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Taking as a base structural properties of the tetradymite-like layered chalcogenide compounds, a novel ternary GeBi4Te4 phase was predicted and synthesized. The polycrystal of this compound was synthesized and its single-crystal was grown by the vertical Brigman-Stokbarger method. The phase composition of obtained samples was analyzed by differential thermal analysis (DTA), X-ray powder diffraction (XRD), and scanning electron microscope (SEM). It was determined that the novel phase melts peritectially at 538 °C and has the following lattice parameter values in a hexagonal configuration: a=4,4071(6)Å, c=17,384(2)Å (sp. gr P3m1). This crystal structure is considered a derivative of tetradymite-like layered chalcogenides and consists of alternating Bi bilayers and GeBi2Te4 septuple packets.

Nanocrystals of group 5 tetradymites M2X3 (where M = Bi and Sb, X = Se and Te) are of high technological relevance in modern topological nanoelectronics. However, there is a current lack of a systematic understanding to predict the preferred nanocrystal morphology in experiments where commonly-used equilibrium thermodynamic models appear to fail. In this work, using first-principles DFT calculations with a rationally-extended ab initio atomistic thermodynamics approach coupled to implicit solvation models and Gibbs-Wulff shape constructions, we demonstrate that this absence of predictive power stems from the limitation of equilibrium thermodynamics. By re-tracing and carefully addressing with a more realistic chemical potential definition, we illustrate this shortcoming can be overcome and afford a more rational route to size-engineer and shape-design highly-functional group 5 tetradymite nanoparticles for targeted applications.

Bi8Te3 is a member of the tetradymite homologous series, previously shown to be compositionally and structurally distinct from hedleyite, Bi7Te3, yet inadequately characterized structurally. The phase is identified in a sample from the Hedley district, British Columbia, Canada. Compositions are documented by electron probe microanalysis and structures are directly imaged using high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). Results confirm that Bi8Te3 has an 11-atom layer structure, in which three Bi-Bi pairs are placed adjacent to the five-atom sequence (Te-Bi-Te-Bi-Te). Bi8Te3 has trigonal symmetry (space group R3¯m) with unit cell dimensions of a = ~4.4 Å and c = ~63 Å calculated from measurements on representative electron diffraction patterns. The model is assessed by STEM simulations and EDS mapping, all displaying good agreement with the HAADF STEM imaging. Lattice-scale intergrowths are documented in phases replacing Bi8Te3, accounting for the rarity of this phase in nature. These results support prior predictions of crystal structures in the tetradymite homologous series from theoretical modeling and indicate that other phases are likely to exist for future discovery. Tetradymite homologues are mixed-layer compounds derived as one-dimensional superstructures of a basic rhombohedral sub-cell. Each member of the series has a discrete stoichiometric composition and unique crystal structure.

We used high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) to image the crystal structures of four minerals in the Bi4X3 isoseries (X = Te, Se, S), a subgroup of the tetradymite homologous series: ikunolite (Bi4S3), laitakarite (Bi4Se2S), joséite-B (Bi4Te2S), and joséite-A (Bi4TeS2). The four minerals are isostructural and interpretable in terms of regular stacking of seven-atom packages: [Bi–S–Bi–S–Bi–S–Bi], [Bi–Se–Bi–S–Bi–Se–Bi], [Bi–Te–Bi–S–Bi–Te–Bi], and [Bi–S–Bi–Te–Bi–S–Bi], respectively. The four phases are mixed-layer structures representing the Bi2kTe3 (k = 2) module within the tetradymite series. Diffraction patterns confirm they are seven-fold superstructures of a rhombohedral subcell with c/3 = d~1.89–1.93 Å. Modulation along the d* interval matches calculations of reflection intensity using the fractional shift method for Bi4X3. Internal structures can be discerned by high-resolution HAADF STEM imaging and mapping. Paired bismuth atoms are positioned at the outside of each seven-atom layer, giving the minerals a modular structure that can also be considered as being composed of five-atom (X–Bi–X–Bi–X) and two-atom (Bi–Bi) sub-modules. The presence of mixed sites for substituting cations is shown, particularly for Pb. Moreover, Pb may be important in understanding the incorporation of Ag and Au in Bi–chalcogenides. Visualisation of crystal structures by HAADF STEM contributes to understanding relationships between phases in the tetradymite homologous series and will play an invaluable role in the characterization of potential additional members of the series.

In this paper, we describe a thorough study of the structural and magneto-transport properties of Mn-doped Bi2Te3 thin films grown by magnetron sputtering. The substitution of bismuth from manganese was performed by repeating ten times an alternating deposition of Bi2Te3 and Mn layers. The crystal structure is the tetradymite with the ( $00l$ ) preferential orientation. Magnetoconductance data shows weak anti-localization phenomena at low temperatures. The presence of ferromagnetism is also demonstrating a strong anomalous Hall effect (AHE) and the sign of AHE resistances changes from negative to positive as the Mn concentration increases.

Research subject. In this work, we investigated the crystals of pyrite, one of the key gold-bearing minerals, from the Berezovskoe (the Middle Urals) deposit using modern research approaches.Materials and methods. Samples for the analysis were collected from the ladder sulphide-quartz veins and related berezites in the Ilinskaya, Pervopavlovsk and Vtoropavlovsk dykes of the Berezovskoe deposit. The ores were studied using the methods of optical microscopy, X-ray microanalysis (PCMA), scanning electron microscopy (SEM) and LA-ICP-MS. The latter method was largely used to examine pyrite. Along with pyrite, the materials under study included faded ore, galena, and such rare occurring minerals as aikinite, cosalite, tetradymite and tsumoite. Results. According to the point and profile analysis, as well as grain mapping, the main impurity elements in the stu died samples are found to be Co, Ni and As. The distribution of these elements has shown a zonal character: the amounts of Co and Ni tend to increase and that of As tends to decrease towards the grain centre. In the pyrite samples, Cu, Zn and Pb occur either in the form of their sulphide micro-inclusions or as evenly distributed admixtures. The pyritic ore of later genera tions in the Pervopavlovsk dyke is established to contain gold in amounts of up to 22 g/t, with Au being zonally distributed. The goldbearing variety of pyrite is characterized by abnormally low contents of Co and Ni, as well as by an increased content of As (up to 8000 g/t). Conclusion. A common character of the distribution of main impurity elements in the pyritic ores in the studied dikes indicates similar conditions of their crystallization. The presence of late-generation pyrite with fine gold in the Pervopavlovsk dike evidences to a heterogeneous distribution of gold mineralization therein, likely due to the multistage character of the latter. This may also be an indicator of the concentration of ore columns, which fact requires further elucidation.

Own Se minerals, first established in primary ores of VMS deposits of the Urals, are described. Instrumental neutron activation analysis of bulk ore samples, mineral monofractions and local methods of analysis: LA-ICP- MS, electron probe microanalysis and analytical electron microscopy were used. CSe in ores of the Urals to 977 g/t. Significant positive correlation of Se with Te, S, Fe, Co, Mo, Hg, Bi is characteristic. Selenium is con- centrated in the main sulfides, mainly in pyrite (73 g/t), chalcopyrite 49 g/t, pyrrhotite 48 g/t; in sphalerite usually

In general, Bi2Te3 and related alloys show the best thermoelectric performance at near-room temperature region below about 423 K, which is in some cases not high enough for waste heat recovery. In order to raise the operation temperature on the basis of Bi2Te3 technology, S element was introduced into Bi2Te3 to synthesize a ternary tetradymite compound, Bi2Te2S, and the thermoelectric properties were analyzed. In this study, Bi2S3 was considered, instead of using elemental S, to avoid the issues arising from the volatility of S. Compared with Bi2Te3, undoped Bi2Te2S shows higher Seebeck coefficients (Smax = −210.9 μV K−1 at 523 K) but also higher resistivity (ρmin = 26.5 μΩ m at 323 K), resulting in decreased power factor (PFmax = 1.49 mW K−2m−1 at 373 K). However, low thermal conductivity (κmin = 0.987 WK−1m−1 at 473 K) produced higher ZT at T ≥ 423 K than Bi2Te3, reaching about 0.66 at 473 K. At the same time, the bipolar conduction was reduced due to the enlarged band gap of about 0.22 eV, which was estimated from the S-T curve. After additional hot deformation at 793 K, undoped Bi2Te2S shows remarkably improved values of power factor (PFmax = 2.62 mW K−2m−1 at 323 K) and ZT (ZTmax = 0.86 at 473 K), which was ascribed to increased carrier concentration. In addition, the highly anisotropic transport properties of Bi2Te2S were suggested to be another origin, which was revealed by the first-principles calculations. In summary, Bi2Te2S is a promising candidate for thermoelectric generation at the intermediate temperature region 473–573 K where Bi2Te3 shows degraded performances.

The gold-bearing deposits of southeastern East Sayan have been categorized according to mineral composition. The most important classification criterion is the composition of productive ore mineral assemblages specific to each of the distinguished types, whereas the use of other criteria results in the inevitable overlap of different structural, compositional, or genetic features of deposits. Eight mineral types of deposits have been determined, which characterize the main gold-bearing mineral ore parageneses: gold-polysulfide, gold-quartz, gold-telluride, gold-tetradymite, gold-antimony, gold-bismuth-sulfosalt, gold-pyrrhotite, and gold-fahlore. The regional metallogenic units are structural-metallogenic zones somewhat differing by the nature of mineralization. Thus, in the Bokson-Gargan metallogenic zone, the gold-quartz, gold-polysulfide, and gold-pyrrhotite types of deposits prevail, while in the western part of the zone, the gold-telluride and gold-bismuth-sulfosalt types are widespread. In the Ilchir zone, gold-fahlore deposits are developed, while in the Khamsarinskaya zone, gold-tetradymite and gold-stibnite. It has been established that the mineral types of deposits depend on the composition of the host rock complexes: gold-quartz, gold-polysulfide, and gold-pyrrhotite types form in association with ophiolites and Archean basement rocks. At granitoid-massif-related deposits, base-metal minerals assume the leading role: Bi sulfosalts, stibnite, tetradymite, and tellurides. The gold-fahlore type forms in carbonate sequences. The proposed classification makes it possible to group all of the known gold-bearing deposits of southeastern East Sayan; it can also be applied to adjacent regions.

Polycrystalline thermoelectric elements of n-type Bi2(Te0.95Se0.05)3 and p-type (Bi0.25Sb0.75)2Te3 were fabricated by modified Bridgman technique, followed by electrospark cutting. A thermoelectric micromodule, consisting of 12 legs with an Ni anti-diffusion barrier and high-temperature SnSb solder between them, was assembled. To investigate thermoelements under conditions close to operating ones, the micromodule was annealed at 443 K for 1000 h. It was revealed that after annealing for more than 40 h, the near-contact zone of the n-type legs degraded, leading to a complete break of the micromodule junctions. Our results revealed that during annealing, the SnSb solder flowed into the unprotected side surface of the legs, and contacted with the cleavage planes along which tin can diffuse into the thermoelement volume. In contrast, the p-type legs were not affected by the contact with the solder. Different impacts of the solder on n- and p-type legs were explained in the framework of density functional theory (DFT) calculations. Substitution, diffusion and thermodynamic stability calculations showed that Bi to Sn substitution is energetically more beneficial than Sb to Sn substitution. Additionally, it was calculated that for the Bi2Te3 + Sn system, it is more beneficial to form a TeSn and Bi phase, while an Sb2Te3 + Sn system is thermodynamically stable.

Native aluminum was discovered in 2004 at Hochwurten, Goldberg mountain group, Upper Carinthia, Austria. The discovery site is close to the Wurtenkees (glacier), where the dominant rock (Central gneiss) was exposed during the retreat of the glacier. Here, also veins with gold-bearing ores associated with tellurides (tetradymite, tsumoite, joseite-A) and Ag–Pb–Bi-sulfosalts are exposed and were mined intermittently during the last centuries. Native aluminum occurs at some distance (several 100 m laterally and vertically) to the veins as an isolated crystalline aggregate measuring 10 × 3 mm, and a closely associated flake (200 µm length), which was used for most of the studies. Both occur on gneiss and are intensely intergrown with it. Two groups of inclusions in the aluminum were observed and studied by SEM and EPMA. Group one consists of Bi–Te–(S)–(O) minerals, such as tetradymite, Bi2Te2S, tsumoite, BiTe, tellurobismuthite, Bi2Te3, bismuth and a montanite-type secondary mineral. The other group contains a new phase with composition (Al,Si)19Fe4, rare grains of hollisterite (Al3Fe), and abundant Zn,Mg-bearing metallic nano-phases. A transition zone is developed between native aluminum and albite, a constituent of the gneiss, and is characterized by strongly changing concentrations of aluminum, silicon, iron and sulfur. Micro-computed tomography studies reveal that the Al metal is clearly intermixed with the host rock and not just juxtaposed over it. To shed further light on the origin of the Al metal, SIMS Mg isotopic measurements were carried out on the Austrian aluminum and on selected synthetic alloys with similar composition. A thorough discussion about the possible naturalness of this native aluminum and its possible formation is presented. The paper aims at augmenting the rare, assured knowledge of native metal formation/alteration under crustal and subcrustal conditions.

Актуальность исследования определяется необходимостью освещения новых данных по петрологии, геохимии субвулканических пород и эпитермальному Ag-Au оруденению Красноярского рудного поля Горного Алтая. С субвулканическими штоками гранитоидов пространственно и парагенетически связаны различные типы оруденения: меди, кобальта, мышьяка, вольфрама и золота. Впервые для Горного Алтая исследован высоко-серный тип Ag-Au оруденения. Цель исследования: изучить петрологические, геохимические особенности пород и оруденения Красноярского месторождения с использованием экспериментальных диаграмм, позволяющих выявлять генетические проблемы и физико-химические особенности петро-рудогенезиса. Методы исследования включали изучение состава горных пород с применением лазерно-абляционного анализа методом индуктивно-связанной плазмы на спектрометре «ОРTIMA&4300» с высокой чувствительностью определения элементов в Лаборатории Института минералогии, геохимии и кристаллохимии редких элементов (г. Москва). Изотопный состав серы и кислорода определён на масс-спектрометре МИ 1201В в той же лаборатории. Результаты. Главными рудогенерирующими объектами в Красноярском рудном поле являются субвулканические штоки гранитоидов среднего девона коргонского комплекса, которые относятся к пералюминиевому типу с варьирующими характеристиками по магнию и железу. В породах проявлен тетрадный эффект фракционирования РЗЭ W-типа. Концентрации Au и Ag в породах увеличиваются с уменьшением величины тетрадного эффекта фракционирования РЗЭ W-типа. Глубинный магматический очаг эволюционировал в сторону повышения его уровня с формированием резко кислотно-серных характеристик и формированием околорудных аргиллизитов. Оруденение Красноярского месторождения представлено серией сближенных кварцевых жил, с образованием своеобразного линейного штокверка. Руды сформированы в три стадии: существенно сульфидную, теллуридную и пострудную. Основные рудные минералы: пирит, галенит, сфалерит, тетраэдрит, теннантит, электрум, тетрадимит, редко – алтаит, гессит, энаргит, люцонит. Основные жильные минералы: кварц, кальцит, хлорит, сидерит, каолинит, монтмориллонит, иллит. Концентрации золота в рудах варьируют от 0,5 до 29,6 г/т, серебра – от 15 до 5000 г/т. Соотношение Ag/Au в рудах варьирует от 135 до 150 и позволяет относить Красноярское месторождение к Ag-Au типу. Температуры гомогенизации газово-жидких включений в кварце разных генераций от стадии к стадии снижались от 265 до 175 °С. Фугитивность серы снижалась от первой стадии (–10–11) ко второй (–15–16), f Te2 повышалась от (–15) до (–10) и f О2 от (–39,5) до (–37). Изотопы серы и кислорода свидетельствуют о магматогенном источнике серы и метеорном – кислорода.

We report the observation of a non-trivial spin texture in Dirac node arcs, novel topological objects formed when Dirac cones of massless particles extend along an open one-dimensional line in momentum space. We find that such states are present in all the compounds of the tetradymite M$_2$Te$_2$X family (M$=$Ti, Zr or Hf and X$=$P or As), regardless of the weak or strong character of the topological invariant. The Dirac node arcs in tetradymites are thus the simplest possible, textbook example, of a type-I Dirac system with a single spin-polarized node arc., Main Text + Supplementary Information, 12 pages, 11 figures

Three-dimensional topological insulators are exotic materials with unique properties. Tetradymite type binary chalcogenides of bismuth and antimony, as well as their mixed crystals, belong to prototypical TIs. Potential device applications of these materials require in-depth knowledge of their stability in the ambient atmosphere and other media maintained during their processing. Here we investigated the reactivity of mixed crystals with anion substitution, Bi2(Se1-xTex)3 and Sb2(Se1-xTex)3, towards molecular oxygen using both in situ and ex situ X-ray photoelectron spectroscopy. The results indicate that, in contrast to cation substitution, partial substitution of tellurium by selenium atoms leads to anomalously high surface reactivity, which even exceeds that of the most reactive binary constituent. We attribute this effect to anion ordering that essentially modifies the bond geometry, especially the respective bond angles as modeled by DFT.

Gold-associated pathfinder minerals have been investigated by identifying host minerals of Au for samples collected from an artisanal mining site near a potential gold mine (Kubi Gold Project) in Dunkwa-On-Offin in the central region of Ghana. We find that for each composition of Au powder (impure) and the residual black hematite/magnetite sand that remains after gold panning, there is a unique set of associated diverse indicator minerals. These indicator minerals are identified as SiO2 (quartz), Fe3O4 (magnetite), and Fe2O3 (hematite), while contributions from pyrite, arsenopyrites, iridosmine, scheelite, tetradymite, garnet, gypsum, and other sulfate materials are insignificant. This constitutes a confirmative identification of Au pathfinding minerals in this particular mineralogical area. The findings suggest that X-ray diffraction could also be applied in other mineralogical sites to aid in identifying indicator minerals of Au and the location of ore bodies at reduced environmental and exploration costs., Comment: 16 pages, 6 figures, 3 tables

We report $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{NMR}$ measurements in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}:\mathrm{Ca}$ and ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}:\mathrm{Mn}$ single crystals using $^{8}\mathrm{Li}^{+}$ implanted to depths on the order of 100 nm. Above $\ensuremath{\sim}200\phantom{\rule{4pt}{0ex}}\mathrm{K}$, spin-lattice relaxation reveals diffusion of $^{8}\mathrm{Li}^{+}$, with activation energies of $\ensuremath{\sim}0.4\phantom{\rule{4pt}{0ex}}\mathrm{eV}$ $(\ensuremath{\sim}0.2\phantom{\rule{4pt}{0ex}}\mathrm{eV})$ in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}:\mathrm{Ca}$ $({\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}:\mathrm{Mn})$. At lower temperatures, the NMR properties are those of a heavily doped semiconductor in the metallic limit, with Korringa relaxation and a small, negative, temperature-dependent Knight shift in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}:\mathrm{Ca}$. From this, we make a detailed comparison with the isostructural tetradymite ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}\mathrm{Se}$ [McFadden et al., Phys. Rev. B 99, 125201 (2019)]. In the magnetic ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}:\mathrm{Mn}$, the effects of the dilute Mn moments predominate, but remarkably the $^{8}\mathrm{Li}^{+}$ signal is not wiped out through the magnetic transition at 13 K, with a prominent critical peak in the spin-lattice relaxation that is suppressed in a high applied field. This detailed characterization of the $^{8}\mathrm{Li}^{+}$ NMR response is an important step toward using depth-resolved $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{NMR}$ to study the low-energy properties of the chiral topological surface state in the ${\mathrm{Bi}}_{2}{\mathrm{Ch}}_{3}$ tetradymite topological insulator.

Due to the very limited quantity of associated tetradymite, both mineralogical and geochemical research on tetradymite is scarce and incomplete. By taking advantage of the discovery of the Dashuigou tellurium deposit in Tibet Plateau, the authors conducted mineralogical studies on tetradymite. The authors present new mineralogical data including reflectance, micro-pressure hardness, chemical compositions focusing on its chemical formula Bi2.00Te1.89S0.95~1.00, unit cell parameters (a = 4.239 Å, c = 29.595 Å) and lattice parameters (a = 10.172 Å, v = 154.391 Å3), pyroelectricity (N type), and stable isotopes including sulfur and lead. The authors find that: δ34S‰ of tetradymite varies between −0.5~2.1 with a 15-sample average of 0.56, similar to that of meteorites and rocks from the mantle, indicating that the sulfur is from the mantle; lead isotopes of the tetradymite formed in the late metallogenic epoch is different from that of both pyrite and pyrrhotite formed in the early metallogenic epoch, further indicating that the three minerals formed in different metallogenic epochs; lead isotope compositions reveal that tellurium ore bodies emplaced in a quick process mainly in the form of ore magma; lead of the deposit is primarily from the mantle with some captured from the Earth’s crust. These findings help fill in large gaps of information for the mineral tetradymite.

The phase equilibria of the Ag–Ge–Sb–Te system in the part Ag8GeTe6–Ge–GeTe–Sb2Te3 were investigated by the electromotive force (EMF) method. The determined phase relations were used to express the chemical reactions. The potential-forming reactions were performed by applying electrochemical cells (−) C | Ag | Ag2GeS3-glass | D | C (+), where C is graphite, Ag2GeS3-glass is the fast purely Ag+ ions conducting electrolyte, and D is an equilibrium mixture of phases. According to the experimental data on the EMF versus temperature of each electrochemical cells, analytical equations for the Gibbs energies of GeSb8Te13, GeSb6Te10, GeSb4Te7, GeSb2Te4, Ge2Sb2Te5, Ge3Sb2Te6, and Ge4Sb2Te7 compounds were obtained. The thermodynamic properties of silver-saturated tetradymite-like compounds have been calculated for the first time. A good correspondence between experimental values and structure data reported in the literature has been established.

Phase-pure crystalline Bi2Se3 and Bi2Te3 nanoparticles are formed in reactions of [C4C1Im]3[Bi3I12] (C4C1Im = 1-butyl-3-methylimidazolium) with [C4C1Pyr][ESiMe3] (E = Se or Te; C4C1Pyr = 1-butyl-1-...

Coupled dissolution–reprecipitation (CDR) reactions and low-melting point chalcophile elements (LMCE) melt scavenging are effective mechanisms for gold remobilization and are important for the formation of Te-Au deposits. The Dabaiyang deposit is a typical Te-Au deposit in the Zhangjiakou district and contains tellurides, including altaite, hessite, petzite, tetradymite and tellurobismuthite. Two generations of pyrite have been recognized in the deposit: early pyrite without fractures or alteration (Py1) and later pyrite with more porosity, inclusions and fractures (Py2), and Py2 could be separated into Py2a that containing many fractures without mineral inclusions and Py2b that containing microfractures, micropores and mineral inclusions. Pyrite containing large amounts of mineral inclusions and free of microfractures (Py-MI) has also been recognized, but timing relationships between Py-MI and Py1 (or Py2) is hard to establish. The Pyrite textures indicate that Py2a underwent brittle deformation and that Py2b underwent CDR reactions and Te-melt scavenging. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses show that Py2a contains trace elements similar to Py1, while Py2b contains higher Au, Ag, Te and other trace elements, indicating that brittle fracturing has no effect on element mobilization and reprecipitation, and porous pyrite has Au-Ag-Te concentrations. High Co/Ni ratios and Te contents and low Se contents show that the Dabaiyang deposit has a genetic relationship with magmatic activity. In situ δ34S values of sulfides range from -15.77‰ to -6.09‰ (mostly from -13.89 to -10.06‰), which is consistent with bulk sulfide δ34S values. The negative δ34S values more likely resulted from sulfur isotope fractionation in high fO2 hydrothermal fluids. CDR reactions liberated Au, Te, Ag and other trace elements from pyrite and formed porous textures. Then, Te-rich melts scavenged Au from fluid and wallrocks during migration. Finally, the melt precipitated as mineral inclusions in pores or fractures in pyrite. CDR reactions and LMCE melt scavenging played an important role in upgrading the ores and the occurrence of visible native gold in the Dabaiyang gold deposit, as well as other Te-Au deposits in the Zhangjiakou district.

Thermoelectric effects are one of the promising ways to utilize waste heat. Novel approaches have appeared in recent decades aiming to enhance thermoelectric conversion. The theory of energy filtering of free carriers by inclusions is among the latest developed methods. Although the basic idea is clear, experimental evidence of this phenomenon is rare. Based on this concept, we searched suitable systems with stable structures showing energy filtering. Here, we report on the anomalous behavior of Cr-doped single-crystal Bi2Se3 that indicates energy filtering. The solubility of chromium in Bi2Se3 was studied, which is the key parameter in the formation process of inclusions. We present recent results on the effect of Cr-doping on the transport coefficients on a wide set of single crystalline samples. Magnetic measurements were used to corroborate the conclusions drawn from the transport and X-ray measurements.

In the gold placers of the Subpolar Urals, silver nuggets have been found for the first time. Galena, cassiterite, wolframite, cosalite, tetradymite, ferberite, cobaltine, tellurojoseite, and native bismuth are associated with silver. The silver is generally represented by subrounded and angular gray particles of up to 2–2.5 cm in size. The particles have a lumpy, slightly flattered, elongated shape. Sometimes, Au and Hg admixtures are detected in the composition of the silver. Inclusions of fine particles of gold and mineral phases of bismuth and tellurium are encountered. The results of studies show the widespread development of Au–Ag–Bi–Te mineralization, original occurrences of which are currently unknown. The relatively poor roundness of the silver nuggets and the presence of the coarse-grained gold, which is also poorly rounded, point to the proximity of the original sources to the gold-bearing placers.

The Laowan Au − Ag − Te deposit (containing greater than 100 t Au), located at the center of the Qinling − Dabie orogenic belt in central China, represents a breakthrough in gold prospecting in the Tongbai district. A tunnel geological survey and microscope-based mineral identification, combined with EMPA/EDS mapping and LA-ICP-MS analysis, were used in this study to determine the mineral types present. The sequence of formation and symbiosis were determined using the Au-hosting mineral geochemical element typomorphism to provide a basis for Au enrichment and the sources of material and ore − forming fluids. The results indicate that: (1) Tellurides were widespread in the main metallogenic auriferous pyrites, consisting of petzite, calaverite, tellurobismuthite, tetradymite, volynskite, and hessite. The vertical zonation of different telluride combinations indicates that mineral distribution shows the vertical zoning characteristics of upper Ag and lower Bi. (2) Petrographic analyses indicate that 5 generations of pyrite formed during the ore-forming stage (Py1, Py2, Py3, Py4, and Py5). LA-ICP-MS analytical data showed that Py3 and Py4 were rich in Au − Ag − Bi − Te, with a correlation between gold and tellurium. Auriferous pyrites were rich in both As and Te, and the enrichment of Au was unrelated to As. Te is an important scavenger of gold, the effect of As is not obvious. (3) From 250 °C to 200 °C, logfTe2 and logfS2 decreased from − 13.0 to − 8.3 and − 14.7 to − 8.6 to − 15.2 to − 11.2 and − 16.7 to − 10.5, respectively. fTe2, fS2 and temperature were the conditions controlling variations in the telluride combination. (4) The occurrence of tellurides, the correlation of Au − Ag − Bi − Te elements and enrichment of Te and Bi, combined with previous isotopic geochemical data, indicate that the ore-forming fluids and metals might be stemmed from the mantle-derived magmatic system, which could have provided materials, sufficient heat energy, volatiles, and components for the gold mineralisation.

The newly discovered Anfangba gold deposit is hosted in the Middle Triassic pumpellyite-actinolite facies metamorphosed turbidites in the western Qinling Orogen, Central China. It is characterized by a pyrite-quartz vein type, a medium-high temperature, and the development of visible gold and abundant bismuthides. It is the first reported Au-Bi-associated deposit in this area and remains poorly understood. In this study, the mineral paragenesis has been studied to further understand ore formation, including sulfides (pyrite, chalcopyrite, pyrrhotite, bornite, bismuthinite, tetrahedrite and arsenopyrite), Cu-Bi(Sb) sulfosalts (emplectite, wittichenite, and skinnerite), sulfoselenide (unnamed sulpho-tellurian nevskite), tetradymite group minerals (joseite-A, joseite-B and tetradymite), native bismuth and electrum. The physicochemical conditions of the ore-forming process can be estimated based on the mineral paragenetic sequence. The calculated logαH2S and logfO2 of the main mineralization stage are higher than −2.25 and lower than −37.96, respectively. EPMA mapping indicated that ore-forming fluid with low sulfur and oxygen fugacities may have played an important role in provoking the activity of the semimetals such as Bi, Sb, Se and Te. This may have result in the formation of accessory minerals, including native bismuth, skinnerite and an unnamed sulpho-tellurian nevskite via coupled dissolution-reprecipitation (CDR) reactions. Mineralography, EPMA and LA-ICP-MS analysis have revealed a close relationship between Au mineralization and Bi-blebs. It suggests that the “liquid bismuth collector model” contributed to the Au enrichment of the Anfangba deposit. As the coexistence of native bismuth and bismuthinite is commonly seen in different types of hydrothermal gold deposits, the presence of Bi-melts and the influence of the “liquid bismuth collector model” in these gold deposits may have been underestimated.

The Shuangqishan gold deposit is the largest gold deposit in the Dehua ore cluster of Fujian Province. The gold orebodies are located in the metamorphic rock of Neoproterozoic Daling Formation. Representative genetic models of Shuangqishan gold deposit include epithermal gold deposit, orogenic gold deposit and granitoid-related gold deposit. Based on the comprehensive research of pyrite Rb-Sr geochronology, telluride mineralogy and pyrite LA-ICP-MS trace element, we intend to discuss the genesis of the Shuangqishan gold deposit. The Rb-Sr isotopic dating of gold-bearing pyrite indicates that mineralization age of the Shuangqishan gold deposit is 153.5 ± 2.4 Ma, which is the same as that of the granite porphyry dyke (zircon U-Pb age = 153.4 ± 1.2 Ma) in the mining area. The main gold-bearing mineral is native gold, with a fineness of >920, additional gold-bearing mineral is electrum, with a fineness of 677 ~ 741. The gold-bearing polymetallic sulphide quartz veins contain a large amount of tellurbimuth (Bi2Te3), rucklidgeite (PbBi2Te4) and tetradymite (Bi2Te2S). The Shuangqishan gold deposit’s characteristic combination of Au-Bi-Te elements is analogous to that of typical magmatic-hydrothermal deposit. The estimated log f Te2 versus log f S2 conditions of telluride mineralization at 250 °C are –13.0 ~ –9.5, –14.7 ~ –10.5, respectively. LA-ICP-MS trace element analysis of gold-bearing pyrite shows that the pyrite is As-poor and has high content of Te, Bi, Pb, Co and Ni, but has low content of Au and As. The typical As-poor pyrite indicates that the Shuangqishan gold deposit is the magmatic hydrothermal gold deposit. Te displays a high positive correlation with Bi and Pb, indicating that Te, Bi and Pb occur as Bi-telluride micro-inclusion in pyrite. Our research shows that the Shuangqishan gold deposit is the magmatic hydrothermal gold deposit formed in the late Jurassic.

Unlike tremendous works on the electronic structures of tetradymite compounds, studies of their thermal properties are relatively rare. Here, first-principles calculations and Boltzmann theory are combined to investigate the phonon transport of such kind of layered materials. Using four binary tetradymites as prototypical examples, it is interesting to find that the weak van der Waals (vdW) interactions play an important role in determining their lattice thermal conductivities, which are obviously higher than those without the consideration of vdW, especially for the out-of-plane direction. In principle, such enhanced phonon transport can be attributed to the decreased interlayer spacing caused by the presence of vdW, which effectively reduces the strong anharmonicity of the systems. Indeed, we observe relatively smaller Grüneisen parameter together with larger phonon group velocity and relaxation time. Our theoretical work demonstrates the vital importance of the seemingly weak vdW forces in predicting the phonon transport properties of various layered structures.

Tetradymite-type Bi2Se3 is synthesised via a solid-state method, and its phase evolution in Li, Na and K half-cells is experimentally investigated. Ex-situ X-ray diffraction data is analysed with the Rietveld method, indicating intercalation, conversion and alloying reactions for all systems. Direct evidence of alloying is observed in the cases of the Li and Na systems while alloying is inferred for the K system. In addition, a preliminary study of the performance of Bi2Se3 as an electrode material for rechargeable Li, Na and K-half cells is undertaken. High initial capacities of 560, 680 and 1000 mAh/g for Li, Na and K respectively are observed. However, capacity fade is severe in all cases, with 10th cycle capacity decreases of 68%, 79% and 90% respectively. This poor cyclability is likely attributable to the large volume changes that accompany the conversion and alloying reactions. Finally, the magnetic properties of the resultant intercalated materials are investigated. Li intercalation induces a divergence between zero-field cooled and field cooled curves below 150 ​K, whereas Na and K intercalation do not have significant effects on the observed magnetic properties.

Tetradymite-type Sb2Te3 is synthesised via a solid-state method, and its electrochemical phase evolution in Li, Na and K half-cells is experimentally investigated. Ex-situ X-ray diffraction data is analysed with the Rietveld method, revealing the occurrence of conversion reactions for all systems. Direct evidence of alloying and intercalation reactions is observed in the case of the Li system, while alloying is inferred for the K and Na systems. For the first time, Li intercalated Sb2Te3 is synthesised and a preliminary investigation of its magnetic properties is undertaken. Li intercalation does not significantly influence the magnetic phase transition temperature and does not appear to induce superconductivity. In addition, a preliminary study of the performance of Sb2Te3 as an electrode material for rechargeable Li, Na and K-half cells is undertaken. High initial capacities of 588, 521 and 906 mAh/g for Li, Na and K cells respectively are observed. However, capacity fade is rapid in all cases, with second discharge capacities dropping to 396, 173 and 98 mAh/g. This poor cyclability is generally associated with the large volume changes and irreversibilities associated with the conversion and alloying reactions. The capacities continue to decrease during extended cycling, with tenth cycle discharge capacities of 195, 26 and 24 mAh/g for Li, Na and K half cells respectively.

Based on first-principles calculations and symmetry arguments, we reveal that the non-centrosymmetric ternary tetradymite BiSbTe3 possesses exotic dual topological features of Weyl semimetallic phases with Z 2 index (1:000). The results show that the helical Dirac-type surface states protected by the time-reversal symmetry are present in the vicinity of the Brillouin zone center, which is consistent with the experimental report. Furthermore, we show that four pairs of Weyl points reside exactly at the Fermi level, which are guaranteed to be located on high-symmetry planes due to mirror symmetries. The helical surface states and the projected Weyl nodes are well separated in the momentum space, facilitating their observations in experiments. This work not only uncovers a unique quantum phenomenon with dual topological features in the tetradymite family but also paves a fascinating avenue for exploring the coexistence of multi-topological states with wide applications.

Despite the ubiquitous nature of the Peltier effect in low-dimensional thermoelectric devices, the influence of finite temperature on the electronic structure and transport in the Dirac heterointerfaces of the few-layer graphene and layered tetradymite, Sb2Te3 (which coincidently have excellent thermoelectric properties) are not well understood. In this work, using the first-principles density-functional theory calculations, we investigate the detailed atomic and electronic structure of these Dirac heterointerfaces of graphene and Sb2Te3 and further re-examine the effect of finite temperature on the electronic band structures using a phenomenological temperature-broadening model based on Fermi–Dirac statistics. We then proceed to understand the underlying charge redistribution process in this Dirac heterointerfaces and through solving the Boltzmann transport equation, we present the theoretical evidence of electron–hole asymmetry in its electrical conductivity as a consequence of this charge redistributio...

The Hall coefficient, resistivity, and thermoelectric power of quaternary tetradymite-like layered materials in the pseudoternary system Sb2Te3–GeTe–Bi2Te3 have been measured in the temperature range 100–800 K. The results demonstrate that all of the samples studied in the Sb2Te3–GeTe–Bi2Te3 system are p-type and have high hole concentration due to point defects. Plots of lnσ against 1/T in the intrinsic region were used to evaluate the band gap (ΔE) of two materials: GeSb3.91Bi0.03Te6.91(ΔE = 0.22 eV) and GeSbBiTe4 (ΔE = 0.197 eV).

The 1.89 Ga Valimaki massif is located in the northern Lake Ladoga area (Priladozhje). It is differentiated from wehrlites and pyroxenites to highly alkaline gabbro and diorites. Ilmenite-titanomagnetite ores confined to the pyroxenite portion of the massif form several bodies worked out as early as the 19th – early 20th century. High-grade titanomagnetite ores typically contain high concentrations of TiO2 (2.4–6.4 %), V2O5 (0.54–0.8 %) and MnO (0.16–0.3 %). Titanomagnetite with ilmenite disintegration lamellae contains 0.6–1 % V; Mn concentration in ilmenite is 1–1.87 % in the ores and up to 4.65– 6 % in disseminated mineralization in gabbro-diorites. Ores with disseminated-veinlet Cu-S-mineralization were found to contain noble metals such as Au, Pt and Pd (total concentration 0.3–1 g/t). Sulphides are represented by chalcopyrite and pyrite; sphalerite (Fe 6–9 %), pyrrhotite, argentopentlandite, galena, Se-galena, molybdenite, cobaltite and Ag-Bi-Te phases (hessite, stutzite, tellurobismuthite and tetradymite) are common. Minerals Pd and Pt – michenerite, froodite, merenskyite, Rh-sperrylite, and electrum, were revealed in the Valimaki massif for the first time.

We report thermoelectric transport properties of Pb 1- x Sn x Bi 2 Te 4 ( x = 0, 0.25, 0.5, 0.75 and 1) compounds. They exhibited n -type conduction behavior up to x = 0.5, while it changed to p -type due to the explosive hole generation at relatively high Sn contents. Their complicated charge transport behavior was interpreted by high-temperature Hall measurements and also by the first-principles calculation based on Boltzmann transport equation. Effects of the Sn content on the density of state (DOS) effective mass was investigated, and its relation to the observed Seebeck coefficients and power factors of the compounds has been explained.

Tellurides have been identified in VMS mineralization at Yuinmery and Austin in the Archean Youanmi Terrane, Yilgarn Craton, Western Australia. Tellurides identified at Yuinmery include: petzite, stutzite, hessite, tellurobismuthite, altaite, rucklidgeite, melonite, mattagamite and a nickel-cobalt telluride with chemical composition similar to cobaltian melonite which has previously only been reported once before. Tellurides and related minerals identified at Austin include: stutzite, volynskite, tellurobismuthite, tetradymite, tsumoite, rucklidgeite, altaite and a mineral with the formula (Bi,Pb)3(Te,Se,S)4 corresponding to the rare mineral poubaite. The tellurides are interpreted to have been deposited with the base metals on and immediately below the sea floor by very hot fluids during a period of quiescence in the volcanism. The mineral assemblage suggests that the fluids in both areas had high ƒTe2 and were oxidising but close to the pyrrhotite-pyrite boundary. The presence of Ni and Co tellurides at Yuinmery but not at Austin is probably due to the derivation of the fluids at Yuinmery from mafic volcanism whereas at Austin the succession is dominantly felsic. The metamorphic grade at Austin is higher than that at Yuinmery and this may have resulted in some re-crystallization of tellurides and tellurosulfides.

An occurrence of vein U-Mo mineralization is located in the Majerská valley near Čučma, about 7 km to the NNE of the district town of Rožňava (Eastern Slovakia). Mineralization is hosted in the acidic metapyroclastics of the Silurian Bystrý Potok Fm. (Gemeric Unit), and originated in the following stages: (I.) quartz I, fluorapatite I, (II.) quartz II, fluorapatite II, zircon, rutile chlorite, tourmaline, (III.) uraninite, molybdenite, U-Ti oxides, (IV.) pyrite I, ullmannite, gersdorffite, cobaltite, (Va.) galena, bismuth, tetradymite, joséite A and B, Bi3(TeS)2 mineral phase, (BiPb)(TeS) mineral phase, ikunolite, (Vb.) minerals of the kobellite–tintinaite series, cosalite, (VI.) pyrite II, (VII.) titanite, chlorite, and (VIII.) supergene mineral phases. The chemical in-situ electron-microprobe U-Pb dating of uraninite from a studied vein yielded an average age of around 265 Ma, corresponding to the Guadalupian Epoch of Permian, the obtained data corresponds with the age of Gemeric S-type granites. The age correlation of uraninite with the Gemeric S-type granites and the spatial connection of the studied mineralization with the Čučma granite allows us to assume that it is a Hercynian, granite-related (perigranitic) mineralization.

The Qiyugou gold deposit, located in the Xiong’ ershan area of the North China Craton, contains abundant bismuth-sulfosalts that are closely associated with gold mineralization. Pyrite is the dominant Au-hosted mineral, and has been formed in three generations (Py1, Py2, and Py3). Py1 grains, generally intergrown with milky quartz, are coarse (>1 mm), euhedral in shape, and Au-depleted in composition. In contrast, subhedral Py2 grains, associated with light gray quartz, are medium to coarse (0.2–3 mm) and are enriched in gold that is both invisible and visible. Py3 grains (0.1–0.5 mm), intergrown with abundant sulfide minerals, are relatively fine and Au-depleted. The time-resolved LA-ICP-MS depth profiles of the Py2 grains indicate that invisible gold occurs as either solid solution or nano-particles of native gold and electrum. Visible gold occurs as small blebs in the Py2 grains where inclusions of native bismuth , galenobismutite, lillianite homologs, tetradymite, and galena are also present. In addition, it is common that electrum in microfracture infillings or along grain boundaries of the Py1 and Py2, are intergrown with bismuthinite derivatives, Bi-Cu sulfosalts , emplectite, tetradymite, chalcopyrite , galena, and Py3. Based on textural relationships and mineral assemblages, calculation of physicochemical conditions show that gold was formed in conditions of fTe2 = ~10−11 and fS2 = ~10−11 to 10−12 for Py2, and fTe2 = ~10−9 to 10-11and fS2 = ~10−10 to 10−11 for Py3. We thus proposed that such physicochemical conditions may have triggered the precipitation of Bi melt, and sulfidation driven by cooling or increase in sulfur content results in the transformation of the Au-Bi liquid into a stable assemblage of native gold and bismuthinite. These bismuth minerals are associated with native gold/Au-bearing minerals, indicating that the Au mineralization of the Qiyugou gold deposit might be genetically associated with Bi melt. The present study highlights the role of Bi as important gold scavengers in arsenic-deficient ore-forming fluid.

Thin Bi2Se3 layers are promising material for many optical and optoelectronic applications. In this work, thin crystalline layers of Bi2-chalcogenides were deposited on highly cleaned glass substrates by vacuum thermal evaporation technique. The optical properties of the concerned layers were investigated with ultraviolet–visible-near infra-red (UV–Vis–NIR) spectra. The effect of thickness reduction and the annealing treatment have been studied. Thinning the film to few nanometers resulted in a significant enhancement of light transmission through the prepared materials. Also, simultaneous reduction of layer's thickness and annealing treatment significantly improved the optical transmission. Such transmissivity enhancement opens avenues for transparent electrode applications.

We report crystal growth and Raman spectroscopy characterization of pure and mixed bulk topological insulators. The series comprises of both binary and ternary tetradymite topological insulators. We analyzed in detail the Raman peaks of vibrational modes as out of plane Ag, and in plane Eg for both binary and ternary tetradymite topological insulators. Both out of plane Ag exhibit obvious atomic size dependent peak shifts and the effect is much lesser for the former than the latter. The situation is rather interesting for in plane Eg, which not only shows the shift but rather a broader hump like structure. The de convolution of the same show two clear peaks, which are understood in terms of the presence of separate in plane BiSe and BiTe modes in mixed tetradymite topological insulators. Summarily, various Raman modes of well-characterized pure and mixed topological insulator single crystals are reported and discussed in this article., Comment: 17 Pages Text + Figs

Chemical composition and mode of occurrences of (Au, Ag)Te2 minerals such as calaverite (AuTe2), sylvanite (AuAgTe4) and krennerite ((Au, Ag)Te2) in epithermal gold telluride ores from Suzaki, Kawazu and Teine are examined. In the ores from Suzaki, (Au, Ag)Te2 minerals occur in microbands of tellurides and fine quartz. The minerals in telluride bands change from krennerite, via calaverite-native tellurium, to sylvanite, in the order of crystallization. A sample from Kawazu contains sylvanite and native tellurium with stutzite, hessite and tetradymite in the coarser gray quartz part. The Teine sample also contains sylvanite and native tellurium with barite and quartz. The peak patterns of XRD of calaverite, krennerite and sylvanite from Suzaki are almost identical to that of JCPDS 43–1472, JCPDS 8–20 and JCPDS 9–477, respectively. The Te, Au, Cu, and Ag contents of calaverite from Suzaki range from 56.4 to 57.9 wt.%, from 41.6 to 42.6 wt.%, from 0.28 to 0.45 wt.% and from 0.14 to 0.31 wt.%, respectively, corresponding to the formula Au0.97Ag0.01Cu0.02Te2. The Te, Au, Ag, and Cu contents of krennerite from Suzaki range from 59.6 to 61.4 wt.%, from 31.3 to 33.6 wt.%, from 4.91 to 6.13 wt.% and from 0.66 to 0.80 wt.%, respectively, corresponding to the formula Au0.71Ag0.22Cu0.05Te2 with Au and Ag ranging from 0.68 to 0.74 and from 0.20 to 0.25, respectively. The Te, Au, Ag, and Cu contents of sylvanite from Suzaki range from 61.5 to 63.4 wt.%, from 24.1 to 27.4 wt.%, from 10.0 to 12.5 wt.% and from 0.00 to 0.12 wt.%, respectively. The Te, Au, Ag, and Cu contents of sylvanite from Kawazu range from 62.7 to 63.3 wt.%, from 23.5 to 24.1 wt.%, from 12.0 to 12.5 wt.% and from 0.09 to 0.16 wt.%, respectively. The Te, Au, Ag, Cu and Fe contents of sylvanite from Teine range from 61.8 to 63.5 wt.%, from 23.6 to 24.7 wt.%, from 11.9 to 13.3 wt.%, from 0.01 to 1.65 wt.% and from 0.00 to 0.02 wt.%, respectively. The average formulae of sylvanite from Suzaki, Kawazu, and Teine are expressed as Au1.06Ag0.94Cu0.02Te4, Au1.00Ag0.95Cu0.02Te4 and Au1.01Ag0.95Cu0.06Te4, respectively. Judging from the mineral assemblages of these ores and other localities, Au–Te mineralization in the Japanese Islands can be divided into four types: native gold–calaverite at Date and Agawa, krennerite(−native tellurium) at Osore-zan and Mutsu, sylvanite–native tellurium–hessite at Teine, Kawazu, Kobetsuzawa, and Kato, and polyminerallic assemblages at Suzaki and Kushikino. The pH–Eh diagram of aqueous tellurium species and tellurium minerals at 250°C indicates that (Au, Ag)Te2 minerals in epithermal gold telluride mineralization would have been formed under middle to low Eh and acidic (to intermediate) pH conditions. It is possible that dilute tellurium-containing fluid would scavenge dilute gold.

The low energy band structure near the band gap determines the electrical performance of thermoelectric materials. Here, by using the hybrid-density functional theory (hybrid-DFT) calculations, we calculate the low energy band structure of Bi2Te3, Sb2Te3, Bi2Se3 and Sb2Se3 in tetradymite phase. We find that the band structure characteristics are very sensitive the selection of the exchange energy functional. The predictability of the band gaps and band degeneracies is not enhanced in hybrid-DFT calculations, as compared to DFT calculations. The poor prediction of low energy band structures is originated from the poor prediction of interlayer distances and the high structure sensitivity on the band gap. We conclude that the hybrid DFT calculations are not superior to DFT calculations when predicting band structures of tetradymite Bi2Te3, Sb2Te3, Bi2Se3 and Sb2Se3 thermoelectric materials., 11 pages, 2 tables, 0 figures

The Beiya deposit, located in the Sanjiang Tethyan tectonic domain (SW China), is the third largest Au deposit in China (323 t Au @ 2.47 g/t). As a porphyry-skarn deposit, Beiya is related to Cenozoic (Himalayan) alkaline porphyries. Abundant Bi-minerals have been recognized from both the porphyry- and skarn- ores, comprising bismuthinite, Bi–Cu sulfosalts (emplectite, wittichenite), Bi–Pb sulfosalts (galenobismutite, cosalite), Bi–Ag sulfosalt (matildite), Bi–Cu–Pb sulfosalts (bismuthinite derivatives), Bi–Pb–Ag sulfosalts (lillianite homologs, galena-matildite series), and Bi chalcogenides (tsumoite, the unnamed Bi 2 Te, the unnamed Ag 4 Bi 3 Te 3 , tetradymite, and the unnamed (Bi, Pb) 3 (Te, S) 4 ). Native bismuth and maldonite are also found in the skarn ores. The arsenopyrite geothermometer reveals that the porphyry Au mineralization took place at temperatures in the range of 350–450 °C and at log f S 2 in the range of − 8.0 to − 5.5, respectively. In contrast, the Beiya Bi-mineral assemblages indicate that the skarn ore-forming fluids had minimum temperatures of 230–175 °C (prevailing temperatures exceeding 271 °C) and fluctuating f S 2 – f Te 2 conditions. We also model a prolonged skarn Au mineralization history at Beiya, including at least two episodes of Bi melts scavenging Au. We thus suggest that this process was among the most effective Au-enrichment mechanisms at Beiya.