Sulphidizing reactions in the flotation of oxidized copper minerals,II. Role of the adsorption and oxidation of sodium sulphide in the flotation of chrysocolla and malachite

The rate of consumption of sulphide in the sulphidizing reactions of malachite and chrysocolla has been measured. The oxidation of sulphide ions at the surface of sulphidized chrysocolla was shown to take place. The influence of thiosulphate anions on the xanthate flotation of sulphidized malachite and chrysocolla was investigated and it was shown to depress the flotation of chrysocolla strongly.The result suggest, that the presence of thiosulphate as a product of simultaneous oxidation can be one of the reasons for the more difficult flotation of sulphidized chrysocolla.     

Flotation of oxidized minerals of copper using a new synthetic chelating reagent as collector

A new synthetic reagent containing a mixed aliphatic-aromatic structure, with a hydrocarbon chain and an aminothiophenol chelating group, has proven to be an effective collector for the flotation of chrysocolla minerals. The flotation is optimum in the narrow pH range of 5.5 to 6, falls sharply at pH 5, and is moderate in the pH range 7 to 11. Infrared spectra indicate that copper aminothiophenolate chelates are formed on the surface of the chrysocolla under the conditions of maximum flotation.     

The effect of thermal treatment on the flotation of chrysocolla

Flotation studies using a Hallimond tube have been carried out on purified samples of chrysocolla. The results confirm that by heating the sample to 550°C, flotation of the sulphidized sample with amyl xanthate is considerably improved. Flotation with sodium dodecyl sulphate is also considerably higher. The recovery with cationic collectors is not modified by the thermal treatment.Electrophoretic mobility measurements and flotation studies using benzene instead of air for the collection of the particles suggest that the increase in flotation after thermal treatment is a consequence of (1) an increase in the solubility of copper ions and their adsorption on to the surface of the particles, and (2) an increase of the intrinsic hydrophobicity of the particles due to condensation of some of the free silanol groups on their surface.     

自然铜、铜合金矿物及其矿床形成机理新探索

描述了自然铜、铜合金矿物及其矿床形成的新机制。在岩浆及热液中，铜及铜合金可呈氢化物、羧基配合物及纳米粒子活性、迁移、富集形成自然铜矿床，或经以后的地质事件，长期、多次迁移富集，叠加形成富而大的自然铜矿床。在表生条件下，铜的硫化矿物被氧化分解，可形成亚铜的硫代硫酸盐及氯配合物，部分可形成铜的硫酸盐配合物迁移，由于硫代硫酸盐被氧化，亚铜岐化可形成高纯度的自然铜，但它易氧化形成孔雀石、蓝铜矿、赤铜矿、黑铜矿、硅孔雀石等，因此很难形成自然铜矿床。     

Aspects of the mineralogy and hydrometallurgy of chrysocolla,with special reference to the Cuajone,Peru, ores

Chrysocolla in the Cuajone ores appears to be microcrystalline and to exhibit a fibrous structure.Sulphuric acid leaching of the chrysocolla is facilitated by a microcracked surface structure. A marked surface structural change is evidenced as hydrogen ions replace the copper. The end result is a noncontinuous surface layer of silica from which the copper has been essentially completely removed.The results of this study provide confirmatory evidence for the structure and hydrometallurgy of chrysocolla.     

Copper mineralization in sedimentary cover associated with tectonic elements and volcanism in Israel

Copper mineralization occurs within the thick Cretaceous to Neogene sedimentary cover of central and northern Israel. Two distinct types of copper-rich anomalies are encountered. One form of copper mineralization is characterized by the presence of copper minerals such as malachite, atacamite, paratacamite, chrysocolla, and/or chalcopyrite forming veins and concretions within the sedimentary host rocks. The second type of copper enrichment is found dispersed within iron oxide veins associated with enrichments of other trace metals such as Ni, V, Zn, Co, Mo, and As. Both forms of copper anomalies lie along and are confined to the vicinity of tectonic elements. These features may be the surface expression of the longitudinal faults of the Dead Sea Rift Valley, of the transverse shear zone of southern and central Negev, or of the EW-trending horsts and grabens of central Israel. In many cases the copper anomalies are found near to or at the contact of volcanic bodies of intermediate to basic composition; in others, they are found in the vicinity of thermal springs. The fault zones may have provided conduits along which solutions, in places possibly briny, could have risen and leached subsurface mineralized volcanic or sedimentary bodies.     

The stabilizing effect of Na2S on the collector coating of chrysocolla

The heterogeneous reaction between natural and sulphidized chrysocolla and potassium amyl xanthate in solution is investigated.It is found that, together with the consumption of large amounts of xanthate, particles composed of the reaction products are spontaneously released from the surface of chrysocolla giving rise to a colloidal dispersion. In principle the mechamism is related to the peptizing effect of the excess xanthate ions that are found when Cu²⁺ and X^? ions are made to react in a homogeneous phase.In sulphidized chrysocolla this phenomenon is markedly reduced, showing that Na₂S has a stabilizing effect on the collector coating.Flotation experiments performed with aqueous amyl dixanthogen emulsions show that stable adhesion occurs only on properly sulphidized chrysocolla. It is believed that the mechanism controlling adhesion in this case is similar to that which determines the stability of the collector layer.     

The geochemistry of gossans associated with Sarcheshmeh porphyry copper deposit,Rafsanjan, Kerman,Iran: Implications for exploration and the environment

The Sarcheshmeh copper deposit is one of the world's largest Oligo-Miocene porphyry copper deposits in a continental arc setting with a well developed supergene sulfide zone, covered mainly by a hematitic gossan. Supergene oxidation and leaching, have developed a chalcocite enrichment blanket averaging 1.99% Cu, more than twice that of hypogene zone (0.89% Cu). The mature gossans overlying the Sarcheshmeh porphyry copper ores contain abundant hematite with variable amounts of goethite and jarosite, whereas immature gossans consist of iron-oxides, malachite, azurite and chrysocolla. In mature gossans, Au, Mo and Ag give significant anomalies much higher than the background concentrations. However, Cu has been leached in mature gossans and gives values close or even less than the normal or crustal content (< 36.7 ppm). Immature gossans are enriched in Cu (160.3 ppm), Zn (826.7 ppm), and Pb (88.6 ppm). Jarosite- and goethite-bearing gossans may have developed over the pyritic shell of most Iranian porphyry copper deposits with pyrite–chalcopyrite ratios greater than 10 and therefore, do not necessarily indicate a promising sulfide-enriched ore (Kader and Ijo). Hematite-bearing gossans overlying nonreactive alteration halos with pyrite–chalcopyrite ratios about 1.5 and quartz stringers have significant supergene sulfide ores (Sarcheshmeh and Miduk). The copper grade in supergene sulfide zone of Sarcheshmeh copper deposit ranges from 0.78% in propylitized rocks to 3.4% in sericitized volcanic rocks, corresponding to the increasing chalcopyrite–pyrite or chalcocite–pyrite ratios from 0.3 to 3, respectively. Immature gossans with dominant malachite and chrysocolla associated with jarosite and goethite give the most weakly developed enrichment zone, as at God-e-Kolvari. The average anomalous values of Au (59.6 ppb), Mo (42.5 ppm) and Ag (2.6 ppm) in mature gossans associated with the Sarcheshmeh copper mine may be a criterion that provides a significant exploration target for regional metallogenic blind porphyry ore districts in central Iranian volcano–plutonic continental arc settings. Drilling for new porphyry ores should be targeted where hematitic gossans are well developed. The ongoing gossan formation may result in natural acidic rock drainage (ARD).     

Angélica Copper Deposit: Exotic Type Mineralization in the Tocopilla Plutonic Complex of the Coastal Cordillera, Northern Chile

The Angélica copper deposit is situated at the southernmost sector of the Jurassic Tocopilla plutonic complex in the North Chilean Coastal Cordillera. This deposit occurs in monzonitic to monzodioritic rocks, and has platelike orebodies with no appreciable hydrothermal alteration nor sulfide mineralization. The mineralized zones are located in the western side of the two main normal faults with NE and NW orientations, and are characterized principally by impregnation of supergene copper products of atacamite and minor amounts of chrysocolla, lavendulan and “black copper”. Generally, chrysocolla is more abundant at a distal NE sector of the deposit. The black copper is Cu‐Fe‐Mn‐Si‐Cl‐rich multimineral aggregates composed of atacamite with minor amounts of quartz, pseudomalachite, dioptase, neotocite, gypsum, paratacamite and melanothallite, and its surface exhibits nanometer‐sized cylindrical morphologies. All these characteristics suggest an exotic origin for the Angélica copper deposit. A few vein‐type copper deposits situated at the southwestern sector along the NE‐oriented fault are inferred as the possible source of the Angélica copper deposit.     

Epigenetic hydrothermal origin of native copper and supergene enrichment in the Vista Alegre district,Paraná basaltic province,southernmost Brazil

Native copper is widespread in the Lower Cretaceous Paraná basaltic province, southern Brazil, both as films in fractures and as massive balls in amygdules. The focus of this investigation is on the large concentration of occurrences (n = 85) that forms the Vista Alegre district in the border region of Rio Grande do Sul and Santa Catarina states. The high average of 220 ppm Cu content of the basalts resulted in ore of native copper, Cu oxides, abundant chrysocolla in the top of mineralizations, and minor malachite and azurite. Native copper is associated with dioctahedral and trioctahedral smectites, zeolites (heulandite and clinoptilonite), quartz, and calcite, typical of a low-T (100–150°C) hydrothermal alteration assembly. The PGE distribution shows enrichment in Pd in relation to Pt both in basalts and in native copper, supporting the hypothesis of hydrothermal origin of the mineralization. No evidence was found of direct precipitation of copper from the lava; based on field and petrographic evidence, integrated with BSE images, EPMA analyses, EGP contents of native copper, and bulk rock analyses, this is an epigenetic hydrothermal copper mineralization, followed by supergene enrichment.     

Genetic types of Tatarian red beds in Orenburg Ural region

Approximately 700 m (2240 ft) of an Upper Permian red bed, sequence is lithologically described and the various depositional environments (continental, mixed, marine) evaluated. Minor amounts of malachite and chrysocolla were observed in the continental sandstone phases. The study demonstrates the application of the facies — cycle procedure (transgression and regression). — L. W. LeRoy.     

Copper isotopes as monitors of redox processes in hydrothermal mineralization

The stable copper isotope composition of 79 samples of primary and secondary copper minerals from hydrothermal veins in the Schwarzwald mining district, South Germany, shows a wide variation in δ⁶⁵Cu ranging from −2.92 to 2.41‰. We investigated primary chalcopyrite, various kinds of fahlores and emplectite, as well as supergene native copper, malachite, azurite, cuprite, tenorite, olivenite, pseudomalachite and chrysocolla. Fresh primary Cu(I) ores have at most localities copper isotope ratios (δ⁶⁵Cu values) of 0 ± 0.5‰ despite the fact that the samples come from mineralogically different types of deposits covering an area of about 100 by 50 km and that they formed during three different mineralization events spanning the last 300 Ma. Relics of the primary ores in oxidized samples (i.e., chalcopyrite relics in an iron oxide matrix with an outer malachite coating) display low isotope ratios down to −2.92‰. Secondary Cu(I) minerals such as cuprite have high δ⁶⁵Cu values between 0.4 and 1.65‰, whereas secondary Cu(II) minerals such as malachite show a range of values between −1.55 and 2.41‰, but typically have values above +0.5‰. Within single samples, supergene oxidation of fresh chalcopyrite with a δ value of 0‰ causes significant fractionation on the scale of a centimetre between malachite (up to 1.49‰) and relict chalcopyrite (down to −2.92‰). The results show that—with only two notable exceptions—high-temperature hydrothermal processes did not lead to significant and correlatable variations in copper isotope ratios within a large mining district mineralized over a long period of time. Conversely, low-temperature redox processes seriously affect the copper isotope compositions of hydrothermal copper ores. While details of the redox processes are not yet understood, we interpret the range in compositions found in both primary Cu(I) and secondary Cu(II) minerals as a result of two competing controls on the isotope fractionation process: within-fluid control, i.e., the fractionation during the redox process among dissolved species, and fluid-solid control, i.e., fractionation during precipitation involving reactions between dissolved Cu species and minerals. Additionally, Rayleigh fractionation in a closed system may be responsible for some of the spread in isotope compositions. Our study indicates that copper isotope variations may be used to decipher details of natural redox processes and therefore may have some bearing on exploration, evaluation and exploitation of copper deposits. On the other hand, copper isotope analyses of single archeological artefacts or geological or biological objects cannot be easily used as reliable fingerprint for the source of copper, because the variation caused by redox processes within a single deposit is usually much larger than the inter-deposit variation.     

Effect of surface oxide/hydroxide products on the collectorless flotation of copper-activated sphalerite

The change in collectorless flotation of sphalerite with pH and Cu(II) concentration was correlated with the type and proportion of species present on the sphalerite surface. The solution and surface species were determined using a combination of analytical techniques including zeta potential measurement and X-ray photoelectron spectroscopy. An optimum copper concentration for maximum sphalerite flotation was identified, beyond which flotation decreased. This decrease in flotation coincided with the precipitation of copper hydroxide in neutral to mildly alkaline pH conditions. The hydrophobic polysulfide and hydrophilic copper hydroxide species were the main surface species influencing sphalerite flotation.     

西藏驱龙铜矿区水地球化学特征及其对铜矿化指示作用

驱龙斑岩铜矿床是近年发现的有望达到超大型规模的斑岩铜矿床。矿区地表水发育,矿区下游沿主水系发育数千米长的孔雀石沉淀带。讨论了河道中孔雀石沉淀的主要控制因素、雨季前后水中元素含量的变化和水地球化学异常对矿床位置和矿区找矿远景地段的指示作用。     

Sulphidizing reactions in the flotation of oxidized copper minerals,I. Chemical factors in the sulphidization of copper oxide

The rate and extent of the heterogeneous reaction that takes place between dissolved sodium sulphide and synthetic tenorite is studied for a wide range of sodium sulphide to copper oxide ratios. Besides the sulphidization with the formation of a copper-sulphide layer, a substantial oxidation of sulphide ions takes place at the surface of the solid. The extent of both types of reactions is quantitized by combining specific analytical methods.The results are discussed in terms of possible mechanisms and of their implications in the sulphidization process applied in the flotation of oxidized copper ores.     

Selective chemical extraction of Cu from selected mineral and soil samples: enhancement of Cu geochemical anomalies in Southern Portugal

The study described herein concerns the application of selective chemical extractions on metal-bearing minerals and soils to geochemical exploration. Specifically, the study aims at the detection of anomalous soils in the vicinity of two mineralized zones in Southern Portugal.A kinetic study of the selectivity of partial chemical extractions applied to Cu minerals has been carried out in order to establish a systematic procedure (reagents, extraction plateau, etc.) which could be recommended for soils of the two study zones. It is shown that: (1) NH₄ acetate dissolves malachite, azurite and cuprite completely and chrysocolla, conicalcite and atacamite only partially; (2) hydroxylamine hydrochloride dissolves chrysocolla and conicalcite only partially; (3) H₂O₂ dissolves chalcopyrite only partially; (4) NH₄ oxalate (U.V.) dissolves conicalcite and atacamite only partially; (5) mixed-acid attack dissolves residual chalcopyrite, chrysocolla, atacamite and conicalcite.A total of 740 soil samples were collected from the Salgadinho and Tinoca areas. The Cu mineralization in the Salgadinho area is situated in an Upper-Devonian Volcanic-Siliceous Complex. The weathering products of the mineralization are mainly amorphous iron oxides, goethite and hematite. The Cu mineralization in Tinoca area is located in the Arronches-Campo Maior belt, where stratiform Cu mineralization is found. The weathering products of the mineralization are mainly malachite, amorphous iron oxides, goethite and hematite.In order to identify the Cu-bearing phases and the extraction plateau, the −80 mesh fraction of two soil samples was submitted to an extraction procedure using the following reagents in sequence: NH₄ acetate, hydroxylamine hydrochloride, NH₄ oxalate (dark), NH₄ oxalate (U.V.) and finally strong acids.In soils from the Salgadinho and Tinoca areas, the use of NH₄ oxalate (U.V.) in single dissolution which would incorporate those phases dissolved by NH₄ acetate and NH₄ oxalate (dark), gives the broadest anomalous surface and higher contrast for Cu than acid digestion. The analysis of NH₄ oxalate (U.V.) extractions, instead of acid digestion, can thus be recommended for both areas.     

Characterization and pore structure analysis of a copper ore containing chrysocolla

The physical and chemical characteristics of a chrysocolla-bearing copper ore have been investigated with special emphasis on elucidation of its pore structure through gas adsorption techniques. The effect of such variables as particle size and outgassing temperature on the pore structure and size distribution has been investigated in detail. The results obtained show that the chrysocolla is a microporous solid and that its microporous nature can be considerably altered by heat treatment around 550°C. A possible reason for the so-called “thermal activation of chrysocolla” has been postulated.     

Depression mechanisms of sodium bisulphite in the xanthate-induced flotation of copper activated sphalerite

The effect of sodium bisulphite on the xanthate-induced flotation of copper-activated sphalerite has been studied using batch flotation testing, surface analysis techniques (XPS and ToF-SIMS), and FTIR. The various techniques have been used to identify the mechanisms of interaction of sulphite ions with both collector and the sphalerite surface. The results indicate that sodium bisulphite depressed the flotation of sphalerite particles pre-treated with copper and xanthate at pH 9 with nitrogen and air purging. It was found that sodium bisulphite interacts with the sphalerite surface, as well as with xanthate in its adsorbed state. Based on the evidence obtained in the present study, and in conjunction with previous work, the mechanisms involved in the depression of the xanthate-induced flotation of copper-activated sphalerite by sulphite are proposed. It is suggested that copper xanthate decomposition on the surface of the activated sphalerite and the decomposition of the hydrophobic copper-sulphide-like species on the sphalerite surface are the active mechanisms for sphalerite depression by sodium bisulphite.     

新疆托克逊县库米什铜矿地质特征

库米什西北铜矿区位于拱拜孜大断裂和桑树园子大断裂共同组成的韧性剪切带以南部位，有利于矿的富集．1：20万区域化探扫面显示出Cu、Pb、Zn、Co、Ni等元素多以高背景值出现．通过研究库米什区域上以及矿区上的地层、构造、侵入岩等因素，铜矿的规模、形态、产状等因素，孔雀石化是找铜矿的一个重要标志，侵入岩的发育为矿的运移和富集提供了通道．     

Modeling and control in the mineral processing industries

After having rapidly presented the main devices necessary for control in the mineral processing industries, the authors outline the problems encountered when modeling such systems. The model identification is more or less delicate according to whether one considers a knowledge model (ball mill and cell flotation models are given) or a representation model (copper flotation in Pyhäsalmi is given). The principal control modes currently used are proposed as examples (feedforward and feedback control) and some optimizing methods are summarized.