Sulfide Occurrences Research Articles

Spatio-temporal variability of organic matter contents in the waters of the Caspian Sea

We analyzed spatio-temporal changes in concentrations and elemental compositions of dissolved organic matter in the waters of the Caspian Sea over the period 2010–2015. These studies showed that over the past 5 years of lowering of sea levels, mean concentrations of Corg and Norg remained virtually unchanged, whereas concentrations of Porg decreased more than three-fold, suggesting a qualitative change in organic matter. Based on data averages, concentrations of Corg, Norg, and Porg in Southern waters were slightly higher than in the North and Middle-Caspian waters during the monitoring period. In deep areas at the border region of hydrogen sulfide occurrence, concentrations of Corg, Norg, and Porg increase. Hence, the presence of hydrogen sulfide in the deep waters of the Derbent and South Caspian basins, and the corresponding increase in organic matter contents, indicates no radical improvement of vertical mixing of the sea in these areas during the eight years of our regression model. Moreover, according to the carbohydrate distribution, organic substances of petroleum hydrocarbons contribute considerably to a common pool.

Platinum Mineralization in Multimetal Gold–Polymetallic, Au–Bi, Cu–Mo Porphyry, Cu–Ni, Titanomagnetite, and Copper–Sulfide Ore Deposits and Occurrences of the Upper Amur Region (Far East, Russia)

New data on platinum mineralization in ores, metasomatic rocks, concentrates, and tailings and wastes of some gold–polymetallic, Au–Bi, Cu–Mo porphyry, Cu–Ni, and titanomagnetite ore deposits and occurrences of the Upper Amur Region are presented. The contents of platinoids, Au and Ag in multimetal ores of gold-polymetallic, Au–Bi, Cu–Mo porphyry, Cu–Ni, and titanomagnetite ore deposits and ore occurrences are given. In addition, recommendations on the necessity of continuing scientific studies, revision, and resampling works in the search for platinoids in other complex ores of deposits and occurrences of the Upper Amur Region are given.

Primary iron sulfides in CM and CR carbonaceous chondrites: Insights into nebular processes

AbstractWe have carried out a systematic study involving SEM, EPMA, and TEM analyses to determine the textures and compositions of sulfides and sulfide–metal assemblages in a suite of minimally to weakly altered CM and CR carbonaceous chondrites. We have attempted to constrain the distribution and origin of primary sulfides that formed in the solar nebula, rather than by secondary asteroidal alteration processes. Our study focused primarily on sulfide assemblages associated with chondrules, but also examined some occurrences of sulfides within the matrices of these meteorites. Although sulfides are a minor phase in carbonaceous chondrites, we have determined that primary sulfide grains are actually a major proportion of the sulfide grains in weakly altered CM chondrites and have survived aqueous alteration relatively unscathed. In minimally altered CR chondrites, we have determined that essentially all of the sulfides are of primary origin, confirming the observations of Schrader et al. (). The pyrrhotite–pentlandite intergrowth (PPI) grains formed from crystallization of monosulfide solid solution (mss) melts, while sulfide‐rimmed metal (SRM) grains formed from sulfidization of Fe,Ni metal. Micron‐sized metal inclusions in some PPI grains may have formed by co‐crystallization of metal and sulfide from a sulfide melt that experienced S volatilization during the chondrule formation event, or alternatively, may be a remnant of sulfidization of Fe,Ni metal that also occurred during chondrule formation. Sulfur fugacity for SRM grains ranged from −18 to −10 (log units) largely in agreement with predicted solar nebular values. Our observations show that understanding the formation mechanisms of primary sulfide grains provides clues to solar nebular conditions, such as the sulfur fugacity during chondrule formation.

Constraints on the source of Cu in a submarine magmatic-hydrothermal system, Brothers volcano, Kermadec island arc

Most magmatic-hydrothermal Cu deposits are genetically linked to arc magmas. However, most continental or oceanic arc magmas are barren, and hence new methods have to be developed to distinguish between barren and mineralised arc systems. Source composition, melting conditions, the timing of S saturation and an initial chalcophile element-enrichment represent important parameters that control the potential of a subduction setting to host an economically valuable deposit. Brothers volcano in the Kermadec island arc is one of the best-studied examples of arc-related submarine magmatic-hydrothermal activity. This study, for the first time, compares the chemical and mineralogical composition of the Brothers seafloor massive sulphides and the associated dacitic to rhyolitic lavas that host the hydrothermal system. Incompatible trace element ratios, such as La/Sm and Ce/Pb, indicate that the basaltic melts from L’Esperance volcano may represent a parental analogue to the more evolved Brothers lavas. Copper-rich magmatic sulphides (Cu > 2 wt%) identified in fresh volcanic glass and phenocryst phases, such as clinopyroxene, plagioclase and Fe–Ti oxide suggest that the surrounding lavas that host the Brothers hydrothermal system represent a potential Cu source for the sulphide ores at the seafloor. Thermodynamic calculations reveal that the Brothers melts reached volatile saturation during their evolution. Melt inclusion data and the occurrence of sulphides along vesicle margins indicate that an exsolving volatile phase extracted Cu from the silicate melt and probably contributed it to the overlying hydrothermal system. Hence, the formation of the Cu-rich seafloor massive sulphides (up to 35.6 wt%) is probably due to the contribution of Cu from a bimodal source including wall rock leaching and magmatic degassing, in a mineralisation style that is hybrid between Cyprus-type volcanic-hosted massive sulphide and subaerial epithermal–porphyry deposits.

Sulfur isotope's signal of nanopyrites enclosed in 2.7 Ga stromatolitic organic remains reveal microbial sulfate reduction.

Microbial sulfate reduction (MSR) is thought to have operated very early on Earth and is often invoked to explain the occurrence of sedimentary sulfides in the rock record. Sedimentary sulfides can also form from sulfides produced abiotically during late diagenesis or metamorphism. As both biotic and abiotic processes contribute to the bulk of sedimentary sulfides, tracing back the original microbial signature from the earliest Earth record is challenging. We present in situ sulfur isotope data from nanopyrites occurring in carbonaceous remains lining the domical shape of stromatolite knobs of the 2.7-Gyr-old Tumbiana Formation (Western Australia). The analyzed nanopyrites show a large range of δ34 S values of about 84‰ (from -33.7‰ to +50.4‰). The recognition that a large δ34 S range of 80‰ is found in individual carbonaceous-rich layers support the interpretation that the nanopyrites were formed in microbial mats through MSR by a Rayleigh distillation process during early diagenesis. An active microbial cycling of sulfur during formation of the stromatolite may have facilitated the mixing of different sulfur pools (atmospheric and hydrothermal) and explain the weak mass independent signature (MIF-S) recorded in the Tumbiana Formation. These results confirm that MSR participated actively to the biogeochemical cycling of sulfur during the Neoarchean and support previous models suggesting anaerobic oxidation of methane using sulfate in the Tumbiana environment.

Constraints from geochemistry and oxygen isotopes for the hydrothermal origin of orthoamphibole mafic gneiss in the New Jersey Highlands, north-central Appalachians, USA

Rare exposures of orthoamphibole mafic (Oam) gneiss of Mesoproterozoic age in the north-central Appalachians are confined to the northwestern New Jersey Highlands where they form thin lens-shaped bodies composed of gedrite and sparse anthophyllite, oligoclase (An13–An20), biotite, magnetite, and local fluorapatite, rutile, and ilmenite. The gneiss is penetratively foliated and has sharp, conformable contacts against enclosing supracrustal paragneiss and marble. Orthoamphibole mafic gneiss is characterized by low SiO2 (48±2.5wt%), CaO (1.9±1.3wt%), and high Al2O3 (18±1.2wt%), Fe2O3 (10.5±1.6wt%), and MgO (12±2.3wt%). Trace element abundances overlap those of unaltered amphibolites in the study area and, coupled with δ18O values of 9.45±0.6‰ (VSMOW) from gedrite separates, support an origin from a basalt protolith.The geochemical and isotopic data are consistent with the formation of Oam gneiss through sea floor hydrothermal alteration of basalt at low temperature of 150–200°C. Mass-balance calculations indicate gains during alteration mainly in MgO and Al2O3 and losses in CaO, Sr, and light rare earth elements. Our results are compatible with the pre-metamorphic alteration of the basalt protoliths through chloritization and plagioclase dissolution that produced a Mg-rich and Ca-poor rock. Subsequent metamorphism of this chlorite-rich rock to the current mineral assemblage of Oam gneiss took place at ca. 1045Ma, during the Ottawan phase of the Grenvillian Orogeny. The close spatial association in the study area of Oam gneiss bodies and sulfide occurrences suggests an affinity to the style of mineralization associated with volcanogenic massive sulfide (VMS)-type deposits.

GEOCHEMICAL CHARACTERISTIC OF AG-BEARING MINERALS OCCURRING IN COPPER ORE DEPOSIT AT THE FORE-SUDETIC MONOCLINE

Silver is the most important associated element in the copper ore deposit of the Fore-Sudetic Monocline. Besides its own minerals, such as native silver, amalgams, stromeyerite, mackinstryite, jalpaite and Cu-Fe-Ag system sulphides, the silver occurs as isomorphic substitutions in copper minerals. The aim of this work included geochemical characterization of Ag-bearing minerals and correlation of the occurrence of Ag-enriched Cu sulphides with the areas of native silver and amalgam mineralization. Distribution of silver in the ore deposit distinctly correlates with Cu concentrations, and the areas of the strongest Cu mineralization are accompanied by high silver concentrations. Results of the scanning electron microscopy and electron microprobe analysis indicate that the Cu sulphides contain up to several wt.% Ag as isomorphic substitutions. Distribution of Ag in Cu sulfides does not show regularity, as demonstrated by wide diversity of Ag contents in various minerals, ranging from 0.0X to dozen wt.% Ag.

Sulfide chemistry and sulfur isotope characteristics of the Cenozoic volcanic-hosted Kuh-Pang copper deposit, Saveh county, northwestern central Iran

The several-hundred-m-thick Eocene-Oligocene volcanic units in the Urmia-Dokhtar magmatic arc in northwestern Central Iran host stratabound and fault-controlled copper mineralization. The Kuh-Pang deposit (2.8Mt at 1.65wt% Cu, 0.52g/t Au, 34g/t Ag) has vein-style copper mineralization, with primary Cu-sulfides of chalcopyrite, bornite, chalcocite and digenite, and supergene Cu-sulfides of chalcocite, covellite, malachite and azurite, in a tectonic–hydrothermal breccia zone within rhyodacite and andesite flows. The mineralization is accompanied by a variety of alterations including silicic, carbonate, argillic and advanced argillic within a broad-scale propylitic halo. The main ore formation is related to hydrothermal breccias, and has a close association with silicic and argillic alterations. Sulfides formed during hydrothermal alteration, as indicated by: 1) the occurrence of disseminated sulfides in the groundmass of hydrothermally altered rocks, 2) the co-precipitation of sulfides and alteration minerals (e.g., kaolinite, alunite) in the cement of hydrothermal breccias, and 3) the occurrence of sulfides filling fissures and voids of hydrothermally altered rocks (vuggy quartz). The main mineralization stages include: (i) pre-ore stage with pyrite and arsenopyrite, (ii) main ore-stage with chalcopyrite, bornite, chalcocite I and digenite, and (iii) late-ore and supergene enrichment stage with chalcocite II and covellite. Electron microprobe analyses of pyrite show that As, Cu and Co are the most abundant minor elements. Back-scatter electron imaging of pyrite shows zoning features that closely reflect variations in the As/S ratio. High Cu concentration in pyrite is probably related to the presence of sub-micrometer particles and aggregates of chalcopyrite or other Cu-bearing sulfide minerals. Silver is preferentially enriched in supergene chalcocite and covellite. The mineral assemblage indicates a trend from intermediate to high sulfidation state, and arsenopyrite geothermometry defines temperatures for the pre-ore sulfides ranging from 250 to 370°C. The sulfur isotope composition of pre-ore pyrite and arsenopyrite shows a δ34S range of −1 to 3‰, indicating a magmatic sulfur-source. The copper sulfides have lower δ34S values (−9 to −3‰), indicating that the ore-forming fluids gradually became SO42−-enriched and relatively oxidized during Cu mineralization. The tectono-magmatic setting, mineral assemblage and hydrothermal alteration, including advanced argillic and silicic zones, suggest that the Kuh-Pang copper deposit is a high sulfidation epithermal deposit in a volcanic arc terrain.

A multi‐disciplinary characterisation of Heath Steele belt deposits, Bathurst Mining Camp: a basis for identifying new targets for the exploration

ABSTRACTAlthough the Bathurst Mining Camp has been explored for more than 40 years, high‐resolution airborne geophysical survey has led to the detection of several new volcanogenic massive sulphide occurrences in the region. The discovery of these concealed exploration targets depended directly on the knowledge of the multi‐parameter signature of the major deposits and the search for the repeatability of these signatures in other regions. The Heath Steele B deposit, within the southern part of the Bathurst Mining Camp, together with an associated magnetite‐rich iron formation and adjacent tuffaceous sedimentary rocks, produced strong, co‐extensive magnetic and conductivity anomalies. However, the strong anomalies observed in the geophysical data can be related to non‐mineralised lithology such as mafic dykes or graphite. So a direct identification of exploration targets using geophysical data only can be difficult. For this reason, the joint interpretation of geophysical and geochemical signature can considerably improve the identification of new deposits. Using these techniques, we identify three new possible targets, characterised by local magnetic and apparent conductive highs. Two of these areas are located in the Heath Steele belt, and their geochemistry has been studied in detail. The proximity of these targets (less than 1.5 km) from known occurrences of hydrothermal sediments (magnetite, siderite, and stilpnomelane) confirms their exploration potential. The fourth identified area is most likely associated with a regional anomaly related to an unmapped ferromagnetic structure and was earlier disregarded as a possible target. The joint interpretation of geophysical and geochemical data allowed us to identify two new targets for exploration and to exclude one area interpreted as associated with a regional anomaly. Therefore, the search parameters (physical proprieties and hydrothermal sediment geochemical pattern distribution) are established with a success index of 75%. The index was limited by the absence of geochemistry data over the third target. The procedure presented in this paper can be used to search for new targets elsewhere in the Bathurst area and even in other base metal regions.

Mesoproterozoic base metal sulphide deposits in the Namaqua Sector of the Namaqua-Natal Metamorphic Province, South Africa: a review

The Mesoproterozoic Namaqua Sector of the east-west trending Namaqua-Natal Metamorphic Province (NNMP) located in the Northern Cape Province is underlain by supracrustal rocks and abundant felsic intrusive rocks that have been subjected to medium to high grade metamorphism and polyphase deformation. It is the host to world class base metal sulphide resources that have been mined for more than a century. Most of these mines are no longer in production such that the Cu-Pb-Zn-Ag mines in the Aggeneys-Gamsberg Ore District (A-GOD), with a total output of 1.8 million ton (Mt) per annum, are the only current significant producers. Development of the supergiant Gamsberg zinc deposit commenced in 2015 and will add a further 4 Mt per annum (250 000 t of zinc) to the output with the mine eventually becoming one of the larger zinc producers in the world. The Namaqua Sector of the NNMP has been subdivided into several lithologically distinct, structural discontinuity bounded Subprovinces and Terranes, each with its characteristic base metal sulphide deposits. The most extensive and best mineralized of these is the Bushmanland Subprovince where the ~1300 Ma stratabound polymetallic Broken Hill-type meta-SEDEX deposits contain total resources exceeding 500 Mt of Zn-Pb-Cu-Ag ore. Further east much smaller and subeconomic stratabound deposits occur at Putsberg (Cu-Zn-Pb-Ag) and Adjoining Geelvloer (Zn-Cu-Pb-Ag-Au). Magmatic ore deposits include minor magnetite-copper skarn/iron-oxide-copper-gold (IOCG) deposits associated with syntectonic granitoids (~1200 Ma) in the east and small syntectonic gabbronorite hosted Ni-Cu-(Co) occurrences at Hondekloof (~1170 Ma) to the southwest. The mined-out Okiep Copper District in the west hosts an abundance of small, syn- to late-tectonic mafic cupriferous intrusions (~1030 Ma), which collectively contributed some 100 Mt of ore yielding ~2 Mt of blister copper. The Areachap Terrane in the far eastern part of the Namaqua sector of the NNMP has a number of stratabound volcanogenic massive sulphide (VMS) Zn-Cu (Ag-Au) deposits of variable tonnage and hosted by intermediate to mafic meta-volcanic and meta-sedimentary rocks (~1300 Ma). The largest of these, the world class Prieska deposit (47 Mt) has been mined out. The remainder of the deposits are small (1.5 to 9 Mt), of low grade and uneconomic. The Terrane has been intruded by a suite of poorly mineralized mafic to ultramafic rocks (~1180 Ma) of which the high tonnage (114 Mt) but low grade Jacomynspan Ni-Cu deposit, is the most significant. The Richtersveld and Gordonia Subprovinces are poorly mineralized whereas the Kaaien Terrane has no Mesoproterozoic mineralization of any significance. The Gordonia Subprovince hosts the small magmatic Oup Ni-Cu-(Co) deposit (~1150 Ma) and is the only massive sulphide occurrence in the Subprovince. Both domains however, have minerals deposits associated with the regionally extensive post-tectonic Namaqualand pegmatite belt (~1000 Ma) which is a resource of beryl, tantalite, wolframite, cassiterite, micas, and feldspar. The Mesoproterozoic stratabound deposits of the Namaqua Sector of the NNMP are all of similar age and terrane bounded. Their different characteristics are the result of relative position within a subduction related plate tectonic setting. The siliciclastic hosted deposits of the Aggeneys-Gamsberg Ore District are interpreted to have formed in a continental sub-basin whereas the more chemogenic-volcanogenic hosts of the Putsberg and Adjoining Geelvloer deposits have the lithological characteristics associated with a back arc basin. The VMS deposits of the Areachap Terrane are linked to a mature island arc and were located more proximal to the subduction zone. The younger magmatic, mainly Ni-Cu and Cu deposits are syn- to post-tectonic, formed over a timespan of ~150 Ma, do not appear to be terrane specific and are considered to have been generated from basaltic magma during partial melting of subcontinental lithospheric mantle. Localization of intrusive suites can be the result of crustal thinning or proximity to major zones of dislocation such as the Pofadder Shear Zone and Boven Rugzeer Shear zone. The exploration success within the Namaqua Sector of the NNMP has been significant and effectively all known deposits, apart from those of the Okiep Copper District, were discovered using basic airborne and ground geophysical methods, soil geochemistry, lithological mapping and limited remote sensing during the 1970’s and early 1980’s. Future exploration should focus on the use of advanced airborne, ground and down-the-hole geophysics supported by remote sensing, soil and lithogeochemistry, the use of heavy mineral tracers and a workable geological ore deposit model. Over the last 35 years, the area has shown a decrease in the number of operating mines and commodity production, in particular copper. Although several areas show exploration potential, the Aggeneys-Gamsberg Ore District offers the best brown fields target whereas initiation of mining of the known smaller deposits is dependent on the revival of the currently depressed commodity demand and price.

Application of ASTER and Landsat 8 imagery data and mathematical evaluation method in detecting iron minerals contamination in the Chadormalu iron mine area, central Iran

Satellite images are widely used to map geological and environmental features at different map scales. The ability of visible to near-infrared (VNIR) scanner systems to map gossans, rich in iron and associated with weathered sulfide occurrences, as well as to characterize regoliths, is perhaps one of the most important current applications of this technology. Initial results of this study show that advanced space-borne thermal emission and reflection (ASTER), VNIR, and short-wave infrared radiometer scanner systems can be used successfully to map iron ores. By applying internal average relative reflectance, false color composite, minimum noise fraction transform, and mathematical evaluation method (MEM) techniques, iron contaminations were successfully detected in the Chadormalu iron mine area of central Iran. An attempt was also made to discriminate between the geogenic and anthropogenic iron contaminations in the vicinity of the Chadormalu iron deposit. This research compares ASTER and Landsat 8 data images and the MEM with the band ratio method in a full scope view scale and demonstrates ASTER image data capability in detecting iron contaminations in the Chadormalu area. This indicates that ASTER bands 3, 2, and 1 have a higher spatial (15 m) resolution compared with sensors used in previous works. In addition, the capability of the MEM in detecting Fe-contaminants, unlike the color judgments of the band ratio method, can discriminate between iron pollution in an alluvial plain and the Fe-contents of the host and country rocks in the study area. This study proved that Landsat 8 data illustrate exaggeration both in the MEM and band ratio final results (outputs) and cannot display iron contamination in detail.

Modification of an ancient subcontinental lithospheric mantle by continental subduction: Insight from the Maowu garnet peridotites in the Dabie UHP belt, eastern China

Orogenic mantle-derived peridotites commonly originate from the subcontinental lithospheric mantle (SCLM) and thus provide a key target to investigate the modification of the SCLM by a subducting slab. The Maowu ultramafic rocks from the Dabie ultrahigh-pressure (UHP) metamorphic belt have formerly been debated as representing cumulates or mantle-derived peridotites. Detailed petrological and geochemical data presented in this study provide new constraints on the origin and formation of the peridotites involving melt depletion in the ancient SCLM and deep crustal metasomatism. The Maowu garnet dunites have refractory bulk compositions characterized by high Mg# (91.9–92.0) and Ni (2537–2892ppm) values and low Al2O3 (0.26–0.76wt.%), CaO (0.05–0.32wt.%), TiO2 (<0.03wt.%), Pd/Ir (0.40–0.46) and 187Os/188Os (minimum 0.11461) values. The Paleoproterozoic model ages (TRD=2.1Ga, TMA=2.3Ga) of the most refractory dunites represent minimum estimates for the age of the initial melt extraction. The extremely depleted nature, high olivine Fo (92.7–93.9), high Cr# (82–87) of spinel, and Re–Os isotopic data suggest that the Maowu garnet dunites are the residues of ~40% partial melting and represent a Paleoproterozoic fragment of the SCLM beneath the southeastern margin of the North China craton. Many garnet orthopyroxenite veins crosscutting the Maowu dunites preserve abundant metasomatic textures and show variable enrichment in incompatible elements. Mineral and whole-rock chemistry indicate that these veins represent metasomatic products between the wall dunites and silica-rich hydrous melts under UHP conditions. The veins show large variations in platinum-group element (PGE) signatures and Re–Os isotopes. The garnet-poor orthopyroxenite veins are characterized by low Al2O3 (<2wt.%) and S (<31ppm) contents and have PGE patterns and 187Os/188Os ratios similar to the wall dunites, whereas the garnet-rich orthopyroxenite veins have high Al2O3 (>6wt.%) and S (99–306ppm) contents and show melt-like PGE patterns and high 187Os/188Os ratios (up to 0.36910). These features, combined with the occurrence of interstitial sulfides in the garnet-rich orthopyroxenite veins, suggest that crust-derived sulfur-saturated silicate melts may have significantly modified the PGE signature and destroyed the Re–Os systematics of the SCLM. However, when the crust-derived silicate melts became sulfur-depleted, such melts would not significantly modify the PGE patterns, radiogenic Os-isotope compositions or the Re-depletion model ages of the SCLM. Consequently, deep crust-mantle interactions in continental subduction zones could induce high degrees of Os isotopic heterogeneity in the SCLM wedge.

The forms of occurrence and geochemistry of sulfides in hard coal deposits of the Libiąż Beds in the Upper Silesian Coal Basin, Southern Poland

Samples of coal from the eastern part of the Upper Silesian Coal Basin, between Jaworzno and Libiąz, were collected from test boreholes and underground excavations in the Janina Coal Mine, southwest Poland. The No. 111-119 hard coal seams are in the upper part of the Cracow Sandstone Series (the Libiąz Beds, Westphalian D). Macroscopically, iron sulfides (pyrite and marcasite) found in hard coal seams are usually in vein and impregnation forms. On the basis of microscopic observations, the following forms of iron sulfides occurrence in the studied coal were observed: framboidal pyrite, euhedral crystals, skeletal and massive vein forms, or pocket-like (impregnation) forms. On the basis of SEM-EDS analysis and X-ray diffraction it can be stated that the iron sulfides observed in coal are a mixture of pyrite and marcasite. WDS analysis in the micro area revealed the chemical composition of sulfides. The iron sulfides contain admixtures of Pb, Hg, Zn, Cu, Au, Ag, Sb, Co, and Ni. There was no As and Cd found in the examined minerals. It has been shown that the tested iron sulfides do not include significant admixtures. There is only a slight enrichment in lead in the vein forms of sulfides. In addition to the iron sulfides, individual inclusions of galena and sphalerite within the pyrite and marcasite have been observed.

Preliminary Design of a Trench Cutter System for Deep-Sea Mining Applications Under Hyperbaric Conditions

Seafloor massive sulfides (SMSs) are formed as precipitation products from hot hydrothermal fluids as a result of mixing with cold seawater and are mostly found at depths between 1500 and 3600 m. These deposits are formed in tectonically active zones of oceans (midocean ridges and “back-arc” spreading systems) and are the result of the global heat transfer from the mantle in the oceanic crust. As these fluids mix with the cold surrounding seawater, metal sulfides in the water are precipitated on or in the nearby seabed. The appearance of the solid mineral occurs as cylindrical chimney structures: the so-called black and white smoker (caused mainly by the presence of iron, copper, zinc, and sulphur). Larger sulfide occurrences are mostly originated in several generations of hydrothermal cycles, and they form deposits that can range from several thousands to about million tons. SMS contains pyrite (iron), galena (lead), sphalerite (zinc), and chalcopyrite (copper). Deep-sea mining is concentrating now to exploit such deposits. So far, the only known commercial project is the one developed by Nautilus Minerals, which is based on a horizontal system. This paper describes a preliminary design of a novel cutting tool developed for a vertical mining approach. The vertical mining method is preferred when rough terrain is expected and the device is easy to relocate. Using an atmospheric and hyperbaric cutting model, the cutting energy for two selected SMS deposits has been estimated and validated with real onshore excavation sites performed with a cutting tool normally used for diaphragm wall installation (i.e., the trench cutter technology). Preliminary results suggest that the estimated cutting energy ${\bf E}_{\bf SP}$ is 2.9 times higher with respect to the measured one in atmospheric conditions. This could be because the model considers the worst case scenario, i.e., higher energy due to the maximum cutting forces assumed. This factor has been used to design a cutting tool which is able to work up 2000-m water depth to mine SMS deposits.

Sulphides in Hard Coal Seams from the Orzesze Beds s.s. of Mudstone Series (Westphalian B) in the Eastern Part of the Upper Silesian Coal Basin

Abstract Due to dynamic climatic changes resulting, among others, from the use of coal, the content of harmful substances in coal is of particular importance. Dangerous air pollution resulting from the burning of coal (e.g. As, Se, Hg, Pb, Sb) is often associated with sulfide minerals in coal. The study focused on the sulphides occurring in Polish hard coal deposits. Sulfides are one of the forms of occurrence of sulfur in coal. In this paper, an emphasis has been placed on on the characteristics of forms of occurrence of sulphides on both macroscopic and microscopic scale and on the chemical analysis in the micro area. The study has been conducted for the No. 301–308 seams from the eastern part of the Upper Silesian Coal Basin, stratigraphically belonging to the highest part of the Orzesze Beds s.s. (Westphalian B). The coal samples have been collected from the coal seams in the underground excavations of the following coal mines: Jan Kanty, Sobieski Jaworzno I, Wesoła and Ziemowit hard coal mine. Iron sulfides (pyrite, marcasite) in coal seams of the Orzesze Beds s.s. form various forms of macroscopically visible aggregates. These include massive, vein, pocket-like (impregnation) or dispersed forms. On the basis of microscopic observations, the following forms of occurence of iron sulphides in the tested coal have been determined: skeletal and massive vein forms, massive pocket-like (impregnation) forms, framboidal pyrite and euhedral crystals. The most common form of sulfides in the studied coal seams are vein forms cutting across bedding, usually creating complex dendritic and skeletal forms. Iron sulfides often occur in pocket-like (impregnation) forms, not directly linked with vein forms and fusinite. The WDS analysis in the micro area has revealed the chemical composition of sulfides in eight coal samples. As follows from the analysis, the tested coal seams are dominated by FeS2 iron sulfides. It has been shown that the iron sulfides contained small admixtures of Pb, Hg, Zn, Cu, Ag, Co Sb and Ni. The admixtures of As and Cd have been observed only in individual minerals. Lead, reaching up to 1.06%, has the highest concentration out of all admixtures in pyrite and marcasite. Small amounts of galena, titanium oxides (rutile), monazite and barite have also been found in the tested coal samples. Locally, vein forms, pyrite and dolomite were interlaying each other; the same applies to pyrite and apatite. In addition, dolomite fills part of the cells in fusinite.

Magmatic Cu-Ni-PGE-Au sulfide mineralisation in alkaline igneous systems: An example from the Sron Garbh intrusion, Tyndrum, Scotland

Magmatic sulfide deposits typically occur in ultramafic-mafic systems, however, mineralisation can occur in more intermediate and alkaline magmas. Sron Garbh is an appinite-diorite intrusion emplaced into Dalradian metasediments in the Tyndrum area of Scotland that hosts magmatic Cu-Ni-PGE-Au sulfide mineralisation in the appinitic portion. It is thus an example of magmatic sulfide mineralisation hosted by alkaline rocks, and is the most significantly mineralised appinitic intrusion known in the British Isles. The intrusion is irregularly shaped, with an appinite rim, comprising amphibole cumulates classed as vogesites. The central portion of the intrusion is comprised of unmineralised, but pyrite-bearing, diorites. Both appinites and diorites have similar trace element geochemistry that suggests the diorite is a more fractionated differentiate of the appinite from a common source that can be classed with the high Ba-Sr intrusions of the Scottish Caledonides. Mineralisation is present as a disseminated, primary chalcopyrite-pyrite-PGM assemblage and a blebby, pyrite-chalcopyrite assemblage with significant Co-As-rich pyrite. Both assemblages contain minor millerite and Ni-Co-As-sulfides. The mineralisation is Cu-, PPGE-, and Au-rich and IPGE-poor and the platinum group mineral assemblage is overwhelmingly dominated by Pd minerals; however, the bulk rock Pt/Pd ratio is around 0.8. Laser ablation analysis of the sulfides reveals that pyrite and the Ni-Co-sulfides are the primary host for Pt, which is present in solid solution in concentrations of up to 22ppm in pyrite. Good correlations between all base and precious metals indicate very little hydrothermal remobilisation of metals despite some evidence of secondary pyrite and PGM. Sulfur isotope data indicate some crustal S in the magmatic sulfide assemblages. The source of this is unlikely to have been the local quartzites, but S-rich Dalradian sediments present at depth. The generation of magmatic Cu-Ni-PGE-Au mineralisation at Sron Garbh can be attributed to post-collisional slab drop off that allowed hydrous, low-degree partial melting to take place that produced a Cu-PPGE-Au-enriched melt, which ascended through the crust, assimilating crustal S from the Dalradian sediments. The presence of a number of PGE-enriched sulfide occurrences in appinitic intrusions across the Scottish Caledonides indicates that the region contains certain features that make it more prospective than other alkaline provinces worldwide, which may be linked the post-Caledonian slab drop off event. We propose that the incongruent melting of pre-existing magmatic sulfides or ‘refertilised’ mantle in low-degree partial melts can produce characteristically fractionated, Cu-PPGE-Au-semi metal bearing, hydrous, alkali melts, which, if they undergo sulfide saturation, have the potential to produce alkaline-hosted magmatic sulfide deposits.

Using sediment geochemistry to infer temporal variation of methane flux at a cold seep in the South China Sea

Release of methane from the seafloor throughout the world's oceans and the biogeochemical processes involved may have significant effects on the marine sedimentary environment. Identification of such methane release events in marine sediment records can hence provide a window into the magnitude of ancient seeps. Here, we report on analysis of the geochemical composition of samples in a 12.3 m long sediment core (DH-5) collected from a seep site in the South China Sea (SCS). Our aim has been to investigate whether the evidence for the presence of methane release event within sediments is discernible from solid-phase sediment geochemistry. We show that sedimentary total sulfur (TS), δ34S values of chromium reducible sulfur (δ34SCRS) along with total organic carbon (TOC) and total inorganic carbon (TIC) content can be used to infer the presence of methane release events in cold seep settings. At least three methane release events were identified in the studied core (Unit I at 400–550 cm, Unit II at 740–820 cm, and Unit III at 1000–1150 cm). According to the characteristic of redox-sensitive elements (eg., Mo, U and Mn), we suggest that methane flux has been changed from relatively high (Unit I) to low (Unit II and III) rates. This inference is supported by the coupled occurrence of 34S-enriched sulfides in Unit II and III. AMS 14C dates from planktonic foraminifera in Unit I suggest that high methane flux event occurred at ∼15.4–24.8 kyr BP, which probably resulted in locally-focused aerobic methane oxidation. Overall, our results suggest that TS, TOC, TIC and δ34SCRS have potential for identifying present and fossil methane release events in marine sediments.

Geochemical and Spectral Footprint of Metamorphosed and Deformed VMS-style Mineralization in the Quinns District, Yilgarn Craton, Western Australia*

Volcanic-hosted massive sulfide (VMS) occurrences in the Quinns district are hosted predominantly by ca. 2814–2800 Ma banded iron formation (BIF) within a sequence of rhyolite, basalt, and minor siltstone. The VMS occurrences and their surrounding rocks are folded, metamorphosed, and deeply weathered and variably covered by transported regolith. This study uses an integrated petrological and geochemical approach to map gradients in synvolcanic mineral and element abundances, with the aim of understanding the effects of postvolcanic processes on Archean VMS ore. Rhyolite-dominant footwall rocks and the BIF record kilometer-scale gradients in alteration mineral patterns and geochemistry. Rhyolite exposed throughout the district and intersected by drill holes records distal alteration assemblages of quartz-white mica ± chlorite. At the Austin deposit in the western part of the district, abundant talc and anthophyllite with minor cummingtonite and hornblende are associated with mineralization in the BIF, indicating intense magnesium metasomatism. Further away from mineralization, chlorite is the dominant alteration mineral. Adjacent rhyolite is altered to chlorite in proximal zones and white micas in more distal areas. Approaching known VMS prospects in the eastern half of the district, the rhyolite grades into a 2 × 1 km zone of schistose rhyolite with generally dispersed, but locally abundant, coarse-grained andalusite ± kyanite ± garnet rhyolitic schist. This broad Al-rich silicate alteration zone envelops two discrete 1 km × 500 m proximal alteration zones in rhyolite, defined by chlorite ± talc, with minor disseminated magnetite, pyrite, and chalcopyrite. The northernmost proximal alteration zone lies stratigraphically below the BIF-hosted Cu-Zn-rich gossan exposed near the Tasman prospect. The proximal zones are interpreted to be the result of the interaction between synvolcanic, Mg-rich fluids and rhyolite footwall at the time of VMS mineralization and BIF deposition. In contrast, outer zones of andalusite ± kyanite ± garnet suggest the removal of silica and alkali elements and residual concentration of aluminium in rhyolite footwall by acidic synvolcanic hydrothermal fluids prior to peak regional metamorphism. The mapped patterns in alteration minerals mirror bulk rock geochemical gradients in rhyolite; proximal alteration zones are enriched in Cu, Zn, Ag, Au, Bi, Fe2O3, In, MgO, Mo, S, Se, and Te, with local enrichments in As, Cd, MnO, Pb, and V. These rocks are depleted in Ba, K2O, Li, Na2O, and Rb relative to least-altered rhyolite. Rhyolite located up to 100 m from proximal alteration zones is enriched in Ag, Fe2O3, In, K2O, MgO, S, and V. Banded iron formation hosting massive sulfides is altered to talc, anthophyllite, chlorite, and magnetite; these rocks are enriched in Cu, Zn, Pb, Ag, and Sn, with local enrichments in Bi, In, and MgO. Positive Eu anomalies are associated with mineralized BIF in the Austin VMS deposit and contrast with the mostly flat REE slopes for the BIF sampled from less mineralized areas in the district. The kilometer-scale gradients in hydrothermal alteration minerals and bulk rock geochemistry in rhyolite and the BIF are interpreted to be mostly controlled by synvolcanic hydrothermal alteration related to the development of VMS-related hydrothermal fluid pathways. Metamorphism of the synvolcanic alteration was isochemical, apart from localized metasomatism related to later shear zones or fault zones. The defined alteration mineral and geochemical gradients serve as useful tools for detecting fluid alteration pathways related to VMS systems in complexly deformed and metamorphosed districts globally.

Sulfur isotope patterns of iron sulfide and barite nodules in the Upper Cretaceous Chalk of England and their regional significance in the origin of coloured chalks

AbstractThe relationship between the development of iron sulfide and barite nodules in the Cenomanian Chalk of England and the presence of a red hematitic pigment has been investigated using sulfur isotopes. In southern England where red and pink chalks are absent, iron sulfide nodules are widespread. Two typical large iron sulfide nodules exhibit δ34S ranging from −48.6‰ at their core to −32.6‰ at their outer margins. In eastern England, where red and pink chalks occur in three main bands, there is an antipathetic relationship between the coloured chalks and the occurrence of iron sulfide or barite nodules. Here iron sulfide, or its oxidised remnants, are restricted to two situations: (1) in association with hard grounds that developed originally in chalks that contained the hematite pigment or its postulated precursor FeOH3, or (2) in regional sulfidization zones that cut across the stratigraphy. In the Cenomanian Chalk exposed in the cliffs at Speeton, Yorkshire, pyrite and marcasite (both iron sulfide) nodules range in δ34S from −34.7‰ to +40.0‰. In the lower part of the section δ34S vary from −34.8‰ to +7.8‰, a single barite nodule has δ34S between +26.9‰ and +29.9‰. In the middle part of the section δ34S ranges from +23.8‰ to +40.0‰. In the sulfidization zones that cut across the Cenomanian Chalk of Lincolnshire the iron sulfide nodules are typically heavily weathered but these may contain patches of unoxidised pyrite. In these zones, δ34S ranges from −32.9‰ to +7.9‰. The cross-cutting zones of sulfidization in eastern England are linked to three basement faults – the Flamborough Head Fault Zone, the Caistor Fault and the postulated Wash Line of Jeans (1980) – that have affected the deposition of the Chalk. It is argued that these faults have been both the conduits by which allochthonous fluids – rich in hydrogen sulfide/sulfate, hydrocarbons and possibly charged with sulfate-reducing bacteria – have penetrated the Cenomanian Chalk as the result of movement during the Late Cretaceous or Cenozoic. These invasive fluids are associated with (1) the reduction of the red hematite pigment or its praecursor, (2) the subsequent development of both iron sulfides and barite, and (3) the loss of overpressure in the Cenomanian Chalk and its late diagenetic hardening by anoxic cementation. Evidence is reviewed for the origin of the red hematite pigment of the coloured chalks and for the iron involved in the development of iron sulfides, a hydrothermal or volcanogenic origin is favoured.

Petrography, sulfide mineral chemistry, and sulfur isotope evidence for a hydrothermal imprint on Musina copper deposits, Limpopo Province, South Africa: Evidence for a breccia pipe origin?

The Musina copper deposits are located in the Central Zone of the Limpopo orogenic belt in Limpopo Province, South Africa. We carried out a petrographic, sulfide composition, and δ34S study on samples from Artonvilla and Campbell copper deposits and a country rock granitic gneiss to Artonvilla Mine to place some constrains on the origin of these deposits.The assemblages at both Artonvilla and Campbell Mines of brecciated quartz, potassium feldspar, muscovite, chlorite, calcite, and amphibole are consistent with sericitic alteration. Quartz, amphibole, feldspars, and micas often display angular textures which are consistent with breccias. Sulfur concentrations in pyrite from Artonvilla Mine plot in a narrow range, from 50.2 wt. % to 55.7 wt. %. With the exception of a positive correlation between Fe and Cu, no well defined correlations are shown by data from the Musina copper deposits. The occurrence of sulfides both as inclusions in, or as interstitial phases in silicates, suggests that hydrothermal alteration that affected these deposits most likely helped concentrate the mineralization at the Musina copper deposits. Sulfur concentrations in chalcopyrite samples investigated vary widely whereas the copper concentrations in chalcopyrite are not unusually higher compared to those from chalcopyrite from other tectonic settings, probably indicating that either the Cu in the Musina copper deposits occurs in native form, and/or that it is hosted by other phases. This observation lends support to the Cu having been concentrated during a later hydrothermal event.One sample from Artonvilla Mine (AtCal01) yielded pyrite δ34S values of 3.1and 3.6‰ and chalcopyrite from the same sample yielded a value of 3.9‰. A country rock granitic gneiss to Artonvilla Mine yielded a δ34Spyrite value of 8.2‰. For Campbell Mine samples, one quartz vein sample has a δ34Spyrite value of 0.5‰ whereas chalcopyrite samples drilled from different areas within the same sample yielded values of 0.4 and 0.7‰. The same sample also yielded a δ34Sbornite value of 0.4‰. Another Campbell Mine quartz vein sample yielded a chalcopyrite δ34S value of −0.3‰. Sulfur isotope thermometry for one Campbell Mine quartz vein sample with coexisting sulfides yielded a Δ34Schalcopyrite-bornite value of 359 °C that is consistent with the stability of this mineral pair. Thus, δ34S values from Campbell Mine are consistent with an igneous source for the sulfur. Based on a simple two-end member isotope mixing model, contamination of the sulfur by sulfur derived from granitic country rocks likely occurred at Artonvilla Mine. Based on findings from this study and by other previous investigators, it is concluded that features displayed by the Musina copper deposits are consistent with a breccia pipe origin for the Musina copper deposits.