Mineralogy and geochemistry of hydrothermal sulphide from a submarine volcanic high at 18°36.4'S Central Lau Spreading Center, Southwest Pacific

We report the mineralogy and geochemistry of hydrothermal sulphide from the crater of a volcanic high near 18°36.4′S of the Central Lau Spreading Center.During 1990s,that volcanic structure was reported active and sulphide samples were collected by MIR submersible.A section of a chimney-like structure from the crater-floor was studied here.The Fe-depleted sphalerites,and Co-depleted pyrites in that chimney were similar to those commonly found in low to moderate temperature(<300℃)sulphides from sediment-starved hydrothermal systems.Bulk analyses of three parts of that chimney section showed substantial enrichment of Zn(18%–20%)and Fe(14%–27%)but depletion of Cu(0.8%–1.3%).In chondrite-normalized rare earth element-patterns,the significant negative Ce-anomalies(Ce/Ce*=0.27–0.39)and weakly positive Eu-anomalies(Eu/Eu*=1.60–1.68)suggested sulphide mineralisation took place from reduced low-temperature fluid.The depleted concentration of lithophiles in this sulphide indicates restricted contribution of sub-ducting plate in genesis of source fluid as compared to those from other parts of Lau Spreading Centre.Uniform mineralogy and bulk composition of subsamples across the chimney section suggests barely any alteration of fluid composition and/or mode of mineralisation occurred during its growth.

Atmospheric oxygen-rich direct leaching behavior of zinc sulphide concentrate

The leaching behavior of main metallic sulphides in zinc concentrate under atmospheric oxygen-rich direct leaching conditions was studied through mineralogical analysis. The results show that the sulphides dissolve obviously except pyrite. Based on the relationship between elemental sulfur and the residual sulphides in the leaching residue, the dissolution of sphalerite, chalcopyrite, covellite and galena is assumed to follow the indirect oxidation reactions, where the acidic dissolution takes place firstly and then the released H2S transfers from the mineral surface into bulk solution and is further oxidized into elemental sulfur. The interface chemical reaction is further supposed as the controlling step in the leaching of these sulphides. The direct electrochemical oxidation reactions are assumed to contribute to the dissolution of pyrrhotite, which is controlled by the diffusion through elemental sulfur layer.

FAULT TREE ANALYSIS OF SPONTANEOUS COMBUSTION OF SULPHIDE ORES AND ITS RISK ASSESSMENT

A logic fault tree of mine spontaneous combustion of sulphide ores was built by the fault tree analysis (FTA) based on a lot of mechanism investigation of sulphide ore spontaneous combustion in more than ten mines and review of a great amount of relevant

Leaching Behavior of Complex Copper Sulphide Concentrate with Ferric Chloride by Microwave Irradiation

Microwave assisted leaching of complex copper sulphide concentrate with ferric chloride was investigated, and its mechanism was analyzed. The results show that the leaching rate by microwave irradiation heating is much faster than that by conventional heating.

Comparative study on the passivation layers of copper sulphide minerals during bioleaching

The bioleaching of copper sulphide minerals was investigated by using A. ferrooxidans ATF6. The result shows the preferential order of the minerals bioleaching as djurleite〉bomite〉pyritic chalcopyrite〉covellite〉porphyry chalcopyfite. The residues were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. It is indicated that jarosite may not be responsible for hindered disso- lution. The elemental sulfur layer on the surface of pyritic chalcopyrite residues is cracked. The compact surface layer of porphyry chalcopy- rite may strongly hinder copper extraction. X-ray photoelectron spectroscopy （XPS） further confirms that the passivation layers of covellite, pyritic chalcopyrite, and porphyry chalcopyrite are copper-depleted sulphide Cu4S11, S8, and copper-rich iron-deficient polysulphide CtuFe2S9, resoectivelv. The ability of these oassivation layers was found as Cu4Fe2S9〉Cu4S11〉S8〉iarosite.

IN SITU MEASUREMENT OF BREEDING-FIRE OF SULPHIDE ORE DUMPS

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EXPERIMENTAL INVESTIGATION ON CHEMICAL THERMODYNAMIC BEHAVIOUR OF SULPHIDE ORES DURING SPONTANEOUS COMBUST

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Free-standing ternary metallic sulphides/Ni/C-nanofiber anodes for high-performance lithium-ion capacitors

As a promising energy-storage device,the hybrid lithium-ion capacitor coupling with both a large energy density battery-type anode and a high power density capacitor-type cathode is attracting great attention.For the sake of improving the energy density of hybrid lithium-ion capacitor,the free-standing anodes with good electrochemical performance are essential.Herein,we design an effective electrospinning strategy to prepare free-standing MnS/Co4S3/Ni3S2/Ni/C-nanofibers(TMSs/Ni/C-NFs)film and firstly use it as a binder-free anode for hybrid lithium-ion capacitor.We find that the carbon nanofibers can availably prevent MnS/Co4S3/Ni3S2/Ni nanoparticles from aggregation as well as significantly improve the electrochemical performance.Therefore,the binder-free TMSs/Ni/C-NFs membrane displays an ultrahigh reversible capacity of 1246.9 m Ah g-1at 100 m A g-1,excellent rate capability(398 mAh g-1 at2000 mA g-1),and long-term cyclic endurance.Besides,we further assemble the hybrid lithium-ion capacitor,which exhibits a high energy density of 182.0 Wh kg-1at 121.1 W kg-1(19.0 Wh kg-1 at 3512.5 W kg-1)and remarkable cycle life.

Mineral sulphide-lime reactions and effect of CaO/C mole ratio during carbothermic reduction of complex mineral sulphides

Mineral sulphide （MS）-lime （CaO） ion exchange reactions （MS ＋ CaO = MO ＋ CaS） and the effect of CaO/C mole ratio during carbothermic reduction （MS ＋ CaO ＋ C = M ＋ CaS ＋ CO（g）） were investigated for complex froth flotation mineral sulphide concentrates. Phases in the partially and fully reacted samples were characterised by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The primary phases during mineral sulphide-lime ion exchange reactions are Fe304, CaSO4 Cu2S, and CaS. A complex liquid phase of Ca2CuFeO3S forms during mineral sulphide-lime exchange reactions above 1173 K. The formation mechanisms of Ca2CuFeO3S liquid phase are determined by characterising the partially reacted samples. The reduction rate and extent of mineral sulphides in the presence of CaO and C increase with the increase in CaO/C ratio. The metallic phases are surrounded by the CaS rich phase at CaO/C 〉 1, but the metallic phases and CaS are found as separate phases at CaO/C 〈 1. Experimental results show that the stoichiometric ratio of carbon should be slightly higher than that of CaO. The reactions between CaO and gangue minerals （SiO2 and A1203） are only observed at CaO/C 〉 1 and the reacted samples are excessively sintered.

Interaction effects of flotation reagents for SAG mill reject of copper sulphide ore using response surface methodology

Flotation reagents have a complex behaviour in the beneficiation of base minerals in clayey ores.Interaction effects of reagents on the efficiency of copper flotation for a highly clayey low-grade sulphide ore were investigated using a central composite design.Preliminary results showed that sodium-isopropyl-xanthate(SIPX)and O-isopropyl-N-ethyl-thionocarbamate(IPETC)were found to be the most efficient collectors in the presence of lime as the pH regulator.The effects of dosage of collectors(SIPX and IPETC)and the dosage of methyl-isobutyl-carbonyl(MIBC)as frother on the separation efficiency were evaluated at different pH levels.Based on the analysis of variance(ANOVA),the interaction effects of the collector−pH and collector−frother were significant for the separation efficiency.At the low level of collector dosage,increasing pH from 9 to 11 enhanced copper separation efficiency from 81%to 86%for IPETC and from 77%to 86%for SIPX.Results of ANOVA showed that the maximum copper separation efficiency(88.7%)was obtained at the dosages of 8.6 g/t SIPX,7 g/t IPETC and 20 g/t MIBC at pH 11.Finally,it was concluded that a mixture of SIPX and IPETC collectors was more suitable to treat highly clayey sulphide ores.

Process mineralogy of copper-nickel sulphide flotation by a cyclonic-static micro-bubble flotation column

In our study we investigated a refractory copper-nickel sulfide ore separation by using a cyclonic-static micro-bubble flotation column (FCSMC). The process mineralogy of the main products was studied. Using a scanning electron microscope-energy dispersive system (SEM-EDS) and an X-ray spectrometer the mineral category and content of samples were analyzed. By using a mineral liberation analyzer (MLA) the mineral liberation characteristics were revealed. It is shown that in roughing feed the monomers liberation degree of nickel pyrite and chalcopyrite take up 84.11% and 88.82%, respectively. In tailings, the lost nickel pyrite and chalcopyrite are mainly monomers. Therefore, strengthening the micro-fine particle recovery capacity is the key to increase recovery.

Copper,zinc,and iron bioleaching from polymetallic sulphide concentrate

Bioleaching of low-grade complex Cu&ndash;Zn&ndash;Pb&ndash;Fe&ndash;Ag&ndash;Au sulphide concentrate (of Majdanpek ore body, RTB Bor, Serbia) was carried out in an aerated bioleach reactor in the presence of mesophilic mixed bacterial culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans. A mesophilic acidophiles culture was isolated from the acidic solution of the underground copper mine of Bor, Serbia. The nutrient medium was 9K at pH 1.6. 87% of the particles were <10 &micro;m in size, with a pulp density of 8% (w/v). Bioleaching efficiencies of 89% for zinc, 83% for copper, and 68% for iron can be achieved in the examined conditions. Kinetic analysis shows that the change in leaching corresponds to the Spencer-Topley kinetic model for diffusion-controlled topochemical reactions.

Mechanochemical sulfidization of a mixed oxide-sulphide copper ore by co-grinding with sulfur and its effect on the flotation efficiency

Mechanochemical sulfidization of a mixed sulfide/oxide copper ore by co-grinding with sulfur and additives including Mg(NO3)2 and Fe(NO3)3 salts and iron,aluminum and magnesium powders was investigated for the first time.Also,the influence of sulfidization during the wet-milling process was examined on the separation efficiency and recovery of copper in detail.The results demonstrated that co-grinding with sulfur solely had the best flotation performance at the value of 0.5 wt.%and it was attributed to the possible existence of S\\O bonding on copper oxides surfaces.In addition,adding magnesium nitrate salt,magnesium powder,iron nitrate salt and aluminum powder as additive associated with 0.5 wt%sulfur into ball milling caused the flotation improvement at the amounts of 0.2 wt%,0.2 wt%,0.5 wt%and 0.5 wt%,respectively.Also,the effect of grinding time and sulfidization pH with 0.5 wt%sulfur solely was determined and pH s of 7.5 to 8.5 gave the best results.The highest recovery(75.76%)and separation efficiency(63.44%)were achieved at pH of 7.5 and 8.5,respectively.

Recent Advance in the Electrochemical Detection of Sulphide and Sulphhydryl Species

This article aims at providing a critical review of some most recent developments in the electrochemical detection and measurement of hydrogen sulphide and the related species, which are of great significance to a variety of industries and in environmental moitoring. The molecular recognition processes are initiated by using either an organic precursor or a catalytic complex, leading to extensive ranges of detection. A series of advanced chemical and simulation techniques are used to probe the mechanistic details of the analytical chemistry involved.

A study of self-heating characteristics of a pyrrhotite-rich sulphide ore stockpile

Original surface chemistry of sulphidesis altered upon contact with air, leading to ''oxidation'', which is accompanied by evolution of heat. The current study reports results of an investigation on extent of exothermicity of an experimental nickel-copper sulphide stockpile that was formed at a mining site in Sudbury, Canada. The ore contained pentlandite and chalcopyrite that are accompanied by a large quantity of pyrrhotite. The self-heating characteristics were recorded by temperature sensors placed inside the stockpile. Ambient conditions such as temperature, humidity, and wind velocity were simultaneously recorded. The inner temperature of the stockpile indicated significant fluctuations due to rapid changes, particularly in the outside temperature. The minimum and maximum temperatures recorded in the outside and inside were 5 and 10.5, 44.3 and 32 ℃, respectively. The self-heating capacity of the sulphide ore stockpile observed represents a mild case compared to that experienced by coals. Possible reasons are discussed.

Massive Sulphide Deposits Related to the Volcano-Passive Continental Margin in the Altay Region

The Devonian volcano-passive continental margin in southern Altay is a significant volcanogenic massive sulphide metallogenic belt. Acidic volcanism has been dominant on the inner side of the volcano-passive continental margin, i.e., near the old land, resulting in a Pb-Zn metallogenic sub-belt, in which the ore deposits are hosted by sedimentary rocks in volcanic series, as represented by the large Koktal Pb-Zn deposits. In the central part of the margin far away from the old land, bimodal volcanic formations are well developed, forming volcanics-hosted Cu-Zn metallogenic sub-belts, e.g., the large-scale Ashele Cu-Zn deposit. The Qiaoxiahala sub-belt on the outer side of the margin near the ocean ridge is located at the spreading central trough, where ophiolite suites are developed. This type of deposits is rich in gold and copper, similar to the Cyprus-type Fe-Cu-Au metallogenic sub-belt in metallogenic environment (represented by the Qiaoxiahala medium-scale Fe-Cu-Au deposit). From the old land to the ocean, the mineralizing age becomes younger, i.e., from Early Devonian→Early and Middle Devonian→Middle Devonian, forming a complete metallogenic zoning series on the volcano-passive continental margin. Comparative studies show that the massive sulphide deposits distributed on the volcano-passive continental margin are different from those formed under a plate subduction regime and oceanic ridge environment; the former have their unique features and wide distributions, representing a new type of volcanogenic massive sulphide deposits—the Altay type.

Hydrogen sulphide detection using near-infrared diode laser and compact dense-pattern multipass cell

Sub-ppmv level detection of hydrogen sulphide(H2 S) using a 1.578-μm distributed feedback tunable diode laser combining with wavelength modulation spectroscopy and second harmonic detection scheme is reported. A home-developed novel compact dense-pattern multipass gas cell with an effective optical path length of 29.37 m is used to improve sensitivity and reduce sample volume. Detection parameters are optimized, including modulation frequency and amplitude. The analysis of Allan variance shows that a minimum detectable concentration 60 ppbv is obtained with a lock-in time constant of 10 ms, and a detection limit of 13 ppbv can be achieved by average in 300 s. The demonstrated H2 S sensor has a strong penitential application in natural gas process for regulating and controlling H2 S concentration.

LEACHING OF PRECIOUS METALS FROM COMPLEX SULPHIDE ORES——2.DIRECT LEACHING OF Cu SULFIDE CONCENTRATE BY ACIDIC THIOUREA SOLUTIONS

Recovery of gold and silver from a sulphide concentrate by thiourea leaching was investigat-ed.The effects of various parameters on the process,such as oxidants,the initial concentrationof thiourea and acidity in solutions as well as reaction temperature,were systematically exam-ined.From the results it was confirmed that(a)oxidants had no significant influence on the dis-solution of gold and silver at a fixed initial concentration of thiourea;(b)the initial concentra-tion of thiourea and acidity affected the dissolution rate only in the earliest period of leaching;(c)the rate of the process was controlled by reagent diffusion.The optimum operations wereworked out for the thiourea leaching process of the concentrate.

Study on sulphide capacity of CaO-SiO_2-Al_2O_3-MgO-Fe_tO slags

The sulphide capacity of CaO-SiO2-Al2O3-MgO-FetO slags was studied at 1773 K using gas-slag equilibrium techniques. Utilizing a Pt crucible, the slag was equilibrated with a mixture of gases, namely, CO, CO2, SO2 and N2 to provide the partial pressure of oxygen and sulphur. It was shown that at fixed FetO and Al2O3 contents and a fixed { （%CaO）＋（%MgO）}/（%SIO2） ratio, the sulphide capacity decreases with increasing MgO content. At a constant （%CaO）/（%SiO2） ratio and constant MgO and Al2O3 contents, increasing the FetO content of the slags also results in an increase of the sulphide capacity. The rising basicity of （%CaO）/（%SiO2） from 1.0 to 1.4 at fixed MgO, FetO and Al2O3 contents significantly increases the sulphide capacity.

Organic Composition of Sulphide Ores in the Okinawa Trough and Its Implications

A preliminary organic geochemical study shows that the sulphide ores from the hydrothermal deposit of the Okinawa Trough are generally low in the total organic carbon and extremely low in the soluble organic matter. In the aliphatic hydrocarbon fraction, the n-alkanes range from C15 to C35, with usual maxima in the middle n-C20 region and strong odd-carbon number predominance when n > C25 (CPI = 1.2). The dominant analog in the aromatic fraction is phenanthrene, a polynuclear aromatic hydrocarbon, which provides evidence for hydrothermal activity. The organic matter derived mainly from marine planktonic and terrigenous vascular plants is entrapped in a high-temperature regime such as an active chimney and cooled quickly in the sulphide ores on the seafloor. Organic matter and sulphides are definitely products of a high-temperature alteration. The biomarker compounds indicate that the ores are formed under low Eh and pH conditions—a reducing to anoxic environment, which is favourable for sulphates to be reduced into sulphides by biogenic (bacterial) or abiogenic activity.