuff is wall rock and that the orebodies are cut by a late diorite porphyry dike, the ages of the tuff and the diorite porphyry provide lower and upper time limits on the age of ore formation. The δ13C values of the calcite samples range from-2.5‰ to 2.3‰, the δ18OH2 Oand δDVSMOWvalues of the sulfide stage(Stage Ⅲ) vary from 1.1‰ to 5.2‰ and-111.7‰ to-66.1‰, respectively,and the δ13C, δ18OH2 Oand δDV-SMOWvalues of calcite in one Stage IV sample are 1.5‰,-0.3‰, and-115.6‰, respectively. Carbon, hydrogen, and oxygen isotopic compositions indicate that the ore-forming fluids evolved gradually from magmatic to meteoric sources. The δ34SV-CDTvalues of the sulfides have a large range from-6.9‰ to 1.4‰, with an average of-2.2‰, indicating a magmatic source, possibly with sedimentary contributions. The206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios of the sulfides are 17.9848-18.2785,15.5188-15.6536, and 37.8125-38.4650, respectively, and one whole-rock sample at Weiquan yields206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios of 18.2060, 15.5674, and 38.0511,respectively. Lead isotopic systems suggest that the ore-forming materials of the Weiquan deposit were derived from a mixed source involving mantle and crustal components. Based on geological features, zircon U-Pb dating, and C-H-OS-Pb isotopic data, it can be concluded that the Weiquan polymetallic deposit is a skarn type that formed in a tectonic setting spanning a period from subduction to post-collision. The ore materials were sourced from magmatic ore-forming fluids that mixed with components derived from host rocks during their ascent, and a gradual mixing with meteoric water took place in the later stages.展开更多
The Nage Cu-Pb deposit, a new found ore deposit in the southeast Guizhou province, southwest China, is located on the southwestern margin of the Jiangnan Orogenic Belt. Ore bodies are hosted in slate and phyllite of N...The Nage Cu-Pb deposit, a new found ore deposit in the southeast Guizhou province, southwest China, is located on the southwestern margin of the Jiangnan Orogenic Belt. Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations, and are structurally controlled by EW-trending fault. It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb. Massive and disseminated Cu-Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks. The ore minerals include chalcopyrite, galena and pyrite, and gangue minerals are quartz, sericite and chlorite. The H-O isotopic compositions of quartz, S-Cu-Pb isotopic compositions of sulfide minerals, Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore-forming fluids and metals for the Nage Cu-Pb deposit. The oSCUNBs values of chalcopyrite range from -0.09% to +0.33%0, similar to basic igneous rocks and chalcopyrite from magmatic deposits. J6SCUNBS values of chalcopyrite from the early, middle and final mineralization stages show an increasing trend due to 63Cu prior migrated in gas phase when fluids exsolution from magma, ja4ScDT values of sulfide minerals range from -2.7‰ to +2.8‰, similar to mantle-derived sulfur (0±3‰). The positive correlation between J65CUNBs and ja4SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma. JDu2o- SMOW and JlSOH2O-SMOW values of water in fluid inclusions of quartz range from -60.7‰ to -44.4‰ and +7.9‰ to +9.0%0 (T=260℃), respectively and fall in the field for magmatic and metamorphic waters, implicating that mixed sources for H20 in hydrothermal fluids. Ores and sulfide minerals have a small range of Pb isotopic compositions (208Pb/204pb=38.152 to 38.384, 207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049) that are close to orogenic belt and upper crust Pb evolution curve, and similar to Neoproterozoic host rocks (208Pb/204Pb=38.201 to 38.6373, 207pb/204pb=15.648 to 15.673 and 206pb/204pb=17.820 to 18.258), but higher than diabase (208Pb/204pb=37.830 to 38.012, 207pb/204pb=15.620 to 15.635 and 206pb/204pb=17.808 to 17.902). These results imply that the Pb metal originated mainly from host rocks. The H-O-S-Cu-Pb isotopes tegather with geology, indicating that the ore genesis of the Nage Cu-Pb deposit is post-magmatic hydrothermal type.展开更多
TheWulong lode deposit contains over 80 tonnes of gold with an average grade of 5.35 g/t.It is one of the largest deposits in Dandong City,Liaoning Province in northeast China.Previous studies on the deposit focused o...TheWulong lode deposit contains over 80 tonnes of gold with an average grade of 5.35 g/t.It is one of the largest deposits in Dandong City,Liaoning Province in northeast China.Previous studies on the deposit focused on its geological characteristics,geochemistry,fluid inclusions,and the timing of gold mineralization.However,controversy remains regarding the origin of the ore-forming fluids and metals,and the genesis of the gold deposit.This paper presents zircon UePb and pyrite RbeSr ages and S,Pb,He,and Ar isotopic results along with quartz H and O isotopic data for all litho-units associated with the deposit.Laser ablation inductively coupled mass spectrometry measurements yielded zircon UePb dates for samples of pre-mineralization rocks like granite porphyry dike,the Sanguliu granodiorite,fine-grained diorite,and syn-mineralization diorite,as well as post-mineralization dolerite,and lamprophyre;their emplacement ages are 1261 Ma,1241 Ma,1231 Ma,1201 Ma,1192 Ma,and 1152 Ma,respectively.The pyrite RbeSr isochron age is 1191 Ma,indicating that both magmatism and mineralization occurred during the Early Cretaceous.The d18OH2O values of ore-forming hydrothermal fluids from the quartzepolymetallic sulfide vein stage vary from 4.8&to 6.5&,and the dDV-SMOW values are between67.7&and75.9&,indicating that the ore-forming fluids were primarily magmatic.The noble gas isotope compositions of fluid inclusions hosted in pyrite suggest that the ore-forming fluids were dominantly derived from crustal sources with minor mantle input.Sulfur isotopic values of pyrite vary between 0.2&and 3.5&,suggesting that S was derived from a homogeneous magmatic source or possibly from fluids derived from the crust.The Pb isotopic compositions of sulfides(207Pb/204Pb?15.51 e15.71,206Pb/204Pb?17.35e18.75,208Pb/204Pb?38.27e40.03)indicate that the Pb of the Wulong gold deposit is a mixture of crust and mantle components.Geochronological and geochemical data,together with the regional geological history,indicate that Early Cretaceous magmatism and mineralization of the Wulong gold deposit occurred during the rollback of the subducting Paleo-Pacific Plate,which resulted in lithospheric thinning and the destruction of the North China Craton(NCC),which indicates that the deposit is of magmaticehydrothermal origin.展开更多
The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formati...The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formation process,this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of mineralization.The results indicate that the δ34S values(ranging from 14.0‰ to 17.6‰) of pyrites formed from the two stages have no obvious differences,suggesting that they were not derived from a single magmatic sulfur source.The δ34S values of anhydrite mostly range from 21.9‰ to 28.4‰,similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt(MLYRB).The Pb isotopic compositions of the pyrites of both stages are homogeneous,with values of 208Pb/204Pb,207Pb/204Pb,and-206Pb/204Pb being 38.006-38.257,15.523-15.556,and 17.806-18.052,respectively,indicating a mixed crust-mantle source.The He-Ar results exhibit different compositions of the two stages:the -3He/-4He(R/Ra) and 40Ar/-36Ar values for the early-stage pyrite are 0.46-0.63 and 311-322,respectively,whereas the values for late-stage pyrite are 0.23-0.34 and 305-361,respectively.Both stages of pyrites indicate the multiple sources of the ore-forming fluids,with decreasing amount of magmatic water and increasing amount of modified meteoric water(MASW) during fluid evolution.The Triassic evaporites played an important role in the mineralization process.展开更多
The Sichuan-Yunnan-Guizhou(SYG)Pb-Zn mineral province,which has significant Pb-Zn repositories in China,is situated in the western Yangtze Block.Despite decades of research,the Pb-Zn source of deposits is still disput...The Sichuan-Yunnan-Guizhou(SYG)Pb-Zn mineral province,which has significant Pb-Zn repositories in China,is situated in the western Yangtze Block.Despite decades of research,the Pb-Zn source of deposits is still disputed between the basement rocks,sedimentary wall rocks,or the Emeishan flood basalts.The newly-discovered Laoxiongdong Pb-Zn deposit is hosted by the Late Ediacaran Dengying Formation in the SYG province.Moreover,the Laoxiongdong orebodies lie between regional deep faults and close to the Proterozoic basement and Emeishan basalts.Hence,this deposit represents a good case study on the ore-forming material source for the regional Pb-Zn mineralization.The Laoxiongdong Pb-Zn ores are massive,vein,or disseminated and have mainly sphalerite,galena,pyrite,quartz,and calcite.In this paper,we present new sulfide S-Pb-Zn isotope data of the deposit.The sulfideδ34SCDT values(+11.8 to+16.5‰)suggest that the reduced sulfur was mainly sourced from evaporites in the Late Ediacaran-Cambrian sequences.Pb isotopic ratios(206Pb/204Pb=18.004-18.107,207Pb/204Pb=15.652-15.667,and 208Pb/204Pb=38.037-38.248)suggest that the lead metal was primarily originated from the basement rocks.The sphaleriteδ66Zn values(+0.16 to+0.37‰)are also highly similar(within error)to those of basement rocks(+0.10 to+0.34‰),suggesting a basement-rocks zinc source with minor contributions from the carbonate host rocks and Emeishan flood basalts.The narrow sphalerite Zn isotopic range(0.21‰)also indicates that the Zn isotopic fractionation between the sphalerite and initial fluid was limited during the sphalerite ore precipitation.Therefore,we propose that both the Late Ediacaran Dengying Formation rocks and Proterozoic basement rocks were important ore-forming material source for the Laoxiongdong deposit,whereas the Emeishan flood basalts represent only a minor ore-material source.展开更多
The Tongyu copper deposit, located in the western part of the North Qinling Orogen, China, is one of several volcanic-hosted massive sulphide(VHMS) deposits with industrial value and is also a typical example of min...The Tongyu copper deposit, located in the western part of the North Qinling Orogen, China, is one of several volcanic-hosted massive sulphide(VHMS) deposits with industrial value and is also a typical example of mineralization related to the subduction and metallogenesis during the Caledonian orogeny. We conducted systematic lead-sulphur isotope geochemical analyses of the Tongyu deposit to understand the possible ore-forming material sources and tectonic settings. Twenty-six sulphide samples yielded clustered δ^34SCDT values of 1.13‰-3.36‰, average 2.22‰, and show a tower-type distribution,implying that the sulphur of the Tongyu copper deposit mainly originated from a mantle source. The Pb isotope compositions of sulphides(^206Pb/^204Pb = 17.59225-18.56354, average 18.32020; ^207Pb/^204Pb =15.51770-15.69381, average 15.66217; ^208Pb/^204Pb= 37.99969-39.06953, average 38.52722) are close to the values of the volcanic host rocks(^206Pb/^204PbPb= 18.10678-18.26293, average 18.21158; ^207Pb/^204PbPb =15.63196-15.68188, average 15.65345; ^208Pb/^204PbPb= 38.43676-38.56360, average 38.49171), thus consistent with the Pb in ores and volcanic host rocks having been derived from a common source that was island-arc Pb related to oceanic crust subduction. The northward subduction of the Palaeo-Qinling oceanic crust triggered dehydration of the slab, which generated a large amount of high-oxygen-fugacity aqueous hydrothermal fluid. The fluid rose into the mantle wedge, activated and extracted metallogenic material and promoted partial melting of the mantle wedge. The magma and ore-forming fluid welled up and precipitated, finally forming the Tongyu VHMS copper deposit.展开更多
The Habo alkaline intrusion, which is located in the south of the Sanjiang area, Yunnan Province, China, is a typical Cenozoic alkaline intrusion. There are a series of small to medium-sized Au and Pb–(Zn) deposits a...The Habo alkaline intrusion, which is located in the south of the Sanjiang area, Yunnan Province, China, is a typical Cenozoic alkaline intrusion. There are a series of small to medium-sized Au and Pb–(Zn) deposits around this intrusion. Those deposits are spatially associated with the Habo alkaline intrusion.(1) The d^(34) S values of sulfides from Au deposits range from-1.91 % to 2.69 %, which are similar to those of Pb–(Zn) deposits(-3.82 % to-0.05 %) and both indicate a much greater contribution from magma.(2) The Habo alkaline intrusion has relatively homogeneous Pb isotopic compositions with^(206)Pb/^(204) Pb ranging from 18.608 to 18.761,^(207)Pb/^(204) Pb from 15.572 to15.722 and^(208)Pb/^(204) Pb from 38.599 to 39.110. These Pb isotope ratios are similar to those of Au deposits, whose^(206)Pb/^(204) Pb range from 18.564 to 18.734,^(207)Pb/^(204) Pb from15.582 to 15.738 and^(208)Pb/^(204) Pb from 38.592 to 39.319.Pb ratios in both the intrusion and Au deposits suggest that Pb mainly derived from the depth, probably represents a mixture of mantle and crust. Pb–(Zn) deposits, however,show a decentralized trait, and most of them are similar to that of the alkaline intrusion with^(206)Pb/^(204) Pb ranging from18.523 to 18.648,^(207)Pb/^(204) Pb from 15.599 to 15.802, and^(208)Pb/^(204) Pb from 38.659 to 39.206.(3) In the plumbotectonic diagram^(207)Pb/^(204) Pb versus^(206)Pb/^(204) Pb, almost all of Au and Pb–(Zn) deposits have the same projection area with the Habo alkaline intrusion, which indicates that thosedeposits almost share the same source with the alkaline intrusion.(4) Isotopic age of the Habo alkaline intrusion is36–33 Ma, which is similar to that of Beiya, whose orerelated alkaline porphyries age is 38–31 Ma and molybdenite Re–Os age is 36.9 Ma. Therefore, along with S–Pb isotope traits, we suggest that the Habo Au and Pb–(Zn)deposits should be typically Ailaoshan-Red River Cenozoicalkaline-related deposits and ore-forming ages of these deposits should be later than that of the Habo alkaline intrusion.展开更多
基金supported by the National Natural Science Foundation of China (NSFC) (No. 41772062)
文摘The Dongfengnanshan Cu polymetallic deposit is one representative deposit of the Tianbaoshan ore district in the Yanbian area, northeast(NE) China. There occur two types of ore bodies in this deposit, the stratiform ore bodies and veintype ones, controlled by the Early Permian strata and the Late Hercynian diorite intrusion, respectively. Due to the ambiguous genetic type of the stratiform ore bodies, there has been controversy on the relationship between them and veintype ore bodies. To determine the genetic type of stratiform ore bodies, laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) in situ trace elements and S–Pb isotope analysis have been carried on the sulfides in the stratiform ore bodies. Compared with that in skarn, Mississippi Valley-type(MVT), and epithermal deposits, sphalerite samples in the stratiform ore bodies of the Dongfengnanshan deposit are significantly enriched in Fe, Mn, and In, while depleted in Ga, Ge, and Cd, which is similar to the sphalerite in volcanic-associated massive sulfide(VMS) deposits. Co/Ni ratio of pyrrhotites in the stratiform ore bodies is similar to that in VMS-type deposits. The concentrations of Zn and Cd of chalcopyrites are similar to those of recrystallized VMS-type deposits. These characteristics also reflect the intermediate ore-forming temperature of the stratiform ore bodies in this deposit. Sulfur isotope compositions of sulfides are similar to those of VMS-type deposits, reflecting that sulfur originated from the Permian Miaoling Formation. Lead isotope compositions indicate mixed-source for lead. Moreover, the comparison of the Dongfengnanshan stratiform ore bodies with some VMStype deposits in China and abroad, on the trace elements and S–Pb isotope characteristics of the sulfides reveals that the stratiform ore bodies of the Dongfengnanshan deposit belong to the VMS-type, and have closely genetic relationship with the early Permian marine volcanic sedimentary rocks.
基金financially supported by the National Key Research and Development Program of China (Grant No.2017YFC0601306)the National Natural Science Foundation of China (Grant No.41390444)+1 种基金the Program of the China Geological Survey(Grant No.DD20160344)supported by Team 707, Heilongjiang Bureau of Geological Exploration for Nonferrous Metals
文摘Epithermal gold deposits are typical precious metal deposits related to volcanic and subvolcanic magmatism.Due to the lack of direct geological and petrographic evidences,the origin of the ore-forming fluid is deduced from the spatial diagenesis-mineralization relationship,chronological data,physicochemical characteristics of mineral fluid inclusions,mineral or rock elements and isotopic geochemical characteristics.By objectively examining this scientific problem via a geological field survey and petrographic analysis of the Gaosongshan epithermal gold deposit,we recently discovered and verified the following points:(1) Pyrite-bearing spherical quartz aggregates (PSQA) occur in the rhyolitic porphyry;(2) the mineralization is structurally dominated by WNW- and ENE-trending systems and occurs mostly in hydrothermal breccias and pyrite-quartz veins,and the ore types are mainly hematite-crusted quartz,hydrothermal breccia,massive pyrite-quartz,etc.;(3) the alteration types consist of prevalent silicification,sericitization,propylitization and carbonation,with local adularization and illitization.The ore minerals are mainly pyrite,primary hematite,native gold,and electrum,with lesser amounts of chalcopyrite,magnetite,sphalerite,and galena,indicating a characteristic epithermal low-sulfidation deposit.The ore-forming fluid may have been primarily derived from magmatic fluid exsolved from a crystallizing rhyolitic porphyry magma.Further zircon U-Pb geochronology,fluid inclusion,physicochemical and isotopic geochemical analyses revealed that (1) rhyolitic porphyry magmatism occurred at 104.6 ± 1.0 Ma,whereas the crystallization of the PSQA occurred at 100.8 ± 2.1 Ma;(2) the hydrothermal fluid of the pre-ore stage was an exsolved CO2-bearing H2O-NaCl magmatic fluid that produced inclusions mainly composed of pure vapor (PV),vapor-rich (WV) and liquid-rich (WL) inclusions with a small number of melt-(M) and solid-bearing (S) inclusions;mineralization-stage quartz contains WL and rare PV,WV and pure liquid (PL) inclusions characterized by the H2O-NaCl system with low formation temperatures and low salinities;(3) the characteristics of hydrogen,oxygen,sulfur,and lead isotopes and those of rare earth elements (REEs) provide insight into the affinity between PSQA and orebodies resulting from juvenile crust or enriched mantle.Combined with previous research on the mineralogenetic epoch (99.32 ± 0.01 Ma),we further confirm that the mineralization of the deposit occurred in the late Early Cretaceous,which coincides with the extension of the continental margin induced by subduction of the Pacific Plate beneath the Eurasian Plate.The formation of the ore deposit was proceeded by a series of magmatic and hydrothermal events,including melting of enriched juvenile crust,upwelling,the eruption and emplacement of the rhyolitic magma,the exsolution and accumulation of magmatic hydrothermal fluid,decompression,the cooling and immiscibility/boiling of the fluid,and mixing of the magmatic fluid with meteoric water,in association with water-rock interaction.
基金supported financially by the China Geological Survey project [DD20160123 (DD-16-049, D1522), DD20160050, DD20190370]the Fundamental Research Funds for the Central Universities (310827171122)the National Natural Science Foundation of China (Grant 41672068)。
文摘The supergiant Shuangjianzishan(SJZ) Ag-Pb-Zn deposit is in the southern segment of the Great Hinggan Range(SGHR), northeast China. Previous studies suggest the ore-forming material and fluid originated from the magmatic system, and the mineralization age was consistent with the diagenetic age. However,the relationship between granitic magmatism and mineralization is still unclear in the SJZ. In this study, CH-O-He-Ar and in-situ S-Pb isotope analyses were conducted to determine the sources of ore-forming fluids and metals, which were combined with geochemistry data of SJZ granitoids from previous studies to constrain the relationship between the magmatism and the mineralization. The C-H-O-He-Ar-S-Pb isotopic compositions suggested the SJZ ore-forming material and fluids were derived from a magmatic source, which has mixed a small amount of mantle-derived materials. In addition, the disseminated sulfide from the syenogranite has comparable S-Pb isotopic composition with the sulfide minerals from ore veins,suggesting that the generation of the SJZ ore-forming fluids has a close relationship with the syenogranite magmatism. Combining with the geochemical characters of the syenogranite, the authors proposed that the mantle-derived fingerprint of the SJZ ore-forming fluid might be caused by the parent magma of the syenogranite, which was derived from partial melting of the juvenile lower crust, and underwent the residual melts segregated from a crystal mush in the shallow magma reservoir. The extraction of the syenogranite parent magma further concentrated the fertilized fluids, which was crucial to mineralization of the SJZ Ag-Pb-Zn deposit.
基金funded by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB18030302)the National Key R&D Program of China (2017YFC0602503)the National Natural Science Foundation of China (U1812402, 41430315, 41573011, 41625006)
文摘The Sichuan-Yunnan-Guizhou(SYG)metallogenic province of southwest China is one of the most important Zn-Pb ore zones in China,with^200 Mt ZnPb ores at mean grades of 10 wt.%Zn and 5 wt.%Pb.The source and mechanism of the regional Zn-Pb mineralization remain controversial despite many investigations that have been conducted.The Wusihe Zn-Pb deposit is a representative large-scale Zn-Pb deposit in the northern SYG,which mainly occurs in the Dengying Formation and yields Zn-Pb resources of^3.7 Mt.In this paper,Zn and S isotopes,and Fe and Cd contents of sphalerite from the Wusihe deposit were investigated in an attempt to constrain the controls on Zn and S isotopic variations,the potential sources of ore-forming components,and the possible mineralization mechanisms.Both theδ66Zn andδ34S values in sphalerite from the Wusihe deposit increase systematically from the bottom to the top of the strata-bound orebodies.Such spatial evolution inδ66Zn andδ34S values of sphalerite can be attributed to isotopic Rayleigh fractionation during sphalerite precipitation with temperature variations.The strong correlations between the Zn-S isotopic compositions and Fe-Cd concentrations in sphalerite suggest that their variations were dominated by a similar mechanism.However,the Rayleigh fractionation mechanism cannot explain the spatial variations of Fe and Cd concentrations of sphalerite in this deposit.It is noted that the bottom and top sphalerites from the strata-bound orebodies document contrasting Zn and S isotopic compositions which correspond to the Zn and S isotopic characteristics of basement rocks and host rocks,respectively.Therefore,the mixing of two-source fluids with distinct Zn-S isotopic signatures was responsible for the spatial variations of Zn-S isotopic compositions of sphalerite from the Wusihe deposit.The fluids from basement rocks are characterized by relatively lighter Zn(~0.2‰)and S(~5‰)isotopic compositions while the fluids from host rocks are marked by relatively heavier Zn(~0.6‰)and S(~15‰)isotopic compositions.
基金jointly supported by the National Natural Science Foundation of China(grant nos. 41173062 and 40573032)the 111 project under the Ministry of Education and the State Administration of Foreign Experts Affairs,China(grant no.B07011)
文摘The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks,with a unique combination of barite and witherite.The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 ℃,whereas those from the witherite have two peaks of 165-175 ℃,and 215-225℃,respectively.Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H_2O,although some contains N_2,H_2S,and CH_4.The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members,one dominated by H_2O without other volatiles,and the other containing CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6 in addition to H_2O.CO_2,H_2S,and some CH_4 are interpreted as products of chemical reactions during mineralization.Organic gases(CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6) in the fluids were critical in the formation of barium sulfate versus carbonate.The δ^(34)S values of barite range from 38.26‰ to54.23‰(CDT),the δ^(34)S values of sulfides coexisting with barium minerals vary from 22.44‰ to25.11‰(CDT),and those in the wall rock from 11.60‰ to 19.06‰(CDT).We propose that the SO_4^(2-)generally experienced bacterial sulfate reduction in seawater before mineralization,and some SO_4^(2-)also experienced thermochemical sulfate reduction in hydrothermal system during mineralization.The δ^(13)C values of witherite range from-27.30‰ to-11.80‰(PDB),suggesting that carbon was sourced from organic substances(like CH_4,C_2H_4,and C_2H_6).The formation of witherite was possibly associated with thermochemical sulfate reduction,which caused the consumption of the organic gases and SO_4^(2-) in the hydrothermal solutions,consequently inhibiting barite formation.The important conditions for forming witherite include high fluid temperatures,high Ba^(2+) concentrations,CO_2 in the fluids,low HS^- concentrations,and the subsequent rapid diffusion of H_2S during thermochemical sulfate reduction of the fluids.
基金financially supported by the National Basic Research Program of China(973 Program,No. 2014CB440905)the Key Program of National Natural Science Foundation(No.41430315)the National Natural Science Foundation of China(Nos.41272111 and 41163001)
文摘The Yinchanggou-Qiluogou Pb-Zn deposit,located in the western Yangtze Block,southwest China,is hosted by the Upper Sinian Dengying Formation dolostone.Ore bodies occur in the Qiluogou anticline and the NS-and NNW-trending faults.Sulfide ores mainly consist of sphalerite,pyrite,galena and calcite,with subordinate dolomite and quartz.Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt%Zn and 6.89wt%Pb.The δD(H2O-SMOW) and δ18O(H2O-SMOW) values of fluid inclusions in quartz and calcite samples range from-68.9‰ to-48.7‰ and 7.3‰ to 15.9‰,respectively,suggesting that H2O in the hydrothermal fluids sourced from metamorphic water.Calcite samples have δ13C(PDB) values ranging from-6.2‰ to-4.1‰ and δ18O(SMOW) values ranging from 15.1‰ to 17.4‰,indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates.The δ34S(CDT) values of sulfide minerals range from 5.5‰ to 20.3‰,suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids.The 206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40,15.66 to 15.76 and 38.25 to 38.88,respectively.The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone.This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks.The ore geology and C-H-O-S-Pb isotopic data suggest that the YinchanggouQiluogou deposit is an unusual carbonate-hosted,strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.
基金jointly by National Basic Research Program of China(973 Program) (2007CB411402)the Knowledge innovation project of Chinese Academy of Sciences(KZCX2-YW-Q04-05, KZCX2-YW-111-03)the National Natural Science Foundation of China(No.40573036).
文摘The world-class Huize Pb-Zn deposits of Yunnan province,in southwestern China,located in the center of the Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic province,has Pb+Zn reserves of more than 5 million tons at Pb+Zn grade of higher than 25%and contains abundant associated metals,such as Ag,Ge,Cd,and Ga.The deposits are hosted in the Lower Carboniferous carbonate strata and the Permian Emeishan basalts which distributed in the northern and southwestern parts of the orefield.Calcite is the only gangue mineral in the primary ores of the deposits and can be classified into three types,namely lumpy,patch and vein calcites in accordance with their occurrence.There is not intercalated contact between calcite and ore minerals and among the three types of calcite,indicating that they are the same ore-forming age with different stages and its forming sequence is from lumpy to patch to vein calcites. This paper presents the rare earth element(REE) and C-O isotopic compositions of calcites in the Huize Pb-Zn deposits.From lumpy to patch to vein calcites,REE contents decrease as LREE/ HREE ratios increase.The chondrite-normalized REE patterns of the three types of calcites are characterized by LREE-rich shaped,in which the lumpy calcite shows(La)_N〈(Ce)_N〈(Pr)_N≈(Nd)_N with Eu/Eu~*〈1,the patch calcite has(La)_N〈(Ce)_N〈(Pr)_N≈(Nd)_N with Eu/Eu~*〉1,and the vein calcite displays(La)_N〉(Ce)_N〉(Pr)_N〉(Nd)_N with Eu/Eu~*〉1.The REE geochemistry of the three types of calcite is different from those of the strata of various age and Permian Emeishan basalt exposed in the orefield.Theδ^(13) C_(PDb) andδ^(18)O_(Smow) values of the three types of calcites vary from-3.5‰to-2.1‰and 16.7‰to 18.6‰,respectively,falling within a small field between primary mantle and marine carbonate in theδ^(13)C_(PDb) vsδ^(18)O_(Smow) diagram. Various lines of evidence demonstrate that the three types of calcites in the deposits are produced from the same source with different stages.The ore-forming fluids of the deposits resulted from crustal -mantle mixing processes,in which the mantle-derived fluid components might be formed from degassing of mantle or/and magmatism of the Permian Emeishan basalts,and the crustal fluid was mainly provided by carbonate strata in the orefield.The ore-forming fluids in the deposits were homogenized before mineralization,and the ore-forming environment varied from relatively reducing to oxidizing.
文摘Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, which are widely used to reconstruct the geological/geochemical conditions in paleoenvironments and the evolutionary trajectories of biogeochemical cycles, offer an opportunity to investigate power laws in ancient geological systems. In this study, I focus on the Phanerozoic sedimentary records of carbon, oxygen, sulfur, and strontium isotopes, which have well documented and extraordinarily comprehensive datasets. I perform statistical analyses on these datasets and show that the variations in the sedimentary records of the four isotopes exhibit power-law behaviors. The exponents of these power laws range between 2.2 and 2.9;this narrow interval indicates that the variations in carbon, oxygen, sulfur, and strontium isotopes likely belong to the same universality class, suggesting that these systematic power-law patterns are governed by universal, scale-free mechanisms. I then derive a general form for these power laws from a minimalistic model based on basic physical principles and geosystem-specific assumptions, which provides an interpretation for the power-law patterns from the perspective of thermodynamics. The fundamental mechanisms regulating such patterns might have been ubiquitous in paleoenvironments, implying that similar power-law behaviors may exist in the sedimentary records of other isotopes.
基金funded by the China Geological Survey (No. 1212011220731)
文摘The Weiquan Ag-polymetallic deposit is located on the southern margin of the Central Asian Orogenic Belt and in the western segment of the Aqishan-Yamansu arc belt in East Tianshan,northwestern China. Its orebodies, controlled by faults, occur in the lower Carboniferous volcanosedimentary rocks of the Yamansu Formation as irregular veins and lenses. Four stages of mineralization have been recognized on the basis of mineral assemblages, ore fabrics, and crosscutting relationships among the ore veins. Stage I is the skarn stage(garnet + pyroxene), Stage Ⅱ is the retrograde alteration stage(epidote + chlorite + magnetite ± hematite 士 actinolite ± quartz),Stage Ⅲ is the sulfide stage(Ag and Bi minerals + pyrite + chalcopyrite + galena + sphalerite + quartz ± calcite ± tetrahedrite),and Stage IV is the carbonate stage(quartz + calcite ± pyrite). Skarnization,silicification, carbonatization,epidotization,chloritization, sericitization, and actinolitization are the principal types of hydrothermal alteration. LAICP-MS U-Pb dating yielded ages of 326.5±4.5 and 298.5±1.5 Ma for zircons from the tuff and diorite porphyry, respectively. Given that the tuff is wall rock and that the orebodies are cut by a late diorite porphyry dike, the ages of the tuff and the diorite porphyry provide lower and upper time limits on the age of ore formation. The δ13C values of the calcite samples range from-2.5‰ to 2.3‰, the δ18OH2 Oand δDVSMOWvalues of the sulfide stage(Stage Ⅲ) vary from 1.1‰ to 5.2‰ and-111.7‰ to-66.1‰, respectively,and the δ13C, δ18OH2 Oand δDV-SMOWvalues of calcite in one Stage IV sample are 1.5‰,-0.3‰, and-115.6‰, respectively. Carbon, hydrogen, and oxygen isotopic compositions indicate that the ore-forming fluids evolved gradually from magmatic to meteoric sources. The δ34SV-CDTvalues of the sulfides have a large range from-6.9‰ to 1.4‰, with an average of-2.2‰, indicating a magmatic source, possibly with sedimentary contributions. The206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios of the sulfides are 17.9848-18.2785,15.5188-15.6536, and 37.8125-38.4650, respectively, and one whole-rock sample at Weiquan yields206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios of 18.2060, 15.5674, and 38.0511,respectively. Lead isotopic systems suggest that the ore-forming materials of the Weiquan deposit were derived from a mixed source involving mantle and crustal components. Based on geological features, zircon U-Pb dating, and C-H-OS-Pb isotopic data, it can be concluded that the Weiquan polymetallic deposit is a skarn type that formed in a tectonic setting spanning a period from subduction to post-collision. The ore materials were sourced from magmatic ore-forming fluids that mixed with components derived from host rocks during their ascent, and a gradual mixing with meteoric water took place in the later stages.
基金supported by Science Foundation of Guizhou province (No. 2012-2334)Open Foundation of State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences (Nos. 2011001 and 2009014)National Natural Science Foundation of China (Nos. 41102055 and 41102053)
文摘The Nage Cu-Pb deposit, a new found ore deposit in the southeast Guizhou province, southwest China, is located on the southwestern margin of the Jiangnan Orogenic Belt. Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations, and are structurally controlled by EW-trending fault. It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb. Massive and disseminated Cu-Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks. The ore minerals include chalcopyrite, galena and pyrite, and gangue minerals are quartz, sericite and chlorite. The H-O isotopic compositions of quartz, S-Cu-Pb isotopic compositions of sulfide minerals, Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore-forming fluids and metals for the Nage Cu-Pb deposit. The oSCUNBs values of chalcopyrite range from -0.09% to +0.33%0, similar to basic igneous rocks and chalcopyrite from magmatic deposits. J6SCUNBS values of chalcopyrite from the early, middle and final mineralization stages show an increasing trend due to 63Cu prior migrated in gas phase when fluids exsolution from magma, ja4ScDT values of sulfide minerals range from -2.7‰ to +2.8‰, similar to mantle-derived sulfur (0±3‰). The positive correlation between J65CUNBs and ja4SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma. JDu2o- SMOW and JlSOH2O-SMOW values of water in fluid inclusions of quartz range from -60.7‰ to -44.4‰ and +7.9‰ to +9.0%0 (T=260℃), respectively and fall in the field for magmatic and metamorphic waters, implicating that mixed sources for H20 in hydrothermal fluids. Ores and sulfide minerals have a small range of Pb isotopic compositions (208Pb/204pb=38.152 to 38.384, 207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049) that are close to orogenic belt and upper crust Pb evolution curve, and similar to Neoproterozoic host rocks (208Pb/204Pb=38.201 to 38.6373, 207pb/204pb=15.648 to 15.673 and 206pb/204pb=17.820 to 18.258), but higher than diabase (208Pb/204pb=37.830 to 38.012, 207pb/204pb=15.620 to 15.635 and 206pb/204pb=17.808 to 17.902). These results imply that the Pb metal originated mainly from host rocks. The H-O-S-Cu-Pb isotopes tegather with geology, indicating that the ore genesis of the Nage Cu-Pb deposit is post-magmatic hydrothermal type.
基金supported by the National Key Research and Development Program (Grand Nos. 2018YFC0603804, 2016YFC0600108-09)the National Natural Science Foundation of China (41502093)the Geological Investigation Project of the China Geological Survey (DD20160049)
文摘TheWulong lode deposit contains over 80 tonnes of gold with an average grade of 5.35 g/t.It is one of the largest deposits in Dandong City,Liaoning Province in northeast China.Previous studies on the deposit focused on its geological characteristics,geochemistry,fluid inclusions,and the timing of gold mineralization.However,controversy remains regarding the origin of the ore-forming fluids and metals,and the genesis of the gold deposit.This paper presents zircon UePb and pyrite RbeSr ages and S,Pb,He,and Ar isotopic results along with quartz H and O isotopic data for all litho-units associated with the deposit.Laser ablation inductively coupled mass spectrometry measurements yielded zircon UePb dates for samples of pre-mineralization rocks like granite porphyry dike,the Sanguliu granodiorite,fine-grained diorite,and syn-mineralization diorite,as well as post-mineralization dolerite,and lamprophyre;their emplacement ages are 1261 Ma,1241 Ma,1231 Ma,1201 Ma,1192 Ma,and 1152 Ma,respectively.The pyrite RbeSr isochron age is 1191 Ma,indicating that both magmatism and mineralization occurred during the Early Cretaceous.The d18OH2O values of ore-forming hydrothermal fluids from the quartzepolymetallic sulfide vein stage vary from 4.8&to 6.5&,and the dDV-SMOW values are between67.7&and75.9&,indicating that the ore-forming fluids were primarily magmatic.The noble gas isotope compositions of fluid inclusions hosted in pyrite suggest that the ore-forming fluids were dominantly derived from crustal sources with minor mantle input.Sulfur isotopic values of pyrite vary between 0.2&and 3.5&,suggesting that S was derived from a homogeneous magmatic source or possibly from fluids derived from the crust.The Pb isotopic compositions of sulfides(207Pb/204Pb?15.51 e15.71,206Pb/204Pb?17.35e18.75,208Pb/204Pb?38.27e40.03)indicate that the Pb of the Wulong gold deposit is a mixture of crust and mantle components.Geochronological and geochemical data,together with the regional geological history,indicate that Early Cretaceous magmatism and mineralization of the Wulong gold deposit occurred during the rollback of the subducting Paleo-Pacific Plate,which resulted in lithospheric thinning and the destruction of the North China Craton(NCC),which indicates that the deposit is of magmaticehydrothermal origin.
基金supported by the National Basic Research Program of China(973 Program:2012CB416802)the National Special Research Programs for Non-Profit Trades(Sponsored by MLR,201311136)the Basic Scientific Research Operation Cost of StateLeveled Public Welfare Scientific Research Courtyard (K1203)
文摘The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formation process,this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of mineralization.The results indicate that the δ34S values(ranging from 14.0‰ to 17.6‰) of pyrites formed from the two stages have no obvious differences,suggesting that they were not derived from a single magmatic sulfur source.The δ34S values of anhydrite mostly range from 21.9‰ to 28.4‰,similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt(MLYRB).The Pb isotopic compositions of the pyrites of both stages are homogeneous,with values of 208Pb/204Pb,207Pb/204Pb,and-206Pb/204Pb being 38.006-38.257,15.523-15.556,and 17.806-18.052,respectively,indicating a mixed crust-mantle source.The He-Ar results exhibit different compositions of the two stages:the -3He/-4He(R/Ra) and 40Ar/-36Ar values for the early-stage pyrite are 0.46-0.63 and 311-322,respectively,whereas the values for late-stage pyrite are 0.23-0.34 and 305-361,respectively.Both stages of pyrites indicate the multiple sources of the ore-forming fluids,with decreasing amount of magmatic water and increasing amount of modified meteoric water(MASW) during fluid evolution.The Triassic evaporites played an important role in the mineralization process.
基金financially supported by the National Natural Science Foundation of China(No.41272111)。
文摘The Sichuan-Yunnan-Guizhou(SYG)Pb-Zn mineral province,which has significant Pb-Zn repositories in China,is situated in the western Yangtze Block.Despite decades of research,the Pb-Zn source of deposits is still disputed between the basement rocks,sedimentary wall rocks,or the Emeishan flood basalts.The newly-discovered Laoxiongdong Pb-Zn deposit is hosted by the Late Ediacaran Dengying Formation in the SYG province.Moreover,the Laoxiongdong orebodies lie between regional deep faults and close to the Proterozoic basement and Emeishan basalts.Hence,this deposit represents a good case study on the ore-forming material source for the regional Pb-Zn mineralization.The Laoxiongdong Pb-Zn ores are massive,vein,or disseminated and have mainly sphalerite,galena,pyrite,quartz,and calcite.In this paper,we present new sulfide S-Pb-Zn isotope data of the deposit.The sulfideδ34SCDT values(+11.8 to+16.5‰)suggest that the reduced sulfur was mainly sourced from evaporites in the Late Ediacaran-Cambrian sequences.Pb isotopic ratios(206Pb/204Pb=18.004-18.107,207Pb/204Pb=15.652-15.667,and 208Pb/204Pb=38.037-38.248)suggest that the lead metal was primarily originated from the basement rocks.The sphaleriteδ66Zn values(+0.16 to+0.37‰)are also highly similar(within error)to those of basement rocks(+0.10 to+0.34‰),suggesting a basement-rocks zinc source with minor contributions from the carbonate host rocks and Emeishan flood basalts.The narrow sphalerite Zn isotopic range(0.21‰)also indicates that the Zn isotopic fractionation between the sphalerite and initial fluid was limited during the sphalerite ore precipitation.Therefore,we propose that both the Late Ediacaran Dengying Formation rocks and Proterozoic basement rocks were important ore-forming material source for the Laoxiongdong deposit,whereas the Emeishan flood basalts represent only a minor ore-material source.
基金jointly supported by National Natural Science Foundation of China(Grant Nos.41421002,41272092,and 41030423)MOST Special Fund from the State Key Laboratory of Continental Dynamics,Northwest University,China
文摘The Tongyu copper deposit, located in the western part of the North Qinling Orogen, China, is one of several volcanic-hosted massive sulphide(VHMS) deposits with industrial value and is also a typical example of mineralization related to the subduction and metallogenesis during the Caledonian orogeny. We conducted systematic lead-sulphur isotope geochemical analyses of the Tongyu deposit to understand the possible ore-forming material sources and tectonic settings. Twenty-six sulphide samples yielded clustered δ^34SCDT values of 1.13‰-3.36‰, average 2.22‰, and show a tower-type distribution,implying that the sulphur of the Tongyu copper deposit mainly originated from a mantle source. The Pb isotope compositions of sulphides(^206Pb/^204Pb = 17.59225-18.56354, average 18.32020; ^207Pb/^204Pb =15.51770-15.69381, average 15.66217; ^208Pb/^204Pb= 37.99969-39.06953, average 38.52722) are close to the values of the volcanic host rocks(^206Pb/^204PbPb= 18.10678-18.26293, average 18.21158; ^207Pb/^204PbPb =15.63196-15.68188, average 15.65345; ^208Pb/^204PbPb= 38.43676-38.56360, average 38.49171), thus consistent with the Pb in ores and volcanic host rocks having been derived from a common source that was island-arc Pb related to oceanic crust subduction. The northward subduction of the Palaeo-Qinling oceanic crust triggered dehydration of the slab, which generated a large amount of high-oxygen-fugacity aqueous hydrothermal fluid. The fluid rose into the mantle wedge, activated and extracted metallogenic material and promoted partial melting of the mantle wedge. The magma and ore-forming fluid welled up and precipitated, finally forming the Tongyu VHMS copper deposit.
文摘The Habo alkaline intrusion, which is located in the south of the Sanjiang area, Yunnan Province, China, is a typical Cenozoic alkaline intrusion. There are a series of small to medium-sized Au and Pb–(Zn) deposits around this intrusion. Those deposits are spatially associated with the Habo alkaline intrusion.(1) The d^(34) S values of sulfides from Au deposits range from-1.91 % to 2.69 %, which are similar to those of Pb–(Zn) deposits(-3.82 % to-0.05 %) and both indicate a much greater contribution from magma.(2) The Habo alkaline intrusion has relatively homogeneous Pb isotopic compositions with^(206)Pb/^(204) Pb ranging from 18.608 to 18.761,^(207)Pb/^(204) Pb from 15.572 to15.722 and^(208)Pb/^(204) Pb from 38.599 to 39.110. These Pb isotope ratios are similar to those of Au deposits, whose^(206)Pb/^(204) Pb range from 18.564 to 18.734,^(207)Pb/^(204) Pb from15.582 to 15.738 and^(208)Pb/^(204) Pb from 38.592 to 39.319.Pb ratios in both the intrusion and Au deposits suggest that Pb mainly derived from the depth, probably represents a mixture of mantle and crust. Pb–(Zn) deposits, however,show a decentralized trait, and most of them are similar to that of the alkaline intrusion with^(206)Pb/^(204) Pb ranging from18.523 to 18.648,^(207)Pb/^(204) Pb from 15.599 to 15.802, and^(208)Pb/^(204) Pb from 38.659 to 39.206.(3) In the plumbotectonic diagram^(207)Pb/^(204) Pb versus^(206)Pb/^(204) Pb, almost all of Au and Pb–(Zn) deposits have the same projection area with the Habo alkaline intrusion, which indicates that thosedeposits almost share the same source with the alkaline intrusion.(4) Isotopic age of the Habo alkaline intrusion is36–33 Ma, which is similar to that of Beiya, whose orerelated alkaline porphyries age is 38–31 Ma and molybdenite Re–Os age is 36.9 Ma. Therefore, along with S–Pb isotope traits, we suggest that the Habo Au and Pb–(Zn)deposits should be typically Ailaoshan-Red River Cenozoicalkaline-related deposits and ore-forming ages of these deposits should be later than that of the Habo alkaline intrusion.