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The nature of tennantite (Cu12As4S13), chalcopyrite (CuFeS2) and sphalerite (ZnS) particles’ mixture dissolution in nitric acid (HNO3) media was investigated in this study. The effects of temperature (323–368 K), HNO3 (1–8 mol/L) and Fe3+ (0.009–0.036 mol/L) concentrations, reaction time (0–60 min) and pyrite (FeS2) additive (0.5/1–2/1; FeS2/sulf.conc.) on the conversion of the minerals were evaluated. It has been experimentally shown that the dissolution of the mixture under optimal conditions (>353 K; 6 mol/L HNO3; FeS2/synt. conc = 1/1) allows Cu12As4S13, CuFeS2 and ZnS conversion to exceed 90%. The shrinking core model (SCM) was applied for describing the kinetics of the conversion processes. The values of Ea were calculated as 28.8, 33.7 and 53.7 kJ/mol, respectively, for Cu12As4S13, CuFeS2 and ZnS. Orders of the reactions with respect to each reactant were calculated and the kinetic equations were derived to describe the dissolution rate of the minerals. It was found that the interaction between HNO3 solution and Cu12As4S13, CuFeS2 and ZnS under the conditions investigated in this are of a diffusion-controlled nature. Additionally, the roles of Fe(III) in the initial solution and FeS2 in the initial pulp as catalysts were studied. The results indicated that the increase in Fe3+ concentration significantly accelerates the dissolution of the mixture, while the addition of FeS2 forms a galvanic coupling between FeS2, and Cu12As4S13 and CuFeS2, which also accelerates the reaction rate. The results of the study are considered useful in developing a hydrometallurgical process for polymetallic sulfide raw materials treatment.

The Tiegelongnan porphyry-epithermal deposit (2089 Mt @ 0.53% Cu, 0.08 g/t Au) is host to a large variety of Cu-sulfide minerals, mainly chalcopyrite, bornite, covellite, digenite, enargite, and tennantite. We used LA-ICP-MS to investigate the trace element geochemistry of the Tiegelongnan Cu-sulfides, as well as pyrite, to understand the correlation between sulfides and trace elements, gold in particular, in the porphyry and epithermal systems. Porphyry mineralization consists of stage 1 chalcopyrite-pyrite ± molybdenite, stage 2 chalcopyrite-bornite, and stage 3 covellite. Epithermal sulfides form stage 4 pyrite-alunite, stage 5 digenite-bornite-chalcopyrite, and stage 6 enargite-tennantite ± tetrahedrite. Stage 2 chalcopyrite (S2 Ccp, median = 9.7 ppm Au) is the primary porphyry Au host, and stage 6 tennantite in alunite veins (S6 Tnt-s, median = 98.0 ppm Au) is the major epithermal Au host. These Au-rich sulfides formed under higher oxidation conditions, suggesting that a high oxidation state favors the incorporation of Au in Cu-sulfides. Gold contents in coeval chalcopyrite and bornite are positively correlated to temperature, and Au is enriched in chalcopyrite over bornite at low temperatures (

The goal of this work was to study the bioleaching of arsenic-containing polymetallic concentrate that contained 6.2% Cu, 7.3% Zn and 1.7% As, depending on different temperatures and in the presence of CO2 and molasses in the medium, as well as the difference in the composition of microbial population formed under various conditions. A mixed population of moderately thermophilic and thermotolerant acidophilic microorganisms formed during the continuous bioleaching of copper concentrate was used as an inoculum. The experiments were carried out in a continuous mode in laboratory scale reactors, with a temperature range of 40 °C to 60 °C. To assess the effect of CO2 and molasses on metal leaching and microbial population composition, the experiments were carried out in three reactors: CO2 (~0.01 L/min) was supplied into the first reactor; 0.02% molasses were added to the pulp of the second reactor; and no additional carbon sources were supplied into the control reactor. The highest copper recovery (27%) was achieved at 50°C in the experiment with molasses, while the highest zinc recovery (82.1%) was reached at 45°C in the control experiment. Additional carbon sources affected the extraction of non-ferrous metals only at 60 °C and increased the extraction of copper and zinc by 12.6% and 24.2%, respectively. Both the temperature and carbon source used affected the microbial population composition. The main microbial genera revealed in the populations by next generation sequencing (NGS) were bacteria of the genera Sulfobacillus and Acidithiobacillus, as well as archaea of the genera Ferroplasma, Acidiplasma, and Cuniculiplasma. At low temperatures (40 and 45 °C), Acidithiobacillus, Sulfobacillus, and Ferroplasma predominated, while at temperatures 50–55 °C, the decrease in relative abundance of these genera occurred, and the predominance of Acidiplasma archaea was observed. The usage of both CO2 and molasses led to the increase in Sulfobacillus and Acidiplasma in relative abundance.

The goal of the present work was to study the dependence of the rate of copper and zinc bioleaching from an arsenic-containing copper-zinc concentrate containing 16% Cu, 5.3% Zn, and 1.36% As, on the temperature and the presence of an organic carbon source (yeast extract) in the medium. The main minerals of the concentrate were chalcopyrite (CuFeS2), tennantite (Cu12As4S13), sphalerite (ZnS), and pyrite (FeS2). A mixed culture of moderately thermophilic acidophilic microorganisms oxidizing sulfur and ferrous iron, which was used in the work, consisted of the strains Acidithiobacillus caldus MBC-1, Sulfobacillus thermosulfidooxidans SH-1, and Acidiplasma sp. MBA-1. The experiments were carried out in flasks with 100 mL of mineral medium and 2 g of the concentrate on a rotary shaker for 30 days at temperatures from 40 to 60°C. It was shown that the leaching rate of copper depended both on temperature and on the presence of yeast extract. Copper leaching rate increased with increasing temperature, while zinc leaching was less dependent on the temperature. In the presence of an organic carbon source in the medium, both copper and zinc were actively leached at high temperatures (55 and 60°C), while in experiments with a medium without yeast extract, the activity of non-ferrous metals leaching from the concentrate at these temperatures was much lower. At the same time, at temperatures of 40–50°C, leaching activity was less dependent on the presence of the organic carbon source in the medium.

The goal of the present work was to study the bioleaching of chalcopyrite (CuFeS2), enargite (Cu3AsS4), and tennantite (Cu12As4S13) by pure and mixed cultures of moderately thermophilic microorganisms belonging to the groups predominant in technological processes (Acidithiobacillus caldus MBC-1, Sulfobacillus thermosulfidooxidans SH-1, and Acidiplasma sp. MBA-1) under different conditions (temperature of 40 to 60°C, presence of Fe2+ ions, pyrite (FeS2), and pyrrhotite (FeS)). Bioleaching of copper from chalcopyrite and enargite was shown to depend on temperature and to be almost independent of the composition of microbial culture. Under optimal conditions (50–55°C), after 30 days 25–27 and 14% of copper was leached from chalcopyrite and enargite, respectively. Increase in the temperature up to 60°C led to the inhibition of copper bioleaching from both minerals. The optimal temperature for tennantite bioleaching was 45°C, while the rate of bioleaching was significantly dependent on the composition of the microbial culture. In an experiment with a mixed culture of all three strains, 26% of copper was leached, while in experiments with pure cultures of A. caldus MBC-1, S. thermosulfidooxidans SH-1, and Acidiplasma sp. MBA-1, after 30 days 12, 21, and 18% of copper was leached, respectively. Addition to the medium of Fe2+ as ferrous sulfate resulted in an increased rate of copper leaching from enargite and tennantite, which may be explained by the fact that Fe3+ ions are generated during microbial Fe2+ biooxidation to Fe3+, which is a strong oxidizing agent and plays an important role in the leaching of sulfide minerals. In the presence of pyrite and pyrrhotite, the rates of enargite and tennantite leaching increased, probably due to the presence of Fe3+ ions in the medium, which were generated during the biooxidation of iron sulfide minerals. The results of the work demonstrated that different environmental factors affected the bioleaching of copper minerals in different ways, which is of practical importance, in particular, for planning the trials for bioleaching of mineral raw materials.

This paper describes the nitric acid dissolution process of natural minerals such as ten-nantite, chalcopyrite and sphalerite, with the addition of Fe (III) ions and FeS2. These minerals are typical for the ores of the Ural deposits. The effect of temperature, nitric acid concentration, time, additions of Fe (III) ions and FeS2 was studied. The highest dissolution degree of sulfide minerals (more than 90%) was observed at a nitric acid concentration of 6 mol/dm3, an experiment time of 60 min, a temperature of 80 °C, a concentration of Fe (III) ions of 16.5 g/dm3, and an addition of FeS2 to the total mass minerals at 1.2:1 ratio. The most significant factors in the break-down of minerals were the nitric acid concentration, the concentration of Fe (III) ions and the amount of FeS2. Simultaneous addition of Fe (III) ions and FeS2 had the greatest effect on the leaching process. It was also estab-lished that FeS2 can be an alternative catalytic surface for copper sulfide minerals during nitric acid leaching. This helps to reduce the influence of the passivation layer of elemental sulfur due to the galvanic linkage formed between the minerals, which was confirmed by SEM-EDX. © 2022 by the author. Licensee MDPI, Basel, Switzerland. Russian Science Foundation, RSF: 075-03-2021-051/5, 20-79-00317, FEUZ-2021-0017 Funding: This work was funded by the Russian Science Foundation Project No. 20-79-00317. The SEM-EDX, XRF, XRD analysis were funded by State Assignment, grant No. 075-03-2021-051/5 (FEUZ-2021-0017).

In the Bazhenov Formation, framboidal clusters and nodular pyrite formed in the dysoxic&ndash, anoxic interface within organic-rich sediments. Some nodule-like pyritized bituminous layers and pyrite nodules are similar to pyritized microbial mat fragments by the typical fine laminated structure. Framboidal pyrite of the Bazhenov Formation is enriched in redox-sensitive elements such as Mo, V, Au, Cu, Pb, Ag, Ni, Se, and Zn in comparison with the host shales and nodular pyrite. Nodular pyrite has higher concentrations of As and Sb, only. Strong positive correlations that can be interpreted as nano-inclusions of organic matter (Mo, V, Au), sphalerite (Zn, Cd, Hg, Sn, In, Ga, Ge), galena (Pb, Bi, Sb, Te, Ag, Tl), chalcopyrite (Cu, Se) and tennantite (Cu, As, Sb, Bi, Te, Ag, Tl) and/or the substitution of Co, Ni, As and Sb into the pyrite. On the global scale, pyrite of the Bazhenov Formation is very similar to pyrite from highly metalliferous bituminous black shales, associated, as a rule, with gas and oil-and-gas deposits. Enrichment with Mo and lower Co and heavy metals indicate a higher influence of seawater during formation of pyrite from the Bazhenov Formation in comparison to different styles of ore deposits. Transitional elements such as Zn and Cu in pyrite of the Bazhenov Formation has resulted from either a unique combination of the erosion of Cu&ndash, Zn massive sulfide deposits of the Ural Mountains from one side and the simultaneous manifestation of organic-rich gas seep activity in the West Siberian Sea from another direction

Investigation on the flotation behaviour of enargite (Cu3AsS4) and tennantite ((Cu, Fe)12As4S13) during selective copper flotation was performed using an integrated mineralogical approach. To this end, samples taken from a production block at the Chelopech mine were subjected to a laboratory scale flotation and products characterized through multi-element chemical analyses and mineral mapping using a SEM-based automated mineralogy. Chemistry, modal mineralogy, copper-sulphosalts’ liberation and associations were quantified. Principal component analysis (PCA) was employed to look for relationships between mineralogical features and flotation recovery. High variability in head copper grade was observed in the studied block, with deportment results attributing it to the varied content of enargite and tennantite. Chalcopyrite content was low in the majority of the samples. The close association and the frequently observed interlocking of pyrite and Cu-sulphosalt grains can explain pyrite (and gold) recovery during copper cleaner flotation. Linear equations based on PCA results allow the prediction of Cu-sulphosalts’ recovery with a root mean square error of ±1.32%.

The migration of helium from the crystal lattices of sulfides (pyrite, pyrrhotite, chalcopyrite, bornite, and sphalerite) and sulfosalts (tennantite and tetrahedrite) was studied. It was shown that helium occurs in submicrometer inclusions of uranium- and thorium-bearing minerals. The curves of helium thermal desorption from the sulfide and sulfosalts were obtained by the step-heating method and analyzed on the basis of the single-jump migration model. The interpretation of these data led to the conclusion on the possibility of the U–Th–He dating of pyrite. It was shown that the migration parameters of helium in the other sulfides and sulfosalts are not suitable for their potential use as U–Th–He geochronometer. Based on a comparison of data on helium migration in various minerals, it was suggested that high helium retentivity in some sulfides and arsenides (pyrite and sperrylite) is related to the type of their crystal lattice, packing density, and specific electric resistivity.

The Peschanka deposit and Nakhodka ore field occurring in the Baimka Cu-Mo-Au porphyry-epithermal trend in the western Chukchi Peninsula, Russia are spatially related to monzonitic rocks of the Early Cretaceous Egdykgych Complex. Tetrahedrite solid solution (Tts) was recognized at the deposit and within the ore field in the following assemblages: (1) porphyry stage bornite, chalcopyrite, and molybdenite, (2) transitional (subepithermal) stage sphalerite, galena, chalcopyrite, and As-free pyrite, (3) HS epithermal stage enargite, chalcopyrite and high-fineness native gold, and (4) IS epithermal stage As-rich pyrite, galena, sphalerite, and low-fineness native gold and electrum. The porphyry and subepithermal Tts crystals are oscillatory zoned because of variable contents of Sb and As. The literature data show that similar zoning has been recognized in the Tts crystals in the other porphyry Cu-Mo-Au and transitional assemblages and differs from the other type deposits. Therefore, such a zoning is considered to be a guide to these two mineralization types. No zoning was found in Tts referred to the HS and IS epithermal assemblages within the Baimka trend. The porphyry stage Tts evolves from Fe-rich tennantite ((sb = Sb/(Sb + As) below 0.01, fe = Fe/(Fe + Zn) 0.60–0.80) through oscillatory zoned tennantite enriched in Sb and Zn (sb 0.19–0.37, fe 0.56–0.66) to tetrahedrite enriched in Zn (sb 0.51–0.70, fe 0.39–0.66). This trend is caused by the Sb accumulation and increased fS2. The review of published data shows that such trend is typical of the other porphyry deposit worldwide. Therefore, it is considered to be a guide to distinguish porphyry deposits from the other type deposits containing fahlores and to distinguish porphyry-stage fahlores. The composition of the transitional stage Tts evolves from Zn-rich tetrahedrite (sb 0.56–0.82, fe 0.03–0.05) through Zn-rich tennantite (sb 0.03–0.19, fe 0.11–0.13) followed by Zn-rich oscillatory zoned solid solution (sb 0.03 to 0.69, fe 0.09 to 0.11) to goldfieldite. This evolution testifies to increased fTe2 to the end of transitional stage. The HS stage Tts corresponds to Fe-rich tennantite (sb below 0.05, fe 0.65–1.00) containing high Cuexcess (1.43 apfu). The IS stage Tts evolves from Zn-rich tennantite (sb = 0, fe = 0.44) to Zn-rich tetrahedrite (sb = 0.97, fe = 0.03). The latest Zn-rich tetrahedrite of this assemblage is enriched in Ag (up to 4.1 wt.%) testifying to increasing Ag activity to the end of mineralizing process. The review of literature data shows the similar trend for the transitional and IS Tts in the other porphyry-epithermal systems. Therefore the Tts evolution trend is a criterion to separate porphyry, transitional, IS, and HS Tts.

The paper presents the results obtained when studying material compositions of four samples of refractory copper-bearing ores from the Uzelga deposit along with technological solutions to improve their processing parameters. The refractoriness of ores is associated with a thin dissemination (up to a micron size) and close intergrowth of ore and rock minerals. Ferrous sulfides are represented by a wide range of minerals: pyrite, marcasite and their variety melnikovite, arsenic pyrite and arsenopyrite; sooty melnikovite has a higher flotation activity. The reduction of iron sulfides from 89 to 29 % is followed by a proportional increase of easy-floatable rock minerals to 45 % and clay to 9 %. These properties make these sulfides difficult to process (float) and maintain ore refractoriness. The content of copper sulfides in ore samples varies from 3,32 to 7,29 %; the relative fraction of copper sulfide in a form of tennantite in different deposit samples varies from 29 to 93 %. Copper is also present as chalcopyrite and bornite. The best flotation activity of tennantite can be seen in neutral and weak acid media in contrast with standard flotation mode for chalcopyrite and bornite with butyl xanthate in a high-alkaline calcareous medium. Free grains of copper minerals can be selectively extracted into the intermediate flotation copper concentrates when grinding maximum 60 % of the –71-μm class. The technology of flotation in a low-alkaline medium is developed for refractory copper-bearing ores with variable tennantite content using the M-TF selective sulfhydryl collector in intermediate copper flotations and copper concentrate upgrading cycle; aeration used to suppress melnikovite flotation activity makes it possible to achieve 80 % copper recovery into conditioned copper concentrate. Bornite, tennantite, chalcopyrite and sphalerite disseminated in pyrite make it rational to obtain copper-pyrite, copper-zinc-pyrite products with their yield up to 12 % for pyroand hydrometallurgical processing.

The results of material composition studies of four samples of refractory copper-bearing ores of the Uzelga deposit are presented along with the results of studies of technological solutions to increase their processing parameters. The refractoriness of ores is associated with a thin dissemination up to micron size and close interbreedings of ore and rock minerals. Iron sulfides are presented by a wide range of minerals: pyrite and marcasite, melnikovite, arsenic pyrite, and arsenopyrite; sooty melnikovite has an increased flotation activity. The grinding of iron sulfides from 89 to 29% is followed by a proportional increase in easily floatable rock minerals to 45% and clay to 9%. These properties make these sulfides difficult to process and retain ore refractoriness to the flotation concentration. The content of copper sulfides in ore samples varies from 3.32 to 7.29%; the relative portion of copper sulfide in a form of tennantite in different samples of deposit varies from 29 to 93%. Copper is also present in a form of chalcopyrite and bornite. The best flotation activity of tennantite can be seen in a neutral and slightly acidic medium, in contrast with the standard flotation regime for chalcopyrite and bornite with butyl xanthate in a high-alkaline calcareous medium. Free grains of copper minerals can be selectively extracted into intercycled concentrates during grinding of no more than 60% of the class–71 μm. The technology of flotation in a low-alkaline medium with M-TF selective sulfhydril collector in the intercycle copper flotation and refinement cycle of the copper concentrate is developed for refractory copper-bearing ores with a variable tennantite content. Aeration is applied to suppress the flotation activity of melnikovite, which makes it possible to attain 80% copper recovery into a conditional copper concentrate. The fine inclusions of bornite, tennantite, chalcopyrite, and sphalerite into pyrite makes it rational to obtain copper–pyrite and copper–zinc–pyrite products with a yield up to 12% for pyro- and hydrometallurgical processing, along with the isolation of enriched copper concentrates.

Liancheng is an important Cu–Mo deposit hosted by red-beds in the Mesozoic to Cenozoic Lanping Basin located in the Sanjiang Tethyan Orogen of SW China. The deposit is fault controlled where it has been affected and enriched by four hydrothermal events indicated by four distinct sets of veins and their cross-cutting relationships. A detailed Cu–S–H–O isotopic study is reported here on the mineralization focusing on the source of the metals and fluid, and on the mineralizing processes. The first two hydrothermal events are characterised by CO2 and fluid-rich inclusions with homogenisation temperatures of 124–446 °C and salinities ranging from 0.4 to 24.6 wt% NaCl equiv. The next two hydrothermal events are characterised by liquid–rich fluid inclusions that homogenise at 145–256 °C, with salinities ranging from 1.4 to 22.9 wt% NaCl equiv. The H–O isotope values obtain from the fluid inclusions indicate that the first three hydrothermal events relate to mineralizing fluids derived from a metamorphic source, but the last event includes a mixed metamorphic and meteoric source. Chalcopyrite, tennantite, and bornite from the deposit have δ34S values between −11.5 and 3‰. The δ65Cu values for quartz-Cu sulfide mineralization associated with the second hydrothermal event range from −0.31 to 0.2‰, but carbonate-Cu sulfide mineralization associated with the third hydrothermal event ranges from −1.01 to −1.08‰. The combination of the Cu and S isotopic values and field observations indicate that the controlling factors include structures, the temperature of regional metamorphism, and the pH of the mineralizing fluid. The zation is, therefore, characteristic of an orogenic-type deposit.

The basalt-hosted Semenov-2 hydrothermal field on the Mid-Atlantic Ridge is host to a rather unique Cu-Zn– rich massive sulfide deposit, which is characterized by high Au (up to 188 ppm, average 61 ppm, median 45 ppm) and Ag (up to 1,878 ppm, average 490 ppm, median 250 ppm) contents. The largest proportion of visible gold is associated with abundant opal-A, which precipitated after a first generation of Cu, Fe, and Zn sulfides and before a second generation of Fe and Cu sulfides. Only rare native gold grains were found in earlier sulfides. Fluid inclusions in opal-A associated with native gold indicate precipitation at 300° ± 40°C from fluids of salinity higher than that of seawater (3.5–6.8 wt % NaCl equiv). According to laser ablation-inductively coupled plasma-mass spectrometry analyses, invisible gold is concentrated in secondary covellite (23–227 ppm) rather than in the primary sulfides ( 1,000 ppm) than all other sulfides (1 are more consistent with a mafic signature. Thermodynamic modeling of hydrothermal fluids produced by reactions between various proportions of seawater and basalt or peridotite at 350°C shows that mineral assemblages broadly similar to those of the Semenov-2 deposit can precipitate from fluids produced in a mafic environment, but that Au and Ag minerals are not predicted to precipitate from such fluids over a wide temperature range. These results suggest that an additional contribution to the hydrothermal system is required in order to achieve saturation in precious metals. A magmatic input is suggested by the occurrence of plagiogranites and tonalites dredged on sea floor in the Semenov area, which could be a potential source of Au-rich magmatic fluids, and by mineralogical and geochemical similarities with magma-related, low- to intermediate-sulfidation epithermal systems, namely high Au and Ag grades, high Au/(Cu + Zn + Pb) and Au/Ag ratios, and presence of Ag, Bi, and Te minerals. The likely crucial role of silicic melts in producing high Au and Ag grades suggests that exploration for precious metal-rich, volcanic-hosted massive sulfide deposits should be primarily directed to sites in which evolved igneous rocks occur on sea floor. Both in modern and ancient mafic-hosted deposits, zones characterized by abundant deposition of silica could be good clues to the presence of significant gold.

The results of experimental investigations into the zeta potential of ultrafine sulfides (chalcopyrite, tennantite, galenite, sphalerite, pyrite, and pyrrhotine), the floatability of monomineral fractions of sulfides of the floatation coarseness (–0.1 + 0.05 mm) in a mechanical flotation machine, and the floatability fine particles of sulfide (–0.044 + 0.010 mm) in the Hallimond tube are presented. The preparation procedure of ultrafine powders and sulfhydril collectors to measure the zeta potential is presented. Zeta potentials of the surface of mineral particles and insoluble forms of sulfhydril collectors are investigated in the pH range from 2.0 to 12.5 (an acidic medium was formed by using H2SO4 and basic one by using NaOH or Ca(OH)2), and various values of zeta potentials are found for sulfides in the sodium hydroxide and lime medium. Zeta potentials for all sulfides are negative in the NaOH medium at pH > 9.5, they are positive (1–18 mV) in the Ca(OH)2 medium at pH > 11, and zeta potentials for chalcopyrite are positive in the studied range \(p{H_{Ca{{\left( {OH} \right)}_2}}}\) 9.0–12.5. The values of the isoelectric point in the medium of sulfuric acid and sodium hydroxide are as follows: for chalcopyrite—pH 6.5 and 8.8, for tennantite—pH 3.0, for sphalerite—pH 5.1 and 6.4, for pyrite—pH 3.1 and 8.9, and for pyrrhotine—pH 7.0. In the lime medium, the value for tennantite and sphalerite pH 12.0, for galenite—pH 11.2, for pyrite—pH 9.5 and 11.2, and for pyrrhotine—pH 9.5 and 12.1. Measurements of zeta potentials of ultrafine sulfide particles give the opportunity to refine the interaction mechanism of sulfhydril collectors with sulfides and associate the nonselective recovery of final tailings of sulfides in the highly alkaline lime medium with the contribution of the electrostatic component during the adhesion of ultrafine sulfide particles on bubbles and their mechanical carryout into the froth product.

Ores of the Vasilkovsky deposit include arsenopyrite, pyrite, pyrrhotite, marcasite, gold, chalcopyrite, sphalerite, galena, faded ore (tennantite)S, bismuthine, native bismuth, lellingite, molybdenite, cubanite, bornite, antimonite, relict minerals, magnetite, apatite and apatite chromite, sericite, chlorite, potassium feldspar, tourmaline), quartz, carbonates (siderite, ankerite, calcite), fluorite, barite. Arsenopyrite is the main ore mineral. It contains the bulk of gold, as well as impurities - copper, cobalt, nickel, bismuth, zirconium, titanium, lead, zinc, antimony, silver, molybdenum. Bismuth and its minerals are widespread, they are constantly associated with arsenopyrite, forming intergrowths with native gold, less often with chalcopyrite and faded ore. Native gold is distributed very unevenly, forms the finest precipitates ranging in size from tenths of a micron to 0.063 mm, grows together with quartz, arsenopyrite, pyrite and bismuth minerals. Rich ores were formed by combining bismuthcontaining associations with arsenopyrite. The role of gold in arsenopyrite increases with depth. Ores are of the gold-quartz-sulfide type. Quartz in ore up to 90 %, sulfides from 3 to 5 %. The content of harmful impurities (arsenic) reaches 2 % or more. Ores are refractory, require special technology for the beneficiation and extraction of gold.

This work presents investigations of high-T hydrothermal vent fluids, associated mineral precipitates and volcanic rocks from three submarine volcanos in the South Kermadec intraoceanic arc (Brothers Caldera, Haungaroa Volcano, Macauley Caldera). Mineralogical investigations, vent fluid compositions and fluid inclusion studies are discussed. Reaction path models simulate the influence of host rock compositions and the integrated fluid flux on the formation of massive sulfides. Further models demonstrate how addition of magmatic SO2 to hydrothermal systems generates arc typical magmatic-hydrothermal fluids and influences their REE composition. Vent fluid compositions, as well as salinities and formation temperatures in mineral precipitates from seawater-dominated hydrothermal fluids, point to boiling processes of rising solutions. The investigations demonstrate how magma degassing and boiling are key processes responsible for the chemical diversity of arc hydrothermal fluids.

The paper shows the results obtained in experimental studies of zeta potential of ultrafine sulfides (chalcopyrite, tennantite, galena, sphalerite, pyrite, pyrrhotite); floatability of mono-mineral flotation grade sulfide fractions (–0,1 + 0,05 mm) in the mechanical flotation cell; floatability of sludges (–0,041 + 0,010 mm) in the Hallimond tube with adsorption under foamless flotation conditions. The method for preparation of ultrafine powders and sulfhydryl collectors for zeta potential measurement is provided. The paper studies zeta potential of mineral particle surface and insoluble forms of sulfhydryl collectors in the pH range from 2,0 to 12,5 (acidic medium was prepared using H2SO4, alkali medium was prepared using NaOH or Ca(OH)2). The obtained zeta potentials of sulfides were different for sodium hydroxide and lime media. In NaOH medium at pH> 9,5 zeta potential values of all sulfides were negative; in Ca(OH)2 medium at pH > 11 they had positive zeta potential values (1–18 mV); chalcopyrite zeta potential values are positive in the studied range pHCa(OH)2 = 9,0÷12,5. Isoelectric points were identified for chalcopyrite (pH = 6,5 and 8,8), tennantite (pH = 3,0), sphalerite (pH = 5,1 and 6,4), pyrite (pH = 3,1 and 8,9) and pyrrhotite (pH = 7,0) in sulfuric acid and sodium hydroxide medium; for tennantite and sphalerite (pH = 12,0), galena (pH = 11,2), pyrite (pH = 9,5 and 11,2), pyrrhotite (pH = 9,5 and 12,1) in lime medium. Measurements of zeta potential values of ultrafine sulfide particles make it possible to define more exactly the mechanism of interaction between sulfhydryl collectors and sulfides, associate non-selective extraction of sulfide sludges in high-alkali lime medium with the electrostatic component contribution during adhesion of ultrafine sulfide particles on bubbles and their mechanical removal to the froth.

Here, we report the first documented occurrences of “invisible” gold and silver in seafloor sulfide deposits from an active hydrothermal system on the Central Indian Ridge. A detailed mineralogical and geochemical study of polymetallic sulfides from the Edmond vent field was conducted in order to identify controls on the distribution of precious metals. Bulk samples (N = 18) contain up to 18.7 ppm Au and 1450 ppm Ag, with average concentrations of 2.3 ppm Au and 218.9 ppm Ag. Among them, several Zn-rich chimney fragments and anhydrite-dominated ore samples have higher contents of precious metals than Fe-Cu-rich massive sulfides and silica-rich hydrothermal precipitates. Native gold grains are mainly associated with sphalerite, anhydrite, barite and Fe-oxyhydroxides. Abundant submicroscopic Au-Ag alloys tend to occur along grain boundaries between Cu-Fe sulfides and tennantite, or close to the rims of Fe-poor sphalerite. In contrast to primary electrum with high Ag/Au ratios, the absence of detectable silver in high-purity gold indicates that secondary Au enrichment has probably occurred after a direct co-precipitation with Zn-rich mineral assemblages upon cooling and mixing of vent fluids with cold seawater. A suite of late-stage Ag-rich phases, including argentotennantite, pearceite and acanthite, occur as crack-filling veinlets and patches in low-temperature fahlores, or as tiny inclusions enclosed by pyrite, chalcopyrite and colloform sphalerite. By using HRTEM combined with HAADF-STEM imaging, we have found out that silver is also present in significant quantities as discrete colloidal nanoparticles in tennantite. Minor native copper is closely associated with altered chalcopyrite, sphalerite and covellite, exhibiting signs of dissolution, recrystallization and reprecipitation. Extensive hydrothermal reworking resulted from a long history of high-temperature venting in this field, together with post-depositional supergene replacement processes (involving oxidation, leaching or coupled dissolution-reprecipitation mechanisms facilitated by a permeable porosity generated in primary Cu-Fe sulfides) are considered to be important for the remobilization and local reconcentration of early-formed precious metals, and may have been responsible for the formation of relatively coarse-grained native gold or silver within recrystallized massive sulfides and chimney debris.

Mineralogical, fluid inclusion, and geochemical studies of precious metal mineralization within the Baimka trend in the western Chukchi Peninsula have been preformed. Porphyry copper–molybdenum–gold deposits and prospects of the Baimka trend are spatially related to monzonitic rocks of the Early Cretaceous Egdygkych Complex. Four types of precious metal-bearing assemblages have been identified: (1) chalcopyrite + bornite + quartz with high-fineness native gold enclosed in bornite, (2) low-Mn dolomite + quartz + sulfide (chalcopyrite, sphalerite, galena, tennantite-tetrahedrite) ± tourmaline with low-fineness native gold and hessite, (3) rhodochrosite + high-Mn dolomite + quartz + sulfide (chalcopyrite, sphalerite, galena, tennantite- tetrahedrite) with low-fineness native gold, electrum, acanthite, Ag and Au–Ag tellurides, and Ag sulfosalts, and (4) calcite + quartz + sulfide (chalcopyrite, sphalerite, galena) with low-fineness native gold, Ag sulfides and selenides, and Ag-bearing sulfosalts. Study of fluid inclusions from quartz, sphalerite, and fluorite have revealed that hydrothermal ores within the Baimka trend precipitated from fluids with strongly variable salinity at temperatures and pressures ranging from 594 to 104°C and from 1200 to 170 bar, respectively. An indicator of vertical AgPbZn/CuBiMo geochemical zoning is proposed. The value range of this indicator makes it possible to estimate the erosion level of the porphyry–epithermal system. The erosion level of the Baimka deposits and prospects deepens in the following order: Vesenny deposit → Pryamoi prospect → Nakhodka prospect → Peschanka deposit → III Vesenny prospect.

The Dairi Zn + Pb + Ag deposit is the only giant SEDEX deposit that has been discovered to date in Sumatra. Ore-gangue mineralogy and sulfur isotope studies have been carried out to elucidate the paragenetic sequence, deformation of ore, flow direction of ore forming fluid, and sources of sulfur in the Dairi deposit. Stratiform orebodies hosted by the Julu unit (interbedded dolomitic siltstone and carbonaceous shale; multilayers; accounting for greater than 90% of metal resources) consist of pyrite-rich massive, sphalerite-rich massive, bedded sulfide, galena-rich breccias, and vein ore types, whereas discordant orebodies hosted by the Jehe unit (massive and brecciated arenaceous dolostone) comprise vein and disseminated ore types. Fine-grained, subhedral-euhedral and framboidal pyrite (enriched in Co, Ni, Cu, As, Bi, Ag relative to hydrothermal pyrite) were precipitated in the diagenetic stage, followed by precipitation of pyrite (enriched in Zn, Pb, Mn, Tl relative to diagenetic pyrite), sphalerite, galena, chalcopyrite, pyrrhotite, acanthite, tetrahedrite, tennantite, pyrargyrite, boulangerite, freieslebenite, and diaphorite in the hydrothermal stage derived from the exhaled ore-forming fluid. Metamorphic pyrite (enriched in Co and depleted in Cu, Zn, Mn, Tl, Ag relative to the other pyrites) formed from pyrrhotite (depleted in Co relative to metamorphic pyrite) and soft sulfides were remobilized into pyrite fractures and veins during sub-greenschist metamorphism. Ore-forming fluid ascended through fractures in the Jehe unit (forming the discontinuous orebodies) and then it discharged and flowed from SE to NW on the seafloor (forming the stratiform orebodies). Reduced sulfur for diagenetic pyrite (δ34S = -4.1‰ to + 11.6‰) was supplied by bacteriogenic reduction of Carboniferous seawater sulfate. Hydrothermal sulfur was considered as the source of sulfur for the Jehe-hosted orebodies (δ34S = +3.5‰ to + 8.0‰). The heavier δ34S of sulfides in the Julu-hosted orebodies (δ34S = +6.4‰ to + 28.8‰) suggests large-scale bacteriogenic reduction of Carboniferous seawater sulfate in a restricted, anoxic basin. A bacteriogenic reduced sulfur reservoir, rather than hydrothermal sulfur, may be more plausible to account for the scale of the giant Dairi deposit.

Effect of oxidation treatment using hydrogen peroxide (H2O2) on the floatability of copper sulfide minerals (i.e., chalcopyrite and bornite) and arsenic-bearing copper minerals (i.e., tennantite and enargite) is reported in this study. Pure mineral flotation shows that the floatability of each mineral significantly decreases after the oxidation treatment. Interestingly, flotation of mixed mineral of copper sulfide and arsenic-bearing copper minerals shows that enargite and tennantite exhibit a higher floatability compared to chalcopyrite and bornite after the oxidation treatment followed by the addition of potassium amyl xanthate (PAX). These flotation results indicate a possibility for selective flotation of copper sulfide and arsenic-bearing copper minerals. Indeed, bench-scale flotation tests show that the oxidation treatment using H2O2 and the addition of PAX can deliver a satisfying separation of copper sulfide and arsenic-bearing copper minerals. Difference oxidation products (i.e., CuO, Cu(OH)2, CuSO4, FeOOH, and Fe2(SO4)3) on each mineral surface are likely the cause of this different flotation behavior. Furthermore, these oxidation products may affect the adsorption amount of PAX on each mineral. Indeed, the adsorption tests show that PAX is adsorbed more on tennantite, bornite, and enargite compared to chalcopyrite owing to the formation of CuSO4 and Cu(OH)2 on the mineral surfaces under oxidizing conditions. A possible mechanism is proposed in this study to explain the selective flotation behavior of mixed minerals.

The effects of temperature and the presence of NaCl on bioleaching of chalcopyrite, enargite, and tennantite were studied. Rate of copper extraction from all minerals depended on temperature and was the highest at 45–50 °C. NaCl addition increased rate of copper extraction from chalcopyrite but led to the decrease in copper extraction from enargite and tennantite.

The Kirazliyayla deposit is one of Pb-Zn (±Cu) deposits associated with andesitic volcanism cutting through the metamophics of Karakaya complex. It is a structurally controlled, vein-stockwork style, mesothermal ore deposit. Replacement, brecciation, vein/veinlets, carries, sea-island, and dissemination textures were identified. Pyrite, sphalerite, chalcopyrite, galena, tennantite, and covellite constitute the ore mineral paragenesis. Quartz, calcite and dolomite with kaolinite account for the gangue minerals. Supergene stage is insignificant. The Kirazliyayla mineralization is a Zn-Pb (±Cu) mineralization hosted by tectonically controlled andesitic volcanism within the Karakaya metamorphics and has common features with the other occurrences in the western Anatolia.

Fahlore-group minerals in Oligocene magmatic-hydrothermal deposits from the central and eastern Rhodope area, Bulgaria and Greece (e.g. porphyry-epithermal systems at Pagoni Rachi, Maronia and Kassiteres-Sapes, polymetallic epithermal high- and intermediate-sulfidation veins at Kirki, Perama Hill, Mavrokoryfi, Pefka, Zvezdel-Pcheloyad and Madzharovo, skarn-carbonate replacement deposits at Laki, Davidkovo, Madan, Enyovche and intrusion-related deposits at Kimmeria), cover the whole range of the tetrahedrite-tennantite solid solution series and are dominated by zincian and ferroan varieties reflecting deposition from Zn-(and Fe)-rich fluids. The majority of the studied fahlores are “normal” fully-substituted with Cu (+Ag) close to 10 apfu. However, high-sulfidation epithermal deposits in Greece contain “Cu-excess” tetrahedrite-tennantite; those with extreme high Cu-excess > Fe + Zn occur in transitional high- to intermediate-sulfidation systems, whereas low “Cu-excess” tetrahedrite-tennantite with Zn > Cu-excess + Fe and Fe > Cu-excess + Zn are part of tellurides-bearing intermediate-sulfidation assemblages. The epithermal St. Demetrios and Pefka deposits display the most Cu-rich tetrahedrites (11.039 apfu Cu) and tennantite (11.784 apfu Cu) worldwide. Although Ag substitutes for Cu in the structure of Ag-rich tetrahedrite in several deposits, freibergite with 6.800 apfu Ag occurs only at Mavrokoryfi; in particular, the cadmian freibergite at Mavrokoryfi is the second finding of this variety worldwide. Tellurium-bearing fahlore varieties occur in association with enargite/luzonite and native gold in high-sulfidation ore assemblages. Tetravalent tellurium substitutes for trivalent As and Sb in goldfieldite and Te-rich tennantite and tetrahedrite at Mavrokoryfi, Perama Hill, St. Demetrios and Pefka deposits. Goldfieldite at Mavrokoryfi and Perama Hill is remarkably Te-rich (up to 3.766 apfu and 3.711 apfu Te, respectively), with total metal content of 10.591 apfu and are the closest natural occurrence to the theoretical synthetic endmember Cu10Te4S13. The telluride-bearing fahlores in several epithermal deposits in Greece do not represent decomposition products of early goldfieldite. They are possibly the result of a new influx of Te-rich magmatic volatiles in the system. Decreasing Te (and Cu)-content in tetrahedrite-tennantite solid solution series reflects an evolution from initial high-T, high-sulfidation, oxidizing conditions, towards lower-T and lower-sulfidation, more reduced conditions with time. Fahlores, although they are minor constituents in the studied mineralization types, are carriers of Ag (and Au in goldfieldite) and may be used as an exploration tool, since they are closely associated with either native gold, gold-silver tellurides or Ag-sulfosalts.

The authors discuss flotation of fahl ore. It is proved that tennantite should be separated into an individual copper product in order to enhance overall copper recovery and mitigate ecological impact by means of preventing arsenic volatilization under smelting. Single mineral fractions of pyrite, chalcopyrite, tennantite, secondary sulfides, sphalerite and quartz sampled in the Ural region, as well as the samples of copper-zinc ore containing fahl ore are examined. The research involves oxidation of copper sulfides and pyrite under grinding in different conditions. Concentration of oxygen and sulfur-bearing ions is under control. The differences in oxygen consumption, oxidation of pyrite, tennantite and other sulfides are used to develop the mode of tennantite separation from other copper sulfides, sphalerite and pyrite. Based on the research findings, the authors recommend a flotation technology for copper–zinc pyritic ore with high content of tennantite to separate tennantite and secondary copper sulfides in different flotation circuits at varied pH.

The legacy of copper (Cu) mining at Spania Dolina-Piesky and Ľubietova-Svatodusna (central Slovakia) is waste rock and soil, surface waters, and groundwaters contaminated with antimony (Sb), arsenic (As), Cu, and other metals. Copper ore is hosted in chalcopyrite (CuFeS 2 ) and sulfosalt solid-solution tetrahedrite-tennantite {Cu 6 [Cu 4 (Fe,Zn) 2 ]Sb 4 S 13 –Cu 6 [Cu 4 (Fe,Zn) 2 ]As 4 S 13 } that show wide-spread oxidation characteristic by olive-green color secondary minerals. Tetrahedrite-tennantite can be a significant source of As and Sb contamination. Synchrotron-based μ-XRD, μ-XRF, and μ-XANES combined with electron microprobe analyses have been used to determine the mineralogy, chemical composition, element distribution, and Sb speciation in tetrahedrite-tennantite oxidation products in waste rock. Our results show that the mobility of Sb is limited by the formation of oxidation products such as tripuhyite and romeite group mineral containing 36.54 wt% Sb for samples where the primary mineral chemical composition is close to tetrahedrite end-member. Antimony K -edge μ-XANES spectra of these oxidation products indicate that the predominant Sb oxidation state is 5 + . Arsenic and Cu are also hosted by amorphous phases containing 6.23 wt% Sb on average and these are intergrown with tripuhyite and romeite. Antimony in this environment is not very mobile, meaning it is not easily released from solid phases to water, especially compared to As, Cu, and S. For samples where the primary sulfosalt is close to tennantite composition, the oxidation products associated with tennantite relicts contain 2.43 wt% Sb and are amorphous. The variable solubility of the secondary minerals that have been identified is expected to influence mobility of Sb and As in near-surface environment.

The stoichiometry and kinetics of the hydrothermal reaction of enargite in copper sulphate solutions was investigated in the range 140–300 °C, and particle size under 15 and 50 µm. The stoichiometric experiment was performed at 300 °C, using one gram of sample (96% enargite, 4% tennantite) and 100 mL of copper sulphate solution (10 gpl) at 1.2 pH. Enargite reacted completely after 80 min. A solid product was obtained and characterized by XRD. The main product was chalcocite (M) and some traces of djurleite and chalcocite (Q). Tennantite did not react under these conditions. The kinetic experiments were conducted at 140 °C, 190 °C, 250 °C and 300 °C. From fitted data and Arrhenius equation the calculated activation energy (Ea) was 51 kJ/mol. According to the hydrothermal transformations studied, the reactivity of different phases found in the copper concentrates was bornite > chalcopyrite > covellite > sphalerite > pyrite > enargite > tennantite.