High Concentrations Of Te Research Articles

Distribution of tellurium, selenium, cobalt and gold in sulfide minerals: A case study of the Jiguanzui porphyry-skarn Au-Cu deposit, eastern China

The Jiguanzui deposit is a representative porphyry-skarn Au-Cu deposit in the Mid-Lower Yangtze River metallogenic belt, Eastern China, characterized by significant critical metal (Te, Se, Co) association. Previous study focused on the Te and Se distribution in the ores and pyrite minerals on deposit scale, this study present trace element geochemistry of various sulfide minerals (chalcopyrite, bornite, sphalerite, molybdenite) through LA-ICP-MS analysis, aiming to reveal the distribution of Te, Se, Co, and Au among sulfide minerals in this deposit. Except molybdenite, which host high concentrations of Te and Se, pyrite and chalcopyrite generally have higher Te contents than bornite and sphalerite, whereas bornite and chalcopyrite exhibited relatively high Se concentrations. Cobalt and Au are dominantly hosted in the pyrite and chalcopyrite, respectively, although the highest Au concentration up to 14 ppm was analyzed in pyrite. Principal component analysis of trace element contents and time-resolved LA-ICP-MS signal depth profiles indicate that Te occurred as Te-Ag minerals and mineral inclusions within the sulfides, whereas Se and Co are incorporated into the lattices of sulfide minerals. Principal component analysis of trace element contents in various sulfides exhibit intimate Pb-Bi-(Cu)-Au associations, suggesting that Au is present as tiny mineral inclusions coexisting with either Cu-Bi sulfosalts or Pb sulfides or sulfosalts. This case study also highlights that Te and Se hosted in pyrite are not recoverable with current recycling technologies.

Genesis of the Sanhetun Tellurium–Gold Deposit, Northeast China: Constraints from In Situ Elemental and Sulfur Isotopic Compositions of Pyrite

The Sanhetun tellurium–gold (Te–Au) deposit, located in the Duobaoshan polymetallic metallogenic belt (DPMB) within the eastern section of the Central Asian Orogenic Belt (CAOB), is a newly discovered small-scale gold deposit. The mineralization, with a resource of ≥4 t Au, is mainly hosted in three NNE-trending alteration zones between Early Carboniferous granitic mylonite and Lower Cretaceous volcanogenic-sedimentary formations. The genesis of formation of this deposit is poorly constrained. Here, we report the results of petrographic studies, TESCAN Integrated Mineral Analyzer (TIMA), major and trace element concentrations, and in situ S isotopes of pyrite. The results show that there are four types of pyrite: coarse-grained euhedral Py1, fine-grained quartz-Py2 vein crosscutting Py1, anhedral aggregated Py3, and anhedral aggregated Py4. The pre-ore stage Py1 contains negligible Au, Te, and other trace elements and has a relatively narrow range of δ34S values ranging from −1.20 to −0.57‰. Py2 has higher concentrations of Au and Te and distinctly high concentrations of Mo, Sb, Zn, and Mn with markedly positive δ34S values of 4.67 to 14.43‰. The main-ore stage Py3 contains high Au and Te concentrations and shows narrow δ34S values ranging from −5.69 to 0.19‰. The post-ore stage Py4 displays low Au concentrations with the δ34S values ranging from 2.66 to 3.86‰. Tellurides are widespread in Py3 and Py4, consisting mainly of native tellurium, tetradymite, tsumoite, hessite, and petzite. Especially, tetradymite commonly coexists with native gold. This study highlights the role of Te–Bi–S melt as an important gold scavenger in As-deficient ore-forming fluids.

A study on microstructure evolution of MCrAlY coatings after thermal aging in Te environment

The effects of thermal exposure on tellurium (Te) diffusion behavior in MCrAlY coatings were investigated at 800 °C in Te vapor. The results showed that the diffusion depth of Te in MCrAlY coatings gradually increased with the exposure time, and the dense Cr3Te4 layer formed on the coating surface in the initial stage was no longer continuous, especially under aging conditions with higher Te concentration. The high Cr content of the coating promoted the solid phase transition of the surface reaction product from Cr3Te4 to Cr7Te8, and resulting in the formation of large α-Cr phase either within or beneath the reaction layer during long aging processes. As a result of this phase transition, excess Te atoms were released from Cr3Te4 and continued to diffuse into the coating. Te did not exhibit obvious intergranular diffusion characteristics within the coating. When it encountered Y, it was captured by Y and formed a YTe phase. After aging for 3000 h, Te was distributed throughout the coating, and numerous voids were formed at the interface between the coating and the substrate. These two factors deteriorated the plasticity and adhesion of the coating. Results from molten salt corrosion tests indicated that the high content of Cr and Al in the coating, as well as high densities of grain boundaries providing diffusion pathways, reduced the corrosion resistance of the coating to molten salt.

Effect of grain boundary scattering on carrier mobility and thermoelectric properties of tellurium incorporated copper iodide thin films

Copper iodide (CuI) is a promising p-type transparent semiconductor with many potential applications in range of fields such as transistors, optoelectronics, solar cells, thermal sensors, and energy harvesting. We report compositional, structural, optical, electrical, and thermoelectric properties of optically transparent tellurium (Te) incorporated CuI films, (CuI)1-xTex where x=0–0.09, prepared by ion beam sputtering. The films are composed of γ-CuI with the presence of elemental tellurium clusters in films prepared with high Te concentration sputtering targets. The carrier mobility decreased from 6.9 ± 0.9 cm2V-1s-1 to 0.7 ± 0.1 cm2V-1s-1, and the electrical conductivity from 84.22 ± 8.45 Scm-1 to 3.97 ± 0.40 Scm-1 for the CuI and (CuI)0.91Te0.09 films, respectively, attributed to a transition from polar optical phonon to grain boundary scattering. The change in the mobility-limiting scattering mechanism decreased the power factor from 454 ± 57 μWm-1K-2 for the CuI film to 34 ± 4 μWm-1K-2 for the (CuI)0.91Te0.09 film. Our study shows that modulating the scattering mechanism in transparent thermoelectric materials is a powerful method to tune their thermoelectric properties.

Robust temperature–strain coupling in phase and shape evolution of MoTe2 nanosheets

Molybdenum ditelluride (MoTe2) has a stable semiconducting hexagonal (2H) phase and a metastable metallic distorted octahedral (1T′) phase at the same time, which attracts much attention due to its attractive properties. However, the mechanism of phase and shape evolution in the preparation of MoTe2 is still unclear, which limits the controllable preparation and the wider device application of MoTe2. Here, we prepare few-layer MoTe2 with controllable phase and shape by using MoO3 and Te powders as precursors. With this method, triangle and hexagon 2H MoTe2 can be prepared, and long-strip and irregular 1T′ MoTe2 can be obtained. The phase and shape of as-prepared MoTe2 are determined by the coupling effect in the growth temperature and the lattice strain between 2H and 1T′ MoTe2. Low growth temperature combined with low Te concentration could induce small growth strain potential, leading to the growth of triangle and hexagon 2H MoTe2. While high growth temperature combined with high Te concentration could induce large strain potential, which is conducive to the preparation of long-strip and irregular 1T′ MoTe2. This study deeply investigates the evolution mechanism of phase and shape in MoTe2 growth, which has important guiding significance for the controllable preparation of phase and shape of other two-dimensional materials.

Mineral inclusions in the late bronze age metal objects оf Southern Transurals

The paper is devoted to the determination of copper raw material types based on the analysis of mineral inclusions and the composition of metal objects from the Late Bronze Age settlements of the Southern Transurals (XIX–XIII centuries BC). The composition of alloys, inclusions of sulfdes, oxides and metals of objects was established by scanning electron microscopy. The composition of objects is dominated by copper and tin bronze, with a subordinate role of arsenic bronze. The presence of chalcocite and bornite inclusions in most objects indicates the use of rich ores from secondary sulfde enrichment zone. In comparison with analogs, the low total amount of sulfdes in the Southern Transuralian metal objects may indicate the use of mixed oxide and sulfde concentrates. The high Se and Te concentrations of sulfdes are indicative of using of ores of volcanic-hosted massive sulfde or skarn deposits. Keywords: metal objects, copper, bronze, sulfdes, Late Bronze Age, Southern Transurals

The effects of post-cumulus alteration on the distribution of chalcophile elements in magmatic sulfide deposits and implications for the formation of low-S-high-PGE zones: The Luanga deposit, Carajás Mineral Province, Brazil

ABSTRACT Most of the World's platinum-group element ore deposits occur as thin stratiform layers within layered intrusions. These layers generally contain disseminated base-metal sulfides or chromite. However, cryptic platinum-group element deposits also occur without chromite or base-metal sulfides in what are known as low-S-high platinum-group element deposits. The origin of these deposits is not clearly understood. The Luanga Complex hosts the largest platinum-group elements resource in South America (i.e., 142 Mt at 1.24 ppm Pt + Pd + Au and 0.11% Ni) and hosts both a platinum-group element deposit containing disseminated base-metal sulfides (style 1) and a low-S-high platinum-group element deposit (style 2). It therefore offers the opportunity to compare the two deposit types in the same overall geological setting and consider how the low-S-high platinum-group element deposit could have formed. The first deposit style is termed the Sulfide zone and consists of a 10–50 meter-thick interval with disseminated base metal sulfides, whereas the second style is named low-S-high-Pt-Pd zone and consists of 2–10 meter-thick discontinuous lenses of 1–5 meter-thick sulfide- and oxide-free harzburgite and orthopyroxenite with discrete platinum-group minerals. Secondary assemblages commonly replace primary igneous minerals to a variable extent throughout the deposit, and thus allow for investigating the effects of post-cumulus alteration on the distribution of a wide range of chalcophile elements in a magmatic sulfide deposit at both whole-rock and mineral scale. This study presents the whole-rock distribution of S, platinum-group elements, and Te, As, Bi, Sb, and Se in both mineralization styles and the concentration of trace elements in base-metal sulfides from the Sulfide zone. The Sulfide zone has Pt/Pd ratios around 0.5 and high concentrations of Te, As, Bi, Sb, and Se, whereas the low-S-high-platinum-group element zone has Pt/Pd ratios greater than 1 and much lower Se, Te, and Bi concentrations, but comparable As and Sb contents. This is reflected in the platinum-group element assemblage, comprising bismuthotellurides in the Sulfide zone and mostly arsenides and antimonides in the low-S, high platinum-group elements zone. Moreover, the base-metal sulfides from the Sulfide zone have anomalously high As contents (50–500 ppm), which suggest that the sulfide liquid segregated from a very As-rich silicate magma, possibly illustrated by an average komatiitic basalt that assimilated a mixture of upper continental crust and black shales. We interpret the low-S-high platinum-group elements zone as a product of S loss from magmatic sulfides during post-cumulus alteration of the Luanga Complex. Selenium, Te, Bi, and Pd were also lost together with S, whereas As and Sb were expelled from base-metal sulfide structures and combined with platinum-group elements to form platinum-group minerals, suggesting they may play a role fixating platinum-group elements during alteration. The remobilization of chalcophile elements from magmatic sulfide deposits located in the Carajás Mineral Province may represent a potential source for hydrothermal deposits found in the region.

Trace Element Geochemistry of Chalcopyrites and Pyrites from Golpu and Nambonga North Porphyry Cu-Au Deposits, Wafi-Golpu Mineral District, Papua New Guinea

Studying elemental geochemistry of hypogene sulphides can discriminate the hydrothermal fluids responsible for ore formation. To determine whether Golpu porphyry Cu-Au deposits are related to the Nambonga North porphyry system which is located 2.5 km apart in the Wafi-Golpu Mineral District, Papua New Guinea, we compare the trace element compositions of drill core chalcopyrites and pyrites analysed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). The results for the Golpu chalcopyrites revealed high concentrations of Au, As, Se, Mo, Sb, Te and Bi and lower concentrations of Ag and Zn compared to those from Nambonga. Pd and Pt were below the detection limit in chalcopyrites for both deposits. The results for the Golpu pyrites indicated high concentrations of Pt, Au, Se, Mo, Sb, and Te and lower concentrations of Cu, Zn, As, Ag, Pb, Pd and Bi compared to those from Nambonga North. Au concentrations in the pyrites from both the porphyry deposits were higher compared to chalcopyrites, which mean that pyrite is the Au-bearing sulphide responsible for the higher Au content. In contrast, Cu values in pyrites from Nambonga North are higher than those from Golpu. Overall, it is envisaged that the ore fluids were exsolved at different times during the evolution of both porphyry deposits, although these porphyry centres may be related in space and time.

Trace elements in pyrite and pyrrhotite in the Pitangui Orogenic Au deposit, Pitangui greenstone belt, São Francisco Craton: Implications for the ore-forming fluids and metal sources

Orogenic Au deposits represent one of the largest sources of gold in the world and in Brazil, particularly at the Quadrilátero Ferrífero, southeastern portion of the São Francisco Craton. In the last decades, advances in in-situ analytical techniques allowed a detailed investigation of the chemistry of sulfides. This can reveal information about the origin and composition of the mineralizing fluids, potential sources of metals and sulfur and the fluid-rock interaction during the ore-forming processes. In this paper we combine Electron Microprobe Analysis and LA-ICP-MS analyses to put constraints on the nature and evolution of the Pitangui gold deposit. The Pitangui deposit represents an important Orogenic Au deposit hosted in clastic metasedimentary rocks of the Pitangui greenstone belt, northwestern portion of the Quadrilátero Ferrífero. Detailed drill hole, petrographic observations and in-situ chemical analyses of the hydrothermal alteration zones show that pyrite is the dominant ore mineral in the deposit and two possible origins are suggest including (i) syngenetic pyrite development at the early stages of the greenstone belt evolution and (ii) epigenetic pyrite, which is associated with hydrothermal processes during the Orogenic Au event. Syngenetic pyrite (PyI) has high Co, Bi, Pb, Sb, Te, Se, Ag and Au concentrations. The PyI could represent an important source of metals, a set of trace elements and likely sulfur for the later Orogenic Au mineralization. Epigenetic pyrites (PyII, PyIII and PyIV), conversely, are mainly found in association with hydrothermal minerals and within the mineralized carbonate-quartz-vein. The variations at Co, Ni, Pb, Te, Sn, Se, As, Bi, Sb, Ag, Mo and W in the epigenetic pyrite indicate that the dehydration PGB sequences during orogenesis constitutes the main fluids sources. The PyV, in turn, only appears at metamafic dyke, but its origin remains unclear.

Electronic properties of the bulk and surface states of Fe1+yTe1-xSex.

The idea of employing non-Abelian statistics for error-free quantum computing ignited interest in reports of topological surface superconductivity and Majorana zero modes (MZMs) in FeTe0.55Se0.45. However, the topological features and superconducting properties are not observed uniformly across the sample surface. The understanding and practical control of these electronic inhomogeneities present a prominent challenge for potential applications. Here, we combine neutron scattering, scanning angle-resolved photoemission spectroscopy, and microprobe composition and resistivity measurements to characterize the electronic state of Fe1+yTe1-xSex. We establish a phase diagram in which the superconductivity is observed only at sufficiently low Fe concentration, in association with distinct antiferromagnetic correlations, whereas the coexisting topological surface state occurs only at sufficiently high Te concentration. We find that FeTe0.55Se0.45 is located very close to both phase boundaries, which explains the inhomogeneity of superconducting and topological states. Our results demonstrate the compositional control required for use of topological MZMs in practical applications.

Multistage gold mineralization in the Hadamengou gold deposit in the northern margin of the North China Craton: Insights from in-situ trace element contents and sulfur isotope analyses of pyrite

Abstract The Hadamengou gold deposit is one of the largest gold deposits in the Wulashan-Daqingshan gold mineralization cluster, in the northern margin of the North China Craton. The gold deposit, which is hosted by Archean gneiss, comprises potassic alteration and abundant quartz-pyrite veins, with five types of hydrothermal pyrite associated with gold, tellurides, and sulfides. The earliest stage of pyrite (Py1) occurs as random disseminations within the limited volume of modified quartz-pyrite veins and was formed during or prior to the last episode of metamorphism. Py2, from the potassic and chlorite-sericite alteration zones, is related to the activity of potassic fluids, and contains inclusions of native gold, galena, melonite, electrum, and petzite. Py3, without inclusions, occurs as randomly- disseminated grains within the limited volume of grey quartz-pyrite veins. A few native gold grains are found along fractures of quartz associated with Py3. Py4 occurs as veinlets or aggregates in the milky quartz-pyrite veins and contains the highest Au concentrations. Abundant native gold, calaverite, and electrum occur along the grain boundaries and fractures, or as inclusions within Py4 and quartz. Py5 occurs as rounded and cataclastic shapes within the limited volume of quartz-carbonate veins and is depleted in Au. LA-ICP-MS trace element analysis of the pyrite shows that Py1 has a low content of gold (median of 0.07 ppm) and other trace elements (Ag, Te, Pb, Cu, Bi, and As). Potassic alteration, grey quartz-pyrite veins, and milky quartz-pyrite veins make a very large contribution to the gold endowment, with a relatively high gold content in pyrite, including Py2 (median of 0.8 ppm), Py3 (4.3 ppm), and Py4 (2.5 ppm). Other trace elements (e.g., Ag, Te, Pb, Mo, and Bi) are also significantly enriched within Py2 to Py4. Little or no gold was detected in Py5. Thus the potassic alteration and milky quartz-pyrite veins were major contributors to gold mineralization, based on the volume and Au content of pyrite within the Hadamengou deposit. In-situ LA-MC-ICP-MS sulfur isotope analyses of pyrite show negative values and a narrow range of variation of δ34S (averages of −11.4‰, −11.8‰, −10.5‰, and −9.4‰ for Py2-Py5, respectively), indicating an oxidized magmatic sulfur source for the pyrites in Hadamengou. Additionally, the occurrence of tellurium minerals associated with various pyrites, and the high Te concentration of various pyrites, also suggest that ore-forming fluids were derived from an oxidized alkaline magma. These results, combined with published geochronological data, suggest that during two episodes, Au-rich potassic and SiO2-rich fluids separated from the deep-lying Devonian alkaline magma during ascent along the EW-trending faults, and reacted together with the wall rocks to form potassic and chlorite-sericite alteration zones, resulting in gold precipitation.

Ferromagnetic half-metallicity in half-Heusler AuMnSn:Te Alloy

Identifying a strategy for beneficial band-engineering is vital for the optimization of spintronic materials. In this study, we demonstrate the beneficial effects of electron doping on ferromagnetic (FM) half-Heusler AuMnSn1−xTex (0 ≤ x ≤ 1) using state-of-the-art first-principles methods. By partially substituting the Sn site with a more ionic Te dopant, we predict a FM metal to a FM-half-metallic semiconductor (FM-HMS) transition at Te doping concentration x ∼ 0.125. The FM-HMS is observed to be stable over a wide range of lattice parameters up to a pressure of ∼24.91 GPa. We determined the magnetic phase diagram that shows a phase transition from FM state at low Te concentration dominated by the FM Ruderman-Kittel-Kasuya-Yosida-type exchange to antiferromagnetic state at high Te concentration mediated by the superexchange coupling mechanism. Using the Heisenberg exchange model, we predict a rather high Curie temperature of that increased with increasing pressure. Our results demonstrate a robust scheme for engineering ferromagnetic half-metallicity in the half-Heusler alloy that is promising for spintronic applications.

Role of selenium addition to CdZnTe matrix for room-temperature radiation detector applications

Because of its ideal band gap, high density and high electron mobility-lifetime product, cadmium zinc telluride (CdZnTe or CZT) is currently the best room-temperature compound-semiconductor X- and gamma-ray detector material. However, because of its innate poor thermo-physical properties and above unity segregation coefficient for Zn, the wide spread deployment of this material in large-volume CZT detectors is still limited by the high production cost. The underlying reason for the low yield of high-quality material is that CZT suffers from three major detrimental defects: compositional inhomogeneity, high concentrations of dislocation walls/sub-grain boundary networks and high concentrations of Te inclusions/precipitates. To mitigate all these disadvantages, we report for the first time the effects of the addition of selenium to the CZT matrix. The addition of Se was found to be very effective in arresting the formation of sub-grain boundaries and its networks, significantly reducing Zn segregation, improving compositional homogeneity and resulting in much lower concentrations of Te inclusions/precipitates. Growth of the new quaternary crystal Cd1−xZnxTe1−ySey (CZTS) by the Traveling Heater Method (THM) is reported in this paper. We have demonstrated the production of much higher yield according to its compositional homogeneity, with substantially lower sub-grain boundaries and their network, and a lower concentration of Te inclusions/precipitates.

Trace Metal Distribution in Sulfide Minerals from Ultramafic-Hosted Hydrothermal Systems: Examples from the Kairei Vent Field, Central Indian Ridge

The ultramafic-hosted Kairei vent field is located at 25°19′ S, 70°02′ E, towards the Northern end of segment 1 of the Central Indian Ridge (CIR-S1) at a water depth of ~2450 m. This study aims to investigate the distribution of trace elements among sulfide minerals of differing textures and to examine the possible factors controlling the trace element distribution in those minerals using LA-ICP-MS spot and line scan analyses. Our results show that there are distinct systematic differences in trace element distributions throughout the different minerals, as follows: (1) pyrite is divided into three types at Kairei, including early-stage euhedral pyrite (py-I), sub-euhedral pyrite (py-II), and colloform pyrite (py-III). Pyrite is generally enriched with Mo, Au, As, Tl, Mn, and U. Pyrite-I has high contents of Se, Te, Bi, and Ni when compared to the other types; py-II is enriched in Au relative to py-I and py-III, but poor in Ni; py-III is enriched in Mo, Pb, and U but is poor in Se, Te, Bi, and Au relative to py-I and py-II. Variations in the concentrations of Se, Te, and Bi in pyrite are most likely governed by the strong temperature gradient. There is generally a lower concentration of nickel than Co in pyrite, indicating that our samples precipitated at high temperatures, whereas the extreme Co enrichment is likely from a magmatic heat source combined with an influence of serpentinization reactions. (2) Chalcopyrite is characterized by high concentrations of Co, Se, and Te. The abundance of Se and Te in chalcopyrite over the other minerals is interpreted to have been caused by the high solubilities of Se and Te in the chalcopyrite lattice at high temperatures. The concentrations of Sb, As, and Au are relatively low in chalcopyrite from the Kairei vent field. (3) Sphalerite from Zn-rich chimneys is characterized by high concentrations of Sn, Co, Ga, Ge, Ag, Pb, Sb, As, and Cd, but is depleted in Se, Te, Bi, Mo, Au, Ni, Tl, Mn, Ba, V, and U in comparison with the other minerals. The high concentrations of Cd and Co are likely caused by the substitution of Cd2+ and Co2+ for Zn2+ in sphalerite. A high concentration of Pb accompanied by a high Ag concentration in sphalerite indicates that Ag occurs as Pb–Ag sulfosalts. Gold is generally low in sphalerite and strongly correlates with Pb, suggesting its presence in microinclusions of galena. The strong correlation of As with Ge in sphalerite from Kairei suggests that they might precipitate at medium temperatures and under moderately reduced conditions. (4) Bornite–digenite has very low concentrations of most trace elements, except for Co, Se, and Bi. Serpentinization in ultramafic-hosted hydrothermal systems might play an important role in Au enrichment in pyrite with low As contents. Compared to felsic-hosted seafloor massive sulfide deposits, sulfide minerals from ultramafic-hosted deposits show higher concentrations of Se and Te, but lower As, Sb, and Au concentrations, the latter often attributed to the contribution of magmatic volatiles. As with typical ultramafic-hosted seafloor massive sulfide deposits, Se enrichment in chalcopyrite from Kairei indicates that the primary factor that controls the Se enrichment is temperature-controlled mobility in vent fluids.

Effect of Tellurium Concentration of the Solution on the Structural, Optical and Luminescence Properties of Cadmium Telluride Nanoparticles

Water-soluble cadmium telluride (CdTe) nanoparticles (NPs) were prepared using L-cystine as a capping agent. The reaction was carried out under basic conditions (at pH=11) and refluxed at 100oC for 1 h. In this work, different tellurium (Te) concentrations in the solution of L-cystine functionalized CdTe NPs were prepared at low temperature of 100oC and discussion of its effect was done in detail. The CdTe NPs were analyzed using X-ray diffraction (XRD), ultraviolet-vis and photoluminescence (PL) spectroscopy. Structural parameters estimated by XRD revealed cubic phase of CdTe at lower Te concentrations and hexagonal phase of Te emerging at higher Te concentration. XRD results showed that the NPs consisted of small CdTe nanocrystallites, 3.1-4.5 nm in size. Scanning electron microscopy was used to analyze the surface morphology of the samples and was found that it varied with different Te concentration in the aqueous solution. They consisted of spherical, rod-like and blade-like type of morphologies. The absorption thresholds of the CdTe NPs were red shifted when Te concentration was increased, due to the quantum confinement effects displayed by nanocrystalline CdTe NPs. Optical band gap energy estimated showed a decrease with an increase in the amounts of Te present while the band emissions observed in the PL spectra of CdTe NPs red shifted from 536-559 nm upon an increase in Te ratio. The PL full width at half maximum increased from 49-60 nm with increase in Cd:Te from 1:0.1 to 1:1 displaying narrow size distribution of the NPs. Highest PL intensity was realized for a 1:0.4 Cd:Te molar ratio which is an indication of improved crystallinity.

Metal endowment reflected in chemical composition of silicates and sulfides of mineralized porphyry copper systems, Urumieh-Dokhtar magmatic arc, Iran

The present work attempts to discriminate between the geochemical features of magmatic-hydrothermal systems involved in the early stages of mineralization in high grade versus low grade porphyry copper systems, using chemical compositions of silicate and sulfide minerals (i.e., plagioclase, biotite, pyrite and chalcopyrite). The data indicate that magmatic plagioclase in all of the porphyry copper systems studied here has high An% and Al content with a significant trend of evolution toward AlAl3SiO8 and □Si4O8 endmembers, providing insight into the high melt water contents of the parental magmas. Comparably, excess Al and An% in the high grade deposits appears to be higher than that of selected low grade deposits, representing a direct link between the amounts of exsolving hydrothermal fluids and the potential of metal endowment in porphyry copper deposits (PCDs). Also, higher Al contents accompanied by elevated An% are linked to the increasing intensity of disruptive alteration (phyllic) in feldspars from the high grade deposits. As calculated from biotite compositions, chloride contents are higher in the exsolving hydrothermal fluids that contributed to the early mineralization stages of highly mineralized porphyry systems. However, as evidenced by scattered and elevated log (fH2O)/(fHF) and log (fH2O)/(fHCl) values, chloride contents recorded in biotite could be influenced by post potassic fluids. Geothermometry of biotite associated with the onset of sulfide mineralization indicates that there is a trend of increasing temperature from high grade to low grade porphyry systems. Significantly, this is coupled with a sharp change in copper content of pyrite assemblages precipitated at the early stages of mineralization such that Cu decreased with increasing temperature. Based on EMPA and detailed WDS elemental mapping, trace elements do not exhibit complex compositional zoning or solid solution in the sulfide structure. Nevertheless, significant amounts of Cu and Au are contained in pyrite assemblages as micro- to nano-sized inclusions, especially in the high grade fertile porphyry deposits. However, unexpectedly high concentrations of Te, Se, and Re may be associated with early stage of sulfide mineralization, especially when there is no epithermal lithocap. This may highlight the significance of trace metals partitioning in the sulfides formed at the early stages of mineralization in PCDs.

Element migration of pyrites during ductile deformation of the Yuleken porphyry Cu deposit (NW-China)

The strongly deformed Yuleken porphyry Cu deposit (YPCD) occurs in the Kalaxiangar porphyry Cu belt (KPCB), which occupies the central area of the Central Asian Orogenic Belt (CAOB) between the Sawu’er island arc and the Altay Terrane in northern Xinjiang. The YPCD is one of several typical subduction-related deposits in the KPCB, which has undergone syn-collisional and post-collisional metallogenic overprinting. The YPCD is characterized by three pyrite-forming stages, namely a hydrothermal stage A (Py I), a syn-ductile deformation stage B (Py II) characterized by Cu-Au enrichment, and a fracture-filling stage C (Py III). In this study, we conducted systematic petrographic and geochemical studies of pyrites and coexist biotite, which formed during different stages, in order to constrain the physicochemical conditions of the ore formation. Euhedral, fragmented Py I has low Pb and high Te and Se concentration and Ni contents are low with Co/Ni ratios mostly between 1 and 10 (average 9.00). Py I is further characterized by enrichments of Bi, As, Ni, Cu, Te and Se in the core relative to the rim domains. Anhedral round Py II has moderate Co and Ni contents with high Co/Ni ratios >10 (average 95.2), and average contents of 46.5 ppm Pb and 5.80 ppm Te. Py II is further characterized by decreasing Bi, Cu, Pb, Zn, Ag, Te, Mo, Sb and Au contents from the rim to the core domains. Annealed Py III has the lowest Co content of all pyrite types with Co/Ni ratios mostly <0.1 (average 1.33). Furthermore, Py III has average contents of 3.31 ppm Pb, 1.33 ppm Te and 94.6 ppm Se. In addition, Fe does not correlate with Cu and S in the Py I and Py III, while Py II displays a negative correlation between Fe and Cu as well as a positive correlation between Fe and S. Therefore, pyrites which formed during different tectonic regimes also have different chemical compositions. Biotite geothermometer and oxygen fugacity estimates display increasing temperatures and oxygen fugacities from stage A to stage B, while temperature and oxygen fugacities decrease from stage B to stage C. The Co/Ni ratio of pyrite depends discriminates between the different mineralizing stages in the Yuleken porphyry copper deposit: Py II, associated with the deformation stage B and Cu-enrichment, shows higher Co/Ni ratios and enrichments of Pb, Zn, Mo, Te and Sb than the pyrites formed during the other two stages. The Co/Ni ratio of pyrite can not only apply to discriminate the submarine exhalative, magmatic or sedimentary origins for ore deposits but also can distinguish different ore-forming stages in a single porphyry Cu deposit. Thus, Co/Ni ratio of pyrites may act as an important exploration tool to distinguish pyrites from Cu-rich versus barren area. Furthermore, the distribution of Cu, Mo, Pb, Au, Bi, Sb and Zn in the variably deformed pyrite is proportional to the extent of deformation of the pyrites, indicating in accordance with variable physicochemical conditions different element migration behavior during the different stages of deformation and, thus, mineralisation.

Mineralogy, geochemistry and genesis of the polymetallic crusts and nodules from the South China Sea

Recent marine mineral investigations in the South China Sea (SCS) have found increasingly significant abundances of Fe–Mn polymetallic crusts and nodules with variable substrates and nuclei. There is, however, no systematic and complete study of the SCS crusts and nodules. The lack of mineralogical and geochemical studies affects our explicit understanding of the mineralization characteristics and genesis of the crusts and nodules. In this study, we analyzed a set of SCS polymetallic crusts and nodules obtained from ten sites to determine their mineralogy, chemistry, and Fe and Os isotopes. The SCS crusts/nodules are composed predominantly of vernadite (δ–MnO2) and amorphous Fe oxides/hydroxides. The nodules also contain minor todorokite. TEM imaging and electron diffractions show that the Fe–Mn minerals are nano–sized minerals with very poor crystallinity. Nitrogen adsorption/desorption analysis indicates an average specific surface area of 257.128 m2/g for the SCS crusts and nodules, and main apertures of 2–10nm for their nanopores in the Fe–Mn minerals. It is noteworthy that the SCS crusts/nodules contain substantial amount of terrigenous detritus, suggesting that marginal sea–type Fe–Mn deposits are strongly influenced by terrigenous sedimentary input. Furthermore, geochemical analysis indicates that the SCS crusts/nodules have relatively lower Co (1482ppm), Cu (556.2ppm), Ni (3132ppm), Mo (276.2ppm), and Zn (598.3ppm) compared to open oceanic crusts/nodules, but relatively high concentrations of REY (1647ppm), PGE (234.0ppb), Ba (1056ppm), Pb (1878ppm), Sr (995.9ppm), Te (28.81ppm), and Tl (67.87ppm). Iron isotopic compositions suggest that the Fe sources of the SCS crusts/nodules may have been Fe dissolved in terrigenous (fluvial) inputs. Osmium isotopes indicate that the main ore–forming elements came directly from the ambient seawater, which was mainly influenced by terrigenous inputs, although there may have been mixing with minor mantle–derived signatures.Evidence from mineralogy, major element geochemistry, shale–normalized rare earth element (REE) patterns, and the Fe and Os isotopes suggest that the SCS crusts/nodules are mainly hydrogenetic, whilst the formation of some nodules may have been contributed by minor pore waters of their surrounding sediments. The SCS crusts/nodules had probably much higher growth rates (mean 19.20mm/Ma) than most hydrogenetic Fe–Mn deposits in other open oceans, which are typical of marginal sea Fe–Mn deposits that contain sufficient supply of ore–forming terrigenous detritus.Grades of some critical metals of economic interest (notably Co, Cu, Ni, Mo, and Zn) are slightly lower in the SCS crusts and nodules than in the crust and nodules from Pacific prime mineralization zones. Concentrations of Mn, REY, Pt, Mo, Co, Te, and Bi, however, show relatively high concentrations relative to the continental crust. The SCS crusts and nodules could thus represent a strategic REE, Co and Pt resource, and will likely catalyse additional investigation of seabed resources in the South China Sea.

Anisotropic pressure effects on the Kagome Cu3Bi(SeO3)2O2Cl metamagnet

The anisotropic spin-flip-induced multiferroic property of the Kagome single-crystal Cu3Bi(SeO3)2O2Cl was recently investigated. The doping effects on the structural and magnetic properties of Cu3Bi(Se1−xTexO3)2O2Cl (0 0.6) polycrystalline samples were studied to further explore and manipulate the metamagnetic spin-flip transition. With higher Te concentration, the lattice constants a and b exhibit a linear increase, whereas the lattice constant c gradually decreases, which indicates that the anisotropic expansion and compression effect is induced by Te substitution in the Se site. Subsequently, the antiferromagnetic transition (TN) shifts to a higher temperature, the critical field () of the metamagnetic spin-flip transition increases, and the value of the saturation magnetisation () diminishes. Meanwhile, the effects of isotropic expansion (with Br doping) and compression (with external pressure) do not show a clear influence on the spin-flip phenomena. Our results emphasise the introduction of anisotropic pressure in Cu3Bi(SeO3)2O2Cl, which modulates the magnetic interaction of Cu (I)–O1–Cu (I) and Cu (I)–O1–Cu (II) and, consequently, enhances the of the spin-flip transition.

Investigation of X-ray diffraction limitations upon the analysis of tellurium-atom injection into GaAs epitaxial layers

GaAs lattice “superdilation” caused by an introduced tellurium impurity, which is well known in publications, is experimentally studied. This phenomenon consists in the fact that the GaAs-lattice dilation can be more than 10 times greater than expansion that would appear upon the replacement of arsenic atoms with tellurium atoms if calculations are performed using the current-carrier concentration and Vegard’s law. The given phenomenon has already been observed at n Te > 3 × 1018 cm–3. A series of GaAs epitaxial layers heavily doped with tellurium and grown via metal-organic chemical vapor deposition are investigated using high-resolution X-ray diffractometry (HRXRD), secondary-ion mass spectrometry (SIMS), and the Hall effect. It is demonstrated that, despite a high Te concentration (1020‒1021 cm–3) in the layer and variations in the growth conditions, the concentration estimates based on HRXRD data depend linearly on the results of elemental analysis performed by means of SIMS. The GaAs lattice expands even somewhat slighter as compared to the case where arsenic atoms are replaced with all Te atoms injected into the layer. At the same time, the Hall carrier concentration decreases sharply beginning at 2 × 1020 cm–3. In accordance with the obtained results, the examined phenomenon can be interpreted as the strong compensation of donor and acceptor carriers rather than as superdilation.