Isotopic Compositions Of Sulfides Research Articles

Sulfur Isotopic Composition of Sulfides and Sulfates from Rocks of Carbonatite Complexes of the Devonian Kola Alkaline Province

Sulfur Isotopic Composition of Sulfides and Sulfates from Rocks of Carbonatite Complexes of the Devonian Kola Alkaline Province

Sulfur isotope and trace element geochemistry of sulfides from the unique Yaojialing Zn-Au-Cu deposit, Lower Yangtze River Metallogenic Belt, China: Implications for ore-forming process and exploration

The Yaojialing Zn-Au‑Cu deposit is a porphyry-skarn-epithermal vein-type compound deposit that consists of epithermal vein-type lead‑zinc‑silver orebodies, skarn Zn-Cu-Au orebodies, and porphyry CuAu orebodies from shallow level to depth. We decipher the source and metallogenic mechanism by studying the trace element and S isotopic compositions of sulfides (pyrite, sphalerite, chalcopyrite, and galena) from three types of orebodies. The collected pyrite can be divided into two types. PyI coexists with chalcopyrite, and PyII coexists with sphalerite or galena. In addition, PyI was further divided into PyIa (collected from porphyry copper bodies) and PyIb (collected from skarn copper bodies). PyII can be further divided into PyIIa (collected from skarn-type lead‑zinc ore body) and PyIIb (collected from vein lead‑zinc ore body in strata). Sphalerite and galena from skarn-type PbZn ore bodies and shallow vein-type PbZn ore bodies are named SpI and GnI, and SpII and GnII, respectively.Pyrite and sphalerite trace element thermometers revealed that the temperature of the ore-forming fluids decreased from 500 to 600 °C in the porphyry ore body to 300– 360 °C in the skarn ore body and then to 240– 280 °C in the shallow vein ore body. The decrease in the Co and Ni contents of pyrite collected from deep to shallow depths may indicate that meteoric water precipitated in the late ore-forming hydrothermal system. Rapid crystallization and variations in the physicochemical states (such as temperature, pH, fO2, and geochemical composition) of the fluids resulted in an obvious oscillating zone of euhedral PyI pyrite particles. It also affects the solubility of trace metal elements and leads to the selective entry of these elements into pyrite. PyII also shows obvious zonation characteristics rather than oscillating zonation, indicating that the growth rate of pyrite is relatively slow. Moreover, the relationships between the Au and As contents in the two types of pyrite are different. PyI is coupled, while PyII shows decoupling. We believe that this phenomenon is due to the high content of As in ore-forming fluid systems, which may inhibit the absorption of Au on the surface of pyrite rather than the decoupling of Au and As caused by rapid crystallization, based on the rapid increase in As content and non-oscillating zonation in PyII. According to the analysis of the sulfur isotopes of various sulfides, the solid evidences suggest that the ore-forming materials of each type of orebody in the Yaojialing deposit were mainly derived from magmatic-hydrothermal processes and that the fractionation of sulfur isotopes was the result of variations in physicochemical conditions caused by magma-hydrothermal evolution rather than the addition of foreign sulfur sources.

Discovery, geological setting and mineralization of the Shuvuutai molybdenum deposit, central-southern Mongolia

We document the newly discovered Shuvuutai Molybdenum (Mo) porphyry deposit located in the central-east Mongolian volcanic/-plutonic belt of the southern Altaids. The deposit is characterized by quartz vein- and veinlet-disseminated-type Mo ore bodies mainly hosted in a Late Permian-Early Triassic granitic intrusion. In this study, we provide a detailed study that integrates detailed geology with petrographic, mineralogic, geochemical, and geochronologic date to determine the tectonic setting of the deposit. Fluid inclusion analysis is used to reconstruct the fluid evolution history of the Shuvuutai Mo mineralization system and to understand the origin of the deposit. The ore bodies occur mainly as veins, lenses, and pods in positions from inner intrusions through contact zones to the host rocks distal to causative intrusions. The host rocks are variable in lithology, including granites, porphyries, volcanic breccias and tuffs, and sedimentary rocks. Outward from ore bodies to host rocks, the wall rock alteration is zoned from potassic (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alterations. Two samples from porphyry stock intrusions at Shuvuutai were selected for U–Pb zircon geochronology and trace element composition studies, including the ore-hosting monzodiorite porphyry and quartz syenite porphyry. Our new ages are consistent with, or slightly postdate published zircon U-Pb ages of early phase of monzodiorite porphyry (268–232 Ma) and the main phase of quartz syenite porphyry (251.6 ± 1.7 Ma). Hydrothermal mineralization generally includes four stages, from early to late, represented by (1) potassic feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-sulfide stockworks, and (4) quartz ± carbonate veins or veinlets. The ore-forming fluids were initially magmatic in origin and show high-temperature and high-salinity, containing daughter mineral and CO2-bearing fluid inclusions; and eventually evolved to low-temperature, low-pressure, low-salinity and CO2-poor meteoric water. S isotopic compositions of sulfides from the Shuvuutai Mo porphyry deposit indicate that the source of the ore-forming material was derived from the felsic magma. The Central-Eastern Mongolian volcanic-plutonic belt continues from Mongolia into northeast China, where similar Mo deposits are not yet recognized, suggesting that a new exploration strategy, based on the characteristics and history of the Shuvuutai discovery, is needed for the Chinese segment of the Altaids.

Sources and Evolution of Sulfur Isotopic Composition of Sulfides of the Kharaelakh and Pyasino–Vologochan Intrusions, Norilsk Ore Region

Sources and Evolution of Sulfur Isotopic Composition of Sulfides of the Kharaelakh and Pyasino–Vologochan Intrusions, Norilsk Ore Region

Age and mineralization processes of decratonic lode gold deposits in the southern North China Craton: Constraints from trace elements, in-situ S-Pb isotopes and Rb-Sr geochronology of pyrite from the Chen’er gold deposit

The Chen’er gold deposit, with 27 tons of known Au reserves, is one of the typical gold deposits in the Xiaoqinling district along the southern part of the North China Craton. In order to better understand the gold precipitation time and mineralization process, we report in-situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) trace element analyses, elemental maps, and the Rb-Sr and S-Pb isotopic composition of sulfides from the Chen’er gold deposit with a view to gain insights into the mineralization time and process. Trace element analyses and elemental maps of pyrite show that the content of As is low and has no correlation with Au, indicating As is unlikely to have controlled the Au incorporation into pyrite. Gold mainly occurs as solid solutions in the Py Ⅰ and Py Ⅱ, and as Au-Ag and/or Au-Te sub-micrometer inclusions in Py III. The Rb-Sr isotopic data on sulfides from the Chen’er deposit yielded an isochron age of 129.2 ± 3.4 Ma, which overlaps with the previously reported 40Ar/39Ar age of hydrothermal mica, indicating that the gold mineralization occurred in the Early Cretaceous. The in-situ sulfur isotope values of sulfides from stage Ⅱ to stage III fluctuate significantly (the average value decreases from 4.95 to −0.24‰) and were affected by physicochemical parameters of the mineralization process, especially ƒO2. In addition, the δ34S values are in a narrow range (-1.34 to 5.24‰), indicating a magmatic source for the sulfur. In-situ Pb isotopic compositions of the pyrite and galena of stage Ⅱ and stage III are relatively constant with 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb values in the range of 37.264–37.595, 15.364–15.423, 16.992–17.078, respectively, indicating a mixed mantle-crust origin. Based on the new geochronological, geochemical and isotopic data presented in this study, and combined with those from previous studies, we suggest that the lode gold deposits in the Xiaoqinling district are magmatic hydrothermal ore deposits, with metal and ore-forming fluid originating primarily from the mantle, coupled with the cratonic reactivation during the Early Cretaceous.

Magmatic-hydrothermal origin for Carlin-type Au deposits: Evidences from in-situ S-Pb isotopic compositions of sulfides, the Chang’an Au deposit, southern Ailaoshan tectonic zone

The Chang’an Au deposit is a large Au deposit located in the south of the Ailaoshan-Red River tectonic zone, southwestern margin of the South China block. The deposit exhibit characters similar to Carlin-type Au deposits in Nevada and Dian-Qian-Gui “Golden Triangle”, including tectonic evolution (deformed and rifted cratonic margins), orebody controlled by lithology and structure and invisible Au ionically bound in arsenian pyrite and pyrite. Mineralization is controlled by a strike-slip fault and occurs as barren milky quartz veins, disseminated gold-bearing pyrite and arsenopyrite in the Early Paleozoic sandstone, siltstone and limestone. Gold is invisibly and ionically bound in arsenopyrite and pyrite or locally occurs as isolated native gold crystals (micron scale). Wall rock alteration includes sulfide, silicic, sericite and decarbonized alterations. Three hydrothermal mineralizing stages (I, II, III) can be identified: milky quartz-pyrite (I), quartz-sericite-pyrite-arsenopyrite (II) and dolomite-calcite-quartz (III). Different from those deposit in Dian-Qian-Gui, numerous plutons intruded in and around the mine. The syenite dikes are pyritized, thus, formed prior to the mineralization while lamprophyre dikes are unaltered and crosscut by the syenite dikes. The syenite dikes yielded zircon U − Pb ages of ca. 35.8 Ma and the lamprophyre yielded similar Ar-Ar age of ca. 36.6 Ma, largely constraining the age of Au mineralization. In situ S–Pb isotopic compositions for ore pyrite and arsenopyrite were measured by fs-LA-MC-ICP-MS. Sulfides from Chang’an show a uniform range from –6.4‰ to + 4.6‰, a typical characteristic of magmatic-derived S. Such sulfur isotopic compositions are similar to those of sulfides from Carlin-type Au deposits, but different from those of sulfides from orogenic-type deposit, which commonly exhibit a wide range of δ34S values. Pb isotopic ratios of pyrite and arsenopyrite are similar to those of the intrusive rocks in the deposit with more radiogenic Pb, suggesting that the metal is probably sourced from the coeval intrusive rocks and sedimentary wall rocks. Combined with the low Au concentrations of the sedimentary wall rocks, Au in the Chang’an deposit are probably sourced from the intrusive rocks. Differences between the Chang’an deposit and typical orogenic-type Au deposit include: (1) Orebodies in the Chang’an deposit exhibit transitional contact relationship with the host rocks and boundaries between them are defined by cut-off grade while these boundaries in typical orogenic-type deposits are clearly defined. (2) Sulfidized and decarbonized alterations are quite significant in the Chang’an deposit but commonly absent in typical orogenic-type deposits. (3) The Chang’an deposit have lower CO2 contents of ore-forming fluids and more shallow ore-forming depth relative to typical orogenic-type deposits. Based on the ore deposit geology, dating and isotopic data, the Chang’an mineralization is similar to typical Carlin-type gold deposit, formed by ore fluids originated from a deep magmatic S source in an post-collisional intracontinental setting at ca. 36 Ma.

Active microbial sulfate reduction in fluids of serpentinizing peridotites of the continental subsurface

Serpentinization of peridotites in Earth’s mantle is associated with the generation of hydrogen and low molecular weight organics that could support subsurface life. Studies of microbial metabolisms in peridotite-hosted environments have focused primarily on methanogenesis, yet DNA sequences, isotopic composition of sulfides and thermodynamic calculations suggest there is potential for microbial sulfate reduction too. Here, we use a sulfate radiotracer-based method to quantify microbial sulfate reduction rates in serpentinization fluids recovered from boreholes in the Samail Ophiolite, Oman and the California Coast Range Ophiolite, USA. We find that low levels of sulfate reduction occur at pH up to 12.3. These low levels could not be stimulated by addition of hydrogen, methane or small organic acids, which indicates that this metabolism is limited by factors other than substrate availability. Cellular activity drops at pH > 10.5 which suggests that high fluid pH exerts a strong control on sulfate-reducing organisms in peridotites.

Constraints of S–Pb–Sr Isotope Compositions and Rb–Sr Isotopic Age on the Origin of the Laoyingqing Noncarbonate-Hosted Pb–Zn Deposit in the Kunyang Group, SW China

The Laoyingqing Pb–Zn deposit is located on the southwestern margin of the Yangtze block and on the east side of the Xiaojiang deep fault in the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic triangle area (SYGT). This deposit was first discovered in the silty and carbonaceous slate of the Middle Proterozoic Kunyang Group that is structurally controlled by thrust faults and anticlines. This study is aimed at investigating whether the Laoyingqing deposit has the same ore-forming age and type as other Pb–Zn deposits related to the Pb–Zn metallogenic system and prospecting prediction of the deep and peripheral areas of the deposits in the SYGT. Based on the sphalerite Rb–Sr age dating and S–Sr–Pb isotopic composition analysis of the Laoyingqing Pb–Zn deposit, the following results were obtained. First, the Rb–Sr isochron age of sphalerite is 209.8 ± 5.2 million years (Ma), consistent with the ages of most Pb–Zn deposits in the SYGT (approximately 200Ma), thereby potentially indicating that these Pb–Zn deposits may have been formed synchronously during the late Indosinian orogeny. Second, the Pb isotopic compositions of sulfides show a linear trend on the average crustal Pb evolution curve in 207Pb/204Pb vs. 206Pb/204Pb plot. In addition, Pb isotopic ratios were consistent with the age-corrected Pb isotopic ratios of basement rocks, consequently suggesting that the source of mixed crustal Pb is mainly derived from basement rocks. Combined with the initial 87Sr/86Sr ratios of sphalerite between the (87Sr/86Sr)200Ma value of the basement rocks and that of the Upper Sinian–Permian carbonates, it can be concluded that the ore-forming metals were mainly derived from basement rocks. Third, sulfur isotopic composition of sphalerite from the Laoyingqing deposits shows δ34SCDT values that range mainly from -2.62‰ to 1.42‰, which is evidently lower than the δ34SCDT values of sulfides (8–20‰) from other Pb–Zn deposits in the SYGT. This can be interpreted as a result of mixing with reduced S that was mainly derived from the thermochemically reduced S in the overlying strata and a small amount of reduced S produced by the pyrolysis of S-containing organic matter. We conclude that the Laoyingqing deposit and most of the Pb–Zn deposits in the SYGT are Mississippi Valley-type deposits, thereby providing new ideas for investigating the deep and peripheral areas of Pb–Zn deposits.

Geological, sulfur isotopic, and mineral trace element constraints on the genesis of the Xiyi Pb–Zn deposit, Baoshan Block, SW China

The recently discovered Xiyi Pb–Zn deposit in Yunnan Province, SW China, contains 1.2 Mt of Pb and Zn metal. It is located within the Baoshan Block, in the Sanjiang Tethys orogenic belt and is hosted along fractures within carbonates of the Lower Carboniferous Xiangshan Formation. The deposit is hosted by veins within NE–SW trending strike-slip and steeply dipping NW–SE trending normal fault zones. The formation of the deposit involved sedimentary, hydrothermal, and supergene oxidation stages. The hydrothermal stage associated with mineralization include three sub-stages (i) a steeply-dipping quartz–calcite-rich sphalerite sub-stage; (ii) a polymetallic sulfide sub-stage; and (iii) a vein-host calcite–pyrite sub-stage. The deposit is enriched in Pb, Zn, Sb, Cd, Ag, and U, and depleted in Ni, Se, Ti, and Co. The ores have total rare-earth element (REE) concentrations of 17.4–186 ppm and are enriched in the light REE (LREE) with (La/Yb)N ratios of 3.75–9.23 and strongly positive Eu (Eu/Eu* = 1.42–4.60) and slightly negative Ce (Ce/Ce* = 0.70–0.88) anomalies. The positive Eu anomalies and LREE enrichment suggest that the ore-forming fluids were exsolved from a concealed intrusion during magmatic degassing. The S isotopic compositions of sulfides and sulfates indicate that S within the deposit was derived from both magmatic sources and barite within the hosting carbonates via thermochemical sulfate reduction. In-situ LA–ICP–MS analysis indicates that sphalerite within the deposit is texturally and chemically variable, with elevated Fe, Mn, Cd, Cu, Ag, Sb, Sn, Pb, and Tl contents. In comparison, galena within the deposit is enriched in Sb, Ag, Cd, Sn, and Tl, and pyrite has elevated Ag, As, Sb, and Pb contents. The trace element compositions of sphalerite and galena indicate that the Xiyi deposit may be the product of a distal hydrothermal event although the direct genetic relationship is not clear. The fracture-hosted nature, mineral assemblages, geochemistry, and mineral S isotopic and trace-element compositions of the Xiyi Pb–Zn deposit indicate that it is an epigenetic carbonate-hosted Pb–Zn deposit. This study also indicates that sphalerite is a more useful mineral than galena in terms of using mineral trace-element geochemistry to discriminate different deposit types.

Isotopic Compositions of Sulfides in Exhumed High‐Pressure Terranes: Implications for Sulfur Cycling in Subduction Zones

AbstractSubduction is a key component of Earth's long‐term sulfur cycle; however, the mechanisms that drive sulfur from subducting slabs remain elusive. Isotopes are a sensitive indicator of the speciation of sulfur in fluids, sulfide dissolution‐precipitation reactions, and inferring fluid sources. To investigate these processes, we report δ34S values determined by secondary ion mass spectroscopy in sulfides from a global suite of exhumed high‐pressure rocks. Sulfides are classified into two petrogenetic groups: (1) metamorphic, which represent closed‐system (re)crystallization from protolith‐inherited sulfur, and (2) metasomatic, which formed during open system processes, such as an influx of oxidized sulfur. The δ34S values for metamorphic sulfides tend to reflect their precursor compositions: −4.3 ‰ to +13.5 ‰ for metabasic rocks, and −32.4 ‰ to −11.0 ‰ for metasediments. Metasomatic sulfides exhibit a range of δ34S from −21.7 ‰ to +13.9 ‰. We suggest that sluggish sulfur self‐diffusion prevents isotopic fractionation during sulfide breakdown and that slab fluids inherit the isotopic composition of their source. We estimate a composition of −11 ‰ to +8 ‰ for slab fluids, a significantly smaller range than observed for metasomatic sulfides. Large fractionations during metasomatic sulfide precipitation from sulfate‐bearing fluids, and an evolving fluid composition during reactive transport may account for the entire ~36 ‰ range of metasomatic sulfide compositions. Thus, we suggest that sulfates are likely the dominant sulfur species in slab‐derived fluids.

A Case History of Applying In situ Analysis of the Sulfur Isotopic Compositions of Sulfides from Ores of the Largest Deposits in the Bodaibo Synclinorium (Eastern Siberia)

The experience of applying the laser ablation technique to study the sulfur isotopic compositions of pyrite and arsenopyrite samples from gold deposits of the Baikal–Patom highland is discussed. The experimental procedure is described. All studied samples were found to display δ34S and δ33S values in strict compliance with the law of mass-dependent sulfur isotope fractionation. Regular lightening of the sulfur isotope composition in the course of crystal growth for pyrites from the Sukhoi Log deposit and the isotopic homogeneity of pyrite and pyrrhotite from the Golets Vysochaishii deposit were established. The conclusion that the sulfur isotopic homogeneity of sulfides in the ores occurs probably owing to metamorphism within the Mama–Oron belt was made.

Fluid Inclusions, Stable Isotopes, and Geochronology of the Haobugao Lead‐Zinc Deposit, Inner Mongolia, China

AbstractThe Haobugao deposit, located in the southern segment of the Great Xing'an Range, is a famous skarn‐related Pb‐Zn‐(Cu)‐(Fe) deposit in northern China. The results of our fluid inclusion research indicate that garnets of the early stage (I skarn stage) contain three types of fluid inclusions (consistent with the Mesozoic granites): vapor‐rich inclusions (type LV, with VH2O/(VH2O + LH2O) < 50 vol %, and the majority are 5–25 vol %), liquid‐rich two‐phase aqueous inclusions (type VL, with VH2O/(VH2O + LH2O) > 50 vol %, the majority are 60–80 vol %), and halite‐bearing multiphase inclusions (type SL). These different types of fluid inclusions are totally homogenized at similar temperatures (around 320–420°C), indicating that the ore‐forming fluids of the early mineralization stage may belong to a boiling fluid system. The hydrothermal fluids of the middle mineralization stage (II, magnetite‐quartz) are characterized by liquid‐rich two‐phase aqueous inclusions (type VL, homogenization temperatures of 309–439°C and salinities of 9.5–14.9 wt % NaCl eqv.) that coexist with vapor‐rich inclusions (type LV, homogenization temperatures of 284–365°C and salinities of 5.2–10.4 wt % NaCl eqv.). Minerals of the late mineralization stage (III sulfide‐quartz stage and IV sulfide‐calcite stage) only contain liquid‐rich aqueous inclusions (type VL). These inclusions are totally homogenized at temperatures of 145–240°C, and the calculated salinities range from 2.0 to 12.6 wt % NaCl eqv. Therefore, the ore‐forming fluids of the late stage are NaCl‐H2O‐type hydrothermal solutions of low to medium temperature and low salinity. The δD values and calculated δ18OSMOW values of ore‐forming fluids of the deposit are in the range of −4.8 to 2.65‰ and −127.3‰ to −144.1‰, respectively, indicating that ore‐forming fluids of the Haobugao deposit originated from the mixing of magmatic fluid and meteoric water. The S‐Pb isotopic compositions of sulfides indicate that the ore‐forming materials are mainly derived from underlying magma. Zircon grains from the mineralization‐related granite in the mining area yield a weighted 206Pb/238U mean age of 144.8 ±0.8 Ma, which is consistent with a molybdenite Re‐Os model age (140.3 ±3.4 Ma). Therefore, the Haobugao deposit formed in the Early Cretaceous, and it is the product of a magmatic hydrothermal system.

He, Ar, and S isotopic compositions and origin of giant porphyry Mo deposits in the Lesser Xing’an Range–Zhangguangcai Range metallogenic belt, northeast China

The Lesser Xing’an Range–Zhangguangcai Range metallogenic belt, located at the eastern segment of the Central Asian metallogenic domain, hosts two giant Mo porphyry deposits, the Early Jurassic Luming deposit and the Middle Jurassic Daheishan deposit. In this study, the He–Ar and S isotopic compositions of sulfides from different hydrothermal stages of the Daheishan and Luming deposits were determined. Fluid inclusions hosted in pyrites shown that 3He/4He ratios of the Luming and Daheishan deposit range from 0.02 to 0.32 Ra, and 0.7 to 2.5 Ra, respectively. 40Ar/36Ar ratios of the Luming and Daheishan deposit range from 313.3 to 535.1, and 309.9 to 360.6, respectively. He and Ar isotopic compositions suggest that the ore-forming fluids of the Luming deposit are mainly crustal-derived fluids, with near atmospheric Ar and crustal He values. Mantle-derived fluids are a minor component. In contrast, the ore-forming fluids of the Daheishan deposit are a mixture between a crust-derived fluid and a mantle-derived fluid. The δ34S values of the sulfide samples from the Luming deposit (4.98–7.14‰) and the Daheishan deposit (1.83–2.88‰) indicate that the sulfur in the ore-forming fluids was primarily derived from granitic magma. The isotopic compositions across the stages within one deposit have no variability. The similar He–Ar and S isotopic compositions of the sulfides from the different Mo-bearing hydrothermal stages of these two giant Mo deposits indicate that the overprinting of the multiple stages of Mo-bearing hydrothermal fluids may be a key factor in the formation of giant porphyry Mo deposits. Meanwhile, the westward subduction of the Paleo-Pacific plate might have played an important role for the formation of the giant Mo deposits in the Lesser Xing’an Range–Zhangguangcai Range metallogenic belt.

Sulfur Isotopic Composition of Sulfides of the Au-Te Ore Mineralization in Podgolechnoe and Samolazovskoe Gold-Ore Deposits (Aldan Shield, Russia)

This work presents the results of an analysis of the sulfur isotopic composition of pyrites from different metasomatic rocks of the Samolazovskoe and Podgolechnoe (Central Aldan ore district) deposits. The sulfur isotopic ratio of pyrite from ore-bearing metasomatic rocks of the Podgolechnoe deposit is characterized by δ34S values varying in a range from –1.8 to –5.5 ‰; that of pyrite from the Samolazovskoe deposit is in a range from –6.9 to –12.3‰. This is in agreement with the suggestion that a magmatic source made a significant contribution to the formation of the ore-forming fluid.

Sulfur Isotopic Composition of Sulfides in Skarn and Vein Mineralization of the Dal’negorsk Ore Region (Primorye)

The S isotopic composition in the ore-forming minerals galena and sphalerite was studied in different Ag–Pb–Zn deposits of the region. It was pointed out that the δ34S modal values range from–1.2 to +6.7‰ in the minerals with a positive value for the skarn mineralization. In the flyschoid formation, the vein-type mineralization is characterized by negative and positive values. The narrow range of δ34S values indicates the marginal-continental type of the mineralization and the multiple origins of its sources.

Zircon U–Pb and molybdenite Re–Os geochronology, with S isotopic composition of sulfides from the Chah-Firouzeh porphyry Cu deposit, Kerman Cenozoic arc, SE Iran

The Chah-Firouzeh deposit with about 100 Mt ore reserves @ 0.5% Cu is a porphyry copper deposit located 14km west of the Meiduk deposit in the northern section of the Kerman Cenozoic Magmatic Assemblage (KCMA), southeastern Iran. The mineralization is associated with a porphyry quartz-monzodiorite to quartz-diorite stock, which intruded into Eocene volcanic rocks consisting of andesite, basalt, and andesitic to dacitic tuff. Hydrothermal alteration types in the area include potassic, phyllic, and propylitic varieties. Silicic alteration locally occurred at the surface, while supergene argillic alteration overprinted the other alterations at shallow levels. Mineralization occurs as quartz-sulfide veinlets and stockworks, as well as disseminations in the porphyry body and volcanic host rocks, in association with potassic and phyllic alteration. Hypogene minerals in the deposit include pyrite, chalcopyrite, magnetite, molybdenite, and bornite. Supergene enrichment is irregularly developed in the Chah-Firouzeh deposit.Zircon U–Pb dating of two representative samples from the Chah-Firouzeh porphyry stock yielded emplacement ages of 16.9±0.4Ma and 16.5±0.2Ma, respectively. The Early-Middle Miocene epoch marks the most important period of porphyry Cu mineralization in the KCMA. During this period, many adakitic magmas intruded the Eocene volcano-sedimentary sequences and formed some of the largest porphyry copper deposits in Iran, such as Sarcheshmeh and Meiduk. Molybdenite Re–Os dating on two samples separated from “B and D type” veinlets show that mineralization occurred at 16.60±0.06Ma and 15.99±0.06Ma, implying a time span of about 0.6Ma for mineralization.The δ34S values for molybdenite, chalcopyrite, and pyrite from “A, B, and D type” veinlets vary from −1.4 to +2.5‰ suggesting a magmatic source for sulfur. The calculated temperatures for sulfide pairs are compatible with those obtained from fluid inclusion microthermometry and show isotope equilibrium due to fluid evolution.

Early Cretaceous tungsten mineralization in Southeastern China: the Wuning example

ABSTRACTThe Wuning tungsten deposits in northwestern Jiangxi are located in the Middle-Lower Yangtze River metallogenic belt of SE China. This article decodes the large tungsten-mineralized ore field by analysing three typical deposits: Shimensi, Dahutang, and Shiwendong. The Shimensi deposit shows three mineralization styles, and the associated hydrothermal alteration mainly includes K-feldspathization, greisenization, chloritization, silicification, and carbonatization. The sulphur isotopic compositions of sulphides in the Dahutang deposit indicate that the sulphur source was homogeneous and closely related to magmatic sulphur. The lead isotopic compositions of sulphides suggest multiple sources that were also closely related to magmatism. The carbon isotopic compositions of calcite indicate that hydrothermal fluids were derived from the granitic magma. Hydrogen and oxygen isotopic compositions of quartz veins indicate that the ore-forming fluids had a magmatic-hydrothermal origin, but mixed with meteoric water. Fluid inclusions from the Shiweidong deposit are low density, indicating medium-high T and low-medium salinity, further suggesting that it was a shallow magmatic-hydrothermal deposit, and the metallogenic hydrotherm mingled with the surface water late in the evolution of the system. Mineralization was related to Early Cretaceous magmatism in eastern China. The subduction of the palaeo-Pacific plate and the subsequent lithospheric delamination reflected transition from a compressional to extensional tectonic regime. The upwelling of the hot asthenosphere triggered partial melting of the Neoproterozoic Shuangqiaoshan Group, with high W background concentrations. The ascent of the magma resulted in the exsolution of the ore-bearing magmatic hydrothermal fluid.

Multiple sulfur isotopes fractionations associated with abiotic sulfur transformations in Yellowstone National Park geothermal springs.

BackgroundThe paper presents a quantification of main (hydrogen sulfide and sulfate), as well as of intermediate sulfur species (zero-valent sulfur (ZVS), thiosulfate, sulfite, thiocyanate) in the Yellowstone National Park (YNP) hydrothermal springs and pools. We combined these measurements with the measurements of quadruple sulfur isotope composition of sulfate, hydrogen sulfide and zero-valent sulfur. The main goal of this research is to understand multiple sulfur isotope fractionation in the system, which is dominated by complex, mostly abiotic, sulfur cycling.ResultsWater samples from six springs and pools in the Yellowstone National Park were characterized by pH, chloride to sulfate ratios, sulfide and intermediate sulfur species concentrations. Concentrations of sulfate in pools indicate either oxidation of sulfide by mixing of deep parent water with shallow oxic water, or surface oxidation of sulfide with atmospheric oxygen. Thiosulfate concentrations are low (<6 μmol L-1) in the pools with low pH due to fast disproportionation of thiosulfate. In the pools with higher pH, the concentration of thiosulfate varies, depending on different geochemical pathways of thiosulfate formation. The δ34S values of sulfate in four systems were close to those calculated using a mixing line of the model based on dilution and boiling of a deep hot parent water body. In two pools δ34S values of sulfate varied significantly from the values calculated from this model. Sulfur isotope fractionation between ZVS and hydrogen sulfide was close to zero at pH < 4. At higher pH zero-valent sulfur is slightly heavier than hydrogen sulfide due to equilibration in the rhombic sulfur–polysulfide – hydrogen sulfide system. Triple sulfur isotope (32S, 33S, 34S) fractionation patterns in waters of hydrothermal pools are more consistent with redox processes involving intermediate sulfur species than with bacterial sulfate reduction. Small but resolved differences in ∆33S among species and between pools are observed.ConclusionsThe variation of sulfate isotopic composition, the origin of differences in isotopic composition of sulfide and zero–valent sulfur, as well as differences in ∆33S of sulfide and sulfate are likely due to a complex network of abiotic redox reactions, including disproportionation pathways.

Pb Isotopic Geochemistry of Carbonate-Hosted Pb-Zn Deposits, NW Guizhou Pb-Zn Metallogenic District, China

The NW Guizhou Pb-Zn metallogenic district is an important part of the Yunnan – Sichuan - Guizhou Pb-Zn metallogenic province (SYG), and also is one of the important Pb-Zn producers in China. We analyzed the Pb isotopic compositions of sulfides, hosting rocks and basement rocks, the results show that the206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios of sulfides range from 18.029 to 19.900, 15.357 to 17.716 and 38.004 to 40.695, respectively. The206Pb/204Pb,207Pb/204Pb and208Pb/204Pb ratios of hosting rocks and basement rocks range from 18.397 to 19.483, 15.545 to 16.700 and 38.204 to 39.140, respectively. This indicates that the compositions of Pb isotopes of sulfides are basically consistent with that of hosting rocks and basement rocks, so the metals were sourced from various strata of carbonate rocks and underlying rocks.

Sulfur isotopic composition of sulfides at the Mangazeya silver deposit, Eastern Sakha-Yakutia, Russia

The succession of the formation of ore zones and sulfur isotope ratio of sulfides at the Mangazeya Ag deposit have been studied. The deposit is located in the Nyuektame Fault Zone in the eastern limb of the Endybal Anticline. The ore zones are hosted in the Middle Carboniferous to Middle Jurassic terrigenous sequences of the Verkhoyansk Complex intruded by the Endybal subvolcanic stock and felsic and mafic dikes. Three ore stages are distinguished: (I) gold-rare metal, (II) cassiterite-sulfide, and (III) silver-base-metal. Products of these stages are spatially isolated. The δ34S of sulfides ranges from −6.4 to +8.0‰. In the sulfides of the gold-rare metal assemblage, this value varies from −1.8 to +4.7‰; in the sulfides of the cassiterite-sulfide stage, −6.4 to +6.6‰; and in the sulfides of the silver-base-metal assemblage, -5.6 to +8.0‰. A sulfur isotope thermometer indicates the temperature of mineral deposition at 315–415°C for the first stage and 125–280°C for the third stage. Possible causes of variable sulfur isotopic composition in sulfides are discussed. The data on the sulfur isotope ratio is interpreted in terms of involvement of magmatic fluid (δ34S ∼ 0) in the mineralizing process along with low-temperature fluid taking sulfur from host rocks (δ34S ≫ 0). Boiling and mixing of magmatic fluid with heated meteoric water were important at the last stage of the deposit formation.