Chalcopyrite Crystals Research Articles

The La Unión Au ± Cu prospect, Camagüey District, Cuba: fluid inclusion and stable isotope evidence for ore-forming processes

The Camaguey district, Cuba, is known for its epithermal precious metal deposits in a Cretaceous volcanic arc setting. Recently, the La Union prospect was discovered in the southern part of the district, containing gold and minor copper mineralization interpreted as porphyry type. Mineralization is hosted in a 73.0 ± 1.5 Ma calc–alkaline I-type oxidized porphyry quartz diorite intrusive within volcanic and volcaniclastic rocks of the early Cretaceous Guaimaro Formation. The porphyry is affected by propylitic alteration and crosscut by a network of quartz and carbonate veinlets and veins. Chlorite, epidote, sericite, quartz, and pyrite are the main minerals in the early veins which are cut by late carbonate and zeolite veins. Late barite pseudomorphously replaces pyrite. Gold is associated with pyrite as disseminations in the altered quartz diorite and in the veins, occurring as inclusions or filling fractures in pyrite with 4 g/t Au in bulk samples, and up to 900 ppm Au in in pyrite. Fluid inclusion and oxygen isotope data are consistent with a H2O–NaCl–(KCl) mineralizing fluid, derived from the quartz diorite magma, and trapped at least at 425°C and 1.2 kbar. This primary fluid unmixed into two fluid phases, a hypersaline aqueous fluid and a low-salinity vapor-rich fluid. Boiling during cooling may have played an important role in metal precipitation. Pyrite δ34S values for the La Union prospect range between 0.71‰ and 1.31‰, consistent with a homogeneous magmatic sulfur source. The fluids in equilibrium with the mineralized rocks have estimated δ18O values from 8‰ to 11.8‰, calculated for a temperature range of 480–505°C. The tectonic environment of the La Union prospect, its high gold and low copper contents, the physical–chemical characteristics of the mineralizing fluids and the isotopic signature of the alteration minerals and fluids indicate that the La Union gold mineralization is similar to the porphyry gold type, even though the ore-related epidote–chlorite alteration can be classified as propylitic and not the classic potassic and/or phyllic alteration. The low copper contents in the prospect could be due to a mineralizing fluid previously saturated in copper, which is indicated by trapped chalcopyrite crystals in high-temperature fluid inclusions. The low-temperature paragenesis, represented by carbonate, zeolite and barite, indicates epithermal overprint. The study shows the potential for other gold porphyry-type deposits in the Cretaceous volcanoplutonic arc of Cuba.

First principles study of electronic structure and optical properties of LiMTe 2 (M=Al, Ga, In) crystals

The results of first principles calculations of the electronic band structure, density of states and frequency dependent dielectric functions of LiAlTe 2, LiGaTe 2 and LiInTe 2 chalcopyrite crystals are reported. The calculations have been carried out within the density functional theory using norm-conserving pseudopotentials and a plane-wave basis. The peculiarities of the imaginary part ε 2( ω) of the complex permittivity are discussed and interpreted on the basis of the obtained band spectra. Our calculations show that the Ga-containing compound is characterized by the largest optical anisotropy compared to Al- and In-containing compounds and, therefore, is the most promising candidate for nonlinear optical applications among considered crystals.

Polarized-thermoreflectance study of the band-edge transitions in Cu(Al_05In_05)S_2 solar-energy related crystal

Polarization dependence of band-edge excitonic transitions in Cu(Al(0.5)In(0.5))S(2) [denoted as Cu(AlIn)S(2)] has been characterized using polarized-thermoreflectance (PTR) measurements with E || <111 > and E perpendicular <111 > polarizations in the temperature range between 30 and 320 K. The measurements were done on as-grown {112} surface of the chalcopyrite crystal. The polarization dependence of the band-edge transitions of Cu(AlIn)S(2) clearly showed that the E(A) exciton is present prominently with E || <111 > polarization while the E(B) exciton appears significantly only in the E perpendicular <111 > polarized spectra. For the unpolarized spectra, both E(A) and E(B) features were combined. The E(A) feature is closely related to the E(0) transition, while the E(B) feature is that of E(0) + Delta(0) transition in the chalcopyrite. The crystal-field splitting energy of Delta(0) of Cu(AlIn)S(2) at the valence-band top is determined accurately by PTR experiments. Temperature dependences of transition energies of E(A) and E(B) transitions were analyzed. The band-edge excitons reveal an anomalous temperature-energy shift with increasing the temperatures from 30 to 320 K due to the variation of Cu d electrons' contribution to valence band that affected by the native defects inside Cu(AlIn)S(2). The PTR technique is more effective in studying the band-edge structure of the chalcopyrite crystal.

Thermoreflectance characterization of band-edge excitonic transitions in CuAlS2 ultraviolet solar-cell material

Near band edge transitions of CuAlS2 chalcopyrite crystals have been characterized using temperature-dependent thermoreflectance (TR) spectroscopy in the temperature range between 30 and 340 K. A lot of interband transition features of EAn=2, EAn=3, EBn=2, EC, ED, EE, and EF were detected in the low-temperature TR spectrum of 3–6 eV at 30 K. Transition energies of the TR features of CuAlS2 are analyzed. Transition origins of the features are evaluated. Optical-electric conversion behavior of CuAlS2 was evaluated by photoconductivity (PC) measurement at 300 K. The PC spectrum reveals that the maximum photoresponse occurs near the energy positions of EAn=2, EAn=3, and EBn=2 features. The features are the fundamental band edge excitons which dominate photoelectric conversion behavior of CuAlS2 ultraviolet solar-energy material.

Carbon spherules in Ni–Cu–PGE sulphide deposits in the Sudbury impact structure, Canada

The formation of Sudbury's economically important magmatic Ni–Cu–PGE sulphide deposits is attributed to superheating of crustal rocks, following meteorite impact at 1.85 Ga. Crustal contamination of magmatic sulphide deposits is thought to be important in the mineralization process and this paper documents the first occurrence of sedimentary carbon in the Sudbury Ni–Cu–PGE sulphides near the base of the Sudbury Igneous Complex (SIC). Spherules of graphitic and more disordered carbon inclusions were found in chalcopyrite crystals, suggesting that carbon has behaved as a chalcophilic element in the impact melt. Samples from the impact structure have been subjected to carbon isotopic analysis and Raman microspectroscopy in order to investigate the relationship between carbonaceous strata of the Huronian basement, the crater-fill impact breccias, and the mineral deposits associated with the Sudbury impact. Carbonaceous material occurs in the impact breccias of the Onaping Formation and this study presents stratigraphically constrained carbon isotopic analysis of the impact breccias. Sulphides from the hydrothermal Zn–Pb–Cu Vermilion–Errington deposits 1.5 km above the SIC were found to contain both carbon spherules and larger irregular carbonaceous flakes, suggesting a genetic link between the Ni–Cu–PGE deposits and the hydrothermal Zn–Pb–Cu mineralization. A shared source of carbon for the Vermilion–Errington mineralization and the cross-cutting anthraxolite veins 100m above the deposits in post-impact carbonaceous shales of the Onwatin Formation is indicated by the similarity in their Raman spectra. This is considered to be carbon remobilized by metamorphic hydrothermal fluids preferentially scavenging disordered carbon from within the Onaping Formation breccias. The occurrence of carbon in the Sudbury Ni–Cu–PGE massive sulphide deposits indicates that carbon from the target rocks played a role in the mineralization process, hitherto unrecognized.

Specific features of electronic and vibrational properties of I-V-V2 crystals

The ab initio density functional method with using pseudopotentials has been applied to calculate the electronic and vibrational spectra of the LiN2 and NaPN2 crystals, with optimization of their structure. The specific features of the crystal structure (highly compressed chalcopyrite) and composition of these crystals manifest themselves in the qualitative similarity of their band spectra and chemical bonding to those of chalcopyrite as well as in some substantial distinctions. The second valence band exhibits four branches instead of two branches, as in chalcopyrite crystals, and involves contributions of the p-states of the P and N atoms rather than the s states of the Group-III cations in the I-III-VI2 chalcopyrite compounds. The top of the valence band is at the side points of the Brillouin zone, the bottom of the conduction band is in the center of the Brillouin zone, and the absorption edge corresponds to the indirect band gap. The contributions of alkali metals to the vibration spectra are significant in the region of low-frequency modes; phosphorus and nitrogen make significant contributions to the modes in the high-frequency region, which is due to the prominent covalent component of bonding between these atoms.

Rb-Sr Geochronology of Chalcopyrite from the Chehugou Porphyry Mo-Cu Deposit (Northeast China) and Geochemical Constraints on the Origin of Hosting Granites

The Chehugou porphyry Mo-Cu deposit is located ca. 300 km north of Beijing in the boundary zone between the Archean North China craton and the Neoproterozoic-Mesozoic Central Asian orogenic belt. Using hydrothermal chalcopyrite from this deposit, we are able to show for the first time that the Rb-Sr isotope system in massive, nonfractured chalcopyrite grains can provide reliable age constraints for Mo-Cu deposits. We analyzed two chalcopyrite samples from slightly different petrogenetic “environments” showing contrasting texture and deformation history. Five 2- to 5-mg fragments of a single nonfractured chalcopyrite grain containing spatially isolated inclusions of K-mica, K-feldspar, and quartz yielded an Rb-Sr isochron age of 256 ± 7 Ma (2σ including λ uncertainty). For this sample, the dense chalcopyrite “matrix” apparently inhibited diffusion of Rb and Sr after chalcopyrite crystallization, and the age should therefore reflect the time of crystallization of chalcopyrite from the Mo-Cu mineralizing fluids. The evidence for Mo-Cu mineralization during the late Permian requires a revision of the previous notion that the Chehugou deposit was formed during the Yanshanian orogeny lasting from 200 to 60 Ma. Fragments of a second chalcopyrite sample that, in contrast to the first, had experienced deformation as indicated by intragranular fractures and alignment of K-mica and K-feldspar inclusions along these fractures. This sample yielded a clearly younger Rb-Sr isochron age of 207 ± 15 Ma (2σ). This age obviously reflects an isotopically open system due to fluid movement and/or prolonged diffusion of Rb and Sr along the fractures. Single biotite crystals from an associated monzogranite yielded an Rb-Sr isochron age of 250 Ma, which is interpreted as a lower age limit for the Mo-Cu mineralization, and the time when the granite cooled below 400° to 300°C. Considering the field evidence for a broadly contemporaneous origin of the Mo-Cu mineralization and the hosting granitoids, we suggest that the granitoids are not much older than ca. 260 Ma. The Mo-Cu–hosting granitoids range in composition from monzogranite to highly evolved syenogranite with high La/Yb and Sr/Y ratios. Initial eNd values of ca. –21 to –23 (Nd crustal residence times of the sources 1.9 to 2.7 Ga) indicate melting of the predominantly Archean North China craton, and a subordinate juvenile mantlederived component. Much older U-depleted lower crustal sources for the granitoids are supported by high initial 208Pb/204Pb ratios. Lithospheric delamination and underplating of hot mantle-derived material may have facilitated crustal melting in a late orogenic to postcollision.

Ferric chloride leaching of chalcopyrite: Synergetic effect of CuCl 2

This work presents a study of the leaching of chalcopyrite in acidic ferric chloride. Two chalcopyrite samples (natural chalcopyrite crystal and chalcopyrite concentrate) were leached under different conditions. The effects of stirring speed and temperature were investigated. It was found that agitation had a negative effect on copper recovery from chalcopyrite during the leaching process. This is explained by the fact that cupric chloride complexes are formed during the leaching process where cupric ion is considered as a stronger oxidant than ferric ion. Agitation sweeps away the cupric chloride complexes formed, whereas, under stagnant conditions cupric chloride complexes accumulate at the reaction interface causing enhanced dissolution of copper. The overall leaching reaction was found to be sensitive to temperature. The shrinking core model was fitted to the data and it was found that the leaching process was controlled by chemical reaction with activation energy of 69 kJ/mole.

LiPN2 and NaPN2 crystals: Structural features and chemical bonding

The band structure spectra, densities of states, and valence and difference densities of LiPN2 and NaPN2 crystals were obtained by DFT self-consistent calculations using the nonlocal pseudopotentials and the localized pseudoorbital basis. Crystal-chemical analysis of these compounds shows that they occupy an intermediate position between the ideal structures of β-cristobalite and chalcopyrite, which manifests itself in the peculiarities of the electronic structure and chemical bonding. The valence band consists of three allowed subbands and differs radically from the typical valence band of chalcopyrite crystals in both subband structure and contributions of the s, p, and d atomic orbitals to the crystal orbitals.

Exploration using till geochemistry and heavy minerals in the ribbed moraine area of southern Finnish Lapland

The geochemistry of different till size fractions and studies of heavy minerals have been used in mineral exploration in the ribbed moraine terrain in southern Finnish Lapland. The Peräpohja Schist Belt and layered intrusions along its southern margin have known potential for economic Au, Co, Cu, Fe, Zn, U and PGE mineralization. In till, high element concentrations related to mineralization in the local bedrock preferentially occur in the near-surface (less than 2 to 3 m depth) of ribbed moraine ridges. The ridges formed subglacially by gouging of local bedrock, which favoured the deposition of rock material derived from the local bedrock surface into till on the surficial part of ridges. The short distance of glacial transport (&lt;500 m) is indicated by clast angularity, the abundance of locally derived boulders in the upper till and at the surface, and by the preservation of euhedral pyrite and chalcopyrite crystals and native Au grains in the heavy mineral concentrates. Detailed studies show that ribbed moraine ridge tops can be used for mineral exploration because they are more likely to be composed of local bedrock than are the sediments comprising the ridge core.

Preferential oxidation of chalcopyrite surface facets characterized by ToF-SIMS and SEM

The use of hydrometallurgical methods for the production of copper from chalcopyrite has become more attractive due to environmental drivers such as lower energy demand and less gaseous emissions such as SO 2. Unfortunately, chalcopyrite is known to be a highly unreactive mineral in hydrometallurgical processes. This work reports that a freshly cleaved chalcopyrite surface exhibits highly selective reactivity depending on the exposed fracture planes. ToF-SIMS was used to qualitatively characterise various fracture planes from freshly cleaved chalcopyrite particles, prior to and after hydrometallurgical treatment (leaching). It was found that prior to treatment certain areas exhibit pronounced contamination from atmospheric hydrocarbons upon fracture, whereas others were highly unreactive and remarkably free from adventitious hydrocarbon contamination. The positive ion spectra recorded from these areas are indeed dominated by peaks from Fe and Cu elements and related compounds. The negative ion spectra for the reactive areas showed a high content of oxidised (sulphur) species. After leaching, the differences between the sites of low and high reactivity were more subtle than prior to this treatment, whereas SEM analysis showed clear evidence for selective attack of ferric sulphate to specific planes after such treatment. Attempts are made to rationalise these observations with regards to selective dissolution based on different exposed chemistries at various cleavage planes within chalcopyrite crystals.

Unusually Cu-rich magmas associated with giant porphyry copper deposits: Evidence from Bingham, Utah

Mass-balance constraints indicate that formation of giant porphyry copper deposits (PCDs) requires either highly efficient collection of Cu from large volumes of magma or unusually Cu-rich parent magmas. Support for the second of these possibilities has been discovered in the form of mafic enclaves with abundant bornite and chalcopyrite in the Last Chance stock, one of the parent intrusions of the giant Bingham PCD, Utah, United States. Mineral assemblages and compositions indicate that the Last Chance enclaves are autoliths consisting of phases that crystallized from the intrusion, and that the intrusion was unusually enriched in Cu. One possible mechanism for generating Cu-rich magmas is fractional crystallization during pyrrhotite undersaturated conditions. The high fO 2 conditions observed for the Last Chance stock may have allowed such an evolution. Alternatively, if the magma has not undergone significant fractionation, early crystallization of chalcopyrite and bornite from the magma would indicate that the lower-crustal source region for the magma probably contained Cu-Fe sulfides. Possible Cu-rich source regions are a subcrustal mafic intrusion with sulfide cumulates, or a deeply buried metamorphic terrane containing Cu deposits such as those in the Curaca Valley (Brazil) or Okiep (South Africa). Heterogeneous distribution of Cu-Fe sulfides in an Okiep-type source terrane would produce local PCDs such as Bingham, or large accumulations of Cu-Fe sulfides, possibly in the form of cumulates in subcrustal intrusions at convergent margins, could produce giant PCD provinces such as those in Indonesia, Papua New Guinea, and central Chile.

Photoluminescence of CdGeP2 and (Cd,Mn)GeP2

Photoluminescence of CdGeP 2 (112) single crystal and CdGeP 2 epitaxial film grown on GaAs (001) substrate have been studied and their spectral similarity found. Spectral bands associated with donor/acceptor transitions peak at close energies for both substances and all are lower than the energy gap of the chalcopyrite crystal. On the other hand, the growth of (Cd,Mn)GeP 2 ferromagnetic layer on CdGeP 2 (112) single crystal was performed to make it possible observation of PL from both the ferromagnetic layer and substrate. The green laser excitation (514, 532 nm) produces a proper photoluminescence similar to that in the undoped CdGeP 2 crystal and film. An extra emission from the ferromagnetic–nonmagnetic heterojunction occurs to extend up to photon energies exceeding E g of the host semiconductor. The short wavelength photoluminescence is to be due to (Cd,Mn)GeP 2 dilute magnetic semiconductor (DMS). This fact states that Mn-doped II–IV–V 2 chalcopyrites are closer to II–VI DMS than to another group III–V DMS, where the heavy Mn-doping suppresses photoluminescence at all. Features of the observed short wavelength emission are discussing based on the temperature and spectral analyses.

Composition, structure and optical properties of sputtered thin films of CuInSe 2

Thin films of copper indium selenide (CuInSe 2) were produced by radio frequency (RF) sputtering due to the ability of this technique to achieve stoichiometric layers and its scalability to large-area devices. Results of energy dispersive analysis of X-rays (EDAX) revealed that the sputtered films were near to stoichiometry for substrate temperatures T Sub not exceeding 200 °C. X-ray diffraction (XRD) patterns indicate that the films exhibited some pattern similar to that of bulk crystals of tetragonal chalcopyrite, predominantly [112] oriented. Based on the XRD patterns, the lattice parameters and grain sizes were examined. The band gap E g, estimated from optical absorption data, was between 0.6–1.08 eV, depending on sputtering conditions such as substrate temperature and bias voltage. High optical absorption coefficients (> 10 4 cm − 1 ) were found.

First-principles calculations of the structural, electronic and optical properties of [formula omitted] and [formula omitted

The structural, electronic and optical properties of two chalcopyrite crystals, AgGaS 2 and AgGaSe 2 , are studied using the full potential linearized augmented plane waves method within the local density approximation. Geometrical optimization of the unit cell (equilibrium volume, c / a ratio, internal parameter u, and bulk modulus) is in good agreement with experimental data. The energy gap is found to be direct for both materials and the nature of the gap crucially depends on the manner in which the Ga 3 d, and Ag 4 d electrons are treated as core or valence states. Results on band structures, density of states, and charge-density distributions are presented. We report also our results on optical properties like the complex dielectric functions and the refractive index n of the AgGaS 2 and AgGaSe 2 crystals. We analyze in detail the structures of the dielectric function observed in the studied energy region.

Magnetic resonance of Mn-related isolated centers and clusters in chalcopyrite crystal of (Zn,Mn)GeP2

Anomalously intense dispersion has been observed in the magnetic resonance signals of manganese clusters in the chalcopyrite crystal ZnGeP2:Mn with a high concentration of manganese. The EPR signals detected correspond to at least two types of isolated manganese ions. One of these apparently possesses acceptor properties, which makes manganese a self-contained impurity for the formation of a ferromagnetic state in accordance with recent theoretical predictions.

Detection of magnetic resonance signals with anomalous dispersion and two types of isolated manganese centers in the chalcopyrite crystal (Zn,Mn)GeP2

Anomalously intense dispersion was observed in the magnetic resonance signals of manganese clusters in the chalcopyrite crystal ZnGeP2:Mn with a high concentration of manganese. The EPR signals detected corresponded to two types of isolated manganese ions. One of these apparently possesses acceptor properties, which makes manganese a self-contained impurity for the formation of a ferromagnetic state in accordance with recent theoretical predictions.

An Analysis of Compositional Variations and Spatial Relationships within Fe-Ni-Cu Sulfide Deposits on the North Range of the Sudbury Igneous Complex

Analytical data sets provided for mineral exploration borehole samples from the McCreedy West mine and other orebodies along the North Range of the Sudbury Igneous Complex have been examined in a series of atomic ratio diagrams designed in order to elucidate the mass transfer processes involved in their genesis. The compositions of ores from the McCreedy West mine display a strongly bimodal distribution. A Cu-poor population (1), largely located along the footwall contact, displays trends consistent with fractionation dominated by pyrrhotite (monosulfide solid solution) crystallization. A Cu-rich population (2), located within the footwall vein system, displays trends consistent with fractionation dominated by chalcopyrite (intermediate solid solution) crystallization. What appears to be a shared trend between the two populations suggests that they are related by derivation from a cognate pair of immiscible sulfide liquids. The compositions of ores for all deposits examined within the Levack embayment on the North Range of the Sudbury Igneous Complex collectively show the same compositional bimodality that is observed at McCreedy West. Compositional relationships displayed by these deposits, individually and collectively, are consistent with the separation of an immiscible, Cu-rich melt during cooling and fractionation of monosulfide solid solution from a less Cu-rich, parental sulfide liquid. The spatial relationships of the two ore populations at McCreedy West and within the Levack embayment suggest that density relations and volume changes associated with the unmixing and crystallization processes have played a major role in the emplacement of footwall orebodies. Spatial relationships of the two ore populations suggest that the various orebodies within the Levack embayment were all emplaced when the basal contact of the Sudbury Igneous Complex was essentially horizontal and that they represent different parts of a cogenetic system emplaced penecontemporaneously within arcuate, upwardly concave, dilational fractures associated with uplift and brecciation of the footwall and local collapse of the hanging-wall rocks.

New magnetic materials in ZnGeP 2-Mn chalcopyrite system

The growth of quaternary solid solutions in the ZnGeP 2-Mn quasi-binary system was studied. Single-crystal thin layers of ZnGeP 2:Mn with a basal crystal structure appurtenant to the chalcopyrite crystal class were grown for the first time. Ferromagnetic behavior of the ZnGeP 2:Mn compound was observed up to a temperature of 350 K.

Optical diagnostics of laser evaporation of CuInS2 polycrystalline compound

In the radiation spectrum of the erosion laser plasma of CuInS2 polycrystalline compound, the presence of resonance spectral lines of CuIn and InI is revealed, as well as of spectral lines which correspond to cascade transitions and of lines from the displaced terms of the copper atom. No intense radiation of positive ions is observed in the spectral range from 200 to 600 nm. The binding energies of Cu–S, In–S, Cu–Cu, In–In, and Cu–In atoms, as well as atomic and orbital bond orders of the CuInS2 cluster, are calculated by the Hueckel pseudoempirical method within the valent approximation. It is found that In(1, 3) atoms inversely centering the lower faces of cations Cu(6, 6I), as well as cations Cu(4, 4I ) and In(5, 5I ) centering the lateral faces of the crystal, do not form strong bonds in the structure. Therefore, in the evaporation processes they must easily evolve from the structure of the CuInS2 chalcopyrite crystal and make a predominant contribution to the radiation spectrum of laser plasma. From the standpoint of energy, the atoms of sulfur and nodal atoms of copper evaporate mainly in the form of combined complexes of CuS molecules. One can assume that the initial growth layers will be obtained with a deficiency in sulfur and with substantial violation of their stoichiometry and the structure of the initial compound.