Influence of frothers on floatability. I. Flotation of single minerals (quartz and synthetic chalcocite)

The flotation and sorption properties of chalcocite and quartz in potassium ethyl xanthate (EtXK), frothers (α-terpineol and n-amyl alcohol), and (xanthate + frother) mixed solutions were investigated. Surface tension and frothing properties of the solutions were also measured.Floatability and sorption properties of the minerals investigated strongly depended on any controlled or uncontrolled change occurring at the mineral surface. Surface oxidation of chalcocite was shown to be an especially important parameter.The frothers studied showed some collecting properties in respect to chalcocite and quartz and influenced the xanthate sorption on chalcocite.Comparison of the flotation recoveries in frother solutions respectively with and without xanthate indicated an occurrence of noticeable collector-frother interactions during formation of the bubble/chalcocite grain aggregate. No such interactions were found for quartz.Influence of the frothers on floatability of the minerals was observed at different frother concentrations but at close values of surface pressure (π) and of retention time (rt).     

Behaviour of Tl relative to K,Rb, Sr and Ba in mineralized and unmineralized metavolcanics from the Dir area,northern Pakistan

Copper mineralization in the Dir area of northern Pakistan is confined to the quartz veins and associated with hydrothermally altered metavolcanics. Chalcopyrite is the main copper-bearing phase with subordinate amounts of bornite, chalcocite, covellite, malachite and azurite. Both mineralized quartz veins and associated unmineralized (least altered) and mineralized (strongly altered) metavolcanics have been analyzed for Cu, Au, Ag, Tl, K, Rb, Ba and Sr. An increase of Cu, Au, Ag, Rb/Sr and Tl/Sr, and a decrease of Sr and K/Rb is observed in both mineralized metavolcanics and mineralized quartz veins. Thallium shows lithophile behaviour in the Dir metavolcanics and no chalcophile behaviour was observed. The Tl/Sr ratio might be an indirect guide for the exploration of volcanic-hosted hydrothermal copper deposits.     

A method for determination of fine-particle flotability

The modification of a Hallimond tube enabling flotation of very fine particles at low recovery by mechanical entrainment is described. Flotation yields of closely sized fractions of quartz and chalcocite are presented.     

Oxidation-Reduction effects in the flotation of chalcocite and cuprite

A laboratory study of the batch flotation of chalcocite from chalcocite-quartz mixtures and of cuprite from cuprite-quartz mixtures with potassium ethyl xanthate as collector has shown that the oxidation-reduction state of the flotation pulp can have a pronounced influence on mineral floatabilities. At pH 11 chalcocite floated over a relatively narrow Eh range of about 300 mV; pH had no influence on the potential of the lower flotation boundary in reducing conditions but had a significant effect on the potential of the upper boundary in oxidizing conditions. Below this upper limit, the floatability was reversible with respect to Eh. Provided the Eh was in correct region chalcocite could be floated in the absence of measurable concentrations of dissolved oxygen.Cuprite displayed a high level of floatability with ethyl xanthate for which, by contrast with chalcocite, no flotation limit in reducing conditions was found; over a small range of potentials close to zero, its behaviour was strongly pH dependent.An attempt to account for the floatabilities of chalcocite and cuprite in terms of the formation of cuprous ethyl xanthate on their surfaces did not lead to correlations with the observed behaviour in reducing conditions but provided a rough correlation with the upper flotation potential limit. It is believed that more detailed and properly controlled comparative flotation studies of the chalcocite-xanthate and cuprite-xanthate systems could help to resolve some of the uncertainties associated with the effects of Eh, pH and oxygen concentration in sulphide mineral flotation.     

Mineralogy, Geochemistry, Fluid Inclusion and Oxygen Isotope Investigations of Epithermal Cu ± Ag Veins of the Khur Area, Lut Block, Eastern Iran

The Khur metallogenic district is located in a volcanic-plutonic belt in the central Lut Block(central eastern Iran). Mineralization occurs in Middle Eocene andesitic tuff and along four main vein systems trending northwest-southeast(Shurk, Mir-e-Khash, Shikasteh Sabz and Ghar-e-Kaftar veins).Microscopic studies reveal that the veins contain bornite, chalcocite, pyrite, tennantite together with minor sphalerite and chalcopyrite as hypogene minerals and chalcocite, digenite, covellite, valleriite,malachite, azurite, atacamite, hematite, and goethite as supergene minerals. The ore bodies are accompanied by narrow but intensely developed wall rock alterations of argillization, carbonatization and silicification. Copper content reaches 6.5, 2.4, 4.2 and 5% in Mir-e-Khash, Shikasteh Sabz, Ghar-eKaftar and Shurk, respectively. Microthermometric measurements of quartz-and calcite-hosted fluid inclusions indicate that the mineralization might be derived from a moderately saline hydrothermal fluid at temperatures between 175-316℃. Calculated δ~(18)O values of water in equilibrium with quartz and calcite for Khur veins suggest that the fluid might have had a magmatic source, but the ~(18)O-depletion was developed through mixing with meteoric water. Copper deposition in Khur veins is believed to have been largely caused by mixing, although wall rock reactions may also have occurred. The Khur veins are classified as volcanic-subvolcanic hydrothermal-related vein deposits.     

河南省皇城山高硫化型浅成低温热液型银矿床识别特征及其找矿意义

经过详细的野外勘查和热液蚀变、矿物标型特征研究,并结合稳定同位素研究资料综合分析,首次提出皇城山银矿床为浅成低温热液矿床中的高硫化型矿床。该矿床以发育多孔状石英岩的硅化带和高级泥化带为特征,组成矿石的金属硫化物以黄铁矿、铜蓝和辉铜矿等高硫金属硫化物组合为标志。矿石中闪锌矿的低Fe高T1和强内反射显示低温闪锌矿标型特征。...     

滇黔交界地区峨眉山玄武岩铜矿化蚀变特征

滇黔交界地区蛾眉山玄武岩铜矿化具层控特征,主要发育于上二叠统蛾眉山玄武岩组第四岩性段下部。矿化主岩为玄武岩流顶部的淬碎玄武质角砾岩和玄武岩流之间的含炭沉积岩;矿石矿物主要为自然铜及其表生氧化产物黑铜矿、赤铜矿、孔雀石等;脉石矿物主要有沥青、炭质物、石英、沸石、方解石、绿帘石等,此外还有少量绿泥石、钠长石、铁阳起石、榍石、辉铜矿、硅孔雀石、铜蓝、褐铁矿等。以玄武岩为主岩的铜矿石典型矿物组合为自然铜 沥青 石英及不含沥青等有机质的自然铜 石英 绿帘石,以含炭沉积岩为主岩的铜矿石典型矿物组合为自然铜 炭质物 沸石 石英( 辉铜矿);原生铜矿化有2个期次：早期铜矿化发生于有机质流体贯人之前,晚期铜矿化发生于有机质流体贯人之后。该类铜矿化的同生火山热液特征不明显,以后生热液矿化为主。淬碎玄武质角砾岩不仅是有机流体的良好储层,也为成矿流体提供了就位空间,是铜矿化层控特征的主要控制因素。有机流体及含碳沉积岩中碳质为成矿物质以自然铜形式沉淀提供了还原条件。     

Primary Ore Mineral Assemblage and Fluid Inclusion Study of the Batu Hijau Porphyry Cu-Au Deposit, Sumbawa, Indonesia

Abstract. The Batu Hijau porphyry Cu‐Au deposit, Sumbawa Island, Indonesia, is associated with a tonalitic intrusive complex. The temperature‐pressure condition of mineralization at the Batu Hijau deposit is discussed on the basis of fluid inclusion microthermometry. Then, the initial Cu‐Fe sulfide mineral assemblage is discussed. Bornite and chalcopyrite are major copper ore minerals associated with quartz veinlets. The quartz veinlets have been classified into ‘A’ veinlets associated with bornite, digenite, chalcocite and chalcopyrite, ‘B’ veinlets having chalcopyrite bornite along vuggy center‐line, rare ‘C’ chalcopyrite‐quartz veinlets, and late ‘D’ veinlets consisting of massive pyrite and quartz (Clode et al., 1999). Copper and gold mineralization is associated with abundant ‘A’ quartz veinlets. Abundant fluid inclusions are found in veinlet quartz consisting mainly of gas‐rich inclusions and polyphase inclusions throughout the veinlet types. The hydrothermal activity occurred in temperature‐pressure conditions of aqueous fluid immiscibility into hypersaline brine and dilute vapor. The halite dissolution (Tm[halite]) and liquid‐vapor homogenization (Th) temperatures of the polyphase inclusions in veinlet quartz range from 270 to 472d?C and from 280 to 454d?C, respectively. The estimated salinity ranges from 36 to 47 wt% (NaCl equiv.). The apparent pressures lower than 300 bars are estimated to have been along the liquid‐vapor‐halite curve for the fluid inclusions having the Th lower than the Tm that trapped the brine saturated with halite, or at slightly higher pressure relative to liquid‐vapor‐halite curve for the fluid inclusions having the Th higher than the Tm that trapped the brine unsaturated with halite. The actual temperature and pressure during the hydrothermal activity at the Batu Hijau deposit are estimated to have been around 300d?C and 50 bars. At such temperature‐pressure conditions, the principal and initial Cu‐Fe sulfide mineral assemblages are thought to be chalcopyrite + bornite solid solution (bnss) for the chalcopyrite‐bearing assemblage, and chalcocite‐digenite solid solution and bnss for the chalcopyrite‐free assemblage.     

Geochemistry and alteration facies associated with epithermal precious metal mineralization in an active geothermal system,northern Lesbos,Greece

Hydrothermal quartz veins associated with gold and silver mineralization and variable amounts of base metal sulfides have been discovered within an active geothermal system in the Megala Therma area of northern Lesbos. This geothermal system is probably a late evolutionary stage in the formation of this mineralization. The veins are hosted in Upper Miocene volcanic rocks of andesitic composition and consist of quartz, adularia, chlorite, sericite, illite, kaolinite, baryte, small amounts of jarosite and alunite, and native gold, pyrite, galena, sphalerite, chalcopyrite, bornite, chalcocite, covellite and goethite. The principal types of alteration which occur in the studied area are: silicification, propylitization, argillic alteration and potassic, phyllic alteration.     

Geology of the High Sulfidation Copper Deposits,Monywa Mine,Myanmar

The 50 km² Monywa copper district lies near the Chindwin River within the northward continuation of the Sunda‐Andaman magmatic arc through western Myanmar. There are four deposits; Sabetaung, Sabetaung South, Kyisintaung, and the much larger Letpadaung 7 km to the southeast. Following exploration drilling which began in 1959, production of copper concentrates from a small open pit started at Sabetaung in 1983. Since 1997, when resources totaled 7 million tonnes contained copper in 2 billion tonnes ore, a heap leach–electro‐winning operation has produced over 400,000 t copper cathode from Sabetaung and Sabetaung South. Ore is hosted by mid‐Miocene andesite or dacite porphyry intrusions, and by early mid‐Miocene sandstone and overlying volcaniclastics including eruptive diatreme facies which the porphyries intrude. District‐wide rhyolite dykes and domes with marginal breccias probably post‐date andesite porphyries in the mine area and lack ore‐grade copper. Host rocks to mineralization are altered to phyllic and advanced argillic hydrothermal assemblages within an outer chlorite zone; hypogene alunite is most abundant at Letpadaung and Kyisintaung. Most mineralization is structurally‐controlled with digenite‐chalcocite in breccia dykes, in steeply dipping NE‐trending sheeted veins, and in stockwork and low‐angle sulfide veins. A high‐grade pipe at Sabetaung grades up to 30% Cu, and much of the ore at Sabetaung South is in a NE‐trending zone of mega‐breccia and stockworked sandstone. The hydrothermal alteration, together with replacement quartz, alunite and barite in breccia dykes and veins, the virtual absence of vein quartz, and the presence of chalcopyrite and bornite only as rare veins and as inclusions within the abundant pyrite, indicate that the deposits are high sulfidation. Regional uplift, resistance to erosion and leaching of the altered and mineralized rocks have resulted in porous limonite‐stained leached caps over 200 m thick forming the Letpadaung and Kyisintaung hills. The barren caps pass abruptly downwards at the water table into the highest grade ore at the top of the supergene enrichment zone, within which copper grade, supergene kaolinite and cubic alunite decrease, and pyrite increases with depth; in contrast, marcasite is mostly shallow. Much of the copper to depths exceeding 200 m below the water table occurs as supergene digenite‐chalcocite and minor covellite. Disseminated chalcocite is mostly near‐surface and hence almost certainly supergene. We infer that during prolonged uplift at all four deposits, oxidation of residual pyrite at the water table generated enough acid to leach all the copper from earlier supergene‐enriched ore; below the water table the resulting acid sulfate solutions partly replaced enargite, covellite, chalcopyrite, bornite and pyrite with supergene chalcocite. Undeformed upward‐fining cross‐bedded conglomerates and sands of the ancestral Chindwin River floodplain overlie the margins of the Sabetaung deposits, form a major aquifer up to 40 m thick, and are a potential host for exotic copper mineralization. A mid‐Miocene pluton is inferred to underlie the Monywa deposits, but the possibility of porphyry‐type mineralization within the district is at best highly speculative.     

Minor and trace elements in bornite and associated Cu-(Fe)-sulfides: A LA-ICP-MS studyBornite mineral chemistry

In situ laser ablation inductively-coupled mass spectroscopy (LA-ICP-MS) has been used to provide a baseline dataset on the minor element contents in hypogene bornite and accompanying Cu-sulfides from 12 deposits with emphasis on syn-metamorphic Cu-vein systems in Norway, and skarn, porphyry and epithermal systems in SE Europe.Bornite contains significant concentrations of both Ag and Bi, especially in the vein and skarn deposits studied and has the potential to be a major Ag-carrier in such ores. Concentrations of up to >1 wt.% of both elements are documented. Measured concentrations appear to be independent of whether discrete Ag- and/or Bi-minerals are present within the analyzed sulfide. Where bornite and chalcocite (or mixtures of Cu-sulfides) coexist, Ag is preferentially partitioned into chalcocite over co-existing bornite and Bi is partitioned into the bornite. Bornite is a relatively poor host for Au, which mimics Ag by being typically richer in coexisting chalcocite. Most anomalous Au concentrations in bornite can be readily tracked to micron- and submicron-scale inclusions, but bornite and chalcocite containing up to 3 and 28 ppm Au in solid solution can be documented. Selenium and Te concentrations in bornite may be as high as several thousand ppm and correlate with the abundance of selenides and tellurides within the sample. Selenium distributions show some promise as a vector in exploration, offering the possibility to track a fluid source. Bornite and chalcocite are poor hosts for a range of other elements such as Co, Ni, Ga and Ge, etc. which have been reported to be commonly substituted within sulfides. Hypogene bornite and chalcocite may have significantly different trace element geochemical signatures from secondary (supergene) bornite.     

The influence of surface oxidation of chalcocite on its floatability and ethyl xanthate sorption

The results obtained from measurements of potassium ethyl xanthate (EtXK) sorption by synthetic chalcocite (Cu₂S) and the results of chalcocite floatability measurements are presented.Five chalcocite samples, denoted as Cu₂S A, B, C, D and E, were used for the measurements. Chalcocite samples of 60–75 μm were prepared in the same manner but were kept under conditions which differed in their degree to prevent surface oxidation by atmospheric oxygen.Chalcocite surface oxidation has a strong effect both on xanthate sorption and on chalcocite floatability. The maximal amount of xanthate abstracted (Q_max) by chalcocite samples from deoxygenated solutions after a long sorption period increases with increasing oxidation of the samples. The Q_max values give information concerning the total amount of surface oxidation products.Chalcocite decreases its floatability with increasing surface oxidation. Most oxidized chalcocite samples required an about 100 times greater collector consumption to obtain the same flotation results than the least-oxidized samples studied.     

Fluid Inclusion Study and Opaque Mineral Assemblage at the Deep and Shallow Part of the Batu Hijau Porphyry Copper-gold Deposit, Sumbawa, Indonesia

The Batu Hijau deposit is the only porphyry type deposit in production in the Sunda‐Banda arc, Indonesia. This study discusses the reason for the localization of copper grade at the deep part of the deposit based on the observation of opaque mineral assemblage. In addition, the formation condition of quartz veins and opaque minerals is discussed on the basis of the fluid inclusion microthermometry. Samples were selected from drill holes SBD100, SBD168, SBD194, SBD254, and SBD257 to cover the wide vertical range. At the Batu Hijau deposit, quartz veins have been classified mainly into four types called A, B, C and D veins, and the A veins contain mainly bornite, often associated with digenite and chalcocite. In addition, magnetite occurs in A veins. However, at the deep part of the deposit, there are quartz veins associated with magnetite, but few copper sulfides such as bornite and chalcopyrite in quartz veins, as observed in SBD257. Quartz veins at depth in SBD257 have abundant magnetite and pyrite. Pyrite in quartz veins at depth in SBD257 mainly occur at the rim of magnetite grains or interstices between them. In quartz veins in SBD254, there are abundant copper sulfides such as bornite and chalcopyrite in spite of the depth. Bornite and chalcopyrite occur as inclusions in magnetite grains in quartz veins in SBD254. Pyrite which often occurs in low grade zone in quartz veins in SBD254 is also recognized at the rims of copper sulfides. This indicates that pyrite in SBD257 and SBD254 formed later than magnetite. On the other hand, blebs of bornite and chalcopyrite inclusions in magnetite grains, which are recognized in quartz veins in SBD168 at shallow high grade part, suggest that the hydrothermal fluid, from which magnetite was deposited also brought the copper sulfides such as bornite and chalcopyrite to the deep part of the Batu Hijau deposit. Therefore, it is concluded that initially the high grade ore zone extended to depth without localization. However due to the later overprinting hydrothermal activity, copper sulfides and magnetite were replaced or dissolved and pyrite was formed, resulting the low grade zone at the deep part of the deposit. Dissolution temperatures (Td) of halite obtained by from fluid inclusion microthermometry show significant differences between SBD168 and other drill holes. The high Td obtained in SBD168 may indicate larger volume of NaCl crystals in hydrothermal fluid at the time of entrapment of the fluid inclusions and formation of other opaque minerals such as magnetite and copper‐iron sulfides. It suggests that the ratio of vapor to brine is also higher at the shallow part of the deposit. The higher vapor to brine ratio may suggest a higher degree of boiling. Removal of vapor phase separated from brine during boiling increases the concentration of substances dissolved in the brine, and this will result in saturation, as evidenced by the salinity and NaCl saturation. The higher degree of boiling suggested by the higher vapor to brine ratio at shallow part may have increased the copper concentration in the brine that may have lead the saturation, resulted in the deposition of copper‐bearing minerals.     

Appareil ignimbritique et minéralisation cuprifère: Alous (Anti-Atlas,Maroc)

Résumé Le gisement d'Alous (4 à 6 Mt à 0,8% Cu) est un exemple apparemment fort rare, de dépôt de cuivre dans un appareil ignimbritique. Celui dans lequel il est installé appartient à une formation volcanique post-orogénique de la fin du Précambrien. Les sulfures de cuivre (chalcocite, bornite avec accessoirement chalcopyrite et pyrite) et les minéraux accompagnateurs (chlorites, séricite, albite, épidote, quartz) ont cristallisé dans des pyromérides au cours du refroidissement de l'ignimbrite. La minéralisation cuprifère est localisée le long de failles radiales et l'on observe une diminution centrifuge des rapports Cu/Fe des sulfures et Mg/Fe des chlorites. Un modèle de circulations hydrothermales associées au volcanisme ignimbritique est proposé: le cuivre aurait été lessivé à partir des laves basiques sous-jacentes puis redéposé sous forme de sulfures le long des failles radiales au cours du refroidissement des ignimbrites.

---

The Alous deposit (from 4 to 6 Mt at 0.8% Cu) is apparently a rare example of copper deposit in ignimbrite volcanos. The volcano from which it comes belongs to a post-orogenic volcanic formation of late Proterozoic age (Anti-Atlas, Morocco). The copper sulphides (chalcocite, bornite with accessory chalcopyrite and pyrite) and associated minerals (chlorites, sericite, albite, epidote, quartz) crystallized during the cooling of the ignimbrite and were included in pyromeride textures. The mineralization is distributed along radial faults and displays, outwards from the volcano center, a decrease of sulphides Cu/Fe ratio and chlorites Mg/Fe ratio. A model of small-scale hydrothermal circulations linked to the volcanic activity is proposed: copper was leached from the underlaying basic lavas then redeposited along radial faults during the ignimbrite cooling.

     

Mineral chemical investigation on sulfide mineralization of the Istala deposit,Gümüşhane,NE-Turkey

The mineralogy of the Istala deposit, Gümüşhane, northeastern Turkey, was studied in detail, and a geochemical investigation was carried out using electron probe micro-analysis (EPMA). Sphalerite, galena, chalcopyrite and pyrite are the major sulfide minerals found in the Istala deposit, with minor amounts of bornite, idaite, tetrahedrite–tennantite, anilite, yarrowite, mckinstryite, covellite and chalcocite. In addition to these, barite and a small quantity of quartz occur as gangue minerals. Based on the textural relations and mineral assemblages, five different stages of crystallization have been recognized. Mineral paragenesis of the first four stages has been found to be similar, whereas clear enrichment has been observed in the modal abundance of the copper sulfide mineral assemblage at the fifth-stage ore formation. Whole-rock geochemical analyses of the Istala ore show an enrichment of Ag content up to 3328 ppm. Optical observations and EPMA study indicated that abundant silver mineralization was found in the Istala ore, especially during the later-stage ore deposition. Repetition to the presence of native silver in the samples, a significant amount of silver was incorporated in bornite, idaite, tetrahedrite–tennantite, anilite, yarrowite, mckinstryite, covellite and chalcocite, whereas a trace amount of silver has been detected in sphalerite, galena, chalcopyrite and pyrite. The homogenization temperatures (T_h) of the primary fluid inclusions were measured between 98 and 284 °C, with frequency peaks around 140 °C, 190 °C and 240 °C. All data obtained support the theory that later stage copper-rich sulfides, formed under the low temperature conditions, are responsible for the large amounts of silver content in the Istala mine.     

Remobilization of gold from a chalcopyrite-pyrite mineralization Hamash gold mine,Southeastern Desert,Egypt

Pyrite, chalcopyrite, and gold occur in quartz veins in granitic rocks and as scattered and disseminated impregnations in shear zones of the highly altered metavolcanics in the Hamash area, Southeastern Desert, Egypt. The minerals are associated in part with pyrrhotite, digenite, tetrahedrite, chalcocite, bornite, and covellite. Pyrite occurs in two forms: (1) idio- to hypidiomorphic coarse crystals with inclusions of preexisting sulfides, and (2) fine-crystalline aggregates. Chalcopyrite occurs in three forms: (1) idiomorphic coarse crystals, (2) fine-crystalline microinclusions, and (3) xenomorphic relicts. Three genetic phases of sulfide mineralization were identified. They are related to the successive cooling of the crystallizing solutions. Gold was hosted in the older sulfide minerals during a high-temperature disorder phase. Native gold was formed during the latest, decreasing-temperature phase through remobilization of auriferous pyrite. Microprobe analysis confirmed that gold and copper are relatively enriched in the late pyrite. Identified surface-alteration products include goethite, limonite, gold, carbonates, and sulfates of iron and copper.     

Diagenesis of Tertiary playa sandstones of Northern Chile; implications for Andean uplift and metallogeny

The Oligo-Miocene Pacencia Group of Antofagasta Province, northern Chile consists of over 2 km of molassic sediments deposited in a series of alluvial fan and playa sub-environments. Sandstones of the Artolla Member, exposed around San Bartolo, represent playa-marginal sandflat deposits and locally host stratiform copper mineralization. A detailed study of these sediments has revealed a complex sequence of diagenetic modifications to the arkosic detrital mineral assemblage. Early dissolution of unstable ferro-magnesian minerals and calcic feldspar resulted in the release of ions into intra-stratal solution and the subsequent formation of a suite of eogenetic authigenic minerals. These include early hematite coatings on framework grains, pore-lining zeolite and pore-filling calcite, gypsum and celestite cements. Syntaxial overgrowths of albite, quartz and less common K-feldspar are well developed. Following early oxidative intrastratal conditions, the influx of acidic fluids derived from mudrocks during mesogenesis resulted in an important secondary porosity generation and the establishment of an acidic, reducing intrastratal environment. This facilitated the subsequent introduction of low temperature mineralizing solutions and formation of the San Bartolo copper deposit. A return to oxidative diagenetic conditions is recorded by late stage overgrowths of K-feldspar and quartz and the oxidation of native copper/chalcopyrite cements to cuprite/tenorite and chalcocite/covellite assemblages. This final telogenetic modification to the mineral assemblage is related to flushing by meteoric waters and provides independent evidence for an important phase of Andean deformation and uplift in the middle to upper Miocene.     

Experimental replacement of chalcopyrite by bornite: Textural and chemical changes during a solid-state process

Chalcopyrite was reacted with covellite and with chalcocite, respectively, between 200°C and 500°C. The ensuing solid-state replacement of chalcopyrite by bornite was studied both texturally and chemically. The relatively oxidizing conditions of the reaction chalcopyrite+covellite result in massive replacement, lacking structural control, where bornite and pyrite form complex intergrowth textures in chalcopyrite. Bornite nucleates around growing pyrite aggregates because of the release of copper and a decrease in volume. Diffusion of sulphur along grain boundaries and fractures largely controls the textural development. Reaction under the relatively reducing conditions involving chalcopyrite+chalcocite results in replacement of chalcopyrite in the sequence where chalcopyrite is replaced by bornite, below about 355°C, and by intermediate solid solution (ISS) and later bornite, above 355°C. The textural development, changing from replacement, apparently uninfluenced by directional properties in the host, to semioriented replacement, is structurally controlled. This suggests that the process is governed by diffusion of copper and iron through a sulphur framework. It is suggested that the observed formation of oriented bornite lamellae in chalcopyrite and in ISS during the chalcopyrite+chalcocite reaction may be explained by replacement exsolution at constant temperature.     

西藏仲巴县天公尼勒铜金矿床地质特征及矿床成因

西藏仲巴县天公尼勒铜金矿床为一小而富的铜金矿床,矿化体赋存于早白垩世闪长岩体外接触带NE—NNE向断裂及其层间破碎带中,控矿岩体的外接触带发育的NW向韧脆性剪切断裂带控制着矿区断裂系统,已知的铜金矿体特征相似,均产于灰黑色结晶灰岩与灰白色大理岩接触部位的断裂破碎带和层间破碎带中;矿石矿物主要有黄铜矿、蓝铜矿、孔雀石、辉铜矿、黄铁矿、赤铁矿、褐铁矿等,脉石矿物为石英、方解石和绿帘石等;成矿经历了岩浆热液期（包括中高温热液阶段和中温热液阶段）和次生氧化期;早白垩世石英闪长岩的侵入、NW—NNE向断裂和层间破碎带是成矿的主要控制因素;矿床的成因类型为岩浆热液交代充填型矿床,其工业类型为构造破碎带蚀变岩型矿床。     

久辉铜矿的透射电镜研究

根据TEM研究,发现产于江西东乡的“辉铜矿”内含有与之紧密共生的久辉铜矿。高分辨象揭示出久辉铜矿的晶体结构,相当于由似六方辉铜矿结构作较长周期的重复堆垛所构成的一种类似于类多型的结构,其中并存在堆垛层错缺陷。此外,作者还发现在久辉铜矿中有与之成拓扑衍生关系的另一种相畴,其b为久辉铜矿的1/4。作者认为该相可能是介于久辉铜矿与辉铜矿之间的亚稳态中间相,并称其为变久辉铜矿(metadjurleite)。