Massive Sulfide Ore Research Articles

The use of continuous centrifugal gravity concentration in grinding circuit. Modified approach for improved metallurgical performance and reduced grinding requirements

The use of centrifugal gravity concentration in the closed-grinding circuit of a gold-containing massive sulphide ore was tested on classifier underflow and overflow. A continuous Knelson CVD6 was retrofitted to the hydrocyclone underflow for recovery of Au and Pb at a coarser feed size. The objective of treatment of overflow was recovering unliberated Au prior to flotation. The tests were performed in actual operating conditions at Nyrstar's Myra Falls Mine. The results of the tests on the cyclone underflow revealed that both liberated and unliberated Au and Pb were recovered by the Centrifugal Variable Discharge (CVD) concentrator. Concentrate grades <60g/Mg Au were attainable at a more than 20% recovery. This application also allowed early and increased Pb recovery before it became gravity unrecoverable by over-grinding. Other benefits included capturing middlings for regrinding as well as potential coarser grinding and increase in mill throughput. A coarse grind also corresponds to a reduction in deformation of Au-particles, and is beneficial for increased Au recovery in downstream processing. Treatment of cyclone overflow by the CVD also provided favourable results. The outcomes included capturing unliberated gold prior to flotation and potentially reducing pumping requirements and reagent consumption. A comparison of the metallurgical performances showed that CVD application on classifier underflow was more effective. The CVD was capable of recovering unliberated gold in sulphides and performed better at a coarser particle size. Therefore, when used with the grinding circuit, a coarser grind can be applied and the CVD could be used to reject gangue at a coarser size.

In situ zircon U–Pb dating and O isotopes of the Neoarchean Hongtoushan VMS Cu–Zn deposit in the North China Craton: Implication for the ore genesis

The Hongtoushan volcanogenic massive sulfide (VMS) deposit is the largest Archean Cu–Zn deposit in China, located in the Qingyuan greenstone belt on the northern margin of the North China Craton. The Cu–Zn mineralization was stratigraphically controlled by the interbeds (~100m in thickness) of mafic–felsic volcanic sets and overlain by banded iron layers. However, the relationship between VMS deposits and associated volcanics has not been examined. This study ultimately clarifies the times and sources of the volcanics and mineralization. Based on in situ zircon U–Pb and O isotope on VMS-hosting mafic, felsic volcanic rocks, banded and massive sulfide ores and postmineralization pegmatite vein, we considered that there were two main formation stages for the Qingyuan Cu–Zn deposits; one was exhalative-hydrothermal sedimentation and another was further Cu–Zn enriched by later hydrothermal processes. The timing of the first stage occurred at 2571±6Ma based on the magmatic zircons in the VMS-hosting mafic volcanic rocks, from which the inherited zircons also indicate the existence of 2.65–3.12Ga ancient supercrustal rocks in the Qingyuan district. A modern mantle-like δ18Ozircon value of 5.5±0.1‰ (2SD) for this volcanism was well preserved in the inherited core domains of ore samples. It suggests that the mafic volcanics was most likely sourced from partial melting of juvenile crust, e.g., TTG granites. A large-scale metamorphic or hydrothermal event is documented by the recrystallized zircons in sulfide ores. The timing is tightly constrained by the hydrothermal zircon U–Pb ages. They are 2508±4Ma for the banded ore, 2507±4Ma for the massive ore and 2508±2Ma for the postmineralization pegmatite vein. These indistinguishable ages indicate that the 2507Ma hydrothermal systems played a significant role in the upgrading of the VMS Cu–Zn orebodies. The weighted δ18O values of hydrothermal zircons show a successively increasing trend from 6.0±0.1‰ (2σ) for the banded ore, 6.6±0.2‰ (2σ) for the massive ore to 7.3±0.2‰ (2σ) for the later pegmatite vein. This variation might be induced by gradual inputting of the δ18O-rich oceanic crust and/or oceanic sediment during the hydrothermal cycling system. Considering its modern mantle-like oxygen isotope composition of 2571Ma volcanism, a submarine volcanic hydrothermal system involving mantle plumes is a preferred setting for the Neoarchean VMS Cu–Zn deposits in the Qingyuan greenstone belt.

A combined fluid inclusion and S–Pb isotope study of the Neoproterozoic Pingshui volcanogenic massive sulfide Cu–Zn deposit, Southeast China

The Pingshui Cu–Zn deposit is located in the Jiangshan–Shaoxing fault zone, which marks the Neoproterozoic suture zone between the Yangtze block and Cathaysia block in South China. It contains 0.45million tons of proven ore reserves with grades of 1.03wt.% Cu and 1.83wt.% Zn. This deposit is composed of stratiform, massive sulfide ore bodies, which contain more than 60vol.% sulfide minerals. These ore bodies are hosted in altered mafic and felsic rocks (spilites and keratophyres) of the bimodal volcanic suite that makes up the Neoproterozoic Pingshui Formation. Metallic minerals include pyrite, chalcopyrite, sphalerite, tennantite, tetrahedrite and magnetite, with minor galena. Gangue minerals are quartz, sericite, chlorite, calcite, gypsum, barite and jasper. Three distinct mineralogical zones are recognized in these massive sulfide ore bodies: a distal zone composed of sphalerite+pyrite+barite (zone I); an intermediate zone characterized by a pyrite+sphalerite+chalcopyrite assemblages (zone II); and a proximal zone containing chalcopyrite+pyrite+magnetite (zone III). A thin, layer of exhalative jaspilite overlies the sulfide ore bodies except in the proximal zone. The volcanic rocks of the Pingshui Formation are all highly altered spilites and keratophyres, but their trace element geochemistry suggests that they were generated by partial melting of the depleted mantle in an island arc setting. Homogenization temperatures of the primary fluid inclusions in quartz from massive sulfide ores are between 217 and 328°C, and their salinities range from 3.2 to 5.7wt.% NaCl equivalent. Raman spectroscopy of the fluid inclusions showed that water is the dominant component, with no other volatile components. Fluid inclusion data suggest that the ore-forming fluids were derived from circulating seawater. The δ34S values of pyrite from the massive sulfide ores range from −3.6‰ to +3.4‰, indicating that the sulfur was primarily leached from the arc volcanic rocks of the Pingshui Formation. Both pyrite from the massive sulfide ores and plagioclase from the spilites have similar lead isotope compositions, implying that the lead was also derived from the Pingshui Formation. The low lead contents of the massive sulfide ores and the geochemistry of their host rocks are similar to many VMS Cu–Zn deposits in Canada (e.g., Noranda) and thus can be classified as belonging to the bimodal-mafic subtype. The presence of magnetite and the absence of jaspilite and barite at the −505m level in the Pingshui deposit suggest that this level is most likely the central zone of the original lateral massive sulfide ore bodies. If this interpretation is correct, the deep part of the Pingshui Cu–Zn deposit may have significant exploration potential.

Tracing low-temperature aqueous metal migration in mineralized watersheds with Cu isotope fractionation

Copper isotope signatures in waters emanating from mineralized watersheds provide evidence for the source aqueous copper in solution. Low-temperature aqueous oxidation of Cu sulfide minerals produces significant copper isotopic fractionation between solutions and residues. Abiotic experimental data of fractionation (defined as Δliquid–solid ‰=δ65Culiquid−δ65Cusolid) are on the order of 1–3‰ and are unique for copper rich-sulfide minerals. Data presented here from ores and waters within defined boundaries of porphyry copper, massive sulfide, skarn, and epithermal ore deposits mimic abiotic experiments. Thus, the oxidation of sulfide minerals appears to cause the signatures in the waters although significant biological, temperature, and pH variations exist in the fluids. Regardless of the deposit type, water type, concentration of Cu in solution, or location, the data provide a means to trace sources of metals in solutions. This relationship allows for tracking sources and degree of metal migration in low temperature aqueous systems and has direct application to exploration geology and environmental geochemistry.

Origin of the Tudun Cu–Ni sulfide deposit in the eastern Tianshan, NW China: Constraints on the geochemistry of platinum group elements

This study documents the geochemistry of sulfide ores of the Tudun Cu–Ni sulfide deposit, located at the western end of the Huangshan–Jing'erquan ore belt in the northern part of eastern Tianshan. The ores have been classified as (1) disseminated sulfide ores, (2) net-textured sulfide ores, and (3) massive sulfide ores.The geochemistry of barren rocks shows Ni and Cu contents ranged 889–1330ppm and 145–253ppm, respectively. The rocks generally contained ~0.10ppb Rh, Ir, Ru and Os, and ~1ppb Pt and Pd, as well as high Cu/Pd ratios (133–246). The contents of Cu, Ni and PGEs in sulfide ores were calculated on a 100% sulfide basis. Total PGEs on a 100% sulfide basis ranged from 13.2ppb to 443ppb (average=144ppb), which were lower than the values in the Huangshandong deposit (average=186ppb) in the eastern Tianshan ore belt, one order of magnitude lower than the Jinchuan deposit, and two orders of magnitude lower than the Noril'sk–Talnakh deposit. The R factor value ranged from 168 to 1810 in sulfide ores of the Tudun deposit, indicating Cu and Ni enrichment, although PGEs enrichment did not reach recoverable grades.In the Tudun deposit, the Pd/Ir ratio of sulfide ores was less than 100, showing weak hydrothermal fluid alteration. The massive sulfide ores exhibited less primitive mantle-normalized PGEs patterns, which are depleted in PPGEs and different from PPGEs-rich intrusions, as well as disseminated and net-textured sulfide ores. In addition, the massive sulfide ores exhibit a strong negative Pt anomaly. This may be due to fractionation of Pt–Fe alloys in the magma batches prior to its intrusion into the staging chamber. It could also be caused by selective Pt leaching from the sulfides by hydrothermal fluids during remobilization within the Tudun chamber.

Optimization of Cu–Zn Massive Sulphide Flotation by Selective Reagents

Selective floatation of base metal sulphide minerals can be achieved by using selective reagents. Sequential floatation of chalcopyrite–sphalerite from Taknar (Iran) massive sulphide ore with 3.5 % Zn and 1.26 % Cu was studied. D-optimal design of response surface methodology was used. Four mixed collector types (Aer238 + SIPX, Aero3477 + SIPX, TC1000 + SIPX and X231 + SIPX), two depressant systems (CuCN–ZnSO4 and dextrin–ZnSO4), pH and ZnSO4 dosage were considered as operational factors in the first stage of flotation. Different conditions of pH, CuSO4 dosage and SIPX dosage were studied for sphalerite flotation from first stage tailings. Aero238 + SIPX induced better selectivity for chalcopyrite against pyrite and sphalerite. Dextrin–ZnSO4 was as effective as CuCN–ZnSO4 in sphalerite–pyrite depression. Under optimum conditions, Cu recovery, Zn recovery and pyrite content in Cu concentrate were 88.99, 33.49 and 1.34 % by using Aero238 + SIPX as mixed collector, CuCN–ZnSO4 as depressant system, at ZnSO4 dosage of 200 g/t and pH 10.54. When CuCN was used at the first stage, CuSO4 consumption increased and Zn recovery decreased during the second stage. Maximum Zn recovery was 72.19 % by using 343.66 g/t of CuSO4, 22.22 g/t of SIPX and pH 9.99 at the second stage.

Effects of temperature, sulfur, and oxygen fugacity on the composition of sphalerite from submarine hydrothermal vents

Experimental studies have shown that temperature, pressure, sulfur fugacity (fS2), and oxygen fugacity (fO2) influence the Fe content of sphalerite. We present compositional in situ data on sphalerite from submarine volcanic-hosted massive sulfide (VHMS) ores of hydrothermal vents from different plate tectonic settings and with variable host-rock compositions. Sphalerite from sediment-hosted vents has systematically higher S contents and Fe/Zn ratios than those of the sediment-starved vents, reflecting an influence of fS2 and fO2 on Fe partitioning between fluid and sphalerite. The Fe/Zn ratios of sphalerite from sediment-starved vent systems apparently increase systematically with the fluid temperatures of the corresponding vents. We conclude that the composition of sphalerite can be used to (1) distinguish between sediment-hosted and sediment-starved hydrothermal processes, and (2) estimate minimum fluid temperatures of sphalerite precipitation from inactive sediment-starved hydrothermal vent sites and fossil VHMS deposits.

Mineralogical and microtextural parameters in metals ores traceability studies

The demand in mineral resources is increasing rapidly, but there is a lack of transparency in the trade of concentrated raw mineral materials because of speculation and involvement in the finance of armed conflicts. Because of the distance between primary extraction and the final production sites it is difficult to check the origin of these products. An identity card is required for mineral commodities, so that trading in the industry can be verified and the traceability of concentrates ensured. This problem may be considered as an inversion process: studying the products sold to identify the original ore. The discriminant parameters are mineralogical composition, identification of textural microfacies of the target minerals, “pseudo-paragenetic sequence”, and the contents and distribution of minor elements of target minerals. For base metal, the selected target minerals are pyrite, for its ubiquity, sphalerite for its ability to host numerous discriminant and potentially valuable minor elements in its lattice and chalcopyrite for its proximity with the two other minerals. The Kolmogorov–Smirnov distance and the Colin–White test are used to compare the chemical composition of the three target minerals. The application to Volcanic Massive Sulfide ore deposits shows that it is possible to distinguish pyrite, sphalerite and chalcopyrite between two ore deposits in the Iberian Pyrite Belt province and seven ore deposits from the Urals province using the selected characteristics. Ore deposits from different provinces may be discriminated using the identity cards, as well as different deposits in the same province.

Magnetite composition in Ni-Cu-PGE deposits worldwide: application to mineral exploration

The concentration of trace elements in magnetite is determined primarily by the geological environment at the time of its formation, which makes magnetite a useful indicator mineral in the exploration of ore deposits. Magnetite is a common accessory mineral in magmatic Ni–Cu–Platinum-Group Element (PGE) sulfide deposits forming primary grains in massive sulfide ore and/or secondary grains during alteration of sulfide ore and host rock. We report magnetite composition from massive and disseminated sulfide samples (n=94), representative of 13 major Ni–Cu–PGE deposits, worldwide, and from a range of geological environments and formation ages (Archean to Permo–Triassic). The samples are divided into 6 different types according to the composition of the parental host magma: (1) komatiite, (2) ferropicrite, (3) picrite–tholeiite, (4) anorthosite–troctolite, (5) flood basalt and (6) impact melt. The minor and trace element composition of magnetite was measured by electron probe micro-analysis and a subset of samples (n=61) by laser ablation-inductively coupled plasma-mass spectrometry.The composition of all primary magnetite, crystallized from an immiscible sulfide liquid, plots on a trend in Ti vs. Cr and V vs. Cr. However, primary magnetite trace element content is controlled by element partitioning during sulfide liquid differentiation, from early-forming Fe-rich monosulfide solid solution (MSS) to Cu-rich intermediate solid solution (ISS). The concentration of most lithophile elements (Cr, Ti, V, Al, Sc, Nb, Ga, Ta, Hf and Zr) is highest in the early-forming magnetite, which crystallized with Fe-rich MSS. The fractionated Cu-rich liquid was depleted in lithophile elements so that late-forming magnetite, which crystallized with the Cu-rich ISS, has a low concentration of these elements. Compatible chalcophile elements partitioning into magnetite depends largely on the co-crystallizing sulfide mineral. Elements such as Ni partition preferentially in Fe-rich sulfide minerals (pyrrhotite or pentlandite) such that coprecipitated magnetite is depleted in chalcophile elements compatible with the sulfides. In contrast, magnetite co-crystallized with Cu-rich ISS is enriched in Ni because Ni is not compatible with the co-crystallizing Cu sulfides. Magnetite composition is also dependent on parental magma composition. Magnetite in massive sulfides from ultramafic parental magmas is most similar in compositions to primitive magnetite from Fe-rich sulfides in fractionated intermediate to mafic hosted orebodies.Two types of secondary magnetite are distinguished from the komatiite-hosted Thompson Ni-deposit (Manitoba, Canada): (1) magnetite formed by replacement of pyrrhotite and (2) magnetite formed during the serpentinization of the ultramafic host rocks. Secondary magnetite is depleted in most trace elements (Ni, Mn, V, Ti, V, Al, Cr), with the exception of Si and Mg, which are enriched.To be useful as a tool for mineral exploration, primary and secondary magnetite should not have the same minor and trace element composition. Primary magnetite from all 13 major Ni–Cu deposits plot in the field for Ni–Cu sulfide deposits in the Ni+Cr vs. Si+Mg discrimination diagram. Secondary magnetite plot outside of the field for Ni–Cu deposits. Therefore using this diagram, we can discriminate between primary and secondary magnetite using the low Ni+Cr content of secondary magnetite. Magnetite is resistant to surficial weathering and destruction during mechanical transport, such that it is a useful indicator mineral in exploration that can be used to detect eroded Ni–Cu–PGE deposits in surficial sediments.

Mapping Changes in a Recovering Mine Site with Hyperspectral Airborne HyMap Imagery (Sotiel, SW Spain)

Hyperspectral high spatial resolution HyMap data are used to map mine waste from massive sulfide ore deposits, mostly abandoned, on the Iberian Pyrite Belt (southwest Spain). Mine dams, mill tailings and mine dumps in variable states of pyrite oxidation are recognizable. The interpretation of hyperspectral remote sensing requires specific algorithms able to manage high dimensional data compared to multispectral data. The routine of image processing methods used to extract information from hyperspectral data to map geological features is explained, as well as the sequence of algorithms used to produce maps of the mine sites. The mineralogical identification capability of algorithms to produce maps based on archive spectral libraries is discussed. Trends of mineral growth differ spectrally over time according to the geological setting and the recovery state of the mine site. Subtle mineralogical changes are enhanced using the spectral response as indicators of pyrite oxidation intensity of the mine waste piles and pyrite mud tailings. The changes in the surface of the mill tailings deserve a detailed description, as the surfaces are inaccessible to direct observation. Such mineralogical changes respond faithfully to industrial activities or the influence of climate when undisturbed by human influence.

Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast-spreading ridges.

Hydrothermal flow at oceanic spreading centres accounts for about ten per cent of all heat flux in the oceans and controls the thermal structure of young oceanic plates. It also influences ocean and crustal chemistry, provides a basis for chemosynthetic ecosystems, and has formed massive sulphide ore deposits throughout Earth's history. Despite this, how and under what conditions heat is extracted, in particular from the lower crust, remains largely unclear. Here we present high-resolution, whole-crust, two- and three-dimensional simulations of hydrothermal flow beneath fast-spreading ridges that predict the existence of two interacting flow components, controlled by different physical mechanisms, that merge above the melt lens to feed ridge-centred vent sites. Shallow on-axis flow structures develop owing to the thermodynamic properties of water, whereas deeper off-axis flow is strongly shaped by crustal permeability, particularly the brittle-ductile transition. About 60 per cent of the discharging fluid mass is replenished on-axis by warm (up to 300 degrees Celsius) recharge flow surrounding the hot thermal plumes, and the remaining 40 per cent or so occurs as colder and broader recharge up to several kilometres away from the axis that feeds hot (500-700 degrees Celsius) deep-rooted off-axis flow towards the ridge. Despite its lower contribution to the total mass flux, this deep off-axis flow carries about 70 per cent of the thermal energy released at the ridge axis. This combination of two flow components explains the seismically determined thermal structure of the crust and reconciles previously incompatible models favouring either shallower on-axis or deeper off-axis hydrothermal circulation.

Mineralogy, Sulfur Isotope and Fluid Inclusion Studies of Hydrothermal Ore at the Hakurei Deposit, Bayonnaise Knoll, Izu‐Bonin Arc

AbstractSulfide and sulfate ore samples collected from the Hakurei deposit of the Bayonnaise knoll were examined for the occurrence and chemical composition of minerals, including the sulfur isotopes and the microthermometry of fluid inclusions. Massive sulfide ore, mineralized volcanic rock, and anhydrite ore occur in descending order, from the seafloor to the bottom of the cored sample. The massive sulfide ore is dominated by sphalerite and accompanied by tennantite, chalcopyrite, and pyrite with lesser amounts of galena, enargite, and covellite. Amorphous silica is commonly precipitated on the surface of the sulfide minerals. As‐bearing minerals such as tennantite, enargite, and luzonite are common, while galena and Sb‐rich tetrahedrite are scarce. The mineral abundance and chemical composition of the minerals differs from that found in chimneys of the deposit. The sulfur isotope compositions in the minerals are +3.1–5.2‰ for sulfides and +19.6–21.8‰ for sulfate minerals. The homogeneous nature of the sulfur isotopes suggests that sulfur incorporated in the Hakurei deposit came from the reduction of aqueous sulfate in seawater.

ASTER, ALI and Hyperion sensors data for lithological mapping and ore minerals exploration.

This paper provides a review of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Advanced Land Imager (ALI), and Hyperion data and applications of the data as a tool for ore minerals exploration, lithological and structural mapping. Spectral information extraction from ASTER, ALI, and Hyperion data has great ability to assist geologists in all disciplines to map the distribution and detect the rock units exposed at the earth’s surface. The near coincidence of Earth Observing System (EOS)/Terra and Earth Observing One (EO-1) platforms allows acquiring ASTER, ALI, and Hyperion imagery of the same ground areas, resulting accurate information for geological mapping applications especially in the reconnaissance stages of hydrothermal copper and gold exploration, chromite, magnetite, massive sulfide and uranium ore deposits, mineral components of soils and structural interpretation at both regional and district scales. Shortwave length infrared and thermal infrared bands of ASTER have sufficient spectral resolution to map fundamental absorptions of hydroxyl mineral groups and silica and carbonate minerals for regional mapping purposes. Ferric-iron bearing minerals can be discriminated using six unique wavelength bands of ALI spanning the visible and near infrared. Hyperion visible and near infrared bands (0.4 to 1.0 μm) and shortwave infrared bands (0.9 to 2.5 μm) allowed to produce image maps of iron oxide minerals, hydroxyl-bearing minerals, sulfates and carbonates in association with hydrothermal alteration assemblages, respectively. The techniques and achievements reviewed in the present paper can further introduce the efficacy of ASTER, ALI, and Hyperion data for future mineral and lithological mapping and exploration of the porphyry copper, epithermal gold, chromite, magnetite, massive sulfide and uranium ore deposits especially in arid and semi-arid territory.

Ferrovalleriite, 2(Fe,Cu)S · 1.5Fe(OH)2: Validation as a mineral species and new data

Ferrovalleriite, ideally 2(Fe,Cu)S · 1.5Fe(OH)2, a layered hydroxide-sulfide of the valleriite group and an analog of valleriite with Fe instead of Mg in the hydroxide block, has been approved by the IMA Commission on New Minerals, Nomenclature and Classification as a valid mineral species. It was found in the Oktyabr’sky Mine, Noril’sk, Krasnoyarsk krai, Siberia, Russia. Ferrovalleriite occurs in cavities of massive sulfide ore mainly consisting of cubanite and mooihoekite. In different cases, it is associated with magnetite, Fe-rich chlorite-like phyllosilicate, ferrotochilinite, hibbingite, or rhodochrosite. Ferrovalleriite forms crystals flattened on [001] (from scaly to tabular; up to 5 mm across and up to 0.3 mm thick), typically split and curved. Occasionally, they are combined into aggregates up to 1.5 × 2 cm. Ferrovalleriite is dark bronze-colored, with a metallic luster and black streak. The Mohs’ hardness is ca. 1; VHN is 35 kg/mm2. Cleavage is perfect parallel to {001}, mica-like. Individuals are flexible and inelastic. D(calc) = 3.72 g/cm3. In reflected light, ferrovalleriite is pleochroic from yellowish to gray; bireflectance is moderate. Anisotropy is strong, with bluish gray to yellowish beige rotation colors. Reflectance values [R1–R2 %, (λ, nm)] are: 15.6–16.6 (470), 14.8–20.5 (546), 14.7–22.3 (589), 14.5–24.1 (650). The IR spectrum shows the presence of (OH) groups bonded with Fe cations and the absence of H2O molecules. The chemical composition of the holotype (wt %; electron microprobe, H content is calculated) is as follows: 0.10 Al, 0.03 Mn, 45.31 Fe, 0.07 Ni, 18.29 Cu, 20.37 S, 15.62 O, 0.98 H, total is 100.77. The empirical formula calculated on the basis of 2 S atoms is: Al0.01Fe2.55Cu0.91S2(OH)3.07 = (Fe1.09Cu0.91)Σ2S2 · (Fe1.342+Fe0.123+Al0.01)Σ1.47(OH)3.07. The structure of ferrovalleriite is incommensurate (misfit); two sublattices are present: (1) sulfide sublattice, space group \(R\bar 3m\), R3m or R32; the unit-cell dimensions are: a = 3.792(2), c = 34.06(3) A, V = 424(1) A3 and (2) hydroxide sublattice, space group \(P\bar 3m1\), P3m1 or P321; the unit-cell dimensions: a = 3.202(3), c = 11.35(2)A, V = 100.8(3) A3. Together with this main polytype modification with three-layer (R-cell, Z = 3) sulfide block, the holotype ferrovalleriite contains the modification with one-layer (P-cell, Z = 1) sulfide block (sulfide sublattice with \(P\bar 3m1\), P3m1 or P321, unit cell dimensions: a = 3.789(4), c = 11.35(1) A, V = 141(5) A3). The strongest reflections in the X-ray powder pattern (d, A-I) are: 5.69–100; 3.268–58; 3.163–36; 1.894–34; 1.871–45.

Segregation and Fractionation of Magmatic Ni-Cu-PGE Sulfides in the Western Jinchuan Intrusion, Northwestern China: Insights from Platinum Group Element Geochemistry

The Jinchuan Ni-Cu-(PGE) deposit is one of the world’s largest magmatic sulfide deposits. Recent studies have suggested that the Jinchuan intrusion originally comprised two individual intrusions, the Eastern and the Western intrusions. The Western intrusion consists of an Upper and a Lower unit. The Upper unit is largely free of sulfides with weakly disseminated sulfides only at the base of the unit; these sulfides are characterized by moderate Cu/Pd ratios of 5,500 to 14,900 and relatively high PGE tenors (PGE in 100% sulfides) in the range of 510 to 1,000 ppb Irsul, 420 to 1,200 ppb Rusul, and 2,900 to 8,000 ppb Pdsul. Disseminated, net-textured and minor massive sulfides in the Lower unit comprise the No. 24 orebody, the third largest at Jinchuan. The disseminated ores have remarkably high Cu/Pd ratios (24,200–85,600) and low PGE tenors in the range of 120 to 560 ppb Irsul, 100 to 480 ppb Rusul, and 430 to 3,600 ppb Pdsul. The net-textured and massive ores contain high IPGE contents (240–820 ppb Irsul and 170–630 ppb Rusul) and Ni/Cu ratios (1.7–11.3), low Pd/Ru ratios (0.53–3.1), and exhibit significant Pt depletion (<300 ppb Ptsul). Additionally, small Cu-rich orebodies occur at the base of the No. 24 orebody or in small intrusions within footwall schists, marbles, and granites beneath the Western intrusion. The Cu-rich sulfides have very low IPGE tenors (1.9–16 ppb Irsul and 6.4–21 ppb Rusul), and Ni/Cu ratios (0.3–2.8), high Pd/Ru ratios (37.3–378), and highly variable Ptsul between 43 and 11,000 ppb. The PGE geochemistry and model calculations indicate that the disseminated sulfides of the Upper and Lower units segregated from PGE-undepleted and -depleted parental magmas, respectively. The PGE-depleted magma had undergone a minor amount of earlier sulfide liquid extraction at depth. Furthermore, this PGE-depleted parental magma had slightly higher PGE contents than the magma from which the sulfides of the Nos. 1 and 2 orebodies in the Eastern intrusion segregated. The significant variations in base and precious metal ratios of the net-textured and massive sulfide ores are attributed to fractionation of the sulfide melts that formed these ores. This led to both migration of the residual Cu-rich sulfide melts away from the early-formed monosulfide solid solution (mss) to form Cu-rich ores as well as back intrusion of the Cu-rich ores into the mss. The negative Pt anomalies of the net-textured and massive sulfides resulted from preferential extraction of Pt into the Cu-rich residual melts due to the presence of As, Te, and Bi.

Geochemistry, U–Pb geochronology, and genesis of granitoid clasts in transported volcanogenic massive sulfide ore deposits, Buchans, Newfoundland

The Buchans Group, central Newfoundland, represents an Ordovician continental bimodal calc-alkaline arc sequence that hosts numerous volcanogenic massive sulfide (VMS) occurrences, including both in situ and mechanically transported sulfide breccia–conglomerate orebodies. Diverse lithic clasts associated with transported deposits include rounded granitoid clasts. Earlier workers have suggested that Buchans Group VMS-hosting felsic extrusive units, small granodiorite intrusions (e.g., Wiley’s Brook), and granitoid cobbles associated with transported ore represent co-genetic products of the same magmatic system. The granitoid cobbles and small granodiorite intrusions are geochemically similar and closely resemble Buchans Group felsic volcanic units. U–Pb zircon age determinations show a (i) 466.7 ± 0.5 Ma crystallization age for the Wiley’s Brook granodiorite (WBG), (ii) 464 ± 4 Ma crystallization age for a granitoid cobble, and (iii) 466 ± 4 Ma maximum deposition age for a conglomerate–sandstone sequence associated with transported ore. Thus, Buchans Group felsic plutonic rocks are within experimental error of felsic volcanism and VMS deposition. Furthermore, εNd (T) (T, time of crystallization) values of four granitoid cobbles (–1.95 to –4.0) overlap values obtained from Buchans Group felsic volcanic units. Our results are compatible with plutonic and volcanic rocks being related through fractional crystallization or partial melting processes but do not support a petrogenetic link between VMS deposition and exposed felsic plutons. Comparisons to modern arc analogues favour exhumation of plutonic rocks by extension along caldera or rift walls and (or) subaerial erosion. Enigmatic rounding of Buchans granitoid clasts was likely accomplished in a subaerial or shallow marine environment, and the clasts transported into a VMS-active basin by mass flows.

Massive sulfide ores of the northern equatorial Mid-Atlantic Ridge

The optimal set of prospecting methods, including geophysical (geoelectrical), geological (mineralogical-geochemical), and hydrological observations, was developed during the long-term investigations of the sulfide mineralization in the northern equatorial zone of the Mid-Atlantic Ridge. The application of these methods made it possible to discover six massive sulfide deposits and considerably extend the boundaries of another two ore objects. The ores associated with ultramafic rocks are characterized by elevated Cu, Au, and Co concentrations. It is established that the ore formation was a multistage process that resulted in the accumulation of large deposits (over 10 million tons).

Mineralogical and geochemical zoning of sediments at the Semenov cluster of hydrothermal fields, 13°31′-13°30′ N, Mid-Atlantic Ridge

New material from eight columns recovered during Cruise 32 of the R/V Professor Logachev in 2009 was used to explore the lithological facies, biostratigraphy, mineralogy, and geochemistry of sediments from the northwestern (active) and eastern (inactive) hydrothermal vent fields of the Semenov cluster. Mineral types of sediments were distinguished, and a general scheme was proposed for the vertical structure of the hydrothermal-sedimentary sequence overlying massive sulfide ores. It was found that the ore-bearing sediments exhibit a vertical zoning in the distribution of mineral assemblages, which are controlled by oxygen activity. The mechanisms of the formation of atacamite, CuCl2 · 3Cu(OH)2, which is a widespread mineral in red iron-oxide bodies replacing sulfides (gossans), were evaluated.

Detailed characterisation of antimony mineralogy in a geometallurgical context at the Rockliden ore deposit, North-Central Sweden

The antimony (Sb) content of the Rockliden complex Zn–Cu massive sulphide ore lowers the quality of the Cu–Pb concentrate. The purpose of this study is to characterise the Sb mineralogy of the deposit. The Sb-bearing minerals include tetrahedrite (Cu,Fe,Ag,Zn)12Sb4S13, bournonite PbCuSbS3, gudmundite FeSbS and other sulphosalts. On a microscopic scale these minerals are complexly intergrown with base-metal sulphides in the ore. Based on these observations mineralogical controls on the distribution of Sb-bearing minerals in a standard flotation test are illustrated. Deposit-scale and rock-related variation in the Sb-content and distribution of Sb-bearing minerals were found. This underlines the importance in understanding the geological background as a basis of a 3D geometallurgical model for Rockliden. Such a model is expected to predict the Sb content of the Cu–Pb concentrate, among other process-relevant factors, and helps to forecast when the Cu–Pb concentrate has to be treated by alternative processes, such as alkaline sulphide leaching, before it is sold to the smelter.

Geological and Geochemical Characteristics of the Huangshilao Stratabound Gold Deposit in the Tongguanshan Orefield, Tongling, East‐Central China

AbstractThe Huangshilao gold deposit (&gt;13.5 t Au) is comprised of stratabound pyrite‐dominant massive sulfide ores, and is distinguished from the skarn Cu, Au, and Cu–Au deposits that are dominant in the Tongguanshan orefield, Tongling, east‐central China. The stratabound orebodies are situated along flexural slip faults along the unconformity between the Upper Devonian Wutong and the Upper Carboniferous Huanglong Formations. The ores, dominated by crystallized pyrite, colloform pyrite, and pyrrhotite, are systematically sampled from the underground stopes along strike drifts. The δ34S values of ore sulfides yield a wide variation from −11.3 to 11.4‰, but mostly within 4–8‰, corresponding to the δ34S range (3.4–8.7‰) of the Yanshanian Tongguanshan and Tianshan quartz diorite intrusions in the Tongguanshan orefield, suggesting a magmatic dominated sulfur source. Few obvious negative δ34S values are induced by an involvement of sedimentation‐related biogenic sulfur. The wide δ34S variation denotes an incongruent physical and chemical interaction of the two sources. Combined analysis of gold contents and sulfur isotopes of the sulfides show that the magmatic hydrothermal solution provides primary metals despite a small quantity that may have been contributed by the sedimentary pyrites. The hydrothermal alteration, thermal metamorphism, trace element concentration in pyrites, and existing aeromagnetic data jointly suggest that the hydrothermal fluid migrated vertically from an intrusion below, along the flexural slip faults, but not laterally from the nearby outcrop of Tianshan stock.