Academic literature on the topic 'Polymetallic massive sulphide'

A comparative paleovolcanic and metallogenic analysis of two massive-sulphide-bearing regions, the Southern Urals and Ore Altai, located in different parts of the Ural-Mongolian folded belt, was performed. Comparison of the geodynamic evolution of these areas, the formation and facies composition of the ore-bearing strata and types of massive-sulphide deposits has led to the conclusion that the regions are similar only in the most general terms. Fundamental differences in the structure and composition of the crust of the regions led to differences in the profile of island-arc magmatism: basaltoid in the Southern Urals and rhyolitoid in Ore Altai. This, in its turn, determined the predominant composition of massive-sulphide mineralization: copper-zinc in the first of the regions and polymetallic — in the second. Opposite tendencies in the evolution of volcanism are also characteristic: homodromic in the Southern Urals and antidromic in the Ore Altai, which resulted in a different position of the types of massive-sulphide deposits in the ore districts: the bottom-up change of copper — massive-sulphide deposits by the massive-sulphide -polymetallic in the Southern Urals and barite polymetallic by massive-sulphide polymetallic and copper- massive-sulphide in the Ore Altai. Significant differences are also in the lateral distribution patterns of mineralization: a more pronounced control of mineralization by paleovolcanic structures of the central type in the Southern Urals and the frequent position of mineralization in intermediate and remote facies of volcanism in the Ore Altai, which is reflected in the prevalence of volcanic sections in the Urals and the majority of the volcanic sections and the larger majority of the volcanic rocks in the Ore Altai, which is reflected in the prevalence of volcanic rocks in the Urals and the majority of the volcanic sections and in the Ore Altai most of the volcanic minerals and the larger majority of the mineral rocks (20–80%) in the strata containing mineralization in the Ore Altai.

A reconnaissance study of 19 volcanogenic massive sulphide deposits in the Notre Dame Bay area indicates Au concentrations of up to 30 ppm (Betts Cove), and elevated gold contents (>1 ppm Au) have been found in samples from 10 additional past producers and developed prospects. Systematic trends in the occurrence of gold are observed in two principal sulphide assemblages: polymetallic, pyrite–sphalerite–chalcopyrite–galena ± arsenopyrite assemblages (type I) and pyrite–chalcopyrite ± sphalerite ± pyrrhotite assemblages (type II). Type I assemblages occur in deposits with dominantly felsic host rocks, whereas type II assemblages are restricted to deposits in mafic-dominated ophiolite sequences. Free gold grains were observed in samples from eight different deposits in both type I and type II assemblages. X-ray emission spectra and electron microprobe analyses of the gold indicate that most grains are electrum, although a Au-bearing telluride occurs at Point Leamington. Ion microprobe analyses indicate that as much as 50% of bulk gold may be present as "invisible gold" locked in pyrite or arsenopyrite (up to 140 ppm Au at Point Leamington). Well-preserved primary depositional features in gold-bearing sulphides from several deposits suggest that the gold in type I assemblages is syngenetic. A strong correlation between gold and a polymetallic suite of Zn, Ag, Pb, As, and Sb, similar to that observed in Kuroko-type massive sulphides and in modern seafloor sulphides, supports a primary origin for gold in type I assemblages. In type II assemblages primary depositional features have been largely destroyed by deformation and annealing of sulphide grains. Gold is locally enriched in Zn-rich sulphides, and sulphides containing abundant pyrrhotite have the lowest gold contents. However, consistent geochemical associations with other elements are not observed, and this may reflect the strong remobilization of gold during structural deformation. The abundant free gold in some type II assemblages is a product of recrystallization during deformation and was derived locally from primary gold originally present in the host sulphides.

The Memphremagog polymetallic massive sulphide deposit occurs at the contact between a pillowed volcanic sequence and a detrital sedimentary sequence consisting principally of shale and greywacke. The deposit, situated about 100 km east of Montréal in the Appalachians of southeastern Quebec, is composed of massive sulphide breccia. Major minerals include pyrrhotite, pyrite, sphalerite, galena, chalcopyrite, and calcite, with minor amounts of arsenopyrite, freibergite ((Cu,Ag,Fe)12Sb4S13), meneghinite (CuPb13Sb7S24), gudmundite (FeSbS), and kersteritic stannite (Cu2(Fe,Zn)SnS4). The mineral assemblage, metal content, and primary textures are comparable to modern sea-floor sulphide mounds enclosed by thick sedimentary sequences deposited in basins such as the Guaymas Basin in the Gulf of California.Although the footwall basalt unit is interstratified with the St-Daniel Formation of the Ophiolite Belt, it possesses a transitional geochemical signature of alkaline affinity that is uncharacteristic of ophiolitic basalts. We propose that this volcanic unit was emplaced within a transtensional basin of a rifted fore-arc system that formed during the Taconic orogeny as a result of diachronous oblique collision of an island- arc system (Ascot–Weedon?) with the North American continent. During magmatic activity, a hydrothermal system was imprinted on the volcanics and underlying sediments. Subsequent hydrothermal fluid emanations led to the formation of the Memphremagog sulphide deposit, which is quite distinct from sulphide deposits generally found within ophiolite belts.

Noble gases have become a powerful tool to constrain the origin and evolution of ore-forming fluids in seafloor hydrothermal systems. The aim of this study was to apply these tracers to understand the genesis of newly discovered polymetallic sulphide deposits along the ultraslow-spreading Southwest Indian Ridge (SWIR). The helium, argon, and sulphur isotope compositions of metal sulphide minerals were measured for a number of active/inactive vent fields in the Indian Ocean. The helium concentrations and isotopic ratios in these ore samples are variable (4He: 0.09–2.42 × 10−8 cm3STP∙g−1; 3He: 0.06–3.28 × 10−13 cm3STP∙g−1; 3He/4He: 1.12–9.67 Ra) and generally greater than the modern atmosphere, but significantly lower than those in massive sulphides from the fast-spreading East Pacific Rise (EPR), especially for three Cu–Fe-rich samples from the ultramafic-hosted Tianzuo and Kairei vent fields. On the contrary, most of the SWIR sulphide deposits have somewhat higher 40Ar/36Ar ratios of trapped fluids (ranging from 290.6 to 303.4) when compared to the EPR ore samples. Moreover, the majority of sulphide minerals from the Indian Ocean have much higher δ34S values (3.0‰–9.8‰, ~5.9 on average, n = 49) than other basaltic-hosted active hydrothermal systems on the EPR. Overall, these He–Ar–S results are well within the range of seafloor massive sulphide deposits at global sediment-starved mid-ocean ridges (MORs), lying between those of air-saturated water (ASW) and mid-ocean ridge basalt (MORB) end members. Therefore, our study suggests that the helium was derived mainly from the MORB mantle by degassing during the high-temperature stage of hydrothermal activity, as well as from a mixture of vent fluids with variable amounts of ambient seawater during either earlier or late-stage low-temperature hydrothermal episodes, whereas the argon in ore-forming fluids trapped within sulphide minerals was predominantly derived from deep-sea water. Additionally, relatively high δ34S values exhibit a great estimated proportion (up to nearly 40%) of seawater-derived components. In summary, sub-seafloor extensive fluid circulation, pervasive low-temperature alteration, shallow seawater entrainment, and mixing processes, may make a larger contribution to the SWIR hydrothermal ore-forming systems, compared to fast-spreading centres.

The Yushui ore deposit, located in the middle section of the Yong’an-Meixian Hercynian depression, is a medium-sized Cu-polymetallic massive sulphide deposit in Eastern Guangdong Province, South China. This deposit is characterized by unusually high copper grade (up to 50–60 wt. % Cu). Other metallic elements, such as lead, zinc and silver, are also economically important in the Yushui ore bodies. The aim of this study was to apply N2–Ar–He systematics, together with organic gases (light-hydrocarbon tracers), to constrain the origin and evolution of ore-forming fluids. The helium-argon isotopes and trace gas compositions of fluid inclusions trapped within metal sulphide minerals were measured for a number of bonanza ores from the Yushui deposit. The noble gas concentrations in the studied samples vary over one to two orders of magnitude (4He: 2.27–160.00 × 10−5 cm3 STP g−1; 3He: 0.53–34.88 × 10−12 cm3 STP g−1; 40Ar: 6.28–37.82 × 10−7 cm3 STP g−1; 36Ar: 1.25–10.40 × 10−9 cm3 STP g−1). Our data show a narrow range of 3He/4He ratios from 0.006 to 0.056 Ra (~0.026 Ra on average, n = 8), which are considerably lower than the modern atmospheric end-member value; whereas the 40Ar/36Ar ratios (ranging from 333.76 to 501.68, with an average of 397.53) are significantly greater than that of air-saturated water. Most of the bornite samples have somewhat higher 3He/4He ratios of trapped fluids when compared to chalcopyrite. Overall, these He-Ar results are well within the range of crustal reservoir, thus implying a predominantly crustal source (originated from Caledonian basement) for ore-forming solutions, with little contribution from mantle-derived fluids. Analysis of the N2–Ar–He composition in Cu-rich sulphides indicates that the Yushui ore-forming fluids were probably derived from formation water (or basinal hot brines). Moreover, organic gas species identified in sulphide-hosted fluid inclusions are mainly composed of C1–C4 alkanes, while the concentrations of unsaturated olefins and aromatic hydrocarbons are very low. In particular, most chalcopyrite samples with relatively low 3He/4He ratios (0.006–0.016 Ra) and 40Ar*/4He values (0.0002–0.0012) are generally characterized by very high CO2/CH4 ratios (~60–102). All these suggest that main-stage Cu-Ag metallogenic processes might have not been affected by high-temperature magmatic activities or superimposed by strong metamorphic overprinting, although some chalcopyrite-rich ores appear to be influenced by later stage hydrothermal processes. In summary, neither magmatic input nor convecting seawater has played an important role in the formation of Yushui copper-polymetallic deposit. The massive sulphide ore bodies were products of water–rock interaction between metal-bearing basinal brines and the host sedimentary strata.

Background. Volcanogenic massive sulphide deposits (VMS) are the most important sources of Cu and Zn; they account for a large share of the world production of Pb, Ag, Au, Se, Te, Bi and Sb, as well as small amounts of many other metals. The polymetallic VMS deposits of economic value of varying degrees are known in the rocks of the Los Pasos Cretaceous Formation, Cuba.Aim. To show the potential of the Cretaceous volcanic deposits of Central Cuba for gold, silver, copper, zinc and lead deposit prospecting.Materials and methods. The study characterises the San Fernando, Independencia, Antonio, Los Cerros VMS deposits and the Boca del Toro and El Sol ore occurrences located in the Los Pasos Formation. The similarities and differences in the mineral and elemental composition and structures of the ores of these objects are described, which underlie the assessment of their economic importance.Results. The latitudinal zoning of VMS and noble metal mineralisation of the Central Cuban ore region is outlined. In the west, copper-VMS deposits with accompanying gold ore objects prevail. In the east, copper-zinc VMS deposits with barite and gold-silver objects are widespread.Conclusions. It is necessary to assume the different erosional sections corresponding to the blocks of the Cretaceous volcanic arc of Central Cuba, which is larger in the west and smaller in the east. Proceeding from the presence of veinlet gold ores, their confinement to tectonic zones and the lack of correlation between noble and chalcophile metals at the San Fernando deposit, as well as significantly different gold-silver ratios in the considered ore objects, it could be assumed that some of the gold-silver ores were formed after VMS. The obtained Au/Ag ratios are close to the ores of the high sulphidation type (high sulphide ores) from similar ore regions of Venezuela and the Kur-il island arc. In this regard, one can expect hidden gold deposits in the west and gold-silver deposits in the east of the studied area.

An analysis of the potential for deposits of critical minerals and elements in Maine presented here includes data and discussions for antimony, beryllium, cesium, chromium, cobalt, graphite, lithium, manganese, niobium, platinum group elements, rhenium, rare earth elements, tin, tantalum, tellurium, titanium, uranium, vanadium, tungsten, and zirconium. Deposits are divided into two groups based on geological settings and common ore-deposit terminology. One group consists of known deposits (sediment-hosted manganese, volcanogenic massive sulphide, porphyry copper-molybdenum, mafic- and ultramafic-hosted nickel-copper [-cobalt-platinum group elements], pegmatitic lithium-cesium-tantalum) that are in most cases relatively large, well-documented, and have been explored extensively in the past. The second, and much larger group of different minerals and elements, comprises small deposits, prospects, and occurrences that are minimally explored or unexplored. The qualitative assessment used in this study relies on three key criteria: (1) the presence of known deposits, prospects, or mineral occurrences; (2) favourable geologic settings for having certain deposit types based on current ore deposit models; and (3) geochemical anomalies in rocks or stream sediments, including panned concentrates. Among 20 different deposit types considered herein, a high resource potential is assigned only to three: (1) sediment-hosted manganese, (2) mafic- and ultramafic-hosted nickel-copper(-cobalt-platinum group elements), and (3) pegmatitic lithium-cesium-tantalum. Moderate potential is assigned to 11 other deposit types, including: (1) porphyry copper-molybdenum (-rhenium, selenium, tellurium, bismuth, platinum group elements); (2) chromium in ophiolites; (3) platinum group elements in ophiolitic ultramafic rocks; (4) granite-hosted uranium-thorium; (5) tin in granitic plutons and veins; (6) niobium, tantalum, and rare earth elements in alkaline intrusions; (7) tungsten and bismuth in polymetallic veins; (8) vanadium in black shales; (9) antimony in orogenic veins and replacements; (10) tellurium in epithermal deposits; and (11) uranium in peat.

Abstract The great interest in the exploitation of sea deposits has in recent years resulted in the creation of many consortia conducting research on various methods of mining and transport to the surface. Exploitation of the shelf areas of crude oil and gas as well as solid minerals is successfully carried out in many places around the world using various methods. More and more often, however, we want to obtain natural resources found at great depths such as polymetallic nodules and massive polymetallic sulphides. This puts much greater demands on scientists and engineers. Unfortunately, solutions developed so far are characterized by high energy consumption. For several years, the authors have been researching new concepts of transport from the seabed. In previous years the authors presented theoretical research results of using a new method involving the use of pyrotechnic materials as a source of energy in transport from the seabed from large depths and experimental ones with the use of potassium nitrate and ammonium nitrate in a controlled pyrotechnic reaction and they compared three conceptions of transport of dredge spoil from the point of view of energy demand. This publication presents the results of the continuation of research, this time on the concept of building an autonomous transport module and its operating principles. The construction of the laboratory stand and the way of conducting experiments are discussed. The results of experimental research are presented, which confirm the possibility of using the discussed concept in transport from the seabed.

Modern society requires a resource supply for the continual development of infrastructure and technology. The discovery of new mineral deposits is challenging as much of North America is covered by Quaternary sediments that obscure bedrock geology. Enhanced methods in exploration geochemistry, capable of detecting mineral deposits through complex cover, must be developed to satisfy global resource demands. Detailed landscape and surficial material mapping over the Lara polymetallic volcanogenic massive sulphide (VMS) deposit were used to establish a landscape evolution model and identify natural processes that govern geochemical responses in shallow soil in glaciated terrain. Upper B horizon soil and physicochemical property measurements were collected along four transects over the deposit and host-rocks and was analyzed by aqua regia ICP-MS/AES, fpXRF and magnetic susceptibility. Select samples were analyzed by sequential extraction and/or for Cu and Zn isotopes to establish the provenance of geochemical responses. Follow-up Ah horizon soil and western hemlock bark samples from a subset of the grid were analyzed by modified aqua regia ICP-MS to determine the role of biochemical cycling. Passive hydrocarbon collector modules were installed at each B horizon soil sample location. Five surficial material domains including till, alluvium and colluvium were identified representing complex alpine glacial and paraglacial processes. Most recent glacial ice flow was valley controlled and sub-parallel to the strike of VMS mineralization as well as a 1-2 m wide pyrite-chalcopyrite stringer zone that occurs 150 m north of the VMS. The highest Zn response occurs over the Lara VMS; however, Cr, Ni, Co and Sc content and magnetic susceptibility indicate this is due to elevated gabbroic content in the till matrix. A response of Zn, Cu, Cd, Mo, Se, Hg, and Te occur over the pyrite zone. Copper isotopes and sequential extraction indicate that geochemical responses are attributed to a clastic source. Zinc, copper, and cadmium in Ah soil and tree bark is controlled by surficial material and geomorphology. Geochemical responses in B horizon soil above the VMS and pyrite zone is interpreted to be caused clastic dispersion of mineralization and mafic host-rocks by glacial transport with negligible input by biochemical cycling.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

The Wolverine polymetallic massive sulphide deposit (6,237,000 tonnes grading 12.7% zinc, 1.3% copper, 1.6% lead, 370.9 g/t silver and 1.8 g/t gold) is located in the Finlayson Lake district (FLD) of southeastern Yukon Territory, Canada. Its discovery .in 1995 contributed to the largest staking rush in the history of Yukon and provided the impetus for scientific research in this poorly studied part of the Yukon Tanana terrane. The deposit occurs in a highly deformed, but coherent, stratigraphic succession of early Mississippian to early Permian metavolcanic and metasedimentary rocks. Regional geologic mapping and lithogeochemical studies are consistent with its formation on the margin of an evolving ensialic back-arc ocean basin, between the Yukon-Tanana terrane and the ancestral North American craton. Local stratigraphy consists of four major units including (from oldest to youngest): (1) quartz- and feldspar-phyric volcaniclastic rhyolite, carbonaceous argillite and rhyolite porphyry; (2) interbedded argillite, aphyric rhyolite and magnetite-carbonate-pyrite exhalite; (3) fragmental rhyolite; and (4) interbedded carbonaceous argillite, greywacke, basalt and rhyolite. Sulphide mineralization occurs at the "Wolverine horizon", which is located at the contact between Unit 1 and Unit 2, and marks a significant change in the character of the volcanism between the footwall and the hanging wall of the deposit. The footwall consists of a sequence of carbonaceous shale, quartzand feldspar-phyric volcaniclastic rhyolite, and minor feldspar-phyric rhyolite sills, whereas the hanging wall consists of intercalated aphyric rhyolite, carbonaceous shale, and carbonate-pyrite exhalite. Two separate Zn-Pb-Ag massive sulphide lenses, situated at the same stratigraphic horizon, comprise most of the Wolverine deposit. They are laterally connected by stratabound, semi-massive replacement-style, Zn-Pb-Ag mineralization. Copper-rich mineralization commonly replaces the Zn-Pb-Ag mineralization at the base of the lenses and in the footwall replacement zones indicating that primary metal and mineral zonation are preserved. Multiple zones of sulphide stringer veins and regions of conformable chloritesericite-carbonate alteration are developed within permeable volcaniclastic rocks of the footwall. Bariumrich phengitic mica, biotite, Mg-rich chlorite, and siderite are associated preferentially with massive sulphide mineralization. The Zn-Pb-Ag massive sulphide lenses formed at 264 ± 33°C, based on the arsenopyrite geothermometer. The sulphide stringer zones formed at slightly higher temperatures (mean = 282 ± 7°C) based, on estimates derived from the composition of associated hydrothermal chlorite. Late-stage quartzchalcopyrite- pyrite veins formed at temperatures between 265°and 353°C (mean = 302 ± 22°C), based on fluid inclusion microthermometry. Mineralizing fluids are low salinity (2.1-8.5 wt.% NaCl equiv.; mean = 6.0), two-phase, aqueous solutions with high liquid-to-vapor ratios. Evidence of fluid boiling or phase separation is absent. Mineralization is estimated to have formed at a minimum water depth of ~ 1048 meters based on the average salinity and temperatures of homogenization. In-situ δ³⁴S values of sulphide minerals from massive sulphide lenses and sulphide stringer veins display a pronounced bimodal distribution with modes of 0.8 ‰ and 12.0 ‰. The lighter δ³⁴S values are near the top of the lenses, whereas the heavier values come from the underlying stringer veins. The δ³⁴S values and existence of two distinct populations, suggest that sulfur was derived by a combination of biogenic and inorganic reduction of seawater sulphate within a partly closed, anoxic basin. Mineralization formed through a combination of seafloor hydrothermal venting from multiple sulphide mounds and sub-seafloor replacement processes. The reduced nature of the ambient bottom water in the basin likely contributed to the preservation of the sulphide mounds. The geologic setting, styles of mineralization, and physico-chemical conditions of the mineralizing fluids all suggest that the Wolverine deposit formed in a geological environment transitional between that which hosts classic bimodal volcanic rock-hosted massive sulphide deposits and that which hosts sedimentary exhalative massive sulphide deposits. The genetic model developed for the Wolverine deposit in this study will benefit exploration in the Finlayson Lake district by providing specific details on the geological setting and local depositional environment necessary for the formation and preservation of these unusual polymetallic deposits.

Mining the extensive accumulations of minerals on the seafloor of the deep ocean might provide important resources, but it also has the potential to lead to widespread environmental impacts. Some of these impacts are unknown, and some may differ for the three main resource types: polymetallic nodules, seafloor massive sulphides, and polymetallic (cobalt-rich) crusts. Here, we detail the mining processes and describe the ecosystems associated with the minerals of interest. We then explain the expected impacts of mining, and discuss their potential effects on deep-ocean ecosystems. We also highlight the missing evidence needed to underpin effective environmental management and regulation of the nascent deep-sea mining industry.

The Finlayson Lake district in southeastern Yukon is composed of a Late Paleozoic arc-backarc system that consists of metamorphosed volcanic, plutonic, and sedimentary rocks of the Yukon-Tanana and Slide Mountain terranes. These rocks host >40 Mt of polymetallic resources in numerous occurrences and styles of volcanogenic massive sulphide (VMS) mineralization. Geochemical and isotopic data from these rocks support previous interpretations that volcanism and plutonism occurred in arc-marginal arc (e.g., Fire Lake formation) and continental back-arc basin environments (e.g., Kudz Ze Kayah formation, Wind Lake formation, and Wolverine Lake group) where felsic magmatism formed from varying mixtures of crust- and mantle-derived material. The rocks have elevated high field strength element (HFSE) and rare earth element (REE) concentrations, and evolved to chondritic isotopic signatures, in VMS-proximal stratigraphy relative to VMS-barren assemblages. These geochemical features reflect the petrogenetic conditions that generated felsic rocks and likely played a role in the localization of VMS mineralization in the district. Preliminary in situ zircon chemistry supports these arguments with Th/U and Hf isotopic fingerprinting, where it is interpreted that the VMS-bearing lithofacies formed via crustal melting and mixing with increased juvenile, mafic magmatism; rocks that were less prospective have predominantly crustal signatures. These observations are consistent with the formation of VMS-related felsic rocks by basaltic underplating, crustal melting, and basalt-crustal melt mixing within an extensional setting. This work offers a unique perspective on magmatic petrogenesis that underscores the importance of integrating whole-rock with mineral-scale geochemistry in the characterization of VMS-related stratigraphy.