Chalcopyrite Grains Research Articles

The distribution of heavy metals in an abandoned mining area; a case study of Strauss Pit, the Drake mining area, Australia: implications for the environmental management of mine sites

Surface water samples from the Drake mining area show elevated metal concentrations, notably cadmium, iron and zinc. A detailed study of a sphalerite /quartz vein from Strauss Pit and chalcopyrite and pyrite from the Adeline mine and Strauss Pit indicate that micro-scale analyses of ores are necessary for environmental management of mine sites. Analyses show that Cd is elevated, up to 2.1 % by weight, and is associated with sphalerite, replacing Zn, or to a lesser extent replacing Pb within small galena grains. High concentrations of Cu are also associated with the Strauss Pit ore as small chalcopyrite grains along the margins of the sphalerite vein, within the central quartz zone of the vein system, and as replacement rims on sphalerite grains. Chalcopyrite from the Adeline mine area, is by comparison, metal poor, but still contains elevated heavy metal concentrations. Whereas, pyrite and chalcopyrite, from Strauss Pit have variable heavy metal concentrations, with chalcopyrite from within sphalerite veins having higher Cd and Zn concentrations than chalcopyrite distal to the veins. Cadmium and other heavy metals within the ores are mobilised during sulphide weathering and enter the drainage network; precipitation of secondary oxidation minerals act as temporary stores for many heavy metals. The complexity of the mineral and heavy metal associations at Strauss Pit suggest that a detailed knowledge of these associations and distributions within ore bodies, and associated waste rocks, are needed by environmental managers of mine sites because the presence of havy metals may greatly affect the decision making process, and management strategies employed.

The distribution and recovery of gold in the Golden Sunlight gold-silver telluride deposit, Montana, U.S.A.

AbstractThe gold balance in an ore deposit where the ore is treated by cyanide is the sum of the ‘visible gold’ that is amenable to cyanidation and ‘visible gold’ and the ‘invisible gold’, which are not amenable to cyanidation. Petrographic analyses, electron and ion microprobe as well as scanning electron microscope studies of ore from the Golden Sunlight deposit, Montana, suggest that periods of relatively poor gold recoveries are primarily due to the presence of inclusions, <25 µm in size, of native gold, petzite, calaverite, buckhornite and krennerite. These are encapsulated in cyanide insoluble grains of pyrite, chalcopyrite and tennantite and are present in the tailings. This contribution probably accounts for 3–25% of the unrecoverable gold processed during the life of the mine. Minor amounts (6–7%) of ‘invisible gold’, as indicated by ion microprobe studies and the presence of up to 5% ‘visible gold’ in buckhornite, which is rare in nature, appears to account for the remainder of the gold budget.

Magmatic sulfides and oxides in volcanic rocks from the Pitcairn hotspot (South Pacific)

The Pitcairn hotspot, located about 60 km east of Pitcairn Island (South Pacific), consists of several active volcanoes 60%) is the main process responsible for differentiating these rock-types from an enriched source. Pyrrhotite and rare chalcopyrite grains in contact with pyrrhotite are observed only in the trachyandesite (3) in disseminated phenocryst clusters, usually in contact with large euhedral titanomagnetite phenocrysts. In addition, large euhedral pyrrhotite flakes, some with hexagonal habit, coat the walls of vesicles. All these pyrrhotite grains show a small range in Fe/S (0.90–0.99). The pyrrhotite in clusters precipitated earlier or simultaneously with titanomagnetite in a magmatic reservoir during crystal-liquid fractionation. Late precipitated vesicle pyrrhotite was formed by diffusion of Fe from the trachyandesitic liquid after the formation of the vesicles. Iron diffused from the glassy groundmass into the vesicle and reacted there with sulfur-bearing volatiles.

An SEM examination of the chalcopyrite disease texture and its genetic implications

AbstractBack-scattered electron imaging with a scanning electron microscope was applied to the intimate association of fine chalcopyrite grains and sphalerite (‘chalcopyrite disease’) in synthesized products and natural specimens, in order to distinguish between diagnostic features of two formation mechanisms: replacement and coprecipitation. In the synthetic chalcopyrite disease in Fe-bearing sphalerite formed by a replacement reaction, chalcopyrite occurs as fine lamellae, which are also observed in relatively Fe-rich growth bands of the natural zoned sphalerite. Ellipsoidal to lens-like habits of chalcopyrite appear in sphalerite that has undergone extensive replacement reactions. These textures may have grown steadily from the lamellar chalcopyrite by consuming the FeS component dissolved in the sphalerite. All the sphalerite samples formed by the coprecipitation mechanism are Fe-poor, hosting triangular or irregularly bleb-like inclusions of chalcopyrite. This variety of chalcopyrite morphology could be attributed to diffusion rates and variations in fluid saturation, and their effect on the rate of crystal growth. Thus, in both replacement and coprecipitation the chalcopyrite habit depends strongly both on the FeS content of the host sphalerite and on kinetic factors, and is significant when interpreting chalcopyrite disease textures in natural samples.

95/05031 Natural gas applications in household waste incineration

Sulphide and carbonate minerals from nine bituminous coal seams of a Paralic Series were investigated by means of polished-section microscopy, scanning electron microscopy and absorption spectral analyses. In addition to syngenetic accumulations of kaolinite, illite and quartz, diagenetic veinlets of subhedral pyrite and marcasite most often occur in vitrinite clast fissures and in post-tectonic fissures, nests and lenses with fusinite. Epigenetic anhedral and subhedral grains of ankerite, dolomite, siderite and calcite are also frequently found in post-tectonic veins. Pyrite replaced some of the marcasite grains and it dominates in older coal seams in the Flora Beds as compared with the Grodziec Beds. Occasionally there are anhedral and subhedral galena, sphalerite and chalcopyrite grains among coal macerals as well as cerussite among post-tectonic carbonate veins. They all represent the only minerals that are abundant in definite chalcophile elements (Cd, Co, Cu, Ni, Pb, Zn). In addition to the minerals just mentioned, the elements occurred in pyrite and ankerite grains, which contained inclusions of fusinite and other minerals (among others, clay and carbonate minerals in pyrite, pyrite in carbonates). Although there is a low content of minerals accumulating Cd, Co, Cu, Ni, Pb and Zn, the minerals significantly influence the average concentration of elements in the coal seams. In the Grodziec Beds, mineral matter, especially carbonates and sulphides, determines (>50%) the concentration of Cd, Cu, Pb and Zn in coal. The basic part of Cd, Co and Ni in the coal seams of the Grodziec Beds and of Co, Cu, Ni, Pb and Zn in coal seams of the Flora Beds originates from organic matter. These regularities can be important, from an ecological perspective, in stating whether the coals investigated are useful for combustion and in chemical processing.

Microstructural Analysis of an Experimentally Deformed Chalcopyrite Grain by Orientation Imaging Microscopy

Microstructural Analysis of an Experimentally Deformed Chalcopyrite Grain by Orientation Imaging Microscopy

Evaluation of the recovery of liberated and unliberated chalcopyrite by flotation columns in a copper cleaner circuit

The behaviour of chalcopyrite in flotation columns in a copper cleaner circuit was evaluated by an image analysis and materials balancing technique to compare chalcopyrite recoveries by cleaner columns with chalcopyrite recovery by conventional cleaner flotation cells. A higher recovery of free chalcopyrite grains smaller than 10 μm was obtained by the column flotation circuit than by the conventional flotation circuit. It was also observed that pyrite and sphalerite particles smaller than 13.3 μm are entrained in the Cu concentrates from both the column and conventional flotation circuits.

Petrographic investigations of seafloor sediments from the Kita-Bayonnaise submarine caldera, Shichito-Iwojima Ridge, Izu-Ogasawara Arc, northwestern Pacific

Abstract Seafloor sediment samples were recovered by box and gravity corers from the Kita-Bayonnaise submarine caldera, Shichito-Iwojima Ridge, Izu-Ogasawara Arc, northwestern Pacific. The samples were separated into heavy, light, and claysized fractions for assessment of the hydrothermal contribution to the sediments of the submarine caldera, and have been determined by microscopy, SEM-EDX, and XRD. Heavy fractions are composed of predominant magnetic minerals, dominant silicates and common sulfides and sulfate, minor sulfosalt, rutile, phosphates, carbonates and Mn-oxyhydroxides. Primary hydrothermal phases are composed of barite, pyrite, sphalerite, chalcopyrite, galena, fahlore, marcasite and rutile. Secondary mineral associations are usually present around galena and chalcopyrite grains. The assemblages of barite-pellet type pyrite-chalcopyrite-sphalerite and sphalerite-chalcopyrite-pyrite with galena or fahlore suggest that hydrothermal mineralization took place in the caldera. The assemblages of epidote-carbonate or chlorite in heavy transparent fractions and of sericite-quartz-feldspar in light fractions are indicative of hydrothermal alteration origin because of only dacite sampled from the caldera. Some of the smectite, chlorite, sericite and kutnahorite in clay-sized fractions could also support the existence of hydrothermal activity. Other minerals consisting of hypersthene, augite, hornblende, quartz, feldspar and biotite are observed in heavy and light fractions as detritus of dacite in the caldera. Significant amounts of sulfides and barite mixtures (ranging from about 1.0 to 3.5 wt.% in treated fractions, 0.063–0.25 mm) in gravity core samples suggest that hydrothermal mineralization took place several times in the caldera. Many lines of evidence indicate the presence of hydrothermal mineralizations associated with Ag and Th in the Kita-Bayonnaise submarine caldera. The mineralogical analyses are powerful for exploring signs of past or present hydrothermal mineralization in submarine calderas.

Tennantite decomposition: Evidence from the Kedabek copper deposit, Azerbaijan

A microscopic study of ores of the Kedabek deposit revealed unusual microtextures of intimate intergrowths of fine grains of chalcopyrite, fahlore (tetrahedrite), arsenopyrite and sphalerite. These textures result from fahlore (tennantite) decomposition. A detailed study of the chemical composition of earlier and later generations of ore minerals and the bulk composition of the products of decomposition of tennantite suggest that the decomposition of tennantite is due to an increase in the activity of antimony. The reason for such an increase is the crystallization of earlier generations of arsenopyrite and tennantite which caused a depletion of arsenic and an increase in the antimony/arsenic ratio in residual solutions.

Oxygen pressure leaching of copper from primary chalcopyrite ore containing pyrite under simulated solution-mining conditions

The leaching of primary porphyry chalcopyrite ore under simulated solution-mining conditions was studied using a packed-bed reactor. A mathematical model incorporating the intrinsic leaching kinetics of chalcopyrite and pyrite grains, the pore diffusion of dissolved oxygen within the ore fragments, liquid-solid mass transfer, and the effect of fluid flow and axial dispersion was formulated and tested for the overall leaching process. The dependence of oxygen solubility on ionic strength of the solution was also incorporated into the model. Satisfactory agreement between model predictions and experimental data was obtained. The model can also predict the rate of the leaching process under different temperatures, oxygen pressures, solution flow rates, and different size distributions of ores.

Elemental sulphur formation during the ferric chloride leaching of chalcopyrite

The formation of elemental sulphur during the FeCl 3 leaching of chalcopyrite has been elucidated. More than 95% S° formation, and less than 5% SO 4 generation, is observed regardless of the leaching time (0–90 h), the FeCl 3 concentration (0–2 M), the HCl concentration (0–3 M) and the chalcopyrite particle size. Furthermore, the relative amounts of S° and SO 4 do not vary systematically with any of the above variables. Surprising is the observation that the presence of air or O 2 in the leach reactor has no significant effect on the relative amounts of S° and SO 4, and this observation was confirmed in separate leaching tests with pure sulphur. The morphology of the elemental sulphur reaction product also was ascertained. Although discrete globules of S° form on large chalcopyrite particles, smaller chalcopyrite grains (<20 μm) become completely enveloped in a continuous layer of sulphur within the first 15 min of leaching. The morphology of the sulphur does not change with the concentration of either FeCl 3 or HCl.

Elemental Sulphur Formation During the Ferric Sulphate Leaching of Chalcopyrite

Abstract The formation of elemental sulphur during the ferric sulphate leaching of chalcopyrite at 95°C has been elucidated. About 94% So formation, and less than 6% SO4 generation, is observed regardless of the leaching time (0–70 h), the Fe2(SO4)3 concentration (0–2 M Fe3+) and the chalcopyrite particle size. Furthermore, the relative amounts of Soand SO4do not vary systematically with any of the above variables. The leaching of extensive polished chalcopyrite surfaces (∼1 cm2) results in the formation of discrete globules of So on a roughened chalcopyrite surface. By contrast, chalcopyrite grains <40 μm quickly become enveloped in a compact layer of elemental sulphur which is likely sufficiently protective to be responsible for the observed non-linear leaching kinetics. Continuation of the leaching process results in the progressive thickening of the sulphur layer and the agglomeration of the individual chalcopyrite particles into larger masses via the sulphur.

Sulphide ooids from the proterozoic Siyeh Formation of Alberta, Canada

Sulphide ooids from 0.5 to 4 mm in diameter occur over a large area in a thin arenite bed near the base of the Proterozoic Siyeh Formation in southwestern Alberta. Examination by optical microscope, scanning electron microscope, and electron microprobe, reveals that the ooids are composed of concentric layers, a few micrometers to a few tens of micrometers thick, of pyrite and chalcopyrite. Covellite is also present in several ooids. Copper sulphides are more abundant towards the centre of the ooids than in the outer shells where pyrite is predominant. A slightly eccentric nucleus of chalcopyrite and/or titanium oxide occurs in several ooids. It is speculated that the ooids grew during early diagenesis of the arenite, and that the source of metals were black argillaceous sediments above and below the arenite. The nucleation of sulphides around detrital grains of chalcopyrite and titanium oxide has an important bearing on metallogenetic models of stratiform copper deposits.

Geology of a disseminated copper deposit near Cerrillos, New Mexico

A small, primary disseminated copper deposit is located in the Cerrillos mining district, Santa Fe County, New Mexico, about one mile north of the town of Cerrillos.Rocks in the Cerrillos district consist of latitic flows and monzonitic and syenitic intrusives of probable Early Tertiary age. The disseminated copper mineralization is located between the Cash Entry and Mina del Tiro mines, around a small, circular coarse-grained monzonite stock that has invaded monzonite porphyry and pink syenite. Spectrographic analysis of 1,600 surface rock samples shows that a copper anomaly forms an annular ring up to 600 feet wide nearly encircling the coarse-grained monzonite stock. The anomalous area contains more than 2,000 ppm copper-in-rock.In the area of the copper anomaly, the mineralization at the surface consists of green copper carbonates and silicates. Drilling has revealed that the mineralization at depth consists of thin veinlets and disseminated grains of chalcopyrite and rare bornite. The best grades of copper mineralization are found in silicified monzonite that also contains secondary biotite. The grade of the oxidized portion of the deposit is essentially the same as that in the unoxidized portion and virtually no secondary enrichment has occurred. As a consequence, the deposit is considered to be a primary disseminated copper deposit, the upper part of which has been slightly modified by surface oxidation.A zone of pyritization associated with strong argillic alteration and turquoise is found outside of the zone of copper mineralization.