Sulfide Sulfur Research Articles

The Application of Sulfur–Metal Mass Ratios in Metal Sulfides in Assessing Prospects for Deep Metallogeny: A Case Study of the Tongshan Copper Deposit in Heilongjiang Province, Northeast China

Sulfur–metal mass ratios (SMMRs) between sulfur and metal elements (Cu, Pb, Zn, Ag, Fe, etc.) in metal sulfides are fixed in idealized compositions, so they should have a relatively fixed proportion in terms of mass without considering the presence of structural defects such as vacancies or substitution elements. Rock bodies with an SMMR of S far greater than the common metal sulfides may contain additional sulfides of other metals. We studied the Tongshan copper deposit in NE China and calculated the mass transfer of various elements in drill hole ZK611 samples. The data show a S influx of 7160 g/t, a Cu influx of 5469 g/t, and an Fe influx of 8796 g/t in the Cu ore body. Below the Cu ores, the average influx is 18,600 g/t of S, 650 g/t of Cu, and 5360 g/t of Fe, which provides an SMMR far above common mineral sulfide values. Further studies indicated that this rock unit contains fine-grained sphalerite and galenite, and when Zn and Pb are included in the rock SMMR calculations, values closer to the mineral sulfides emerge. These results imply that the coordinating balance relationship of S content with Fe and other ore-forming metals could provide direct information for assessing metallogenic prospects.

Метано- и сульфидогенез в озерах полуострова Абрау (Краснодарский край)

The geographical position, tectonic and geological-hydrogeological structure of the basin of the Malyy Liman and Abrau lakes, their landscape features as natural monuments of regional importance located on the territory of the Abrau peninsula of the Krasnodar Territory are described. Using the example of the aquatic landscapes of the Malyy Liman and Abrau lakes and the river of the same name, water and bottom sediments were studied. Hydrochemical parameters, the content of methane and sulfide sulfur in bottom sediments and methane in water as components of aquatic landscapes were studied. The results of the determination of sulfides, as well as the characteristic odor and color of bottom sediments, indicate the presence of free H2S and hydrotroilite (FeS ∙ nH2O) in them. Electron microscopy revealed the presence of hollow spheres in the bottom sediments, which indicates their possible gas saturation. Microinclusions of biogenic pyrite (FeS2), which was formed on fragments of plant and organism residues, were found under an electron microscope. In aerobic-anaerobic conditions of the upper layer of bottom sediments of lakes, pyrite formation occurs both directly through a one-stage process of pyritization of reactive iron, but also through a multi-stage process of pyrite formation from iron monosulfide. It has been established that lakes are exposed to anthropogenic influences, which can increase many times during the holiday season. This leads to their eutrophication and increased meanogenesis, which in turn contributes to the activation of methane emissions into the atmosphere. Specific methane fluxes from the water surface of the Malyy Liman and Abrau lakes have been determined.

Methane and Sulfide Sulfur in Water and Bottom Sediments of Watercourses of the Steppe Zone of the European Part of Russia

Methane and Sulfide Sulfur in Water and Bottom Sediments of Watercourses of the Steppe Zone of the European Part of Russia

Atmosphere and biological impact during sulfide formation in the Archean Central-Vozhma sulfide deposit (Karelia)

Relevance. The need of new knowledge about the early stages of the Earth. Sulfur isotope analysis of sulfide minerals is a powerful tool to understand the processes during the Archaean and Paleoproterozoic. Combined with other data, isotope geochemistry provides an insight into sulfur sources of sulfides from ancient sulfide volcanosedimentary deposits; geochemical factors affecting Archaean sulfide volcanosedimentary ore formation; adjust genetic models and determine the degree of influence of bacteria on the mineral formation. Aim. To identify the sources of sulfur during the formation of sulfide deposits via isotope analysis, and to evaluate bacteria affect mineral formation. Objects. They were obtained from the core of boreholes of Mesoarchaean volcanosedimentary sulfide Central-Vozhma deposit, being a part of the Sumozersko-Kenozersky greenstone belt of the Karelian craton. Methods. Mineralogical studies of rock and ore samples were carried out using optical microscopy; scanning electron microscopy and energy dispersive X-ray spectroscopy. The ratios of four stable sulfur isotopes were analyzed in sulfide minerals of the deposit (33S/32S, 34S/32S, 36S/32S). Results. The results obtained demonstrated the polygenic source of sulfur in sulfides. The sulfides have both positive and negative Δ33S values, indicating the presence of atmospheric sulfur formed under UV photolysis during mineral formation. Sulfide minerals include the following components: Seawater sulfate sulfur of photolytic genesis showed a negative anomaly Δ33S (∼ –0.4‰). It was the source of authigenic pyrite. Sulfides crystallized as a result of biological sulfate reduction demonstrated a narrow range of δ34S values (–2.64‰˂0˂+4.27‰). Elemental sulfur of photolytic genesis mobilized from the host sedimentary rocks by hydrothermal fluids. This sulfur, with a positive Δ33S anomaly (up to +1.6‰) took part in the massive sulfide ores formation.

Hollow-structured cobalt sulfoselenide as cathode host to enhance the kinetics and improve the energy density of lithium-sulfur batteries

Lithium-sulfur batteries are a promising next-generation battery system due to their high energy density, low cost, and environmental friendliness. However, the shuttle effect and resulting low redox kinetics are significant issues that currently hinder their development. The addition of catalysts to accelerate the redox process is a common strategy. Metal sulfide catalysts, in particular, have been widely studied due to their good affinity for sulfur and sulfides. Although metal sulfide show good adsorption performance for lithium polysulfides, their low conductivity does not significantly improve the kinetic performance of the battery. Additionally, the high molecular weight of the inactive sulfide leads to the low actual energy density of the battery. Thus, this study constructed the hollow structural cobalt sulfoselenide by replacing partial elemental sulfur in cobalt sulfide (Co3S4) with the higher metallicity element selenium (Se). This was done to increase catalytic activity and reduce the amount of inactive substances, ultimately leading to an increase in actual energy density. This strategy systematically investigated the electrical conductivity, catalytic activity, and inhibition of the shuttle effect of Co3S2Se2. It was found that cobalt sulfoselenide with a 1:1 ratio of sulfur to selenium exhibited higher catalytic activity than pure cobalt sulfide. Additionally, the hollow structure of cobalt sulfoselenide showed greater performance enhancement than bulk cobalt sulfoselenide. In the assembled lithium-sulfur battery, the initial specific capacity of 1294.7 mAh/g at 0.1C was obtained, and the capacity retention was 77.5 % after 100 cycles. On this basis, the structure–activity relationship between selenium-sulfur ratio and electrochemical properties will provide ideas for the design of microscopic cathode structures.

Geochemical Thermometry of Ore-Bearing Gabbronorites from the Apophisis of the Yoko-Dovyren Massif: Composition, Amount of Olivine, and Conditions of Sulphide Saturation in the Parental Magma

The temperature and compositional parameters of the parental magma of the ore-bearing apophysis DV10 from the Yoko-Dovyren massif are estimated based on the results of thermodynamic modeling the equilibrium crystallization of melts of 24 samples, following the method of geochemical thermometry. Thermometric calculations were carried out using the COMAGMAT-5.3 program with a step of 0.5 mol. % to a maximum degree of crystallization 75–85% under oxygen fugacity controlled by the QFM buffer. The model order of mineral crystallization corresponds to the sequence: olivine (Ol) + + Cr-Al spinel (Spl) → plagioclase (Pl) → high-Ca pyroxene (Cpx) → orthopyroxene (Opx). Silicate-sulfide immiscibility was modeled to occur mostlybefore the onset of plagioclase crystallization, being consistent with sulfide saturation of the parental magma. The results of calculations demonstrate the convergence and intersection of the model liquid lines of descent at temperatures of about 1185°C. When applied to the average composition of the DV10 apophysis, this temperature indicates the existence of a suspension of the original crystals (52.1 wt. % cumulus olivine (Fo83.6), 2.3 wt. % plagioclase (An79.7), 0.24% clinopyroxene (Mg# 88.8), 1 wt. % aluminochromite (Cr# 0.62)) and about 0.2% sulfide liquid in a moderately magnesian melt (53.6 wt. % SiO2, 7.4 wt. % MgO). At that the solubility of sulfide sulfur (SCSS) was estimated to be 0.083 wt. %. This heterogeneous system had a viscosity of 4.71 log. units (Pa · s) and an integral density of 2929 kg/m3. Such rheological properties do not contradict the possibility of the migration and emplacement of the protocumulus mush from the main Dovyren chamber. However, a more probable scenario includes a localized accumulation of olivine in the trough-like part of the DV10 subchamber, which preceded or occurred in parallel to the accumulation of segregated sulfides.

Cd–Pb isotopic characteristics within the Hehuashan carbonate-hosted Pb–Zn deposit, Middle-Lower Yangtze River Metallogenic Belt: Constraints for ore-forming metal sources and implications for exploration

The Hehuashan carbonate-hosted Pb–Zn deposit is a large-scale deposit situated in the Middle-Lower Yangtze-River Metallogenic Belt (MLYRMB) in China. It contains 0.99 million tons of Zn at an average grade of 1.5 % and 0.41 million tons of Pb at an average grade at 1.9 %, accompanied by critical metals of Cd and Ga. The ores are mainly composed of breccia-type and vein-type in the deposit. Though previous chemical compositions of sphalerite showed that Cd is enriched in both two types of mineralization and the sulfide sulfur isotopes research showed that the reduced sulfur is derived from the marine sulfate reduction, the source of ore-forming metals is still unclear. In this research, we studied the non-traditional stable isotope of Cd and the radioactive isotope Pb of the Hehuashan deposit to discuss the ore-forming metal sources and provide genesis constraints to the Hehuashan Pb–Zn deposit. The sphalerite Cd isotopic compositions are relatively concentrated but the Zn/Cd ratios are scattered in the Hehuashan deposit, of which the early-stage sphalerite δ114/110Cd values ranged from 0.21 ‰ to 0.30 ‰ with an outlier of 0.09 ‰, mean of 0.22 ‰ and a wide range of Zn/Cd ratios (78 to 430), and the late-stage sphalerite δ114/110Cd values ranged from 0.09 ‰ to 0.15 ‰ with two outliers of −0.05 ‰ and 0.52 ‰, mean of 0.17 ‰ with also a wide range of Zn/Cd ratios (50 to 286), both stages of Cd isotopic compositions are overlapped with the ranges of diorite and OIB & MORB, implying the Cd is might be derived from the dioritic intrusions of the Hehuashan deposit district, and the varied Zn/Cd ratios imply that the limestone also provided some of ore-forming metals to the both two ore-forming stages. Additionally, the Pb isotopic compositions of galena in the two mineralization stages exhibit a concentrated range (206Pb/204Pb = 18.2806 – 18.4190, 207Pb/204Pb = 15.6262 – 15.6484, and 208Pb/204Pb = 38.5710 – 38.6529) and all the Pb isotopic data points of the Hehuashan deposit are plotted in the right-hand side of the geochron and the overlapped field of marine sediments, Tongling dioritic intrusions, and Lower Triassic limestones in the Tongling area in the diagrams of (207Pb/204Pb)i vs. (206/204Pb)i and in the field (208Pb/204Pb)i vs. (206/204Pb)i, implying that the Pb is mainly derived from the magma of dioritic intrusions and marine sediments. Subsequently, the sulfide Cd–Pb isotopic compositions show that the ore-forming metals in the Hehuashan deposit are mainly originated from the dioritic intrusions and marine sediments. The plots of deposit genesis classification show that the Cd isotopic compositions in the Hehuashan deposit are unsuitable to the plots of δ114/110Cd vs. Zn/Cd ratios, but imply the metals were derived from multi sources. Finally, the Cd-Pb studies of the Hehaushan Pb–Zn deposit show that the earlier Lower Triassic carbonate formations and its contact with dioritic rocks should be ideal exploration targets for Pb–Zn and associated Cd sources in the Tongling mining area.

Precipitation of Ag-Pb-Zn ores of the Poshan vein deposit in the Qinling orogen (central China) by dilution of magmatic hydrothermal fluids

Abstract Constraints on the source, nature, and evolution of ore-forming fluids are crucial for better understanding the ore genesis and mechanisms that lead to metal precipitation. Here, we present results of in situ analysis for quartz oxygen isotopes and sulfide sulfur isotopes, combined with apatite U-Pb age and fluid inclusion data, to provide insights into the source and evolution of ore fluids of the Poshan Ag-Pb-Zn vein deposit in the Qinling orogen, central China. Quartz-carbonate-sulfide veins at Poshan are hosted in lower Paleozoic metavolcanic-sedimentary rocks and structurally controlled by fracture zones associated with the Heqianzhuang anticline. The Ag-Pb-Zn mineralization consists of three stages, which are represented by quartz-pyrite-arsenopyrite (stage I), quartz-carbonate-sulfide-silver minerals (stage II), and quartz-calcite ± native silver (stage III). Apatite texturally associated with galena from stage II has a U-Pb age of 125 ± 14 Ma (2σ; mean square of weighted deviates [MSWD] = 0.9), which suggests that the Poshan deposit formed in the Early Cretaceous and thus significantly postdated the Paleozoic and early Mesozoic orogenic deformation of the Qinling orogen. Aqueous-carbonic fluid inclusions from stages I and II have similar total homogenization temperatures of 263–347 °C and calculated salinities of 1.2–5.1 wt% NaCl equivalent, whereas the values for liquid-dominated aqueous inclusions from stage III are 211–245 °C and 0.5–3.0 wt% NaCl equivalent. Five quartz generations are recognized from the three paragenetic stages, including Qz-1 and Qz-2 from stage I, Qz-3 and Qz-4 from stage II, and Qz-5 from stage III. Based on in situ secondary ion mass spectrometry oxygen isotopic analysis of the five quartz generations (Qz-1 to Qz-5), the calculated δ18Ofluid values for the ore fluids are 7.8‰ to 9.2‰ (mean 8.3‰), −3.2‰ to 8.7‰ (mean 5.6‰), −3.5‰ to 7.4‰ (mean 4.6‰), −4.5‰ to 7.6‰ (mean −0.2‰), and −6.4‰ to 1.4‰ (mean −3.8‰). The oxygen isotopic data and trend among the five quartz generations are best interpreted to represent magmatically derived ore fluid being diluted by modified meteoric water to cause mineralization. Fluid mixing is considered to be the principal mechanism that led to Ag-Pb-Zn precipitation at Poshan. Sulfides coexisting with the quartz generations have δ34SV-CDT values of −1.7‰ to 4.4‰, with no systematic variations among different paragenetic stages. These data, combined with apatite U-Pb age and geologic relations, provide additional evidence for a magmatic origin of the Poshan Ag-Pb-Zn deposit, as inferred from the oxygen isotopes. This study highlights the role of fluid dilution in triggering Ag-Pb-Zn deposition, and sheds light on the origin of silver-polymetallic deposits in orogenic belts.

Iron–Titanium Oxide–Apatite–Sulfide–Sulfate Microinclusions in Gabbro and Adakite from the Russian Far East Indicate Possible Magmatic Links to Iron Oxide–Apatite and Iron Oxide–Copper–Gold Deposits

Mesozoic gabbro from the Stanovoy convergent margin and adakitic dacite lava from the Pliocene–Quaternary Bakening volcano in Kamchatka contain iron–titanium oxide–apatite–sulfide–sulfate (ITOASS) microinclusions along with abundant isolated iron–titanium minerals, sulfides and halides of base and precious metals. Iron–titanium minerals include magnetite, ilmenite and rutile; sulfides include chalcopyrite, pyrite and pyrrhotite; sulfates are represented by barite; and halides are predominantly composed of copper and silver chlorides. Apatite in both gabbro and adakitic dacite frequently contains elevated chlorine concentrations (up to 1.7 wt.%). Mineral thermobarometry suggests that the ITOASS microinclusions and associated Fe-Ti minerals and sulfides crystallized from subduction-related metal-rich melts in mid-crustal magmatic conduits at depths of 10 to 20 km below the surface under almost neutral redox conditions (from the unit below to the unit above the QFM buffer). The ITOASS microinclusions in gabbro and adakite from the Russian Far East provide possible magmatic links to iron oxide–apatite (IOA) and iron oxide–copper–gold (IOCG) deposits and offer valuable insights into the early magmatic (pre-metasomatic) evolution of the IOA and ICOG mineralized systems in paleo-subduction- and collision-related geodynamic environments.

Overview of early cretaceous gold mineralization in the orogenic belt of the eastern margin of the Siberian craton: geological and genetic features

The giant Verkhoyansk-Kolyma gold province, producing more than∼ 3700 t of gold, is one of the most important metallogenic provinces for orogenic gold deposits in the world. The province is located on the eastern margin of the Siberian craton. The main types here are multistage orogenic Au-As and orogenic-like Au-Sb types of mineralization, related to the Late Jurassic-Early Cretaceous metallogeny and the evolution of the convergent margin. These deposits were formed in the environment of late orogeny during two metallogenic stages—the Late Jurassic-Early Cretaceous collision-related (early stage/stage one, 135–150 Ma) and the Early Cretaceous subduction-related (late stage/stage two 114–130 Ma). The common features, differences and genetic nature of the deposits of these two metallogenic stages have been debated for a long time. To improve the understanding of these problematic issues and the genesis of deposits, and control over them by the mantle lithosphere, we consider here the Early Cretaceous orogenic belts of the eastern margin of the Siberian craton. Orogenic belts are related to the development of the paleo-Arctic and paleo-Pacific margins of Siberia. The tectonic, geochronological, mineralogical and geochemical specificity of the deposits of the orogenic belts are shown. A regional metallogenic overview of gold deposits is performed using data on the age of mineralization and the isotopic composition of sulfur sulfides. A preliminary model of the origin of late stage mineralization is proposed in connection with the processes of the Okhotsk-Koryak orogenic belt formation. Increased concentrations of siderophilic and chalcophilic elements, the Ni, Bi minerals presence in the ores, relatively high fineness of gold, predominance of juvenile sulfur in the isotopic composition of sulfide sulfur, аnd the control by large trans-crustal faults as well as spatial and chronological association with initial (dike) magmatism indicate mantle sources of ore fluids. This mineralization within the orogenic belts of the eastern margin of the Siberian craton assumingly appeared due to dehydration of the submerged slab and local upwelling in the mantle in the rear of the active continental margin. The possibility of the gold-bearing fluids existence in such conditions is estimated. The metallogenic specific nature of collision-related and subduction-related orogenic Au is defined. The proposed model can be useful for the analysis of polychronous orogenic Au-As and orogenic-like Au-Sb metallogeny of orogenic belts on craton margins globally.

Possibilities for improving the technology of roasting zinc concentrates

The paper presents an investigation into the oxidation process of zinc sulfide concentrate. A common challenge encountered during the fluidized calcination process is the high concentration of sulfide sulfur in the condensed products, such as the mixture collected at the furnace threshold and in the dust. This scientific work reports the results of laboratory studies aimed at improving the technology of roasting zinc concentrates. The study's objective was to obtain zinc cinders with increased solubility in aqueous solutions by roasting sulfide zinc concentrates. The results show that the optimal composition of the charge for roasting was determined using limestone and wastewater from the processing plant, which contains alkaline earth metal oxides. This composition helped reduce the formation of ferrites and silicates by 1.5-1.7 times.

Combined Bacterial and Pressure Oxidation for Processing High-Sulfur Refractory Gold Concentrate

Microbially assisted bio-oxidation of sulfide concentrates in stirred-tank reactors (stirred-tank reactor bio-oxidation (STRB)) and acid pressure oxidation (POX) are widely used to pretreat refractory sulfide concentrates and increase gold extraction via cyanidation. Continuous STRB requires a comparatively long residence time; however, in some cases, it cannot effectively oxidize some sulfide minerals. POX enables oxidation in a short residence time. At the same time, if a processed concentrate contains a large amount of sulfur, it decreases the ratio of the solid mineral phase to liquid (pulp density) during POX and limits its economic attractiveness. In the present work, experiments were performed to investigate the problems associated with both processing methods for refractory sulfide concentrates. The experiments combined both treatments (STRB and POX) based on the example of a pyrite–arsenopyrite gold-bearing concentrate. The gold recovery from the untreated concentrate via cyanidation reached 58%. Continuous STRB for 2, 4, and 6 days oxidized 43, 74, and 79% of the sulfide sulfur (Ss), respectively. The gold recovery rates from the bio-oxidation residues were 68, 82, and 88%, respectively. The pressure oxidation of both the concentrate and STRB residues increased Ss oxidation by 97–99% and gold recovery by 96–97%. For 2 days, STRB decreased the Ss content and increased the possible liquid-to-solid ratio for POX. The combined processes result in a new promising direction because the POX stage allows high gold recovery, whereas combining STRB and POX provides products for further POX in terms of Ss content and increases POX productivity.

Re-examination of the Aïn Allegua-Aguiba celestite-Pb-Zn salt diapir-related Mississippi Valley-type deposits (Nappes zone, Northwestern Tunisia): New conceptual model

The celestite-rich and Pb-Zn-poor Aïn Allegua deposits are located at the northeastern extremity of the Dougas diapir in the Nappes zone of northern Tunisia. The Sr-Ba-Zn-Pb mineral system studied in this paper is enclosed in a Triassic breccia, labeled cap rock, located between the Triassic diapir and the surrounding Cretaceous to Lutetian marine sediments. It consists of evaporite dissolution float breccia where Triassic dolostone clasts are floating in a Triassic matrix of anhydrite and argillites. Five mineralizing stages are recognized, which are from early to late: celestite (stage 1); hydrothermal dolomite (stage 2); crosscutting galena-barite or sphalerite-galena-barite-calcite (stage 3); (4) fracture and karst filled by barite, celestite, and galena (stage 4); and late supergene mineralization (strontianite, smithsonite, and cerussite) (stage 5). The present study shows that the celestite and Pb-Zn mineralization formed from the circulation in the cap rock of at least three fluids: (1) fluid A (100–150 °C; 10 to 25 wt% NaCl eq.) deposited the celestite; (2) fluid B (125 to 185 °C; 29 to 34 wt% NaCl eq.) deposited the hydrothermal dolomite, and (3) fluid C (temperatures around 90 °C; 14 to 22 wt% NaCl eq.) deposited the calcite that accompanied sphalerite and galena precipitation. The δ34S values for sphalerite and galena fall within a narrow range from + 10.4‰ to + 18.9‰ (avr. 13‰) indicating a homogeneous source of sulfur. The δ34S values of celestite and barite are also relatively homogeneous from + 14.7 to + 23‰ (ave. + 16.5‰) and match those of Tunisian Triassic gypsum and Triassic marine sulfates (δ34S = +15‰). The temperature of deposition together with sulfur isotope data indicate that the reduced sulfur in sulfides was derived through thermochemical sulfate reduction of Triassic sulfate. The lead isotopes in galena show that Pb, and probably Zn and Ba were extracted from the upper crustal rocks. Part of the strontium is derived from the Triassic anhydrite and the other part is probably transported to the cap rock in formation waters. The tectonic setting, the carbonated nature of the host rocks, the epigenetic style of the mineralization, and the mineral associations, together with fluid inclusions data and sulfur and lead isotopes show that the Aïn Allegua deposit belongs to the diapir-related Mississippi Valley-type (MVT) deposits of the Eastern Maghreb salt diapirs province, that formed, as the most of the MVT deposits and districts in the world, from basinal brines with no mixing with metamorphic and/or magmatic fluid or involvement of a heat source from a concealed sill or magmatic intrusion.

Sulfate recycling at subduction zones indicated by sulfur isotope systematics of Mesozoic ultramafic island arc cumulates in the North American Cordillera

The isotopic composition of sulfur in convergent margin-related orthomagmatic sulfides is critical to the debate on: 1) petrological mechanisms of sulfide saturation in relatively oxidized magmatic systems, and 2) the relative contribution of subducted sulfate to the overall sulfur budget of the sub-arc mantle. Magmatic sulfides that crystallize in deep-seated plutonic rocks are less susceptible to isotopic fractionation arising from magmatic degassing and are thus better suited for studies of primary S-isotope compositions of arc magmas than their extensively degassed volcanic counterparts. Isotopic compositions of chalcopyrite and pyrrhotite, which crystallized from trapped immiscible sulfide melt, and secondary fibrous pyrite after pyrrhotite in the Polaris Alaskan-type ultramafic-mafic intrusion (Early Jurassic) of the North American Cordillera were determined by secondary ion mass spectrometry. Chalcopyrite grains from five olivine clinopyroxenites are fresh and homogeneous and they have uniform near-chondritic δ34S values (-0.19 +0.48/-0.32‰; n = 97). In contrast, pyrrhotite (δ34S = -1.6 +2.8/-0.6; n = 34) and secondary pyrite (δ34S = -2.7 +1.8/-4.4‰; n = 21) grains display subchondritic but highly variable δ34S. The marked difference in measured δ34S of different sulfide phases attests to the critical advantage of using in-situ microanalytical techniques over whole-rock isotopic analysis. Pyrite grains from hornfelsed volcanogenic country rocks have elevated S-isotope values (δ34S = +7.4 +1.3/-1.7‰; n = 11). The near- to subchondritic isotopic compositions of sulfides from the Polaris intrusion demonstrate that wall-rock assimilation played a minor role and that sulfur in the Polaris magmas is largely magmatic. Fibrous textures and variable, but negative, δ34S of pyrrhotite and pyrite indicate post-magmatic mobility of sulfur due to low-temperature alteration by hydrothermal fluids. The narrow range of chalcopyrite δ34S, however, indicates that it remained unaffected by hydrothermal processes and equilibrated under uniform magmatic physicochemical conditions. Assuming sulfide liquid immiscibility at T ≥ 800 °C, geochemical modeling of S-isotope fractionation indicates that the Polaris parental magmas had suprachondritic δ34S between +1‰ (at log fO2 = FMQ+1) and +5‰ (at log fO2 =FMQ+2), consistent with the contribution of subducted sulfate to the sub-arc mantle.

Flotation Decarbonization and Desulfurization of a High-Sulfur Bauxite in China

A high sulfur content is one of the challenges in the processing of refractory bauxites in China. The high carbon content of bauxite makes it more difficult to deal with. Desulfurization and decarbonization are the critical issues in the efficient exploitation of high-sulfur bauxite resources. An experimental study on the removal of sulfur and carbon in high-sulfur bauxite is proposed. The sulfur and carbon phases in high-sulfur bauxite were studied via X-ray diffraction and chemistry quantitative analyses. The results show that the sulfur phases in the high-sulfur bauxite mainly exist in the form of sulfide sulfur (pyrite), and the carbon phases in the sample mainly exist in the form of elementary substance carbon. The morphological features of pyrite in the high-sulfur bauxite were analyzed using a microscopic analysis and a scanning electron microscope (SEM). The pyrite exists in minerals in the forms of euhedral, semi-euhedral and other crystalline structures, with a particle size varying from several hundred microns to only a few microns. The raw ore, with a sulfur content of 4.78%, a sulfide sulfur content of 4.20%, a carbon content of 3.10% and an elementary substance carbon content of 2.46% goes through the “one roughing, one cleaning, two scavenging” process after a pre-decarburization, obtaining the total desulfurization recovery of 96.20% with a desulfurization tailing sulfur content of 0.38%, a carbon content of 0.27% and an alumina content of 71.85%, respectively. This work provides technical support for the efficient utilization of high-sulfur and high-carbon bauxite.

Mineralogy and Р-T conditions for the formation of metasomatic rocks of the Voznesenskoye gold deposit (Southern Urals)

Research subject. Mineral associations, their chemical composition, and formation conditions of metasomatic rocks of the Voznesenskoye gold deposit located in the area of the Main Ural Fault in the Southern Urals.Methods. The chemical composition of minerals was studied using a Tescan Vega Compact scanning electron microscope equipped with an Oxford Instruments Xplorer 15 energy-dispersive analyzer. The formation P-T parameters were estimated using a chlorite geothermometer and a dolomite-calcite geothermobarometer.Results and conclusions. Two types of metasomatic rocks were identified: 1) propylites, which make up the outer zones of the metasomatic aureole, and 2) beresite-listvenites, common in its inner parts and hosting gold mineralization. The main propylite minerals were amphibole, orthoclase, albite, and ripidolite. Amphibole is represented by two generations, with the early generation comprising magnesian and actinolite hornblende and the late generation comprising actinolite. The crystallization temperature of ripidolite (307–313°С) corresponds to the temperature range of formation of propylites of the albite-actinolite facies. Beresite-listvenites (association: quartz, albite, chlorite, white mica, and carbonate) were formed at a temperature of 255–338°C and a pressure of 0.48–0.72 kbar. Gold ore mineralization was concentrated in the highest temperature zones of the halo of beresite-listvenite alterations. Such temperature conditions existed in dikes and their exocontact zones disturbed by ruptures. Light mica in beresite-listvenites is represented by sericite and phengite, and carbonate is a paragenesis of calcite and dolomite-ankerite. According to the composition and formation period, chlorite is differentiated into early ferruginous ripidolite and late pycnochlorite, depleted in Fe and enriched in Si, which is probably associated with a decrease in temperature during mineral formation and an increase in the activity of sulfide sulfur in the fluid. Along with an increase in the distance from the ore bodies, pycnochlorite exhibits greater contents of Si and lower contents of AlIV. The observed changes in the pycnochlorite composition are related to a decrease in temperature. The research results indicate the formation of the Voznesenskoye deposit under mesothermal conditions.

Granulated Vivianite in the Cambridge Strait, Franz Josef Land (Barents Sea)

Finding of vivianite is first described in a sediment core raised from the Cambridge Strait, western Franz Josef Land. The vivianite is represented by similar spherules mainly of 200–400 micrometers in diameter and by their rare aggregates. Distribution of the vivianite grains in the core is characterized by three maximal values (up to 2.7 grains per gram of dry bulk sediment), within the time interval of the last 4.1 kyr. Linear and flat shape of the aggregates indicates generation of vivianite at the sediment/water interface. It takes place in the reducing condition and sulfide sulfur deficit in the bottom water relative to bivalent iron. Structure of the vivianite grains varies from the cryptocrystalline porous to the fully crystalline dense one reflecting stages of the vivianite crystallization, likely after coagulation of the ferrous phosphate colloid formed due to the bacterial activity. Signs of vivianite microconcrections mentioned by some authors are not observed.

Crystal Chemistry, Thermal and Radiation-Induced Conversions and Indicatory Significance of S-Bearing Groups in Balliranoite

Crystal-chemical features of a sulfide-bearing variety of the cancrinite-group mineral balliranoite from the Tuluyskoe lapis lazuli deposit, Baikal Lake area, Siberia, Russia, have been investigated using a multimethodic approach based on infrared (IR), Raman, and electron spin resonance (ESR), as well as ultraviolet, visible and near infrared (UV–Vis–near IR) absorption spectroscopy methods, luminescence spectroscopy, electron microprobe analysis, selective sorption of CO2 and H2O from annealing products, and single-crystal X-ray structure analysis. Holotype balliranoite and its sulfate analogue, davyne, were studied for comparison. The crystal-chemical formula of the studied sample from Tultuyskoe is Na5.4K0.1Ca2.4(Si6Al6O24)Cl2[(CO3)0.7(SO4)0.18S*0.95Cl0.1(H2O)0.16], where the content of the wide zeolite channel is given in square brackets; S* is total sulfide sulfur occurring as disordered S2●−, cis- and trans-S4, S52−, minor S3●−, and HS− groups. The presence of S52− and HS− groups, the absence of CO2 molecules, and the association with pyrrhotite and Fe-free pargasite indicate that the studied sample crystallized under highly reducing, low-temperature conditions, unlike holotype balliranoite whose formation was related to the Somma-Vesuvius volcanic complex, Italy. Irradiation of balliranoite from Tultuyskoe with X-rays results in the transformations of polysulfide groups other than S3●− into S3●− in accordance with the scheme: S52− → S2●− + S3●−; 3S2●− → 2S3●− + e−; S4 + S2●− + e− → 2S3●−; S4 + S2●− + e− → 2S3●−; S4 + S52− + e− → 3S3●− (e− = electron).

SULFIDE SULFUR ISOTOPE SOURCES OF THE NEOARCHEAN IRON ORE DEPOSITS IN THE KOSTOMUKSHA GREENSTONE BELT, KARELIA (RUSSIA)

In this paper we provide primary data on multi-isotope sulfur composition of the Neoarchean BIF sulfides of the Kostomuksha greenstone belt in Karelia (the Karelian Craton on Fennoscandian Shield). These sulfides formed at 2760–2740 Ma. Pyrite associated with fine-grained magnetite showed negative δ34S values (up to –7.8‰) and positive Δ33S values (up to +0.7‰). At the same time, pyrrhotite of vein-disseminated ores associated with shale demonstrated both negative δ34S (up to –6‰), and Δ33S values (up to –0.46‰). Based on the obtained data we assume that sulfur for the BIF sulfides was transported from three reservoirs: - atmospheric (photolytic), hydrospheric (seawater sulfate), and magmatogenic. Sulfur isotope ratios in sulfides preserved the evidence of interaction between abiological (atmospheric, hydrothermal) and biological processes (dissimilatory microbial reduction) that occurred during the formation of iron ore deposits of the Kostomuksha greenstone belt in Karelia.

Gold–Sulfide Mineralization in the Manitanyrd Region, Polar Urals, Russia

This article describes the characteristics of gold–sulfide–quartz and gold–sulfide (gold–arsenic) ore occurrences in the Manitanyrd region of the Polar Urals. Ore occurrences are confined to NE-trending shear zones and have the common features of a geological structure. The host rocks are metamorphosed volcanic and volcanic–sedimentary rocks. We analyzed the mineral and chemical composition of the ore mineralization in all studied ore occurrences, showing that they belong to the same mineral type—pyrite–arsenopyrite, with a variable ratio of the main minerals. Arsenic pyrite is present in all ore occurrences. Two stages of ore formation were distinguished: early gold–pyrite–arsenopyrite with finely dispersed gold and late gold–galena–chalcopyrite–sphalerite with coarse gold, fahlore, and sulfosalts Pb, Cu, Bi, Sb. Native gold of the first generation, finely dispersed in arsenopyrite and pyrite, had an average to high fineness (800‰–1000‰) with a relatively low dispersion. Native gold of the second generation was larger, and its fineness in ore occurrences varied; in one of them, it varied from 300‰ to 950‰, while in others, it varied from 800‰ to 950‰. The isotope composition of sulfur in sulfides (δ34S) ranged between −0.2‰ and −8.0‰. δ34S values of sulfides in the range of −0.2‰ to −3.5‰ were similar to meteorite, indicating the participation of a single deep magmatic source of sulfur in the ore formation. According to the study of fluid inclusions, the formation of ore quartz veins occurs in the temperature range of 467–109 °C. The similarity of the geological–structural, mineralogical–geochemical, and isotope–geochemical features of the gold–sulfide–quartz and gold–sulfide occurrences in the area suggest their formation in a single hydrothermal system.