Ppm Te Research Articles

Green Synthesis of Selenium Nanoparticles using Green Coffee Beans: An Optimization Study.

In this study, ultrasonication extraction of some bioactive compounds from green coffee beans was optimized with the response surface method using Box-Behnken experimental design. The best condition was selected as 90.90 W ultrasonic power, 33.63 min sonication time and 30 % solid concentration. The responses obtained under optimum conditions had TPC, DPPH and CUPRAC values identified as 6603.33±2025.94 ppm GAE, 9638.31±372.17 ppm TE and 98.83 mmol, respectively. Microwave-assisted selenium nanoparticle production was carried out using the extract obtained under optimized conditions. The produced selenium nanoparticles showed absorbance between 350-400 nm. The surface morphology and size of the nanoparticles were determined by transmission electron microscopy (TEM) and spherical nanoparticles of about 100 nm were produced. Functional groups affecting the reduction were determined by FTIR analysis. In addition, the produced selenium nanoparticles had amorphous (non-uniform) structure and could maintain their stability at high temperatures.

Modification of MnS inclusion with trace tellurium to improve the machinability of medium-carbon low-sulfur steel

ABSTRACT Under the industrial process conditions, trace tellurium (13 ppm and 22 ppm) was added to medium-carbon low-sulfur steel to optimize the morphology of MnS inclusion and thereby enhance the machinability of the steel. Voller-Beckermann microsegregation model was used to calculate the precipitation thermodynamics and growth kinetics of MnS inclusion. The morphology of observed MnS inclusion is mainly polygonal (type III), the observed microstructures of the steel are bulk-, acicular-ferrite, and pearlite, the inclusions are mainly present in the bulk-ferrite. The calculation results of inclusion relative plasticity show that 13 ppm Te reduces the relative plasticity of inclusions, while at a Te content of 22 ppm, the relative plasticity of inclusions increases by approximately 70%. Compared with the steel without Te, when containing 22 ppm Te, the material has the best machinability, the average cutting force and average surface roughness of steel are reduced by 3.47% and 38.75%, respectively.

Study on the High‐Temperature Evolution and Formation Mechanism of Inclusions in Te‐Treated Resulfurized Special Steel

Te can effectively modify MnS inclusion to improve the anisotropy and machinability of steel. To figure out the mechanism of high‐temperature evolution and formation of inclusions, a high‐temperature confocal laser scanning microscope is used to in situ observe the performance of inclusions. In the steel with 22 ppm Te, Te mainly dissolves in MnS; no MnTe is generated. During the heating process, MnS inclusion remains solid state and no obvious phase change can be observed. In comparison, MnS–MnTe binary inclusion in the steel with 680 ppm Te forms a liquid phase due to the eutectic melting. The further increase of temperature causes the serious evaporation of Te. Based on scanning electron microscopy and energy‐dispersive spectrometry analysis and in situ observation of inclusions at high temperature, the formation mechanism of inclusions during solidification is proposed.

Selenium and tellurium resources in Kisgruva Proterozoic volcanogenic massive sulphide deposit (Norway)

The former mining site at Kisgruva near Kongsberg, Norway, is primarily composed of worked sulphide ore deposits, of hydrothermal origin, which occur within Precambrian metamorphic basement. Though the original targets at the Kisgruva mine site were extraction of copper (Cu), sulphur (S) and iron (Fe), the sulphide ore also contains exceptionally high concentrations of selenium (Se) and tellurium (Te), hosted within selenides (clausthalite and minor naumannite) and tellurides (hessite and minor altaite and tellurobismuthite). Both Se and Te are also present within the sulphide ore in pyrite and chalcopyrite, which contain exceptionally high concentrations of up to 688 ppm Se and 81 ppm Te. Additionally, oxidative weathering of the exposed bedrock has resulted in the accumulation of hyper-enriched, unconsolidated weathered crust deposits at surface (Se up to 1590 ppm; Te up to 63 ppm), containing selenite (SeO32−) and tellurite (TeO32−) ions. Concentrations of Se and Te are subsequently higher in the weathering products than in the sulphide ore, due to fixation on to organic matter (∼0.4% in weathered ore crusts), jarosite (formed from oxidation of sulphides from the primary ore), ferric oxide and hydroxide phases (goethite and haematite). Increasing demand for Se and Te to use in green technologies has led to the reassessment of these orebodies and their associated weathered ore crust deposits. Though these elements are currently considered mining contaminants, this and similar sites may be of future economic importance, particularly as demand for Se and Te continues to rise.

Mineralogy of the Tumanny Au-Ag-Te-Hg epithermal veins, Western Chukchi Peninsula, Russia

The Tumanny Au-Ag-Te-Hg epithermal prospect, Chukchi Peninsula, Russia is located in the near contact zone of the large Vuknei pluton, part of the Early Cretaceous Egdykgych Complex, which is related to the Peschanka porphyry copper deposit and the Nakhodka porphyry-epithermal ore district located 45 km north of Tumanny. Mineralization at Tumanny is characterized by an early carbonate-base metal and a late gold-silver-sulfosalt mineral assemblage. Pyrite of the first assemblage is unzoned and As-poor, and tennantite-tetrahedrite solid solutions (Ttrs) are characterized by a weak oscillatory zoning caused by variable contents of Sb and As, low Ag content, and the widely variable Sb/(Sb + As) values. Pyrite of the second assemblage is zoned and As-rich (up to 5.2 wt%) and Ttrs is weakly zoned and Ag-rich (up to 10.35 apfu) and has a comparatively narrow range of Sb/(Sb + As) value. Electrum, Au-Ag alloy (“küstelite”), Au-Ag-S phases, hessite, polybasite, and imiterite recognized at the prospect belong to the second mineral assemblage. The homogenization temperature of primary fluid inclusions in quartz ranges from 340 to 210 °C and decreased during the mineralizing process; fluid salinity varying from 0.8 to 5.2 wt% NaCl equiv is not evolved during the process. Cores of quartz crystals formed from a boiling fluid, whereas crystal rims appear to have formed from a lower temperature non-boiling liquid. LogfS2 decreased from −8 at the formation of carbonate-base metal assemblage to −16 at the deposition of gold-silver-sulfosalt assemblage as temperature decreased from 340 to 200 °C. Bulk ICP-OES analysis of mineralized samples indicated up to: 38 ppm Au, 908 ppm Ag, 154 ppm Mo, 106 ppm Te, 53 ppm Se, 9246 ppm As, 1284 ppm Sb, and 23 ppm Bi. Cluster analysis of the data obtained identified three geochemical associations corresponding the carbonate-base metal the gold-silver-sulfosalt, and to the overlapped mineral assemblages. The whole-ore composition is controlled by mineralogy of these assemblages. Taking into account the geological setting, mineralogy, composition of minerals, and fluid inclusion data, the Tumanny Au-Ag-Te-Hg prospect is characterized as intermediate sulfidation epithermal style.

Geochemistry of shale and sedimentary pyrite as a proxy for gold fertility in the Selwyn basin area, Yukon

Selwyn basin area strata contain sedimentary pyrite with Au above background levels when analyzed by laser ablation-inductively coupled mass spectrometry. Hyland Group rocks contain framboidal pyrite contents of 670 ppb Au, 1223 ppm As, and 5.3 ppm Te; the mean of all types of sedimentary pyrite in the Hyland Group is 391 ppb Au, 1489 ppm As, and 3.8 ppm Te. These levels are similar to sedimentary pyrite in host lithologies from major orogenic gold districts in New Zealand and Australia. Comparison of whole rock and pyrite data show that rocks deposited in continental slope settings with significant terrigenous input contain pyrite that is consistently enriched in Au, As, Te, Co, and Cu. Although data are limited, whole rock samples of stratigraphic units containing Au-rich pyrite also contain high Au, indicating that most of the Au is within sedimentary pyrite. Based on geologic characteristics and comparison of pyrite chemistry data with whole rock chemistry, Selwyn basin area strata have the necessary ingredients to form orogenic gold deposits: Au-enriched source rocks, metamorphic conditions permissive of forming a metamorphic ore fluid, and abundant structural preparation for channeling fluids and depositing ore.

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.

Trace Element Content of Pyrite from the Kapai Slate, St. Ives Gold District, Western Australia

The Kapai Slate is a continuous, pyrite-rich carbonaceous shale horizon within the St. Ives Au district that is spatially related to high-grade Au mineralization. In situ laser ablation-inductively coupled mass spectrometry (LA-ICPMS) trace element analyses, in situ sensitive high resolution ion microprobe, stable isotope (SHRIMP-SI) S isotope analyses, and optical microscopy pyrite texture analyses were used to examine the different pyrite types in the Kapai Slate and Au deposits. These data were also used to confirm that the trace element signature of sedimentary pyrite can be preserved in rocks that underwent upper to mid-greenschist facies metamorphism and significant hydrothermal overprint. The data were further utilized to gain a more detailed understanding of the ocean conditions during deposition of the Kapai Slate and determine whether some of the Au and S in the St. Ives district could have been sourced from the Kapai Slate. Seven different types of pyrite were identified: fine-grained sedimentary pyrite (Py 1 ), nodular sedimentary pyrite (Py 2 ), remobilized sedimentary pyrite (Py 3 ), coarse-grained, inclusions poor late pyrite (Py 4 ), inclusion-rich magnetite series pyrite (Py 5 ), ore stage pyrite (Py 6 ), and pyrite associated with the mafic units (Py 7 ). Each type of pyrite was found to have distinctive trace element compositions and S isotope signatures. The results of the LA-ICPMS analyses provide evidence for early trace element enrichment in the Kapai Slate sedimentary pyrite (median values of 158 ppm Ni, 387 ppm Co, 82 ppm Cu, 727 ppm As, 1.91 ppm Mo, 13 ppm Se, 0.25 ppm Au, 7.72 ppm Te and 3.36 ppm Ag for Py 1 and 223 ppm Ni, 158 ppm Co, 99 ppm Cu, 856 ppm As, 1.27 ppm Mo, 10.2 ppm Se, 0.57 ppm Au, 10.09 ppm Te, and 6.62 ppm Ag for Py 2 ). Concentrations of Ni and Co are low, relative to other late Archean sedimentary pyrite (median of 813 and 465 ppm, respectively) and Mo levels are near that of the euxinic shales of the similar-aged Jeerinah Formation in the Hamersley Basin, Western Australia. These data suggest that the Kapai Slate was deposited in an anoxic to euxinic basin with relatively low biological productivity. The Δ 33 S and δ 34 S signatures of the sedimentary pyrite suggest two different sources of S. Positive δ 34 S and negative Δ 33 S signatures indicate bacterial reduction of SO 4 2− from seawater, whereas positive δ 34 S and positive Δ 33 S signatures indicate an elemental S 8 source, indicating the pyrite formed later during diagenesis. This S isotope signature is consistent with a transition between a near-sediment environment to a more distal environment source. Analyses of the ore-phase pyrite yield weakly positive Δ 33 S values. This suggests there was a minor contribution of sedimentary S to the more significant oxidized ore-forming fluids, which is consistent with a small contribution of Au from a sedimentary source. Approximations of the degree of sedimentary pyrite destruction in the pyrrhotite/pyrite dominated zones and pyrrhotite/magnetite/pyrite zones of the northern part of the St. Ives district were used to calculate the amount of Au released from the early sedimentary pyrite. The calculation suggests that a minor, though possibly locally significant, amount of Au could have been sourced from the Kapai Slate.

Tellurium resources in New Mexico

Tellurium (Te) is one of the least abundant elements in the crust and tends to form minerals associated with gold, silver, bismuth, copper, lead, and zinc sulfide deposits. There are no primary tellurium mines in the world; most tellurium production comes from the anode slimes generated in metal refining, primarily from copper porphyry deposits. Tellurium is used as an alloying agent in iron and steel, as catalysts, and in the chemical industry. However, future demand and production could increase because tellurium is progressively used in thin film cadmium-tellurium solar panels and some electronic devices. In New Mexico, anomalous amounts of tellurium are found associated with porphyry copper deposits, as well as with gold-silver vein deposits, but were not considered important exploration targets in the past. The only tellurium production from New Mexico has been from the Lone Pine deposit (Wilcox district) in the Mogollon Mountains, where approximately 5 tons of tellurium ore were produced. Gold-tellurides are found with gold, silver, pyrite, and fluorite in fracture-filling veins in rhyolite at Lone Pine, with reported assays as much as 5,000 ppm Te. Tellurium-bearing deposits also are found in the Organ Mountains, Sylvanite, Tierra Blanca, Grandview Canyon, and Hillsboro districts. Additional detailed sampling and geologic mapping are required of the New Mexico deposits to fully understand the mineralogy and economic potential of tellurium.

Synsedimentary to Early Diagenetic Gold in Black Shale-Hosted Pyrite Nodules at the Golden Mile Deposit, Kalgoorlie, Western Australia

Synsedimentary to Early Diagenetic Gold in Black Shale-Hosted Pyrite Nodules at the Golden Mile Deposit, Kalgoorlie, Western Australia

Chemical Characterization of a Mineral Deposit of Economic Interest

ABSTRACTChemical and structural characterization of four representative samples of an ore deposit located in the eastern of Hidalgo State was carried out. According with the results, it could be appreciate some areas showing silicified zones with abundant amounts of disseminated pyrites that are part of a rock unit from early Jurassic consisting in inter - bedded black shales and sandstones. Thus, the contents of base metal were greater than 30 ppm Zn and 9 ppm Cu. Chemical analysis of rock gave the following results; 82 ppm of Ba, 1.64 % Wt. Fe, 0.08 % Wt. Ti, 40.8 % Wt. Si, 20 ppm of Ce, 2.2 ppm Co, 30 ppm Cr, 2.7 ppm Cs, 0.9 ppm Er, 2.5 ppm Ga, 1.6 ppm Gd , 1.5 ppm Ge, 9 ppm La, 71 ppm Li, 104 ppm Mn, 10 ppm Nd , 17 ppm Rb, 2 ppm Se, 9 ppm Sr, 10 ppm Ta, 6 ppm Te, 28 ppm V, 9 ppm Y, and 0.7 ppm Yb, among others. Finally, the values found for precious metals, were; Au &lt; 0.02 ppm, Pd &lt;0.05 ppm, Pt &lt;0.05 ppm. It was inferred that the low content of base metals in outcrop studied, are due to the alteration of the black shales. According to these results, we can consider a stratiform – type mineralization of Pb-Zn which could be prospective for SEDEX – Type deposit. By means of XRD, it was possible to identify; pyrite, chalcopyrite, pyrrhotite, and minor amounts of sphalerite and Co -Ni arsenide.

Genesis of Pyrite-Au-As-Zn-Bi-Te Zones Associated with Cu-Au Skarns: Evidence from the Big Gossan and Wanagon Gold Deposits, Ertsberg District, Papua, Indonesia

The Ertsberg district hosts multiple skarn and porphyry-related deposits, which together comprise one of the largest Cu-Au resources in the world. Earlier skarn Cu-Au deposits at Big Gossan and 2 km along strike to the northwest at Wanagon Gold are overprinted by distinctive late-stage pyrite, sphalerite, arsenopyrite, and native gold with local Bi and Te minerals. The Wanagon Gold deposit contains an estimated 2 million ounces (Moz) of gold; reserves at Big Gossan are 33 million tonnes (Mt) at 2.63 percent Cu, 0.92 g/t Au, and 15.72 g/t Ag. Phlogopite from the Big Gossan occurrence is younger than 2.82 ± 0.04 Ma, based on a new 40Ar/39Ar age from the Big Gossan skarn, and K-feldspar from the Wanagon Gold deposit has a 40Ar/39Ar age of 3.62 ± 0.05 Ma. A K-Ar date (3.81 ± 0.06 Ma) from the Wanagon sill constrains formation of the overprinting skarn Cu-Au and late-stage Wanagon Gold deposit to a period of ca. 0.2 m.y. At Big Gossan, earlier skarn Cu-Au mineralization displays three-dimensional mineralogical, chemical, and temperature zonation. The high-temperature core (defined by low Zn/Cu) plunges to the northwest and is open at depth. Highest Cu grades and greatest development of the overprinting pyrite-Au-As-Zn-Bi-Te association occur to the northwest coincident with northeast-striking faults. Pyrite-Au-As-Zn-Bi-Te occurrences are also distributed in faults and fractures to the north and south of the Big Gossan skarn Cu-Au deposit. At Wanagon Gold, leaching of skarn and sandstone preceded introduction of the pyrite-Au-As-Zn-Bi-Te occurrences. In the sandstone, the pyrite-Au-As-Zn-Bi-Te mineralization was accompanied by K-feldspar (adularia) and minor quartz gangue. In carbonate rocks, no leaching or secondary K-feldspar is apparent; instead, sulfides are accompanied by quartz and dolomite gangue. The {delta}34S of sulfide from skarn Cu-Au and overprinting pyrite-Au-As-Zn-Bi-Te occurrences at both deposits range from –0.7 to +5.1 per mil. Laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) analyses show that later pyrite overprinting both occurrences is distinct from that in the earlier skarn Cu-Au deposits and contains up to 60 ppm Au, 2 percent As, 680 ppm Bi, and 40 ppm Te. The mineralogy of the overprinting occurrences includes native gold, argentian tetrahedrite and tennantite, a silver-antimony sulfide, and Bi and Te-(Ag-Au) minerals including cosalite, bismuthinite, petzite, hessite, altaite, and tetradymite. The fineness of native gold varies with sulfide association. The lowest fineness gold (737–863) occurs with Pb minerals (galena and sulfosalts), and the higher fineness gold (904–974) occurs trapped within pyrite or in association with bismuthinite. Fluid inclusions in sphalerite and quartz in the Big Gossan pyrite-Au-As-Zn-Bi-Te occurrence have an average salinity of 8 wt percent NaCl equiv and an average homogenization temperature of 245°C. Stable isotopes indicate that the inclusion fluids were magmatic. However, a direct genetic relationship to earlier skarn Cu-Au mineralization is not obvious. The pyrite-Au-As-Zn-Bi-Te occurrences are considered to have formed from a fluid with a different composition, possibly the magmatic precursor to fluids commonly recognized in low- and high-sulfidation epithermal deposits that develops at shallow levels and contains significant nonmagmatic (i.e., meteoric) water.

Invisible Gold and Tellurium in Arsenic-Rich Pyrite from theEmperor Gold Deposit, Fiji: Implications for Gold Distribution and Deposition

Gold is found in three different forms in the Emperor gold deposit: as or submicrometer-size inclusions of gold in arsenian pyrite, as visible native gold and/or electrum, and as tellurides (calaverite, krennerite, sylvanite, and petzite). Similarly, Te occurs as invisible tellurium or submicrometer-size inclusions of tellurium in arsenian pyrite, as visible native tellurium, and as tellurides. Scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and secondary ion mass spectroscopy (SIMS) show that pyrite from Emperor is among the most Au- (up to 11,057 ppm Au), Te- (up to 5,796 ppm Te), and As-rich (up to 16.60 wt % As) yet reported from any mineral deposit type. Arsenian pyrite manifests itself as uniformly distributed grains, as As-rich rims on preexisting grains, or as As-rich cores. The estimated proportion of Au as invisible gold at Emperor ranges from 47 to 92 percent, with the remainder of Au occurring predominantly as gold-bearing tellurides. Native gold constitutes <1 percent of the Au budget. Invisible gold is incorporated in the structure of arsenian pyrite, probably as a Au-bearing complex where Au is coordinated as ionic gold (Au + ). The unusually high Au content of Te-bearing arsenian pyrite at Emperor most likely is due to the presence of lamellae of As- and Au-bearing marcasite or Au-bearing arsenopyrite, or a structurally bound Au-Te-bearing complex that allows for greater amounts of Au and As to be incorporated in pyrite than is generally associated with Te-deficient complexes.

Evaluation of a diagnostic leaching technique for gold in native gold and gold ± silver tellurides

A detailed investigation of the stability in cyanide solutions of native gold and gold ± silver tellurides in a flotation concentrate from the Golden Mile, Kalgoorlie, has been undertaken to assess whether leaching under different conditions can be used to quantify the distribution of Au between native gold and gold ± silver tellurides, as suggested by, for example, Chryssoulis and Cabri (1990). The leaching was carried out on +20 μm native gold and gold ± silver tellurides separated from a high-grade flotation concentrate and then diluted with barren quartz. The material leached assayed 270 ppm Au and 118 ppm Te. About 77% of the Au was present as native gold (largely liberated) and about 23% was in gold ± silver tellurides (predominantly calaverite with trace petzite and Au-bearing hessite, also largely liberated). The grainsize of the gold-bearing minerals was mainly in the range 20 μm to 100 μm. The leach conditions used were:- 1. Stage 1: Leaching in dilute cyanide (0.1%) at pH 9.5 for 24 hours to dissolve native gold but not gold ± silver tellurides. 2. Stage 2: leaching the residue from Stage 1 in strong cyanide (2%) at pH 12.5 for 96 hours to dissolve gold ± silver tellurides. Extractions of native gold and gold ± silver tellurides in the two stages of leaching were found to be as follows: Mineral % Extracted % Extracted in Total % in Stage 2 extracted Stage 1 in Stages 1 and 2 Native gold 94 5 99 Calaverite 6 11 17 Au-bearing 53 40 93 hessite (and petzite) The results showed that the bulk of the native gold dissolved in the Stage 1 leach (weak cyanide, moderate pH), along with about half the hessite and petzite but hardly any of the calaverite. The estimate of Au in native gold from the Stage 1 leach corresponded fairly closely to the native gold content as the hessite/petzite concentrations were low. However, although the Stage 2 leach (strong cyanide, high pH) dissolved almost all the remaining hessite/petzite, only a small proportion of the calaverite dissolved. The main conclusions of the investigations are that calaverite is very refractory to cyanidation, much more so than hessite/petzite, and that the diagnostic leaching procedure studied did not provide a good estimate of Au in gold ± silver tellurides. For the diagnostic leach procedure to be effective, a treatment, such as chlorination, which breaks down calaverite prior to the Stage 2 cyanidation is required.

Development of new deep drawing steels by doping with surface active elements

In this study, the effects of doping with the surface‐active elements Ge, Te, Se, As, Sb and Sn in atomic mass contents of 10 to 200 ppm on the texture and drawability of an IF‐steel (FeP06, DIN‐EN 10130) and an ELC‐steel (FeP05, DIN‐EN 10130) were investigated. Twenty‐six ingots were produced by melting and doping in a vacuum‐induction furnace, followed by forging, hot‐rolling and cold‐rolling. The cold‐rolling reduction was ɛ = 72 %. Recrystallization annealing was performed in a batch‐annealing simulation furnace. Subsequently, the orientation distribution function (ODF) and the α, γ, η‐fibre textures of both the cold‐rolled and recrystallized state were measured by means of an X‐ray diffraction goniometer and compared with the undoped reference material.The results indicate that the IF‐steel specimens doped with 100 ppm Te and Se show a significantly enhanced γ‐fibre {111}&lt;110&gt;‐{111}&lt;112&gt; texture compared to the reference specimen. Also the ELC‐steel specimens showed a higher γ‐fibre by doping with atomic mass contents of 10 to 100 ppm Se and Te. To investigate whether the drawability has been improved, Lankford‐value (rm and Δr) measurements by means of tensile tests were applied. The compositions with improved γ‐fibre also showed higher r‐values and therefore confirmed the results of the texture measurements. Se doping was found to be especially beneficial in texture and drawability for both investigated materials. The growth of selenides and tellurides at the surface of Ti4C2S2‐ and Ti2S‐ precipitates was observed by means of scanning transmission electron microscope linescans equipped with field emission gun (STEM‐FEG). Doping with Sb and Sn rendered no notable improvement of the materials, and Ge and As proved to affect the mechanical properties unfavourably.

Grain growth behavior of PbCuTe cable sheathing alloys

Lead alloys are extensively used as sheathing material for power and telecommunication cables. Excellent extrusion properties, high ductility, extremely low recrystallization temperature, good fatigue and creep resistance, make these alloys ideal for cable sheathing application. Though the thickness of the lead sheath is only a few hundred {mu}m, it is a critical component of the cable. The lead layer in the cable is often the limiting factor both during the cable production and during its service phase. Up to several hundred miles of long single piece cables may be required for underground and underwater cables. Cracking in the lead sheath during the cable sheathing extrusion limits the production of such long cables while cracking of the lead sheath due to repeated vibration, creep and recrystallization limits the service life of these cables. The purpose of the present research is to increase the duration of cable extrusion time without compromising sheath integrity by minimizing deleterious precipitate formation and growth. Concentrations of Cu and Te in the commercial alloy are too small to contribute to precipitation strengthening. Therefore their positive influence on mechanical strength should mainly result from the influence of Cu and Te in solution on interdiffusivity and grain boundary mobility.more » The formation of large precipitates observed in Pb-Cu-Te alloys can be minimized and extrusion times increased without negatively affecting mechanical properties if the solute content is reduced to near solid solubility levels. In order to examine the effect of lowering solute content on microstructural stability and mechanical properties, compressive stress-strain behavior of a Pb-50 wt ppm Cu-100 wt ppm Te alloy with solute contents close to the solubility limits and a Pb-400 wt ppm Cu-400 wt ppm Te alloy was examined at room temperature. The grain growth kinetics in these alloys were studied in a temperature range of 100 to 225 C.« less

Multistage evolution of the Calera epithermal Ag-Au vein system, Orcopampa District, southern Peru; first results

In the Orcopampa district, southern Peru, the Calera vein and its splits comprise a complex multistage epithermal fissure vein system of early Miocene age hosted by slightly older silicic and intermediate volcanic rocks. The several veins of the district are hosted by normal faults that strike N 45 degrees E to east-west. The Calera vein system is the largest and economically most important yet discovered in the district. Produced ore and reserves contain over 40 million ounces of silver and 0.4 million ounces of gold.Five paragenetic stages as well as multiple episodes of fracturing, faulting, and hydrothermal brecciation are recognized. The early stage is defined by quartz + or - adularia + or - sericite + or - pyrite altered wall rock and by mineralogically similar veinlets. Altered wall rock rich in adularia borders the vein at depth and yields laterally to sericite-rich rock within a few meters of the vein, whereas altered wall rock with abundant sericite borders the vein in upper levels. Early-stage material is cut and brecciated by several substages of the Mn stage, which are characterized by abundant rhodonite and rhodochrosite containing bands composed largely of sphalerite and other sulfide minerals or tetrahedrite. Rich ores contain 10 2 to 10 3 ppm Te, mainly in hessite (Ag 2 Te). The Mn stage is followed by two quartz-rich substages; the second substage contains tetrahedrite. This quartz stage is in turn succeeded by the bonanza stage, which contains native gold, miargyrite, pyrargyrite, and several other silver sulfosalts and precious and base metal tellurides in quartz gangue; this stage contains about 50 percent of the precious metal values of the Calera system. Late quartz and sphalerite + galena veins with barite, marcasite, and stibnite and hydrothermal breccia dikes of the late stage are volumetrically minor.Ore shoots typically occur in zones of intense fracturing indicated by abundant stockwork veins and vein splits. Based on the form and zoning of the west-plunging main ore shoot, ore-forming fluids appear to have moved diagonally upward. Several superimposed stages have different distributions within the main ore shoot; the Mn stage is better developed at depth and the quartz stage is dominant in upper levels. The Au-rich ores of the bonanza stage are found preferentially in a zone of intersection of vein splits that appears to have controlled fluid flow. Mineralization throughout the district is very similar. The bonanza stage, however, has been identified only in the Calera vein.The paragenetic sequence has resulted from a series of progressively evolving hydrothermal fluids. Initial abundant rhodonite is replaced by rhodochrosite and eventually by quartz as the dominant gangue mineral. The base metal sulfide and tetrahedrite bands must have formed from compositionally very different hydrothermal fluids. The bonanza stage also represents a distinct fluid with much lower Ag/Au, relatively high a Te /a S , and low manganese content. The close spatial and temporal association with dacite dikes and flows, the relatively high Te content of the ores, and the high a Te /a S ratios implied by some of the phase assemblages suggest the involvement of deep-seated hydrothermal fluids.

Volcanic emission of Se, Te, and As from Kilauea volcano, Hawaii

Abstract The Se, Te, and As content of the eruptive gas and of sulfur sublimates from the current (Jan. 1983 through Mar. 1985) east-rift eruption of Kilauea volcano, Hawaii, have been determined. These data, in combination with previous data, suggest that most of the Se and Te in eruptive plumes occur in the particulate fraction while most of the As is in the gas phase. Eruptive emissions to the atmosphere have been estimated at 10 metric tons each of Se and As and 2 tons of Te over the first 14 months of the eruption. Material balance calculations suggest 0.28 ppm Se and 0.017 ppm Te for the initial Kilauean magma content of these elements. Only one-third of the original Se and Te is lost from the magma by degassing.

Préparation de monocristaux de dioxyde de neptunium par transport chimique en phase gazeuse

Neptunium dioxide single crystals were grown by a chemical transport reaction using tellurium tetrachloride as transporting agent in a quartz ampoule at 1050-960°C. The single crystals are cubes up to 1 mm on edge. Characterization was performed by X-ray diffraction and electron microprobe, which indicated a lattice parameter of 5.434 ± 0.001 Å and approximately 200 ppm of impurities, including 30 ppm Te and 70 ppm Si.

Untersuchungen zur atomspektroskopischen spurenanalyse in A IIIB V-halbleiter-mikroproben—IV : Vergleich der bestimmung von tellurspuren im GaP und GaAs durch AAS, AFS und AES

Methods are described for the determination of trace tellurium in acid solution in the absence and presence of the inorganic matrices As, P, Ga, GaP and GaAs and for the direct determination in solid GaP and GAs. The following methods were used: AAS with electrothermal atomization, AFS with electrothermal atomization, and AES with d.c. arc excitation. The conditions for each of the methods were optimized and the analytical results were compared. It is shown that AAS with electrothermal atomization gives the best absolute and also relative limit of detection for trace tellurium (90 pg Te, or 4 ppm Te in GaAs or GaP). Therefore this method is recommended for the determination of trace tellurium in very small samples of A IIIB V-semiconductors.