Sulfides In Rocks Research Articles

Assessment of the Impact of Technogenic Processes Occurring at the Central Concentrating Mill Tailing Dump (Komsomolsky Tin-Ore District) on the Hydrosphere in a Wide Temperature Range

The results of physicochemical modeling of oxidation of sulfide minerals in the Central Concentrating Mill tailing dump (Komsomolsky tin-ore district) with account taken of the cementation zone in the temperature range from–25 to +45°C are given. The Eh-pH parameters for the formation of micropore solutions in technogenic systems have been determined at different host rock–sulfide ratios (95: 5, 90: 10, 80: 20, 60: 40, 40: 60, 20: 80, 10: 90, 5: 95). Crystallization of hypergene minerals from the micropore solutions have been considered, their qualitaitve and quantitative ion compositions have been determined, and their effect on the hydrosphere has been assessed.

Physicochemical Modeling of Sulfide Oxidation Processes in Tailing Dumps of the Kavalerovsky District and Their Impact on the Hydrosphere (Primorsky Krai)

Oxidation of tailings in the tailing dump of Vysokogorskoe deposit (Kavalerovsky district) in the temperature range from 0 to +45°C was simulated with successive exclusion of each of the sulfide minerals present therein (pyrite, pyrrhotite, galena, sphalerite, arsenopyrite, and chalcopyrite). The Eh-pH parameters for anthropogenic mineral formation were determined at different host rock–sulfide ratios (95: 5, 90: 10, 80: 20, 60: 40, 40: 60, 20: 80) in the tailings. Crystallization of supergene minerals was analyzed, qualitative and quantitative ionic compositions of solutions were determined, and their impact on the hydrosphere was assessed.

Mineralogical and geochemical characterization of waste rocks from a gold mine in northeastern Thailand: application for environmental impact protection.

Waste rocks from gold mining in northeastern Thailand are classified as sandstone, siltstone, gossan, skarn, skarn-sulfide, massive sulfide, diorite, and limestone/marble. Among these rocks, skarn-sulfide and massive sulfide rocks have the potential to generate acid mine drainage (AMD) because they contain significant amounts of sulfide minerals, i.e., pyrrhotite, pyrite, arsenopyrite, and chalcopyrite. Moreover, both sulfide rocks present high contents of As and Cu, which are caused by the occurrence of arsenopyrite and chalcopyrite, respectively. Another main concern is gossan contents, which are composed of goethite, hydrous ferric oxide (HFO), quartz, gypsum, and oxidized pyroxene. X-ray maps using electron probe micro-analysis (EPMA) indicate distribution of some toxic elements in Fe-oxyhydroxide minerals in the gossan waste rock. Arsenic (up to 1.37wt.%) and copper (up to 0.60wt.%) are found in goethite, HFO, and along the oxidized rim of pyroxene. Therefore, the gossan rock appears to be a source of As, Cu, and Mn. As a result, massive sulfide, skarn-sulfide, and gossan have the potential to cause environmental impacts, particularly AMD and toxic element contamination. Consequently, the massive sulfide and skarn-sulfide waste rocks should be protected from oxygen and water to avoid an oxidizing environment, whereas the gossan waste rocks should be protected from the formation of AMD to prevent heavy metal contamination.

Efficient extraction of copper and zinc from seafloor massive sulphide rock samples from the Loki’s Castle area at the Arctic Mid-Ocean Ridge

Seafloor massive sulphide (SMS) deposits have been identified as important marine metal resources for the future. However, literature on the recovery/extraction of metals from SMS is currently limited, and to date, no research has been published on the processing of SMS from the active hydrothermal vent field at the Arctic Mid-Ocean Ridge. In this paper extraction of copper and zinc, as economically important metals, from the seafloor massive sulphide rock samples from the Loki’s Castle area at the Arctic Mid-Ocean Ridge was investigated during nitric acid leaching. The results presented are of the various leaching experiments conducted under different conditions to optimise the extraction of copper and zinc. The mineralogical analysis indicated that the main copper and zinc bearing minerals were chalcopyrite and sphalerite, respectively. It was shown that the leaching efficiency and extraction of copper and zinc can be controlled mainly by temperature and acid concentration. The elemental composition and mineralogical data indicated that 95% of copper and zinc bearing minerals were leached out after 3 h, at the solid-to-liquid ratio of 1:10, temperature of 90 °C and acid concentration of 10%.

Waste Rock Biogeochemistry in a Permafrost Environment: Examination of a Cover Design for a Low-Sulfide, Granitic Waste Rock

ABSTRACTAt the Diavik Waste Rock Project's mine-research site, the microbial colonization and oxidation of waste rock sulfide minerals are attenuated by the extreme freeze-thaw cycle of a permafrost environment. The closure design for the waste rock stockpile consists of a low-sulfide waste rock and low-permeability till, covering a relatively higher sulfide waste rock. This design was examined at the mine site through construction of experimental waste rock piles and active zone lysimeters with and without the till cover. Leachate from these experiments indicates variable pH and SO4 concentrations that correlate with sulfide content and the thermal moderating influence of the till cover. The till initially provided a moderated environment for the production of acid, growth of acidophilic Fe- and S-oxidizing bacteria, and enhanced weathering until wet up and freezing of the till and underlying waste rock as a permafrost. Greater sulfide oxidation was observed above the till cover because of greater exposure to the annual freeze-thaw cycle. An examination of the bacterial communities at the genus level indicates the prevalence of Pseudomonas, Rhodanobacter, Sideroxydans, and Thiobacillus in the waste rock. Pseudomonas spp. were dominant in the drier and more extreme temperature environment above the till cover, while Thiobacillus spp. were dominant in the more sulfide-rich, wetter/frozen environment below the till. A decreasing trend in Thiobacillus spp. from the exterior to the interior and an opposing trend in Acidithiobacillus spp. suggest greater acid generation deeper in the waste rock further from the extreme temperature variation of the tundra climate. The presence of the till cover moderated temperature variations, enhanced the initial rate of sulfide oxidation, and allowed for greater microbial diversity, but the freezing of the till cover and underlying waste rock drastically reduced sulfide oxidation and the generation of acid rock drainage. These results highlight the importance of temperature on microbially catalyzed acid production and our ability to use the extreme temperatures of the tundra climate to minimize potential environmental effects from mining through formation of waste rock permafrost.

Geochemical distribution and fate of arsenic in water and sediments of rivers from the Hokusetsu area, Japan

Abstract Study region Hokusetsu Region in Osaka, Japan. Study focus The As contamination was investigated through the geochemical mapping and analysis of river waters and bed sediments over an area of 440 km 2 . Sulfur from sulfides in rocks and dissolved sulfates in water were compared via isotopic analysis to assess their origin and the subsequently released As. The fate of As (transport, binding on settling particles) was evaluated through the total and dissolved fractions of As and trace metals Fe, Mn and Al in river waters. New hydrological insights for the region The geochemical mapping showed that As in river water exceeded the maximum limit concentration of 10 ppb in several places. The highest As levels (waters and sediments) correlated well with the surface geologies, concentrating in a halo around granitic intrusion and nearby faults. The isotopic analysis of sulfur revealed the occurrence of two kinds of sulfide mineralizations responsible for As contamination: one from Late Paleozoic submarine volcanism in sedimentary rocks, and one from Late Cretaceous igneous activities in contact-metamorphosed rocks disseminated with sulfides. The transport of As along river courses occurred mainly as a dissolved species rather than absorbed on Fe/Mn/Al particles, signifying the least role of iron oxy-hydroxides in As adsorption.

Geochemical exploration for supergene copper oxide deposits, Mount Isa Inlier, NW Queensland, Australia

Extensive, variable, and generally thick regolith is a major challenge to mineral exploration in regolith-dominated terranes. The landscape of the Mount Isa Inlier, NW Queensland, Australia, is the product of several episodes of complex weathering, erosion and sedimentation. Weathering profiles were studied from more than 100 drill holes along three traverses crossing the Lady Annie, Mount Kelly and Anthill sulfide deposits to assess the nature, lateral extent and thickness of the supergene Cu oxide mineralization. A typical regolith profile consists, from the base up, of saprock, ferruginous saprolite (Cu-oxide zone), kaolinitic saprolite and silcrete bands (leached zone), and a pedolith of mottled, lateritic duricrust and soil zones. Oxidation of sulfides (primarily pyrite) in host rocks has created an acidic pH gradient, mobilizing Fe, Mn, Cu, Mo, Zn, Co, Ni, As, Bi, In, Sb, Be, P, U and Cd. The acidic pH is buffered by calcareous lithologies of the host rocks, particularly in the vicinity of the primary sulfides at Lady Annie and Mount Kelly resulting in formation of thick, mushroom-shaped Cu oxide halo, in which Cu may reach >15wt.%. The Cu values decrease to <500ppm in the bleached kaolinitic saprolite and silcrete. Conversely, siliceous bedrock lithologies at Anthill act as a weak buffer to the acidic fluids; thus, Fe, Cu and other mobile elements are laterally dispersed from the sulfide ore body and precipitated at different lithological boundaries where they are buffered by carbonates. Therefore, thick kaolinitic saprolite and silcrete are formed over sulfide mineralization, particularly along faults. Ferruginous duricrusts marginal to fault-controlled sulfide mineralization are anomalous in Cu, Zn, Cd, Sb and Be, and thus can be used as useful medium in geochemical exploration. Gold, Ag, Pb and As are residually concentrated in pedolith and kaolinitic saprolite over the primary sulfide mineralization. Thus, these elements can be used effectively as pathfinder elements, particularly in truncated landscape, where pedolith is eroded and the exposed kaolinitic saprolite is depleted in Cu. Ferruginous soil (850–300, 300–80 and <80μm size fractions), lag (>1.6 and >7.6mm) and termite mounds have been applied successfully as sampling media for Cu oxide exploration in Anthill. Soil and lag over sulfide mineralization are rich in Fe, As, Pb, Ag, Bi, In, V, U and Mo. The best response over sulfide mineralization is recorded in the >7.6mm ferruginous lag. However, broadest signature of well-defined Au, Bi and In anomalies are better detected using termite mounds than soil and lag. Successful use of soil in exploration for Cu oxide deposits in Mount Isa requires a genetic discrimination between residual and transported origin.

Novel and Unexpected Microbial Diversity in Acid Mine Drainage in Svalbard (78° N), Revealed by Culture-Independent Approaches.

Svalbard, situated in the high Arctic, is an important past and present coal mining area. Dozens of abandoned waste rock piles can be found in the proximity of Longyearbyen. This environment offers a unique opportunity for studying the biological control over the weathering of sulphide rocks at low temperatures. Although the extension and impact of acid mine drainage (AMD) in this area is known, the native microbial communities involved in this process are still scarcely studied and uncharacterized. Several abandoned mining areas were explored in the search for active AMD and a culture-independent approach was applied with samples from two different runoffs for the identification and quantification of the native microbial communities. The results obtained revealed two distinct microbial communities. One of the runoffs was more extreme with regards to pH and higher concentration of soluble iron and heavy metals. These conditions favored the development of algal-dominated microbial mats. Typical AMD microorganisms related to known iron-oxidizing bacteria (Acidithiobacillus ferrivorans, Acidobacteria and Actinobacteria) dominated the bacterial community although some unexpected populations related to Chloroflexi were also significant. No microbial mats were found in the second area. The geochemistry here showed less extreme drainage, most likely in direct contact with the ore under the waste pile. Large deposits of secondary minerals were found and the presence of iron stalks was revealed by microscopy analysis. Although typical AMD microorganisms were also detected here, the microbial community was dominated by other populations, some of them new to this type of system (Saccharibacteria, Gallionellaceae). These were absent or lowered in numbers the farther from the spring source and they could represent native populations involved in the oxidation of sulphide rocks within the waste rock pile. This environment appears thus as a highly interesting field of potential novelty in terms of both phylogenetic/taxonomic and functional diversity.

Mineralogy and mineral chemistry of the metamorphosed and precious metal-bearing Ming deposit, Canada

The Ming deposit in the northwestern Canadian Appalachians is a metamorphosed, bimodal-mafic, precious-metal (Au, Ag)-bearing and Cu-rich volcanogenic massive sulfide (VMS) deposit consisting of several, spatially proximal lenses in a sericite- to chlorite-altered rhyodacitic footwall. The various lenses (1807 Zone, 1806 Zone, Ming South Up Plunge, Ming South Down Plunge, and the Lower Footwall Zone) have variations in Cu, Au, Ag, and Zn grades that reflect varying physico-chemical conditions of ore formation. This study describes the complex ore mineralogy of the orebodies and constrains the genesis of the deposit using field methods, mineralogy, whole rock sulfide geochemistry, and micro-analytical methods.The orebodies are predominantly pyrite, chalcopyrite, with lesser sphalerite, pyrrhotite, and trace galena and arsenopyrite, with the exception of the Lower Footwall Zone, which consists of a high temperature (>320°C) chalcopyrite–pyrrhotite–pyrite±cubanite assemblage. The other orebodies (1806, 1807, Ming South Up Plunge and Down Plunge) contain trace amounts of tellurides (hessite, altaite, tsumoite, unnamed bismuthtelluride), sulfosalts (Ag-poor and Ag-rich tennantite–tetrahedrite, meneghinite, AgSb phases, stannite), and precious metal phases (electrum, AgHg±Au alloys). The 1807 Zone is enriched in Te, Bi, and Se, whereas the 1806 Zone is telluride-free and contains As, Sb, Hg, Au, and Ag. Mineral chemistry of sphalerite shows strong variations in Fe content (1.12–11.04wt.%). Intermediate Fe (4.33–6.33wt.% Fe) and Fe-rich (7.327–11.04wt.% Fe) sphalerite are common in all orebodies, whereas Fe-poor sphalerite (1.12–3.57wt.% Fe) occurs exclusively in the 1807 and 1806 zones. Tennantite-tetrahedrite is typically Ag-poor (0.25–2.19wt.%) in the 1807 Zone, but is significantly enriched in Ag (up to 29.3wt.%) in the 1806 Zone. Galena in the 1807 Zone and Ming South orebodies is commonly myrmekitically intergrown with tellurides and has high concentrations of Te, Bi, Se, and Ag. In contrast, galena in the 1806 Zone is less enriched in Te, Bi, and Se, but high in Ag.Variations in mineralogy, epithermal elements (As, Bi, Hg, Sb, Se, Sn, Te) and precious metal (Ag, Au) content, and mineral chemistry between the different orebodies indicate that they were formed from predominantly reduced, acidic hydrothermal fluids with varying ƒTe2/ƒS2, ƒSe2/ƒS2, and mBi/mSb ratios as temperatures steadily decreased from >300°C to <260°C during ore formation. In the 1807 and Ming South orebodies, late-stage deposition of Te-, Bi-, Se-, Ag-rich galena and tellurides occurred prior to precipitation of Ag-poor tennantite-tetrahedrite, whereas in the 1806 Zone hydrothermal fluids low in ƒTe2/ƒS2, ƒSe2/ƒS2, and mBi/mSb favored the precipitation of Te-, Bi-, Se-poor galena and Ag-rich tennantite-tetrahedrite. A magmatic source for epithermal elements and precious metals is suggested and was part of the depositional history of the Ming deposit.

Evaluation of pH Testing Methods for Sulfidic Mine Waste

Environmental assessment of solid mine waste is required throughout the life of a mine. This has driven the need for tools and practices to understand the current state of net acidity in mine wastes. Rinse and paste pH tests are commonly used in the initial screening of waste to provide a preliminary evaluation of its current net acidity. Such pH tests are particularly useful for assessing the chemistry of first flush waters draining sulfidic rocks and wastes. In this study, we compared nine different pH tests (rinse and paste pH tests as well as soil tests of the International Organization for Standardization ISO 10390:2005; American Society for Testing and Materials ASTM D4972-01 2007; Standards Australia AS4969.2-2008), using three different sulfidic rock samples and the acid–base accounting standard KZK-1. We observed significant variability in measured pH for the same samples using the different test methods. We show that different rinse and paste pH methods using different grain sizes and extraction solutions can result in different risk classification for ARD assessments. We recommend carrying out pH measurements using 0.01 M CaCl2 solution, which results in more rapid, reproducible, and precise analyses than using deionised water.

Reduction of acid rock drainage using steel slag in cover systems over sulfide rock waste piles.

The extraction of gold, coal, nickel, uranium, copper and other earth-moving activities almost always leads to environmental damage. In metal and coal extraction, exposure of sulfide minerals to the atmosphere leads to generation of acid rock drainage (ARD) and in underground mining to acid mine drainage (AMD) due to contamination of infiltrating groundwater. This study proposes to develop a reactive cover system that inhibits infiltration of oxygen and also releases alkalinity to increase the pH of generated ARD and attenuate metal contaminants at the same time. The reactive cover system is constructed using steel slag, a waste product generated from steel industries. This study shows that this type of cover system has the potential to reduce some of the adverse effects of sulfide mine waste disposal on land. Geochemical and geotechnical characterization tests were carried out. Different proportions of sulfide mine waste and steel slag were studied in leachate extraction tests. The best proportion was 33% of steel slag in dry weight. Other tests were conducted as follows: soil consolidation, saturated permeability and soil water characteristic curve. The cover system was numerically modeled through unsaturated flux analysis using Vadose/w. The solution proposed is an oxygen transport barrier that allows rain water percolation to treat the ARD in the waste rock pile. The results showed that the waste pile slope is an important factor and the cover system must have 5 m thickness to achieve an acceptable effectiveness.

Capturing the complete stress–strain behaviour of jointed rock using a numerical approach

SummaryThis paper presents the results of a series of numerical experiments using the synthetic rock mass (SRM) approach to quantify the behaviour of jointed rock masses. Field data from a massive sulphide rock mass, at the Brunswick mine, were used to develop a discrete fracture network (DFN). The constructed DFN model was subsequently subjected to random sampling whereby 40 cubic samples, of height to width ratio of two, and of varying widths (0.05 to 10 m) were isolated. The discrete fracture samples were linked to 3D bonded particle models to generate representative SRM models for each sample size. This approach simulated the jointed rock mass as an assembly of fractures embedded into the rock matrix.The SRM samples were submitted to uniaxial loading, and the complete stress–strain behaviour of each specimen was recorded. This approach provided a way to determine the complex constitutive behaviour of large‐scale rock mass samples. This is often difficult or not possible to achieve in the laboratory.The numerical experiments suggested that higher post‐peak modulus values were obtained for smaller samples and lower values for larger sample sizes. Furthermore, the observed deviation of the recorded post‐peak modulus values decreased with sample size. The ratio of residual strength of rock mass samples per uniaxial compressive strength intact increases moderately with sample size. Consequently, for the investigated massive sulphide rock mass, the pre‐peak and post‐peak representative elemental volume size was found to be the same (7 × 7 × 14 m). Copyright © 2015 John Wiley &amp; Sons, Ltd.

Microorganisms in subterranean acidic waters within Europe's deepest metal mine

The Pyhäsalmi mine, central Finland, has operated as a deep metal mine since 1967. It currently reaches a depth of almost 1500 m, making it the deepest mining operation in Europe. Around 900,000 m3 of metal-rich, extremely acidic water are pumped out of the mine each year. The near constant air temperature of ∼24 °C together with exposure of sulfidic rock surfaces to air and water, have created an environment that is highly suitable for colonization by acidophilic mineral-oxidizing microorganisms. Using a combined cultivation-dependent and molecular approach, indigenous bacteria in waters at two depths within the mine, and of an acid streamer sample were identified and isolated. Iron-oxidizing chemolithotrophs (Acidithiobacillus and Leptospirillum spp., and “Ferrovum myxofaciens” were the most abundant bacteria in mine water samples, whereas the acid streamer community contained a greater proportion of heterotrophic acidophiles (Ferrimicrobium acidiphilum and a gammaproteobacterium related to Metallibacterium scheffleri). The most abundant isolates obtained from both water and streamer samples were all strains of Acidithiobacillus Group IV, a proposed separate species of iron-oxidizing acidithiobacilli that has not yet been classified as such. Archaea were also detected in water and streamer samples using molecular methods, but most were not identified and no isolates were obtained.

Orogenic gold and rare metal deposits of the Upper Kolyma District, Northeastern Russia: Relation to igneous rocks, timing, and metal assemblages

The Upper Kolyma district is the most important part of the Yana–Kolyma gold province, administratively located in Magadan Oblast, Russia. To date, historic production of the region is about 90Moz of gold, mostly from placers, but with about 5% contribution from lode deposits. Two major types of gold deposits are distinguished in the region: (1) Au-quartz veins related to regionally metamorphosed rocks; and (2) granitoid-related Au. Besides gold, tin deposits are also wide-spread and can be distinguished as: (1) Sn-quartz veins, (2) Sn-silicate-sulfide veins, and (3) Sn-polymetallic veins. Quartz-molybdenite (porphyry Mo) and Ag-polymetallic (Ag-quartz) veins are less abundant. Metamorphic zones and major regional faults are the most important factors of control for the Au-quartz veins. Granitoid intrusions are the most important ore-controlling factor for other deposit types.Field relationships between Au-quartz vein, granitoid-related Au mineralization and intrusions, as well as the 40Ar/39Ar dating reveal several pulses in formation of the Upper Kolyma gold deposits. The majority of granitoid-related Au deposits and occurrences in the region are related to the oldest (150Ma) metaluminous granitoid plutons of the subduction nature. 40Ar/39Ar dates for Au-quartz mineralization in the Upper Kolyma district correspond mostly to 139–125Ma, which is a period of less intense igneous and metamorphic activity in the area. We interpret these ages to indicate vein formation by metamorphic fluids, boiling from uplift and decompression, following Early Cretaceous collision-induced metamorphism. Most Sn-quartz, Sn-silicate-sulfide, Sn-polymetallic veins, as well as Ag-polymetallic and U-REE mineralization relates to the ca. 80Ma plutons, emplaced in an extensional setting.The 40Ar/39Ar data, obtained for Au-quartz vein mineralization, were used as a basis to develop a genetic model that assumes a time interval (from 1 to 15m.y.) between the ore-mobilizing processes and the timing of ore deposition. Such an interval can be interpreted by virtue of the regional uplift and irregular drop in pressure of fluid systems as the main factors of ore deposition.Iron- and As-bearing sulfides are typical for all hardrock deposits of the Upper Kolyma district, and they reflect the event and/or remobilization of gold. Pyrite is the main sulfide in greenschist metaturbidities and igneous rocks. Metamorphism of turbidites resulted in pyrite–pyrrhotite transformations with sulfur, arsenic, and metal mobilization. Arsenopyrite assemblages, usually dominating in the ores of all deposit types of the district, are products of geochemical evolution of the above-mentioned mobilized sulfur and arsenic. The Au-quartz vein deposits are characterized by pyrite–arsenopyrite assemblage, and arsenopyrite has almost a stoichiometric composition; the granitoid-related Au- and Sn-quartz veins are characterized by lollingite–arsenopyrite assemblage and As/S>1 in arsenopyrite; the Sn silicate-sulfide and Sn-polymetallic veins are characterized by pyrite–pyrrhotite–arsenopyrite assemblage and stoichiometric arsenopyrite; the Ag-polymetallic and quartz molybdenite veins are characterized by pyrite–arsenopyrite assemblage and As/S<1 in arsenopyrite. However, some deposits do not agree with the above-mentioned criteria, which can be explained either by overprinting of several mineralization types in an individual deposit or by metamorphism of its ores. The results demonstrate high importance of re-mobilization of metals due to the later hydrothermal and thermal events.

Chemical and Isotopic Characteristics of the Water and Suspended Particulate Materials in the Yangtze River and Their Geological and Environmental Implications

Chemical and Isotopic Characteristics of the Water and Suspended Particulate Materials in the Yangtze River and Their Geological and Environmental Implications

Isotopic fluid changes in a Neoproterozoic porphyry–epithermal system: The Uruguay mine, southern Brazil

Identifying the source, origin and time of emplacement of copper and gold deposits in the Neoproterozoic volcano-sedimentary and plutonic series of southern Brazil is a longstanding research goal. In this geological context, the Camaquã and Lavras do Sul areas are reported to be a post-collisional domain related to the Braziliano–Pan-African Orogenic Cycle. This study focused on the Uruguay open-pit mine through a detailed assessment of the mineralogy, geochemistry and (S, O, H and C) stable isotopes of pyrite, chalcopyrite, clay minerals and carbonates as veins or disseminated sulfides in sedimentary rocks. The results indicate that the Camaquã mine is a low-sulfidation epithermal-type deposit with sulfide precipitations related to a mixture of magmatic (δ34S=1 to 4‰; δ18O: 3 to 9‰) and meteoric waters (δ18O=−4 to −12‰) and a temperature varying from 350 to 80°C. Ore precipitation is associated with sequential sulfide crystallization exhausting the S magmatic source.

Modeling of sulfide oxidation in tailings dumps of the Kavalerovsky district and their impact on the hydrosphere (Primorsky Krai, Russia)

The results obtained in modeling of drainage waters in tailings dumps of deposits in the Kavalerovsky district in the temperature range from 0 to +45°C are reported. The Eh-pH parameters of the technogenic mineral formation systems at various rock sulfide ratios in the tailings (95: 5, 90: 10, 80: 20, and 60: 40) were determined. The crystallization of supergene minerals from micropore solutions was studied. The qualitative and quantitative ion composition of the minerals and their effect on the surface and ground waters in the district were determined.

The mineralizing fluid in the Piaba gold deposit, São Luís cratonic fragment (NW-Maranhão, Brazil) based on fluid inclusion studies in quartz veins

Piaba is the first gold mine to operate in the Sao Luis cratonic fragment, NW-Maranhao, northern Brazil. The geological setting comprises chiefly metavolcano-sedimentary sequences (Au- rizona Group) and subduction-related granitoids (Tromai Intrusi- ve Suite), formed in island arc between 2240 and 2150 Ma. Gold mineralization is hosted in a fine-grained granophyric granodiorite (Piaba Granophyre) and in a subvolcanic andesite of the Aurizona Group. The mineralized zone is confined within the limits of the Piaba fault (ENE-WSW-trending brittle-ductile shear zone) and con- sists of quartz veins and veinlets and accompanying hydrothermal haloes (chlorite + muscovite + carbonate + pyrite + chalcopyrite + gold) disposed in stockwork geometry. Petrographic, microthermo- metric and microRaman spectroscopic studies of quartz have defined two- and three-phase aqueous-carbonic fluid inclusions produced by heterogeneous trapping during phase separation, in addition to late aqueous fluids. The mineralizing solution is an aqueous-carbonic fluid composed of CO 2 (5 – 24 mol%), H 2 O (74 – 93 mol%), N 2 (≤ 1 mol%) and CH4 (≤ 1mol%). It presents low salinity (5.5 wt.% NaCl equivalent) and density of 0.96 – 0.99 g/cm 3 ). Ore deposition occurred at 267 – 302 oC and 1.25 – 2.08 kbars, corresponding to 4 – 7 km in depth, in agreement with the structural information. The P-T-X and reduced characteristics (log ƒO 2 -31.3 to -34.3) of the fluid, combined with host rock sulfidation, altogether indicate that gold has been transported as a sulfur complex and that ore deposition occurred in response to phase separation and lowering of the sulfur activity and ƒO 2 during fluid-rock interaction.

The redox state, FeO content, and origin of sulfur‐rich magmas on Mercury

MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) orbital observations of Mercury have revealed elevated S abundances, Ca‐S and Mg‐S correlations, and a low upper limit for ferrous iron in surface silicates. These data indicate the presence of Ca and/or Mg sulfides in volcanic rocks and a low oxygen fugacity (fO2) in their parental magmas. We have evaluated coupled fO2 and fS2 values and FeO contents in Mercury's magmas from silicate‐sulfide equilibria and empirical models for silicate melts and metallurgical slags. The evaluated fO2 at 1700–1800 K is 4.5 to 7.3 log10 units below the iron‐wüstite buffer. These values correspond to 0.028–0.79 wt % FeO, implying that Fe must be also present in sulfides and metal and are also consistent with the composition of the partial melt of an enstatite chondrite. This derived upper limit for FeO is substantially lower than the limits obtained from reflectance measurements of Mercury's surface materials. The low fO2 and FeO values provide new constraints for igneous processes on Mercury as well as the formation, evolution, and internal structure of the innermost planet.

District to Camp Controls on the Genesis of Komatiite-Hosted Nickel Sulfide Deposits, Agnew-Wiluna Greenstone Belt, Western Australia: Insights from the Multiple Sulfur Isotopes

The Agnew-Wiluna greenstone belt of Western Australia is the largest komatiite-hosted nickel sulfide belt in the world and contains two world-class Ni-Cu-(PGE) deposits and a host of smaller deposits. This study focuses on the broader scale geology of this greenstone belt in order to understand the key controls on the genesis of the komatiite-hosted Ni-Cu-(PGE) deposits, with specific focus on camp to district controls. We apply multiple sulfur isotopes to this geologic framework and conclude not only that the addition of crustal sulfur is a prerequisite for ore genesis in komatiite systems, but above all that the sulfur required to generate world-class deposits is most likely derived from barren volcanic massive sulfide lenses, which are spatially and genetically associated with felsic volcanic and volcaniclastic sequences that were emplaced coevally with large komatiitic sills and channelized lava flows. Multiple sulfur isotope data can be utilized in exploration at the deposit to district scales. At the deposit scale, the spatial pattern of mass-independent S isotope values (Δ 33 S) provides crucial insight into the identification of proximal high-grade and high-tenor ores in mineralized systems. In fact, sulfur data reflect the assimilation process that occurred upon komatiite emplacement, whereby hot turbulent magma thermomechanically eroded and assimilated exhalative sulfides spatially located close to vent with negative to near zero Δ 33 S values, whereas less turbulent flows interacted with distal sulfidic shales having Δ 33 S values above 0 per mil. Accordingly, the spatial variation of multiple sulfur isotope values in magmatic sulfides and associated host rocks may be utilized as a vector towards high-grade ores of poorly known systems. At the district scale, rather than ascertaining what controls the distribution of komatiite-hosted Ni-Cu-(PGE) deposits, the appropriate question to ask is what controls the distribution of country rock sulfides, considering that exhalative sulfides may be crucial to ore genesis in komatiite systems. We propose that felsic lava domes unambiguously mark their vents and can be directly mapped or inferred from gravity data. This work provides the first step in identifying district-scale control on komatiite-hosted Ni-Cu-(PGE) deposits. This is the scale that has high impact on exploration for new komatiite-hosted nickel sulfide belts globally.