Copper Sulfide Minerals Research Articles

The kinetics of dissolution of synthetic covellite, chalcocite and digenite in dilute chloride solutions at ambient temperatures

An experimental study of the comparative kinetics of dissolution of various synthetic copper sulphides (covellite, chalcocite, and digenite) in dilute chloride solutions has been carried out at ambient temperatures such as could be encountered in the heap leaching of secondary copper sulphide minerals. The dissolution of sized synthetic covellite particles was carried out in dilute HCl solutions containing known concentrations of copper(II) and iron(III) at controlled potentials. The results show that the rate of dissolution is similar at potentials of 600 and 650 mV, but is predictably less at a potential of 550 mV. The rate of dissolution is remarkably similar to that of chalcopyrite under similar conditions and is largely independent of Cl − and HCl concentration in the range 0.2 to 2.5 M and 0.1 to 1 M respectively. The effect of temperature is significant and an activation energy of 71.5 kJ mol − 1 was derived which confirms a chemical or electrochemical rate-determining reaction on the mineral surface. A mineralogical study of the residue after leaching shows that most of the sulphur is associated with unreacted covellite and occurs as isolated globules on the surface with over 90% of the unreacted covellite surface free of sulphur. Dissolution of synthetic chalcocite and digenite is rapid compared with that of covellite under the same conditions. At a potential of 500 mV, the relatively rapid initial dissolution of chalcocite and digenite does not proceed beyond about 50% and 45% copper dissolution, respectively, as predicted from the thermodynamics. These results confirm the formation of a covellite-like phase as an intermediate which cannot be leached at a potential of 500 mV. An increase in the potential results in rapid dissolution of this “secondary covellite,” relative to primary covellite. These results provide useful information for the conditions that should be used for the heap leaching of ores containing secondary copper sulphide minerals.

Comparative bioleaching and mineralogy of composited sulfide ores containing enargite, covellite and chalcocite by mesophilic and thermophilic microorganisms

Column testing was conducted to evaluate the potential for copper extraction from composited samples of Newmont Mining Corporation's Yanacocha Verde deposit in Peru. The Mineral Liberation Analysis (MLA) revealed that the composites contained various amount of copper sulfide minerals. Comparative bioleaching was conducted with consortia of mesophilic iron-oxidizing bacteria containing species of Acidithiobacillus and Leptospirillum for bioleaching at ambient laboratory temperature (20–22 °C) and with a mix of a thermophilic archaea culture containing Acidianus, Metallospheara and Sulfolobus at 65 °C. Enargite- and covellite-rich composites exhibited low copper extraction ranging from 7.3% to 27.1% based on column head/residue assays from columns after more than 300 days of bioleaching at room temperature with mesophilic bacteria. Chalcocite rich composites responded to mesophilic bacteria bioleaching with extractions ranging from 50 to 90% based on head/residue assays. High copper recovery from secondary chalcocite and low copper recovery from the primary copper minerals enargite and covellite are consistent with the performance of mesophilic bacteria. Thermophilic archaea proved advantageous for bioleaching primary enargite and covellite at 65 °C with copper extractions ranging from 60 to 98% over 335–346 days. Copper extractions from chalcocite-rich composites using thermophilic archaea were similar to those with room temperature mesophilic bacteria bioleaching. Semiquantitative XRD analysis and Mineral Liberation Analysis (MLA) were performed for mineralogical investigation with respective heads, and mesophilic and thermophilic residues. MLA confirmed only chalcocite leached under mesophilic conditions with partial leaching of covellite; and all copper minerals were leached under thermophilic conditions.

Effect of thiosulphate salts on ammoniacal thiosulphate leaching of gold

Gold leaching with calcium, sodium and ammonium thiosulphate salts was investigated in both pure gold and ore leaching systems. The type of thiosulphate salts was found to influence significantly the solution and surface chemistry, and hence the leaching of pure gold and the pyrite concentrate in the ammoniacal thiosulphate solutions. Calcium thiosulphate gave a higher gold extraction rate with negligible consumption of thiosulphate in the leaching of pure gold. Sodium thiosulphate had the least thiosulphate consumption and the lowest gold extraction rate in the leaching of pure gold. Ammonium thiosulphate had a better gold extraction rate than sodium thiosulphate, but had the highest thiosulphate consumption due to lower solution pH in the leaching of pure gold. The difference in the leaching of pure gold by the thiosulphate salts was attributed to the ability of ion-pair formation of thiosulphate ion with the cations. The mineralogy affected substantially the gold leaching of the ores with different thiosulphate salts. The leaching of the sulphide gold ore with a low-sulphide content followed the same trend as the leaching of pure gold, where the dissolution behaviour of gold with different thiosulphate salts governed the gold extraction rate. In contrast, the extraction rate of gold from the pyrite concentrate was dependent not only on the leaching behaviour of gold but also on the interactions of the associated sulphide minerals. Ammonium thiosulphate had a marginally higher gold extraction rate from the pyrite concentrate than calcium thiosulphate, due to the greater extent of leaching of the copper sulphide minerals in the ammonium thiosulphate solution. The thiosulphate consumption was the lowest in the leaching of the pyrite concentrate with calcium thiosulphate. Sodium thiosulphate had the lowest gold extraction rate from the pyrite concentrate despite low thiosulphate consumption. Ammonium thiosulphate is preferred for the leaching of high-sulphide ores and calcium thiosulphate is preferred for the leaching of low-sulphide ores.

Simulation of solute transportation within porous particles during the bioleaching process

A mathematical model, accounting for the sulfuric acid and ferric ions diffusion and the copper sulfide mineral leaching process, was developed for an ore particle by considering its porous structure. It was simulated with the simulation tool COMSOL Multiphysics. The simulation results show that the highest acid and ferric concentrations near the particle surface are apparent, while the concentrations in the central particle increase slightly as the less-porous ore core with low permeability prevents the oxidation from penetrating. The extraction of the mineral near the particle surface is the maximum, mainly because of ample sulfuric acid, ferric ions, bacteria, and oxygen available for the leaching process. Because of low oxidation concentration in the central part of the particle, the reaction rate and copper sulphide conversion are small. The simulation shows good agreement with the experimental results.

Effect of N-substituents on performance of thiourea collectors by density functional theory calculations

Abstract Using density functional methods, some properties were studied such as the energies and compositions of frontier molecular orbitals and the atomic charges, which are related to the reactive behavior of thioureas containing different N-substituent groupings. The calculation results indicate that the N-substituent groupings have significant effect on the flotation performance of thiourea collectors. The order of electron-donating ability is N-propyl-N′-benzyl-thiourea (PBZYTU)>N-propyl-N′-ethyl-thiourea (PETU) >N-propyl-N′-allyl-thiourea (PALTU)≫ N-propyl-N′-acetyl-thiourea (PACTU) >N-propyl-N′-ethoxycarbonyl-thiourea (PECTU) >N-propyl-N′-benzoyl-thiourea (PBZOYTU), and the order of feedback-electron-accepting ability is PBZOYTU>PACTU>PECTU≫ PALTU>PETU>PBZYTU. This implies that PBZOYTU, PACTU or PECTU can react with copper atoms having (t 2g) 6(e g) 3Cu(II) or t 6e 4Cu(I) configuration on the surfaces of copper sulfide minerals through normal covalent bond and back donation covalent bond, and exhibit excellently collecting performance for copper sulfide minerals. These are consistent with the experimental data reported in the literatures.

Comparison of Metals Leaching from CCA- and ACQ-Treated Wood in Simulated Construction and Demolition Debris Landfills

Pressure-treated wood is often disposed of in landfills in the United States, very frequently in construction and demolition (C&D) debris landfills. C&D debris landfills in many states are not equipped with liner systems to protect groundwater. With the voluntary withdrawal of chromated copper arsenate (CCA) treated wood for most residential applications in January 2004, copper-based wood preservatives, including alkaline copper quaternary (ACQ), are more widely used. To evaluate the impact of metal losses from ACQ-treated wood disposed in C&D debris landfills and compare to those of CCA-treated wood under similar conditions, leachates from three simulated C&D debris landfills (lysimeters) were collected and analyzed for over a period of one year. The wood component in one lysimeter (the control lysimeter) contained pallet wood; the second lysimeter contained CCA-treated wood, and the third contained ACQ-treated wood. Each lysimeter was buried in an active landfill for temperature control. Several batch leaching tests [including the standardized toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP)] were also conducted for comparison purposes. Although the two lysimeters containing treated wood had elevated copper concentrations within the waste matrix, the concentration in the leachate samples from these lysimeters was below detection for Cu (<4 μg/L) throughout the duration of the experiment, likely a result of precipitation as copper sulfide mineral in the reducing conditions of the simulated C&D landfills. As expected, the lysimeter containing CCA-treated wood showed elevated concentrations of arsenic and chromium, with maximum concentrations of 1.16 mg/L and 0.2 mg/L respectively. Greater amounts of boron (B) leached from ACQ-treated wood than CCA-treated wood or pallet wood debris. The results suggest that copper leaching will not be a major concern upon the disposal of ACQ-treated wood in C&D debris landfills. Arsenic leaching from CCA-treated wood remains a concern for unlined C&D debris landfills.

Assessment of Microbial Adhesion in Mixed Cultures to Sulfide Minerals Using CARD-FISH Techniques

The adhesion of microorganisms to minerals is one of the least understood aspects of bioleaching processes. Mineral and microorganism type are determinant factors affecting the capacity of a microbial community to form biofilms in these processes. In this paper the adhesion capacity of different microorganisms to different copper sulfide minerals generally present in bioleaching processes was studied. The minerals, chalcosite, chalcopyrite and pyrite were used and the composition of the microbial population which adhered to the mineral surfaces was determined using the Catalyzed Reporter Deposition Fluorescent In Situ Hybridization (CARD-FISH) technique. This technique involves the fluorescent marking of the cells using specific DNA probes and their observation with a confocal microscope. Three probes were used against the microorganisms: Acidithiobacillus ferooxidans, Acidithiobacillus thiooxidans and Leptospirillum. Polished fragments of the three minerals were placed in a tube with a culture medium which was inoculated with cells from a mixed culture capable of growing at 25°C. The adhered microorganisms were counted with CARD-FISH and compared with the total count which was carried out with DAPI staining. The results show that microorganisms adhered indistinctly to pyrite and chalcopyrite but not chalcosite. It was also observed that in pyrite 60% of the adhered microorganisms were Acidithiobacillus thiooxidans, 35% Acidithiobacillus ferrooxidans, and 1 % Leptospirillum. The remaining 4% were unidentified microorganisms.

Analysis of Sulfur Metasecretome in Mixed Cultures of Acidithiobacillus Thiooxidans and Acidithiobacillus Ferrooxidans

The role of biomolecules in bioleaching of copper sulphide minerals carried out by bacterial consortia with predominating acidithiobacilli species is of outmost interest. The proteomic analysis on bioleaching bacterial strains have been focused up to date on full Acidithiobacillus ferrooxidans proteome, allowing the identification of proteins belonging to the general stress response, phosphate limiting conditions and the ones linked to the periplasmic fraction. Our study shows for the first time the differential expression of secreted proteins by means of standard proteomics between pure cultures of Acidithiobacillus thiooxidans and in mixture with A. ferroxidans (metasecretome) grown in sulfur, where a set of proteins is de novo synthesized in the mixed culture, identifying an Omp40-like protein possibly related to bacterial adhesion, an hypothetical protein PSEEN2944 with unknown function and up-regulation of a cytochrome c biogenesis protein, findings that give an insight into the role of proteins at the sulfur – bacteria interface, highlighting the outputs of bacterial interactions in biomining environments at the protein secretion level.

Normalization of Quantitative Real-Time PCR Data of Identified Genes from an Industrial Bioleaching Operation

A strategy for the monitoring and control of genetic expression in an industrial bioleaching process of copper sulphide minerals is developed in order to understand more fully this process and investigate optimization possibilities. The aim of this research is to find a group of housekeeping genes to normalize the genetic expression data associated to the metabolic functions from industrial bioleaching samples obtained through specific real-time PCR. The data includes the quantification of the previously identified genes in the industrial process in samples from different strips (heap sections) and times. Two studies were carried out, one with the gene expression data associated to each species and the other with the expression data from all the genes detected in the industrial process, during a period of 18 months, using the VBA applet geNorm [1]. The first analysis showed that for the archaea Ferroplasma acidiphilum, the gene with the most stable expression codifies to the ribosomal protein S4 (rpS4) and secondly the mercury reductase gene (merA). In the case of Acidithiobacillus ferrooxidans DM and D2 strains, genes merA and pyruvate dehydrogenase (pdhA) presented similar factors of stability. In the community analysis it was concluded that the gene with the most stable expression was pdhA of A.ferrooxidans. A new analysis was done including other genes using geNorm to define the most stable genes for the whole community. In the community analysis it was concluded that the gene with the most stable expression was pdhA of A.ferrooxidans and merA of F.acidiphilum.

The measurement of chalcopyrite content in rocks and slurries using magnetic resonance

A prototype mineral analyser using magnetic resonance has been configured with two sensors for measurement of the copper sulphide mineral chalcopyrite (CuFeS 2) in ores and slurries. In the first configuration, a sensor was optimised to quantify chalcopyrite content in rock fragments. The detection limit for these measurements was estimated at 15 mg of contained chalcopyrite in rock fragments of mass range of 1.4–3.7 g. The magnetic resonance results correlated with separate quantitative X-ray diffraction measurements of chalcopyrite content. The second configuration was used to quantify chalcopyrite content in mineral slurries. Tests on prepared slurry samples with known chalcopyrite concentration were performed, yielding a standard error of 0.1 wt% across the sample range of 0.5–4.0 wt%. Measurements on a commercial mineral slurry were also performed. The design of an online industrial analyser is discussed with reference to processing slurries with high solid loadings, containing phases such as chalcopyrite and other minerals.

Flotation of mixed copper oxide and sulphide minerals with xanthate and hydroxamate collectors

Sherwood Copper’s Minto Mine processes a high grade copper–gold deposit in Yukon, Canada. The ore mined is from a primary copper sulphide deposit with separate additional deposits of copper oxides. In conjunction with Ausmelt Chemicals, Minto is currently investigating options to recover copper oxide and sulphide minerals using flotation by blending their primary sulphide ore with oxide ores. The blend used in this laboratory scale investigation was 70% sulphide ore and 30% oxide ore on a weight basis. The copper sulphides present in the blend were bornite and chalcopyrite, while the oxides were malachite and minor azurite. From previous flotation investigations of mixed copper oxide and sulphide minerals using xanthate and hydroxamate collectors it was hard to distinguish the impact of the alkyl hydroxamate collector on sulphide recovery as the sulphide and oxide minerals occurred naturally together. In the case of the Minto operation the copper oxide and sulphide minerals occur in separate ore deposits and can be treated separately or blended together. This investigation has shown that using n-octyl hydroxamates (AM28 made by Ausmelt Limited) in conjunction with traditional sulphide collectors can successfully simultaneously recover copper sulphides and oxides by flotation from blended ore minerals. The copper sulphide recovery did not decrease when processing the blended ore compared to treating the sulphide ore independently. At a blend of 70% sulphide ore and 30% oxide ore, the rougher scavenger copper recovery was as high as 95.5%. The copper recovery from the blended ore using a mixture of collectors was shown to be superior to the recovery obtained using only xanthate after controlled potential sulphidisation.

Bacterial leaching of chalcopyrite and bornite with native bioleaching microorganism

A native mesophilic iron-oxidizing bacterium, Acidithiobacillus ferrooxidans, has been isolated (30°C) from a typical, lead-zinc concentrate of Dachang Mine in the region of Liuzhou located in the southwest of China. Two typical copper sulfide minerals, chalcopyrite and bornite, were from Meizhou Copper Mine in the region of Guangdong Province, China. Variation of pH and cell growth on time and effects of some factors such as temperature, inoculation cell number, and pulp density on the bioleaching of chalcopyrite and bornite were investigated. The results obtained from the bioleaching experiments indicate that the efficiency of copper extraction depends on all of the mentioned variables, especially the pulp density has more effect than the other factors on the microorganism. In addition, the results show that the maximum copper recovery was achieved using a mesophilic culture. The copper dissolution reached 51.34% for the chalcopyrite while it was 72.35% for the bornite at pH 2.0, initial Fe(II) concentration 9 g/L and pulp density 5%, after 30 d.

Influence of pyrometallurgical copper production on the environment

In this paper the influence of pyrometallurgical treatment of copper sulphide minerals and pyrite on the environment from the aspect of ambient air pollutions is considered. Results of emission of SO 2 and particulate matter from the location with the most pollution are presented. According to the results it could be seen that the Bor’s citizen were exposed to the high concentration of SO 2 and arsenic which were found to be multiple over the Serbian legislative limits during 2007. Also, the reasons and consequences of this pollution were analysed.

Determination of activity coefficients and relative partial molar free energies for copper sulfide mineral bioleaching solutions by ion-selective electrode

This work reports the results about the determination of mean activity coefficients and relative partial molar free energies for copper sulfide mineral bioleaching solutions by potentiometric method at 25 °C. The experimental potentiometric data were obtained by combining a diamond film—cupric ion-selective electrode (Cu(II) ISE), containing a KNO 3 filling solution, and an Ag/AgCl electrode. The measurements were performed, at constant ionic strength, in different series of copper sulfide mineral bioleaching solutions. The non-ideal behavior of the system was described on the base of the Pitzer ion-interaction model for mixed salts. Meanwhile, the relative partial molar free energies of bioleaching solution were obtained. The determination of the thermodynamic properties offers a basic data for the study of copper sulfide mineral bioleaching solutions.

Effect of temperature on the bioleaching of chalcopyrite concentrates containing different concentrations of silver

The primary copper sulfide mineral chalcopyrite (CuFeS 2) is recalcitrant to both chemical and biological leaching, due to the supposed passivation of the mineral surface by sulfur and/or ferric iron compounds. Previous work has shown that addition of soluble silver can enhance solubilisation of copper from chalcopyrite by acidophilic bacteria. Silver may also be present in the concentrate itself. Here we describe the bioleaching of chalcopyrite concentrates with silver contents varying from < 1 to 1500 g/t by consortia of thirteen species of mesophilic bacteria and eleven species of moderately thermophilic acidophiles in shake flask cultures incubated at between 30 °C and 45 °C. The compositions of the microbial consortia that established in each culture were determined using a combined cultivation-based and biomolecular approach. The most effective solubilisation of copper from the 1500 and 800 g/t Ag-concentrates occurred at 30 °C, while concentrates that contained < 1 and 26 g/t of silver displayed the opposite (and predicted) pattern of mineral dissolution increasing with incubation temperature. The type strain of Acidithiobacillus ferrooxidans was the sole dominant iron-oxidising autotroph in the 800 and 1500 g/t silver concentrates, and was present in similar numbers to Leptospirillum ferrooxidans in the < 1 and 26 g/t silver concentrates, leached at 30 °C. Obligate and facultatively heterotrophic acidophiles (e.g. Acidiphilium and Gram-positive acidophiles) were also usually present, but in much smaller numbers. In contrast, at 45 °C the dominant (or sole) bacterium present at day 30 was the iron/sulfur-oxidising mixotroph Sulfobacillus thermosulfidooxidans. Sulfobacillus spp. also tended to dominate cultures incubated at 37 °C, although other bacteria, including At. ferrooxidans, were present in some mineral leachates. Highly efficient dissolution of copper (76 to > 98% over 30 days) from the 1500 g/t chalcopyrite concentrate at 30 °C was achieved using pure and mixed cultures of At. ferrooxidans. The results indicated that chalcopyrite concentrates that contain significant concentrations of silver are highly amenable to bioleaching at relatively low temperatures, using well-known acidophilic micro-organisms.

Structural and NMR Studies of the Hexameric Copper(I) Complex with N‐n‐butyl‐N′‐ethoxycarbonyl‐thioureate

AbstractThe copper sulfide mineral flotation collector, N‐n‐butyl‐N′‐ethoxycarbonyl‐thiourea (H2bectu), and the 1:1 hexameric copper(I) thioureate complex, [Cu(Hbectu)]6, have been characterized by single crystal X‐ray diffraction. H2bectu crystallizes in the triclinic space group $\rm P{\bar 1}$ with a = 5.2754(4), b = 9.0042(7), c = 12.6030(9) Å, α = 80.528(6), β = 90.173(6), γ = 76.472(7)°. An intramolecular N‐H···O hydrogen bond between the thioamide proton and carbonyl oxygen forms a planar six‐membered ring in the central core of the molecule with C=O, C=S and C‐N bond lengths in accord with those reported for other N‐alkyl/aryl‐N′‐acyl‐thiourea compounds. [Cu(Hbectu)]6 crystallizes in the monoclinic space group C2/c with a = 23.269(5), b = 13.243(4), c = 23.037(7) Å, β = 91.81(2)° as discrete hexameric clusters disposed about a crystallographic centre of symmetry with a Cu6S6 core consisting of two Cu3S3 chair‐shaped rings linked by coordination of the deprotonated amide nitrogen atom to a copper atom in the adjacent ring. The six ligands assemble as a paddlewheel structure with the ethoxy and n‐butyl substituents packing in an alternating head to tail arrangement. Temperature dependent solution 1H NMR spectroscopic studies show that the hexameric structure of the complex is maintained in solution.

Investigation of the effect of N-substituents on performance of thionocarbamates as selective collectors for copper sulfides by ab initio calculations

Using ab initio methods, we calculated some properties such as the energies and compositions of frontier molecular orbitals and the atomic charges which are related to the reactive behavior of thionocarbamates containing different N-substituent groupings. The results of the calculations indicate that the efficiencies of N-substituent thionocarbamates depend on the investigated parameters, and the N-substituent groupings have significant effect on flotation performance of thionocarbamates as selective collectors for copper sulfide minerals. The order of electron-donating ability is O-isobutyl- N-ethyl-thionocarbamate (IBETC) > O-isobutyl- N-allyl-thionocarbamate (IBALTC) ≫ O-isobutyl- N-acetyl-thionocarbamate (IBACTC) > O-isobutyl- N-ethoxycarbonyl-thionocarbamate (IBECTC), and the order of feedback-electron-accepting ability is IBACTC ≈ IBECTC ≫ IBALTC > IBETC. This implies that IBECTC or IBACTC can react with copper atoms having (t 2g) 6(e g) 3Cu(II) or t 6e 4Cu(I) configuration on the surfaces of copper sulfide minerals through normal covalent bond and back donation covalent bond, but the interaction of IBECTC or IBACTC with iron atoms having (t 2g) 6(e g) 0Fe(II) or (t 2g а) 3(e g а) 2Fe(III) configuration on the surface of iron sulfide minerals is very weak. IBECTC or IBACTC have excellent performance in these agents as flotation collectors with improved collecting power for copper sulfide minerals and selectivity against iron sulfide minerals. The theoretically obtained results are consistent with the experimental data reported in the literature.

Formation of hydrocarbon gaseous compounds during bioleaching of copper sulphide minerals with mesophilic microorganisms

An experimental study was conducted for assessing the formation of hydrocarbon gaseous compounds during bioleaching of copper sulphide ores with mesophilic microorganisms. Three different mineral samples were used: a pyrite concentrate, a chalcopyrite concentrate and a copper sulphide ore rock from El Teniente mine, Chile, containing 1.2% copper. Mineral samples were bioleached in 250 ml shake flasks containing 100 ml of basal medium inoculated either with a pure strain of Acidithiobacillus ferrooxidans or a natural bacteria consortium obtained from the acid leaching of the El Teniente copper ore in columns. Each sealed shake flask system was fed with a flow of synthetic air and the exit stream was passed through a column containing an adsorbent material and next through a water trap to avoid back-contamination with air from the environment. Compounds present in the adsorbent material after 90 days of bioleaching were analysed using a gas chromatography mass spectrometry technique with a procedure that detects 162 different hydrocarbon gaseous compounds. Experimental results permitted to identify the formation of significant amounts of five different types of hydrocarbon gaseous compounds: di-,tri- and penta-methyl benzene, 11th-ethyl alkane and branched alkanes. The number of formed gaseous hydrocarbon compounds increased in experiments conducted with the natural bacterial consortium, where their formation appears to be enhanced by the presence of heterotrophic microorganisms. This work provides the first experimental evidence of the formation of hydrocarbon gaseous compounds in bioleaching.

Magmatic evolution of the Mantos Blancos copper deposit, Coastal Range of northern Chile: insight from Sr–Nd isotope, geochemical data and silicate melt inclusions

AbstractThe Mantos Blancos copper deposit (500 Mt at 1.0% Cu) was affected by two superimposed hydrothermal events: (i) phyllic alteration related to a rhyolitic dome emplacement and brecciation at ca 155 Ma; and (ii) potassic, sodic and propylitic alteration at ca 142 Ma, coeval with stocks and sills emplacement of dioritic and granodioritic porphyries, that locally grade upwards into polymictic magmatic hydrothermal breccias. Major hypogene copper sulfide mineralization is related to the second event. A late‐ore mafic dike swarm cross‐cuts all rocks in the deposit. Two types of granodioritic porphyries can be distinguished from petrographic observations and geochemical data: granodiorite porphyry I (GP I) and granodiorite porphyry II (GP II), which resulted from two different trends of magmatic evolution. The concave shape of the rare earth element (REE) distribution pattern together with the weak or absence of negative Eu anomalies in mafic dikes, dioritic and GP I porphyries, suggest hornblende‐dominated fractionation for this magmatic suite. In contrast, distinct negative Eu anomalies and the flat REE patterns suggest plagioclase‐dominated fractionation, at low oxygen fugacity, for the GP II porphyry suite. But shallow mixing and mingling between silicic and dioritic melts are also likely for the formation of the GP II and polymictic breccias, respectively. Sr‐Nd isotopic compositions suggest that the rhyolitic dome rocks were generated from a dominantly crustal source, while the GP I has mantle affinity. The composition of melt inclusions (MI) in quartz crystals from the rhyolitic dome is similar to the bulk composition of their host rock. The MI analyzed in quartz from GP II and in the polymictic magmatic hydrothermal breccia of the deposit are compositionally more evolved than their host rocks. Field, geochemical and petrographic data provided here point to dioritic and siliceous melt interaction as an inducing mechanism for the release of hydrothermal fluids to form the Cu mineralization.

Investigation of the selectivity of ethoxylcarbonyl thionocarbametes during the flotation of copper sulfides

In this study, the flotation performances of ethoxycarbonyl thionocarbamate (ECTC), dialkyl thionocarbamate (DATC) and xanthate copper sulfide collectors are compared by the structure-reactivity relationship using generalized perturbation theory and density functional calculation at the B3PW91/6-31G(D) level. The electron-donating power of xanthates is strong and, therefore, xanthates can strongly react with metal cation on the surfaces of copper and iron sulfide minerals through the formation of normal covalent bonds. This explains the poor selectivity of xanthates and also the high pH levels (above 13) required for the flotation separation of copper/iron sulfide minerals. DATC’s are more selective for copper sulfide flotation, particularly against gangue iron sulfides. Although less powerful than xanthates, DATCs can perform copper/iron flotation separation at lower operating pH (commonly at pH levels below 11.5). ECTCs use an ethoxycarbonyl replacing an alkylN-substituent in DATCs. The presence of the ethoxycarbonyl group effectively changes the functional group of collector from -C(=S)NH- to -C(=S)NHC( = O)-. The strong electron-withdrawing ethoxycarbonyl group adjacent to the C=S group decreases the electron density of the sulfur atom, which improves ECTC’s selectivity against iron sulfide minerals at slightly alkaline conditions. The lowest unoccupied molecular orbit (LUMO) of ECTC, which is constituted by the pz-orbit of every atoms in the conjugate -O-C(=O)-N-C(=S)-O- group and which is pleased with accepting richly d-orbital electrons (feedback electrons) from the (t2g)6(eg)3Cu(II) or t6e4Cu(I) configuration of copper cation on the surfaces of copper sulfide minerals, resulted in the formation of dative π-bond. The iron atom, which has a (t2g)6Fe(II) or (t2ga)3(ega)2 Fe(III) configuration on the surfaces of iron sulfide minerals (Fe(III) is the predominant composition at alkaline conditions), has difficulty in offering its d-orbital electrons (feedback electrons) to ECTC’s LUMO. ECTC collectors are powerful for copper sulfide minerals and very selective against iron sulfides, which has been further confirmed by UV spectra and bench-scale and industrial-scale flotation tests.