Sulfur isotopic composition of the Tianqiao Pb-Zn ore deposit,Northwest Guizhou Province,China：Implications for the source of sulfur in the ore-forming fluids

The Tianqiao Pb-Zn ore deposit of Guizhou Province, China, is located in the mid-east of the Si-chuan-Yunnan-Guizhou Pb-Zn-Ag multi-metallic mineralization area, which is representative of the Pb-Zn ore de-posits in this area. It consists of three main orebodies, whose Pb+Zn reserves are more than 0.2 million ton. This paper analyzes the sulfur isotopic composition of these orebodies. The data show that the ore minerals (galena, sphalerite, pyrite) in these orebodies are enriched in heavy sulfur, with δ34SV-CDT values varying between 8.35‰ and 14.44‰, i.e. the δ34SV-CDT values of pyrite are between 12.81‰ and 14.44‰, the mean value is 13.40‰; the δ34SV-CDT values of sphalerite are range from 10.87‰ to 14.00‰, the mean value is 12.53‰; the δ34SV-CDT values of galena are range from 8.35‰ to 9.83‰, the mean value is 8.84‰, and they have the feature of δ34Spyrite>δ34Ssphalerite>δ34Sgalena, which indicates the sulfur isotope in ore-forming fluids has attained equilibrium. The δ34S V-CDT values of the deposit are close to those of sulfates from carbonate strata of different ages in the ore-field (15‰), which suggests that the sulfur in the ore-forming fluids should be derived from the thermo-chemical sulfate reduction of sulfates from the sedimentary strata.     

Regional Metallogenesis of the Chang’an Gold Ore Deposit in Western Yunnan: Evidences from Fluid Inclusions and Stable Isotopes

<正>The Chang'an gold ore deposit in western Yunnan is located at the southern segment of the Ailaoshan metallogenic belt.The ore bodies are preserved in fractured Ordovician sedimentary clastic rocks.The gold-bearing minerals occur dominantly in sulfide-quartz veins.Fluid inclusion analysis shows that the Chang'an gold ore deposit is characterized by epithermal gold mineralization at temperatures between 200℃and 280℃at a shallow crustal level.The mineralizing fluids have intermediate to low salinity(6%-18%) and low densities(0.72-1.27 g/cm~3).The ore minerals haveδ~(34)S in a range from -13‰to 3.57‰,concentrated from -2.06‰to 3.57‰with an average of 1.55‰.The ~(206)Pb/~(204)Pb,~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb values are 18.9977-19.5748,15.7093-15.784,39.3814-40.2004 respectively.These isotope data suggest that the ore-forming elements were mainly derived from mixed crustal and mantle sources.The Chang'an gold ore deposit and Tongchang Cu-Mo deposit are closely related to each other in their spatial distribution and age of formation.They have similar sources of mineralizing elements and identical ore-forming metal elements,and show a close relationship in physical and chemical conditions of mineralization.The two deposits constitute an epithermal-porphyry -skarn type Cu-Mo-Au mineralization system in the Tongchang-Chang'an area,which is related to the Cenozoic high-K alkaline magmatism.     

Genesis of the Changba–Lijiagou Giant Pb-Zn Deposit, West Qinling, Central China: Constraints from S-Pb-C-O isotopes

The extensive Changba-Lijiagou Pb-Zn deposit is located in the north of the Xihe–Chengxian ore cluster in West Qinling. The ore bodies are mainly hosted in the marble, dolomitic marble and biotite-calcite-quartz schist of the Middle Devonian Anjiacha Formation, and are structurally controlled by the fault and anticline. The ore-forming process can be divided into three main stages, based on field geological features and mineral assemblages. The mineral assemblages of hydrothermal stage I are pale-yellow coarse grain, low Fe sphalerite, pyrite with pits, barite and biotite. The mineral assemblages of hydrothermal stage II are black-brown cryptocrystalline, high Fe shalerite, pyrite without pits, marcasite or arsenopyrite replace the pyrite with pits, K-feldspar. The features of hydrothermal stage III are calcite-quartz-sulfide vein cutting the laminated, banded ore body. Forty-two sulfur isotope analyses, twenty-five lead isotope analyses and nineteen carbon and oxygen isotope analyses were determined on sphalerite, pyrite, galena and calcite. The δ34 S values of stage I(20.3 to 29.0‰) are consistent with the δ34 S of sulfate(barite) in the stratum. Combined with geological feature, inclusion characteristics and EPMA data, we propose that TSR has played a key role in the formation of the sulfides in stage I. The δ34 S values of stage II sphalerite and pyrite(15.1 to 23.0‰) are between sulfides in the host rock, magmatic sulfur and the sulfate(barite) in the stratum. This result suggests that multiple S reservoirs were the sources for S2-in stage II. The δ34 S values of stage III(13.1 to 22‰) combined with the structure of the geological and mineral features suggest a magmatic hydrothermal origin of the mineralization. The lead isotope compositions of the sulfides have 206 Pb/204 Pb ranging from 17.9480 to 17.9782, 207 Pb/204 Pb ranging from 15.611 to 15.622, and 208 Pb/204 Pb ranging from 38.1368 to 38.1691 in the three ore-forming stages. The narrow and symmetric distributions of the lead isotope values reflect homogenization of granite and mantle sources before the Pb-Zn mineralization. The δ13 CPDB and δ18 OSMOW values of stage I range from-0.1 to 2.4‰ and from 18.8 to 21.7‰. The values and inclusion data indicate that the source of fluids in stage I was the dissolution of marine carbonate. The δ13 CPDB and δ18 OSMOW values of stage II range from-4 to 1‰ and from 12.3 to 20.3‰, suggesting multiple C-O reservoirs in the Changba deposit and the addition of mantle-source fluid to the system. The values in stage III are-3.1‰ and 19.7‰, respectively. We infer that the process of mineralization involved evaporitic salt and sedimentary organic-bearing units interacting through thermochemical sulfate reduction through the isotopic, mineralogy and inclusion evidences. Subsequently, the geology feature, mineral assemblages, EPMA data and isotopic values support the conclusion that the ore-forming hydrothermal fluids were mixed with magmatic hydrothermal fluids and forming the massive dark sphalerite, then yielding the calcite-quartz-sulfide vein ore type at the last stage. The genesis of this ore deposit was epigenetic rather than the previously-proposed sedimentary-exhalative(SEDEX) type.     

The Zhaxikang Vein‐type Pb‐Zn‐Ag‐Sb Deposit in Himalayan Orogen,Tibet: Product by Overprinting and Remobilization Processes during Post‐collisional Period

The Zhaxikang Pb-Zn-Ag-Sb deposit, the largest polymetallic deposit known in the Himalayan Orogen of southern Tibet, is characterized by vein-type mineralization that hosts multiple mineral assemblages and complicated metal associations. The deposit consists of at least six steeply dipping veintype orebodies that are hosted by Early Jurassic black carbonaceous slates and are controlled by a Cenozoic N–S-striking normal fault system. This deposit records multiple stages of mineralization that include an early period(A) of massive coarse-grained galena–sphalerite deposition and a later period(B) of Sb-bearing vein-type mineralization. Period A is only associated with galena–sphalerite mineralization, whereas period B can be subdivided into ferrous rhodochrosite–sphalerite–pyrite, quartz–sulfosalt–sphalerite, calcite–pyrite, quartz–stibnite, and quartz-only stages of mineralization. The formation of brecciated galena and sphalerite ores during period A implies reworking of pre-existing Pb–Zn sulfides by Cenozoic tectonic deformation, whereas period B mineralization records extensive openspace filling during ore formation. Fluid inclusion microthermometric data indicate that both periods A and B were associated with low–medium temperature(187–267°C) and low salinity(4.00–10.18% wt. Na Cl equivalent) ore-forming fluids, although variations in the physical–chemical nature of the period B fluids suggest that this phase of mineralization was characterized by variable water/rock ratios. Microprobe analyses indicate that Fe concentrations in sphalerite decrease from period A to period B, and can be divided into three groups with Fe S concentrations of 8.999–9.577, 7.125–9.109, 5.438–1.460 mol.%. The concentrations of Zn, Sb, Pb, and Ag within orebodies in the study area are normally distributed in both lateral and vertical directions, and Pb, Sb, and/or Ag concentrations are positive correlation within the central part of these orebodies, but negatively correlate in the margins. Sulfide S isotope compositions are highly variable(4‰–13‰), varying from 4‰ to 11‰ in period A and 10‰ to 13‰ in period B. The Pb isotope within these samples is highly radiogenic and defines linear trends in 206 Pb/204 Pb vs. 207 Pb/204 Pb and 206 Pb/204 Pb vs. 208 Pb/204 Pb diagrams, respectively. The S and Pb isotopic characteristics indicate that the period B orebodies formed by mixing of Pb–Zn sulfides and regional Sbbearing fluids. These features are indicative of overprinting and remobilization of pre-existing Pb–Zn sulfides by Sb-bearing ore-forming fluids during a post-collisional period of the Himalayan Orogeny. The presence of similar ore types in the north Rhenish Massif that formed after the Variscan Orogeny suggests that Zhaxikang-style mineralization may be present in other orogenic belts, suggesting that this deposit may guide Pb–Zn exploration in these areas.     

Geochemical Characteristics of the Jinjiazhuang Ultrabasic Rock—Type Gold Deposit in Chicheng County,Hebei Province

The Jinjiazhuang gold deposit occurs in the Zhangjiakou gold field,Northwest Hebei.The ore bodies are mostly hosted in Xiaozhangjiakou ultrabasic rocks dominated by diopsidite.Electron microprobe analyses indicate that the deposit is characterized by the enrichment of some platinum group elements in principal metallic minerals such as chalcopyrite,galena,sphalerite and pyrite,and the presence of millerite,Stable isotope studies show that carbon,sulfur and most of the metallogenic elements were probably derived largely from the host Xiaozhangjiakou ultrabasic rocks and that it is possible that the ore-forming fluid was predominted by meteoric water.     

Genesis of the Bianjiadayuan Pb-Zn polymetallic deposit,Inner Mongolia,China:Constraints from in-situ sulfur isotope and trace element geochemistry of pyrite

The Southern Great Xing'an Range(S(GXR)which forms part of the eastern segment of the Central Asian Orogenic Belt(CAOB)is known as one of the most important Cu-Mo-Pb-Zn-Ag-Au metallogenic belts in China,hosting a number of porphyry Mo(Cu),skarn Fe(Sn),epithermal Au-Ag,and hydrothermal veintype Ag-Pb-Zn ore deposits.Here we investigate the Bianjiadayuan hydrothermal vein-type Ag-Pb-Zn ore deposit in the southern part of the SGXR.Porphyry Sn± Cu± Mo mineralization is also developed to the west of the Ag-Pb-Zn veins in the ore field.We identify a five-stage mineralization process based on field and petrologic studies including(i)the early porphyry mineralization stage,(ii)main porphyry mineralization stage,(iii)transition mineralization stage,(iv)vein-type mineralization stage and(v)late mineralization stage.Pyrite is the predominant sulfide mineral in all stages except in the late mineralization stage,and we identify corresponding four types of pyrites:Pyl is medium-grained subhedral to euhedral occurring in the early barren quartz vein;Py2 is medium-to fine-grained euhedral pyrite mainly coexisting with molybdenite,chalcopyrite,minor sphalerite and galena;Py3 is fine-grained,subhedral to irregular pyrite and displays cataclastic textures with micro-fractures;Py4 occurs as euhedral microcrystals and forms irregularly shaped aggregate with sphalerite and galena.LA-ICP-MS trace element analyses of pyrite show that Cu,Pb,Zn,Ag,Sn,Cd and Sb are partitioned into pyrite as structurally bound metals or mineral micro/nano-inclusions,whereas Co,Ni,As and Se enter the lattice via isomorphism in all types of pyrite.The Cu,Zn,Ag,Cd concentrations gradually increase from Pyl to Py4,which we correlate with cooling and mixing of ore-forming fluid with meteoric water.Py2 contains the highest contents of Co,Ni,Se,Te and Bi,suggesting high temperature conditions for the porphyry mineralization stage.Ratios of Co/Ni(0.03-10.79,average 2.13)and sulphur isotope composition of sulfide indicate typical hydrothermal origin for pyrites.The δ~(34)S_(cDT) values of Pyl(0.42‰-1.61‰,average1.16‰),Py2(-1.23‰to 0.82‰,average 0.35‰),Py3(—0.36‰to 2.47‰average 0.97‰).Py4(2.51‰--3.72‰,average 3.06‰),and other sulfides are consistent with those of typical porphyry deposit(-5‰to 5‰),indicating that the Pb-Zn polymetallic mineralization in the Bianjiadayuan deposit is genetically linked to the Yanshanian(Jurassic-Cretaceous)magmatic-hydrothermal events.Variations of δ~(34) S values are ascribed to the changes in physical and chemical conditions during the evolution and migration of the ore-forming fluid.We propose that the high Sn content of pyrite in the Bianjiadayuan hydrothermal vein-type Pb-Zn polymetallic deposit can be used as a possible pathfinder to prospect for Sn mineralization in the surrounding area or deeper level of the ore field in this region.     

Isotopic Compositions of Sulfur in the Jinshachang Lead–Zinc Deposit, Yunnan, China, and its Implication on the Formation of Sulfur-Bearing Minerals

The Jinshachang lead–zinc deposit is mainly hosted in the Upper Neoproterozoic carbonate rocks of the Dengying Group and located in the Sichuan–Yunnan–Guizhou(SYG) Pb–Zn–Ag multimetal mineralization area in China.Sulfides minerals including sphalerite,galena and pyrite postdate or coprecipitate with gangue mainly consisting of fluorite,quartz,and barite,making this deposit distinct from most lead–zinc deposits in the SYG.This deposit is controlled by tectonic structures,and most mineralization is located along or near faults zones.Emeishan basalts near the ore district might have contributed to the formation of orebodies.The δ34S values of sphalerite,galena,pyrite and barite were estimated to be 3.6‰–13.4‰,3.7‰–9.0‰,6.4‰ to 29.2‰ and 32.1‰–34.7‰,respectively.In view of the similar δ34S values of barite and sulfates being from the Cambrian strata,the sulfur of barite was likely derived from the Cambrian strata.The homogenization temperatures(T ≈ 134–383°C) of fluid inclusions were not suitable for reducing bacteria,therefore,the bacterial sulfate reduction could not have been an efficient path to generate reduced sulfur in this district.Although thermochemical sulfate reduction process had contributed to the production of reduced sulfur,it was not the main mechanism.Considering other aspects,it can be suggested that sulfur of sulfides should have been derived from magmatic activities.The δ34S values of sphalerite were found to be higher than those of coexisting galena.The equilibrium temperatures calculated by using the sulfur isotopic composition of mineral pairs matched well with the homogenization temperature of fluid inclusions,suggesting that the sulfur isotopic composition in ore-forming fluids had reached a partial equilibrium.     

Lead isotope geochemical characteristics of Pb-Zn-Cu deposits on the southwestern margin of Tarim, and their significance

The polymetallic(Pb,Zn,Cu,etc) ore belt on the southwestern margin of Tarim is one of the major regions with the greatest prospecting potential in Xinjiang.Reported in this paper are the lead isotope data for 66 sulfide samples(including 50 galena samples,15 chalcopyrite samples and 1 pyrite sample) collected from such representative deposits as Tamu,Tiekelike,Kalangu,Abalieke,etc.in this ore belt.The Pb isotopic ratios of 206 Pb/204 Pb,207 Pb/204 Pb and 208 Pb/204 Pb in the galena samples range from 17.931 to 18.176,15.609 to 15.818 and 38.197 to 38.944,with the average values of 18.017,15.684 and 38.462,respectively.Those in the chalcopyrite samples range from 17.926 to 18.144,15.598 to 15.628 and 38.171 to 38.583,with the average values of 18.020,15.606 and 38.262,respectively.The pyrite sample has the Pb isotopic ratios of 206 Pb/204 Pb,207 Pb/204 Pb and 208 Pb/204 Pb to be 17.980,15.604 and 38.145,respectively.In combination with the previous Pb isotope data for sulfides,it is found that there is only a slight variation in the Pb isotopic composition of galena,chalcopyrite,sphalerite and pyrite in the ore belt.However,there is some difference in Pb isotopic characteristics between galena and chalcopyrite,especially the Pb isotopic composition of galena shows an obvious linear correlation with some other relevant parameters(e.g.β and γ).The comprehensive analysis suggested that lead in galena(maybe including sphalerite and pyrite) was derived principally from wall rocks and underlying basement,and that in chalcopyrite only originated from the basement.The single-stage model ages of these sulfides couldn’t indicate the time limit of metallogenesis(Pb,Zn,Cu,etc.),and the positive linear correlations for the Pb isotopic composition of galena are of no single-stage and two-stage Pb-Pb isochron significance.Furthermore,there are significant differences in Pb isotopic composition characteristics between the genetic type of deposits in this polymetallic ore belt and the Mississippi Valley type(MVT).In addition,the authors also pointed out that there is a phenomenon of differentiation(not paragenesis) for lead and copper elements during the process of metallogenesis in this ore belt.     

Geology, Fluid Inclusion and Isotopic Study of the Neoproterozoic Suoi Thau Copper Deposit, Northwest Vietnam

The Sin Quyen-Lung Po district is an important Cu metallogenic province in Vietnam, but there are few temporal and genetic constraints on deposits from this belt. Suoi Thau is one of the representative Cu deposits associated with granitic intrusion. The deposit consists of ore bodies in altered granite or along the contact zone between granite and Proterozoic meta-sedimentary rocks. The Cu-bearing intrusion is sub-alkaline I-type granite. It has a zircon U-Pb age of ~776 Ma, and has subduction-related geochemical signatures. Geochemical analysis reveals that the intrusion may be formed by melting of mafic lower crust in a subduction regime. Three stages of alteration and mineralization are identified in the Suoi Thau deposit, i.e., potassic alteration; silicification and Cu mineralization; and phyllic alteration. Two-phase aqueous fluid inclusions in quartz from silicification stage show wide ranges of homogenization temperatures(140–383℃) and salinities(4.18wt%–19.13wt%). The high temperature and high salinity natures of some inclusions are consistent with a magmatic derivation of the fluids, which is also supported by the H-O-S isotopes. Fluids in quartz have δD values of –41.9‰ to –68.8‰. The fluids in isotopic equilibrium with quartz have δ~(18)O values ranging from 7.9‰ to 9.2‰. These values are just plotted in the compositional field of magmatichydrothermal fluids in the δD_(water) versus δ~(18)O_(water) diagram. Sulfide minerals have relatively uniform δ~(34)S values from 1.84‰ to 3.57‰, which is supportive of a magmatic derivation of sulfur. The fluid inclusions with relatively low temperatures and salinities most probably represent variably cooled magmatic-hydrothermal fluids. The magmatic derivation of fluids and the close spatial relationship between Cu ore bodies and intrusion suggest that the Cu mineralization most likely had a genetic association with granite. The Suoi Thau deposit, together with other deposits in the region, may define a Neoproterozoic subduction-related ore-forming belt.     

Helium and argon isotopic compositions of the Longquanzhan gold deposit in the Yishu fault zone and their geological implications

The Longquanzhan gold deposit hosted in granitic cataclasites with mylontization of the foot wall of the main Yishui-Tangtou fault. 3He/4He ratios in fluid inclusions range from 0. 14 to 0. 24 R/Ra,close to those of the crust-source helium. 40Ar/36Ar ratios were measured to be 289-1811, slightly higher than those of atmospheric argon. The results of analysis of helium and argon isotopes suggested that ore-forming fluids were derived chiefly from the crust. The δ18O values of fluid inclusions from vein quartz range from -1.78‰ to 4.07‰, and the δD values of the fluid inclusions vary between -74‰ and -77‰. The hydrogen and oxygen isotope data indicated that the ore-forming fluid for the Longquanzhan gold deposit had mixed with meteoric water in the process of mineralization. This is consistent with the conclusion from the helium and argon isotope data.     

Geological and isotopic evidence for magmatic-hydrothermal origin of the Ag–Pb–Zn deposits in the Lengshuikeng District,east-central China

The Lengshuikeng ore district in east-central China has an ore reserve of ～43 Mt with an average grade of 204.53 g/t Ag and 4.63 % Pb?+?Zn. Based on contrasting geological characteristics, the mineralization in the Lengshuikeng ore district can be divided into porphyry-hosted and stratabound types. The porphyry-hosted mineralization is distributed in and around the Lengshuikeng granite porphyry and shows a distinct alteration zoning including minor chloritization and sericitization in the proximal zone; sericitization, silicification, and carbonatization in the peripheral zone; and sericitization and carbonatization in the distal zone. The stratabound mineralization occurs in volcano-sedimentary rocks at ～100–400 m depth without obvious zoning of alterations and ore minerals. Porphyry-hosted and stratabound mineralization are both characterized by early-stage pyrite–chalcopyrite–sphalerite, middle-stage acanthite–native silver–galena–sphalerite, and late-stage pyrite–quartz–calcite. The δ³⁴S values of pyrite, sphalerite, and galena in the ores range from ?3.8 to +6.9‰ with an average of +2.0‰. The C–O isotope values of siderite, calcite, and dolomite range from ?7.2 to ?1.5‰ with an average of ?4.4‰ (V-PDB) and from +10.9 to +19.5‰ with an average of +14.8‰ (V-SMOW), respectively. Hydrogen, oxygen, and carbon isotopes indicate that the hydrothermal fluids were derived mainly from meteoric water, with addition of minor amounts of magmatic water. Geochronology employing LA–ICP–MS analyses of zircons from a quartz syenite porphyry yielded a weighted mean ²⁰⁶Pb/²³⁸U age of 136.3?±?0.8 Ma considered as the emplacement age of the porphyry. Rb–Sr dating of sphalerite from the main ore stage yielded an age of 126.9?±?7.1 Ma, marking the time of mineralization. The Lengshuikeng mineralization classifies as an epithermal Ag–Pb–Zn deposit.     

Sulphur- and lead-isotope geochemistry of the Arapuçandere lead–zinc–copper deposit,Biga Peninsula,northwest Turkey

The Arapuçandere Pb–Zn–Cu ore body is a typical vein-type lead–zinc deposit of the Biga Peninsula, and is currently being mined for lead and zinc. In the study area, Permian–Triassic metamorphic rocks, Triassic metaclastic and metabasic rocks, Oligocene–Miocene granitoids, Miocene volcanic rocks, and Quaternary terrigenous sediments crop out. The ore deposits developed as Pb–Zn–Cu-bearing veins along faults in Triassic metasandstone and metadiabase. Microscopic studies reveal that the veins contain galena, sphalerite, chalcopyrite, pyrite, marcasite, covellite, and specular hematite as ore minerals, and quartz, calcite, and barite as gangue minerals. Analysed sulphur-isotope compositions (δ³⁴S_VCDT) of galena, sphalerite, and chalcopyrite range from ? 5.9 to ? 1.9‰ (average ? 3.4‰), from ? 5.5 to ? 1.7‰ (average ? 4.2 ‰), and from ? 3.5 to ? 0.9‰ (average ? 2.6‰), respectively; that of H₂S in the hydrothermal fluid was in the calculated range of ? 5.8 to +0.1‰ (average ? 2.5‰). These isotopic values suggest that magmatic sulphur dominates in sulphides, mixed with minor, isotopically light sulphur. Because no contemporaneous magmatic activity is associated with mineralization, it may be assumed that sulphur was leached from the surrounding Triassic units, mainly from metabasic, partly from metaclastic rocks. Lead-isotope studies indicate a model age of 114–63 Ma for the lead reservoir, in accord with possible sulphur-bearing local source rocks. Thus, the sulphur and lead deposited in the studied ore veins were probably leached from Triassic metabasic and metaclastic rocks some time during the Early Cretaceous to the Palaeocene.     

Geochemical,fluid inclusion and isotopic (O,H and S) constraints on the origin of Pb–Zn ± Au vein-type mineralizations in the Eastern Pontides Orogenic Belt (NE Turkey)

The mineralization area (Altınpınar, Torul–Gümüşhane) is situated in the Southern Zone of the Eastern Pontides Orogenic Belt (EPOB), which is one of the important metallogenic provinces in the Alpine–Himalayan belt and is intruded by the late Carboniferous granitic rocks (Gümüşhane Granitoid), an early to middle Jurassic volcano-sedimentary unit consisting mainly of basaltic–andesitic volcanic and pyroclastic rocks (Şenköy Formation) and Eocene basaltic–andesitic volcanic rocks (Alibaba Formation). The studied Pb–Zn ± Au mineralizations are related to silica veins ranging from a few millimeters to a maximum of 40 cm in thickness and are localized within fracture zones developed along the contact between the Gümüşhane Granitoid and Şenköy Formation. Silicic, sulfidic, hematitic, argillic, intense chloritic and carbonate alteration are the most common types from the fault lines toward the outer zones. Cavity filling and banded structures are widely observed. The mineral paragenesis comprises galena, sphalerite, pyrite, chalcopyrite, tennantite and quartz. Mineral chemistry studies indicate that ion exchange occurs between Zn and Fe in sphalerites, and the Zn/Cd ratio of sphalerites varies between 50.65 and 144.64. The homogenization temperatures measured from fluid inclusions vary between 170 °C and 380 °C, especially between 250 °C and 300 °C, and the wt.% NaCl eqv. salinity of ore-forming fluids is between 2.4 and 7.3 (4.7 on average), supporting an epithermal system in their origin. The values of sulfur isotopes, which are obtained from pyrite and galena minerals, range between − 8.3‰ and − 2.3‰, indicating that sulfur, which enables mineral formation, originates from magmatic genesis. The average formation temperature of the ore is 317 °C as determined with a sulfur isotope geothermometer. The values of oxygen and hydrogen isotopes vary between 8.5‰ and 10.2‰ and − 91‰ and −73‰, respectively. With regard to the compositions of oxygen and hydrogen isotopes, fluids comprising the mineralization are formed by the mixture of magmatic water and meteoric water. This situation is supported by the fact that the increase in the homogenization temperature indicates dilution with surface water but depends on the increase in the salinity of fluid inclusions. Considering all the data, it is clear that the studied mineralization is an epithermal vein-type mineralization that is related to granitic magmas.     

相山西部牛头山铅锌矿化体成矿物质来源:原位硫同位素的制约

近年来,在相山铀矿田的西部牛头山地区深部发现了铅锌矿化体,其成因机制不明.为探讨牛头山铅锌矿化体物质来源,开展了硫化物原位硫同位素分析研究.根据硫化物矿物之间的充填和包裹关系判断,铅锌矿化体金属硫化物形成的先后顺序是:黄铁矿形成最早,方铅矿和闪锌矿次之,细脉状黄铜矿形成最晚.利用LA-MC-ICP-MS技术对矿化体中几种金属硫化物分别进行了系统的原位硫同位素分析.结果显示:黄铁矿、闪锌矿、方铅矿、细脉状黄铜矿的δ34S值介于-4.8‰~+5.4‰之间,各硫化物矿物之间硫同位素未达到完全平衡分馏,利用黄铁矿δ34S值得到的矿化流体δ34S_ΣS值（总硫同位素组成）近似为+3.7‰,与共生矿物对（闪锌矿-方铅矿）图解法得到的闪锌矿和方铅矿沉淀时矿化流体的δ34S_ΣS值（+3.2‰）相近,表明形成牛头山铅锌矿化体的矿化流体δ34S_ΣS值大约为+3.7‰,为岩浆硫.结合前人的岩浆岩年龄数据,我们判断该铅锌矿化体金属硫化物的硫可能主要来自次火山岩相花岗斑岩岩浆热液.同一薄片中闪锌矿δ34S值高于共生的方铅矿,表明两者硫同位素基本平衡,利用共生矿物对（闪锌矿-方铅矿）硫同位素温度计计算得出平衡温度为197~476℃,与前人通过脉石矿物流体包裹体得到的铅锌矿化流体温度基本一致.相山火山盆地与相邻的北武夷黄岗山、梨子坑等产铅锌矿的火山盆地具有相似的成矿条件及成矿物质来源,使相山火山盆地具有良好的铅锌多金属找矿前景.      

Ore geology,fluid inclusions and O-S stable isotope characteristics of Shurab Sb-polymetallic vein deposit,eastern Iran

The Shurab Sb-polymetallic mineralization is a subvolcanic rock-hosted epithermal deposit and located in north Lut Block, eastern Iran. It is one of the most important deposits of the Iranian East Magmatic Assemblage (IEMA) in which numerous Middle-Cenozoic precious and base metals deposits occur. The main lithological units in the area are Paleogene subvolcanic intrusions and minor Jurassic sedimentary rocks. Mineralization occurs as veins in a series of NW-SE and E-W trending faults and fractures in the Eocene-Oligocene dacite and andesite subvolcanic rocks. Mineralization at the Shurab deposit can be subdivided into four stages: pre-ore stage, Cu-Zn-Pb ore stage, Sb-Ag ± As ore stage and post-ore stage. The total sulfide content of the veins in the area is variable, ranging from 1 to 50%, and is dominated by stibnite, chalcopyrite, galena, Fe-poor sphalerite and pyrite with minor chalcostibite, Ag-tetrahedrite and bournonite; gangue minerals are mainly quartz and calcite. Silicic, argillic, propylitic, and sericitic, are the most obvious wall rock alterations. Microthermometric measurements of primary liquid-rich fluid inclusions in quartz and sphalerite indicate that the veins were formed at temperatures between 115 and 290 °C from fluids with salinities between 0.7 and 16.2 wt% NaCl eq., suggesting an epithermal origin. The δ³⁴S values of pyrite, chalcopyrite and galena vary between -2.5 and 0.8‰, and δ¹⁸O values of quartz range between 12.5 and 14.8‰. It is inferred that the Shurab mineralization is of epithermal origin, related to an Eocene-Oligocene magmatic geothermal system involving fluids of magmatic and meteoric origin.     

Sulphur‐isotope study of the massive sulphide orebody at Woodlawn,New South Wales

³⁴S/³²S ratios have been measured in a suite of samples from the stratabound, volcanogenic massive sulphide deposit at Woodlawn, N.S.W. ³⁴S values for the sulphides vary as follows: in the ore horizon, pyrite +6.7 to +9.2%. (mean +8.1‰), sphalerite +5.2 to +8.6‰. (mean +6.9‰), chalcopyrite +6.4 to +7.0‰ (mean +6.7‰) and galena +2.8 to +5.5‰ (mean +4.4‰); in the vein mineralization, the host volcanics—pyrite +8.7 to +11.4%. (mean +9.8‰), sphalerite +7.8 to + 10.3‰ (mean +9.2‰), chalcopyrite; +8.8 to +10.1‰ (mean +9.2‰) and galena +6.9 to +7.2‰ (mean +7.1‰). Barite from the upper ore horizon levels has an isotopic composition of +30.0‰, consistent with its having originated from Silurian ocean sulphate. The general order of ³⁴S enrichment in the sulphides is pyrite > chalcopyrite ～ sphalerite > galena. Isotopic fractionations in the systems galena/sphalerite/pyrite and chalcopyrite/pyrite indicate an equilibration temperature of 275–300°C. This temperature is considered to represent that of sulphide deposition.     

Mineralogy,mineral chemistry,fluid inclusion,and stable isotope investigations of the Kabadüz ore veins,Ordu, NE-Turkey

Hydrothermal vein-type deposits of the Kabadüz region (Ordu, NE-Turkey) are located in Upper Cretaceous andesitic–basaltic rocks and were formed in fault zones along NW–SE direction lines, with thicknesses varying between a few centimetres up to 2 m. The primary mineral paragenesis of the many different ore veins consists of pyrite, chalcopyrite, sphalerite, galena and tetrahedrite–tennantite, with quartz and lesser amounts of calcite and barite as gangue minerals. Electron microprobe analyses indicate that the sphalerite and tetrahedrite–tennantite have low Fe contents, with values less than 3.37 wt.% and 1.56 wt.%, respectively. The very low Ni and Co contents of the pyrites (< 0.04 wt.%) and the Zn/Cd ratio of the sphalerite (~ avg. 100) indicate that the hydrothermal solutions were related to felsic magmatic activity. The homogenisation temperatures and calculated salinity data vary between 180–436 °C and 0.4–14.7 NaCl % eq., respectively. A well-defined negative correlation between the T_h and the salinity data suggests that meteoric water was involved in the hydrothermal solutions. Based on the measured first melting temperatures, CaCl₂, MgCl₂, NaCl and KCl were dominant in the fluid inclusions. The δ³⁴S compositions of the pyrite, chalcopyrite, sphalerite, and galena mineral separates of the investigated ore veins were measured at between 2.14 and − 1.47‰, and the oxygen and hydrogen isotope compositions varied between 7.8–8.5‰ and − 40 − 57‰, respectively. Based on the sulphur, oxygen and hydrogen isotope compositions, magmatic sources were confirmed for the hydrothermal solutions. Taking into account all of the above data and the granitic intrusions around the area, we concluded that younger granitic intrusions were responsible for the ore mineralisation around the Kabadüz region.     

Insights into ore genesis of the Jinding Zn–Pb deposit,Yunnan Province,China: Evidence from Zn and in-situ S isotopes

The Jinding Zn–Pb deposit located in the Mesozoic-Cenozoic Lanping Basin of southwest China has ore reserves of ∼ 220 Mt with an average grade of 6.1% Zn and 1.3% Pb. The mineralization is hosted by sandstone in the Early Cretaceous Jingxing Formation and limestone breccia in the Paleocene Yunlong Formation. Mineralization in both types of host rocks is characterized by a paragenetic sequence beginning with marcasite–sphalerite (Stage 1) followed by pyrite–marcasite–sphalerite–galena (Stage 2), and then galena–sphalerite–pyrite–sulfate–carbonate (Stage 3). Pyrite from these stages have different δ³³S compositions with pyrite from Stage 1 averaging − 9.6‰, Stage 2 averaging − 8.9‰, and Stage 3 averaging + 0.3‰. Sphalerite hosted by the sandstone has similar δ⁶⁶Zn values ranging from 0.10 to 0.30‰ in all stages of the mineralization, but sphalerite samples from the limestone breccia-hosted ore show variable δ⁶⁶Zn values between − 0.03 and 0.20‰. Our data on sphalerite precipitated during the earlier stages of mineralization has a constant δ⁶⁶Zn value and cogenetic pyrite displays a very light sulfur isotope signature, which we believe to reflect a sulfur source that formed during bacterial sulfate reduction (BSR). The Stage 3 sphalerite and pyrite precipitated from a late influx of metal-rich basinal brine, which had a relatively constant variable δ⁶⁶Zn isotopic composition due to open system isotope fractionation, and a near zero δ³³S composition due to the influence of abiotic thermochemical sulfate reduction from observed sulfates in the host rock.     

Late Hercynian polymetallic vein-type base-metal mineralization in the Iberian Pyrite Belt: fluid-inclusion and stable-isotope geochemistry (S–O–H–Cl)

Late Variscan vein-type mineralization in the Iberian Pyrite Belt, related to the rejuvenation of pre-existing fractures during late Variscan extensional tectonism, comprises pyrite–chalcopyrite, quartz–galena–sphalerite, quartz–stibnite–arsenopyrite, quartz–pyrite, quartz–cassiterite–scheelite, fluorite–galena–sphalerite–chalcopyrite, and quartz–manganese oxide mineral assemblages. Studies of fluid inclusions in quartz, stibnite, and barite as well as the sulfur isotopic compositions of stibnite, galena, and barite from three occurrences in the central part of the Iberian Pyrite Belt reveal compelling evidence for there having been different sources of sulfur and depositional conditions. Quartz–stibnite mineralization formed at temperatures of about 200 °C from fluids which had undergone two-phase separation during ascent. Antimony and sulfide are most probably derived by alteration of a deeper lying, volcanic-hosted massive sulfide mineralization, as indicated by δ³⁴S signatures from ?1.45 to ?2.74‰. Sub-critical phase separation of the fluid caused extreme fractionation of chlorine isotopes (δ³⁷Cl between ?1.8 and 3.2‰), which correlates with a fractionation of the Cl/Br ratios. The source of another high-salinity fluid trapped in inclusions in late-stage quartz from quartz–stibnite veins remains unclear. By contrast, quartz–galena veins derived sulfide (and metals?) by alteration of a sedimentary source, most likely shale-hosted massive sulfides. The δ³⁴S values in galena from the two study sites vary between ?15.42 and ?19.04‰. Barite which is associated with galena has significantly different δ³⁴S values (?0.2 to 6.44‰) and is assumed to have formed by mixing of the ascending fluids with meteoric water.