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Background. Some papers describing the deposits and prospects in the Baimka ore zone (Baimka Trend), the Chukotka Autonomous Region have been recently published. It should be noted that those publications concern with the large Peschanka porphyry copper-molybdenum-gold deposit and Nakhodka ore field. At the same time, some copper prospects were found at the zone flanks and their nature is not clear. There are no data available in the literature that would clarify the mineralogy of hydrothermal alteration and ores at those prospects, including Top and Luchik located at the northern flank. To understand the nature of these prospects, we studied in depth mineralogy of hydrothermal alteration and ores.Aim. This study aims to describe mineralogy of metasomatic rocks and ores from the Top and Luchik prospects in the northern part of the Baimka zone, Western Chukotka.Materials and methods. Several dozen polished thin sections were microscopic studied at the Department of Mineralogy of Moscow State University using an optical microscope. The chemical composition of minerals was determined using electron microprobe at the Laboratory of Analytical Techniques of High Spatial Resolution, Department of Petrology and Volcanology, Moscow State University.Results. It was found that propylitic is the major hydrothermal alteration at the prospects studied here. Metasomatic rocks are cut by mineralized quartz and carbonate-quartz veins. Chalcopyrite and pyrite are the major ore minerals; galena, sphalerite, pyrite enriched in As and Sb, and marcasite are minor; Hg-bearing tetrahedrite-(Zn), native gold with the fineness of ~830, petzite, hessite, and acanthite are rare.Conclusions. The data obtained suggest that mineralization at the Top and Luchik prospect is attributed to the epithermal intermediate sulfidation type. Considering the occurrence of the epithermal mineralization in the upper part of the hydrothermal column and the porphyry mineralization in the Baimka zone, the porphyry mineralization is possible at depth at the Top and Luchik prospects.

Gold and silver mineralogy is studied in ores of the Biksizak base-metal deposit (South Urals, Russia). This is a skarn-related carbonate replacement mineralization typical for marginal zones of porphyry-epithermal systems. The variability of precious metals minerals is established. Native gold (fineness 853 to 939) in assemblage with chalcopyrite and sphalerite is the most abundant. A telluride assemblage (tetradymite, hessite, stutzite, petzite, galena, tellurobismuthite, rucklidgeite, altaite and native gold with a fineness of 830–900) and a silver–pearceite–acanthite assemblage (acanthite/argentite, pearceite–polybasite and gold–silver alloy from native gold with fineness of 747 to native silver) are identified. It is shown the exhibited variability is controlled by decreasing the temperature and variations in the tellurium and sulfur fugacities.

Myanmar is endowed with a diverse array of metallic and nonmetallic mineral deposits, a number of which have recently been developed as world-class mines. Tagaung Taung deposit north of Mandalay is a resource approximately 40 km from Mandalay City. The Phayaung Taung gold deposit from the Slate Belt is hosted in phyllite, schist, and quartzite. Mineralization is associated with the stockwork quartz vein system. Wall-rock silicic alteration by cryptocrystalline quartz or amorphous silica is dominant. Phyllic alteration is characterized by sericite, quartz, chlorite, and pyrite with disseminated hematite. Gold occurs in tourmaline-quartz and sulfide-bearing quartz veins. It is associated with pyrite and chalcopyrite as well as Au-Ag-Bi-Te ore assemblages of petzite, hessite, and tellurobismuth. The Phayaung Taung gold deposit shows typical mesothermal characteristics. Scanning electron microscopy with energy-dispersive X-ray analyses revealed the average gold content of electrum grains, i.e., 75.1 wt% Au, with grain sizes ranging from 3 to 40 µm. Moreover, secondary native gold grains were formed with hematite and iron oxides in secondary remobilized/deformed veins at strongly brecciated/oxidized zones. The association between gold and altered sulfides suggests that gold was refractory in sulfides. It can be considered that supergene oxidation extended to deep mineralization veins. Such gold grains had the highest Au content, and are often in almost pure condition. This study discussed the geology, geochemistry, and mineralogy of the Phayaung Taung gold mine in Myanmar. New minerals were identified in the samples obtained from the study area, which were subjected to multiple analyses to determine their properties and understand the relationships between them.

Tellurium has a wide variety of applications, most importantly in the solar energy industry and is eco-toxicologically significant; however, the magmatic-hydrothermal processes causing the pronounced Te enrichment together with Au in some epithermal districts are still poorly constrained. Hydrothermal and alkaline magmatic activity in post-subduction environments are suggested to be a critical component in the evolution of this Te-rich sub-class of low-sulfidation epithermal deposits. Cripple Creek represents an example for a world-class low-sulfidation epithermal Au-Te anomaly in the continental crust. This area represents a natural laboratory to investigate the processes of ore-formation and Au-Te enrichment in alkaline igneous rock-hosted epithermal systems. Here, we present the first micro-analytical approach that combines petrographic observations with in situ LA-ICP-MS analyses and trace element mapping to define the key ore-forming processes of Au and Te in the Cripple Creek epithermal complex. Two main styles of mineralization can be distinguished: (1) low-grade Au disseminated pyrite-rich ores in the permeable brecciated host rocks and (2) high-grade quartz-fluorite veins rich in calaverite (AuTe2), coloradoite (HgTe), petzite (Ag3AuTe2), altaite (PbTe) and native Au. Pyrite trace element mapping revealed distinct variations and decoupling of elements (Au-Te) and element pairs (Au-As vs. Co-Ni) within and between different sites in the epithermal district. This is reflected by the concentric/growth zoning of these elements in pyrite that were interpreted to be caused by fluid boiling associated with the deposition of the low-grade disseminated host rock ores at temperatures between 220 and 350 °C leading to the precipitation of Au, As, Co and Ni from the liquid phase and the preferential partitioning of Te into the vapor phase. The subsequent condensation of the Te-rich vapors in metal-bearing meteoric waters led to the Te precipitation being decoupled from Au in the low-grade ores. The high-grade Au-Te mineralization was likely initiated by the influx of magmatically derived oxidized fluids. Subsequently, fluid temperatures dropped due to mixing with meteoric waters resulting in fluid boiling under low pressure conditions at shallower crustal levels (

The Golden Mile deposit (1767 t Au) in the Archean Yilgarn Craton, Western Australia, is controlled by D2 strike-slip and D3 reverse faults displacing folded tholeiitic greenstones. Granodiorite and monzodiorite dykes emplaced into the faults predate and are synchronous with propylitic and sericite–ankerite alteration overprinted by the ore. Arsenopyrite and chlorite thermometry and fluid-inclusion data indicate ore formation at 420 ± 30 °C and 300 MPa and cooling to the ambient temperature at 10 km depth (250–300 °C). Fimiston refractory ore (7 g/t Au) in propylitic Golden Mile Dolerite is zoned from inner albite–ankerite to outer ankerite–phengite–quartz replacement. Pyrite–magnetite is overprinted by pyrite–hematite ± anhydrite. Arsenical pyrite encloses chalcopyrite, tennantite, gold and tellurides. Gold thio-sulfide complexes, buffered by magmatic SO2 and H2S in the fluid, were destabilised during the ankerite–pyrite replacement of propylitic chlorite, a reaction releasing hydrogen ions for the hydrolitic alteration of adjacent albite. Gold deposition was assisted by declining gold, silver, tellurium and sulfur solubility as the fluid cooled. Dissolved sulfate is recorded in pyrite by negative δ34S (− 10 to − 5‰) at magmatic Δ33S (0–0.2‰). Oroya ore bodies are subdivided into oxidised pyrite lodes (5 g/t Au) in propylitic GMD and reduced lodes (30–120 g/t Au) characterised by Stage 1 silica–pyrite and siderite–chlorite replacement in ankerite-rich wall rocks. Rapid cooling, an acidic fluid and the retrograde solubility of ankerite facilitated replacement and the deposition of minor arsenopyrite, pyrrhotite, chalcopyrite, sphalerite and gold. Locally, the H2S-rich fluid (log fS2 = − 5.8 ± 0.5 bar at 420 °C) was reduced by organic methane. Oroya Stage 2 ore fills crosscutting veins and cements breccia. Quartz, chalcedony, dolomite–ankerite, calcite, V-muscovite, V-chlorite and V-tourmaline form the gangue of pyrite–telluride ± magnetite ore. Altaite–tellurium myrmekites were deposited at ≥ 400 °C as melt droplets together with tellurantimony, altaite, calaverite, montbrayite and petzite. As fluid temperature and tellurium fugacity declined, free gold, krennerite, coloradoite and melonite also crystallised joined by sylvanite and hessite below 350 °C. Finally, trace covellite and digenite precipitated at high fluid sulfidation states.

The giant Jiama polymetallic ore deposit is a porphyry–skarn system in the eastern Gangdese porphyry belt of the Tibetan Plateau. Steeply dipping high-grade massive sulfide veins are classified as lode-type high-sulfidation (HS) mineralization comprising mainly Cu-sulfosalts in Au-poor and Au-rich veins. Au-poor veins contain an As-rich pyrite–enargite–tennantite assemblage, whereas Au-rich veins contain an Sb-rich enargite–luzonite–tetrahedrite–chalcostibite–watanabeite assemblage. The coexistence of pyrite, dendritic muscovite, and euhedral quartz in the Cu-sulfosalts indicates slightly acidic or near-neutral formation conditions. Most Au- and Ag-bearing minerals are inclusions of tellurides (hessite, sylvanite, and petzite) in tennantite–tetrahedrite, and watanabeite. Au and Ag concentrations in tennantite–tetrahedrite, watanabeite, and chalcostibite are much higher than in enargite and luzonite, confirming that they were controlled by intermediate-sulfidation state Cu–As–Sb–S solid solutions, with Au tending to be enriched in Sb-rich minerals compared with As-rich solid solutions. The HS veins overlying the known porphyry intrusion and cutting skarn orebodies in the Jiama deposit constitute a porphyry–skarn–high sulfidation system. The occurrence of HS veins suggests that channels in paleo-fumaroles and the mineralization that resulted may be ascribed to expansion of magmatic vapor. HS veins close to the porphyry intrusion exposed at the surface indicate that shallow epithermal disseminated mineralization was likely removed by rapid regional uplift and erosion of the Gangdese porphyry belt.

The Pefka Cu-Au-Te-In-Se and nearby St Philippos Pb-Zn-Bi-Sn-Ge-Ga-In vein- and breccia-type deposits in western Thrace, Greece, display strong similarities, but also differences in terms of mineralization style, ore mineralogy, and chemistry, and host rock compositions. The Pefka mineralization consists of two crosscutting vein systems with high sulfidation (HS)- and intermediate-sulfidation (IS) assemblages hosted by andesitic lavas and is unusually enriched in In (up to 700 ppm), Te (>1000 ppm), Se (>100 ppm), and Cu (>1 wt%). The main In-carriers are roquesite (CuInS2) and In-bearing “tennantite-(Cu)” and Cu-rich “tennantite-(In)” which contains up to 6.5 wt% In, substituting into the C site. Roquesite is associated with enargite and arsenosulvanite/colusite, as part of the HS assemblage at Pefka. Selenium-bearing galena and a large suite of tellurides including calaverite, sylvanite, petzite, hessite, kostovite, empressite, tellurantimony, and coloradoite, in addition to native tellurium, account for the marked tellurium and selenium enrichment in the ores from Pefka. Tellurides and native gold at Pefka accompany the precipitation of Te-bearing minerals of the tetrahedrite group, such as “stibiogoldfieldite” and “arsenogoldfieldite”, and Cu-excess varieties of tetrahedrite and tennantite. However, the bulk of telluride deposition is associated with normal, fully substituted tetrahedrite-tennantite varieties. The St Philippos deposit is associated with a brecciated fault zone hosted by Eocene sandstones and Oligocene quartz-feldspar porphyry dikes. It is enriched in a large suite of incompatible elements, including Bi (>2000 ppm), Sn (>100 ppm), U (up to 200 ppm), Pb (>1 wt%), Zn (>1 wt%), Mo (up to 62 ppm), Ge (>100 ppm), Ga (up to 466 ppm) and In (up to 222 ppm), contrasting with the element suite defining the nearby Pefka deposit. The main carrier of In, Ga, and Ge is sphalerite (and wurtzite) with In-rich zones in sphalerite containing up to 6.1. wt% In. Germanium and Ga in sphalerite reach concentrations of up to 0.27 and 0.32 wt%, respectively. Sphalerite from the St Philippos deposit is extremely Fe-poor (300 °C) and HS fluid conditions, followed by IS assemblages as temperatures waned. Rhyolitic oxidized magmas are considered to be the sources of metals in the St Philippos deposit; however, their anomalous W, Sn, U, and Bi contents suggest a contamination by crustal rocks. The Cu-Au-Te signature of the Pefka deposit is compatible with a genetic relationship to less fractionated andesitic magmas, although a possible contribution of In from rhyolitic magmas could explain the high In contents of the ore. However, other factors, as for example different metal-deposition mechanisms resulting in metal zonation around causative porphyry centers at depth, may also account for the observed metal endowment in these two deposits. The Sn-Te-In-(Ge-Ga) element association at Pefka and St Philippos is unusual in that it has been previously reported from only a few other places in the world (e.g., Capillitas deposit, Argentina, and the Kawazu deposit, Japan). We conclude based on this exotic mineralization-style that the northeastern part of Greece represents an area of great potential for the exploitation of critical metals and metalloids.

The Baranyevskoe Au-Ag epithermal deposit of low-sulfidation (LS) type is located on the Kamchatka Peninsula in the Neogene-Quaternary Central Kamchatka Volcanic Belt, where Au-bearing quartz veins are usually accompanied by veinlet stockworks. Two economic associations are typical of the Baranyevskoe deposit. The first corresponds to gold-pyrite-quartz association with low-grade native gold (521–738‱) intergrown with pyrite. Some accessory Au-Ag minerals within the early association were also identified: acanthite AgS2, hessite AgTe2, lenaite Ag(Fe,Cu)S2, petzite Ag3AuTe2, utenbogardite Ag3AuS2 and unnamed Ag-Sb-As sulfosalts. The former Au-Ag minerals were most likely formed in the temperature range of 320–330 °C based on the study of arsenopyrite thermometers and fluid inclusions. The second, a gold-sulfosalt-quartz association, includes high-grade native gold (883-941‱) in intergrowth with chalcopyrite. Cuprous phases (bornite, chalcocite, heerite, native copper, Cu-Zn solid solutions), Bi-rich sulfosalts (aikinite PbCuBiS3, emplectite CuBiS2, witticenite Cu3BiS3), stannoidite Cu8Fe3Sn2S12, mawsonite Cu6Fe2SnS8), Au-bearing galena, Te-free and Bi-rich tetrahedrite-tennantite represent this association. Fluid inclusions in gold-sulfosalt-quartz association are characterized by homogenization temperature ranging from 226 to 298 °C, and salinity from 0.4 to 1.2 wt. % NaCl eq.

Gold ore objects in skarns are widespread in geological structures of the Eastern Tuva, but their estimation is considerable difficult due to poor information about mineralogical, geochemical and petrographic peculiarities of ores. The study of the genesis and conditions of gold deposits formation, which are located in skarns, is one of the fundamental scientific disciplines in geological science. The aim of the study is to examine the mineralogical and geochemical peculiarities and conditions of ore formation of the Barsuchy deposit in North-Eastern Tuva. Methods: field work, detailed mineralogical study of ore mineralization using Tescan Vega 3 SBU scanning electron microscope with EMF Oxford Instruments X-act. PT conditions of mineral associations’ formation are determined by fluid inclusion study as well as using geofugometers and mineral paragenesis. Results. The authors have manifested that the gold mineralization of the Barsuchy deposit is post-skarned and has a hydrothermal genesis forming a vein-disseminated mineralization of stockwork-type in quartz-diorites, contact (hornfels, skarns) and hydrothermal-metasomatic formations. Near-ore processes are expressed in beresitization and listwanitization of quartz-diorites, skarns and carbonate rocks. The native gold was formed during two stages. According to the composition of the productive mineral associations, Barsuchy deposit is related to a gold-pyrrhotite-pyrite-chalcopyrite type with the AuTe2 calaverite, petzite, hessite and minerals of the tellurobismuthite-tellurantimony series. The gold-quartz-sulfide mineralization is formed due to aqueous fluids with Na and K chlorides containing CO2 and CH4 with a salinity of 1–10,5 wt. % NaCl-eq. accompanied with Redox-potential changes and the variations of f S2, f Se2, f Te2 and temperature fall of the ore-bearing fluid (the first productive stage is 360–280 °C, the second one – 320–240 °C). According to mineralogical and geochemical features, Barsuchy deposit belongs to gold-sulfide-quartz formation (with less than 5 % sulfides) and is close to Au-Bi geochemical type of deposits.

At the well preserved Yubileynoe VMS deposit (South Urals), sulfide breccias and turbidites contain abundant tellurides represented by hessite, coloradoite, altaite, volynskite, stutzite, petzite, calaverite as well as phases of intermediate solid solution tellurobismuthite – rucklidgeite. There is three generation of tellurides were highlighted: 1) primary hydrothermal tellurides in the fragments of chalcopyrite and sphalerite of chalcopyrite-rich black smoker chimneys; 2) authigenic tellurides in pseudomorphic chalcopyrite and veins of chalcopyrite after fragments of colloform and granular pyrite; 3) authigenic tellurides in pyrite nodules. Authigenic tellurides are widespread in pyrite-chalcopyrite turbidites. In sulfide turbidites and gravelites with fragments of sphalerite-pyrite, pyrite-sphalerite paleosmoker chimneys and clasts of colloform and fine-grained seafloor hydrothermal crusts, primary hydrothermal and authigenic tellurides are less common. Siliceous siltstones intercalated with sulfide turbidites contain pyrite nodules, which peripheral parts contain inclusions of epigenetic tellurides. It is assumed that the source of tellurium for authigenic tellurides were fragments of colloform pyrite and hydrothermal chalcopyrite of pyrite-chalcopyrite chimneys, which dissolved during post-sedimentation processes. The main concentrators of tellurium in clastic ores are pseudomorphic chalcopyrite, which inherits high contents of Te, Bi, Au, Ag, Co, Ni, As from the substituted colloform pyrite, and varieties of granular pyrite, containing microinclusions of tellurobismuthite (Bi, Te), petzite (Au, Ag, Te), altaite (Pb, Te), coloradoite and hessite (Ag, Te).

The Dongping gold deposit is located near the center of the northern margin of the North China Craton. It is hosted in the Shuiquangou syenite and characterized by large amounts of tellurides. Numerous studies have addressed this deposit; the mineral paragenesis and ore-forming processes, however, are still poorly studied. In this contribution, a new mineral paragenesis has been evaluated to further understand ore formation, including sulfides (pyrite, chalcopyrite, galena, sphalerite, molybdenite, and bornite), tellurides (altaite, calaverite, hessite, muthmannite, petzite, rucklidgeite, sylvanite, tellurobismuthite, tetradymite, and volynskite), and native elements (tellurium and gold). Molybdenite, muthmannite, rucklidgeite, and volynskite are reported for the first time in this deposit. We consider the Dongping gold deposit mainly formed in the Devonian, and the ore-forming processes and the physicochemical conditions for ore formation can be reconstructed based on our newly identified ore paragenesis, that is, iron oxides -> (CO₂ effervescence) -> sulfides -> (fTe₂/fS₂ ratio increase) -> Pb-Bi-tellurides -> (condensation of H₂Te vapor) -> Au-Ag-tellurides -> (mixing with oxidizing water) -> carbonate and microporous gold -> secondary minerals -> secondary minerals. The logfO₂ values increase from the early to late stages, while the fH₂S and logfS₂ values increase initially and then decrease. CO₂ effervescence is the main mechanism of sulfides precipitation; this sulfidation and condensation of H₂Te vapor lead to deposition of tellurides. The development of microporous gold indicates that the deposit might experience overprint after mineralization. The Dongping gold deposit has a close genetic relationship with the Shuiquangou syenite, and tellurium likely originated from Shuiquangou alkaline magmatic degassing.

The Oroya Shoot (> 62 t Au) in the giant Golden Mile deposit, Yilgarn Craton, Western Australia is controlled by reverse faults, which offset altered quartz diorite porphyry but are crosscut by a late-mineralization kersantite dyke (> 2642 ± 6 Ma). Oroya stage 1 ore (12–14 g/t Au) is characterized by chert-like quartz, Fe-chlorite, siderite and pyrite (10–20 vol%), minor arsenopyrite, chalcopyrite and sphalerite, and accessory pyrrhotite, gersdorffite, and melonite. Dendritic pyrite and arsenopyrite-chlorite thermometry indicate rapid precipitation from an H2S-dominant fluid of intermediate sulfidation and low oxidation state cooling from 450–400 to 340 °C. Oroya stage 2 ore (120–600 g/t Au) forms veins and breccia filled or cemented by quartz, muscovite (≤ 13.2 wt% V2O3), ankerite, chlorite, and tourmaline (≤ 14.7 wt% V2O3). The assemblage pyrite-arsenopyrite-chalcopyrite brackets telluride deposition. Bornite-chalcopyrite aggregates, sphalerite, and tetrahedrite are associated with native gold, montbrayite, altaite, calaverite, petzite, tellurantimony, coloradoite, and melonite. Myrmekitic altaite-tellurium ± sylvanite and altaite-krennerite symplectites represent melt droplets deposited at > 400 °C and log fTe2 = − 4 bar (400 °C, 200 MPa). Tellurium fugacity declined as the fluid cooled during the deposition of native gold and free telluride grains terminating in melonite replacement at 340–300 °C. Pyrite-nolanite- and pyrite-magnetite-telluride assemblages suggest oxidation states up to 2 log units higher than during stage 1. After telluride deposition, the fluid evolved to a high sulfidation state (log fS2 = − 5 bar at 300 °C) and increased salinity indicated by digenite-covellite and Cl-bearing altaite. The average ore is enriched in lithophile (K, Rb, Cs), siderophile (Fe, V, Ni, W), and chalcophile elements (e.g., Te, Se, Cu, Zn, Pb) implicating local monzodiorite plutons as the fluid source. Stable isotope data from the Oroya kersantite and from Cu-Au skarn and monzodiorite-granodiorite stocks southeast of Kalgoorlie constrain the composition of the magmatic fluid to δ13CPDB = − 3.0 to − 2.2‰ and δ18OSMOW = 8.3 to 9.7‰. In the Golden Mile, the fluid oxygen isotope ratios of the gold ore bodies (8.2 to 9.8‰) are consistent with I-type magmatic water. The fluid carbon isotope ratios of all altered rocks (δ13CPDB = − 1.7 to − 0.5‰) are 13C-enriched, perhaps due to the reduction of fluid CO2 to CH4 by interaction with ferrous greenstones close to the intrusion.

At the well-preserved Yubileynoe VMS deposit (Southern Urals), sulfide breccias and turbidites host abundant tellurides represented by hessite, coloradoite, altaite, volynskite, stutzite, petzite, and calaverite, as well as phases of the intermediate tellurobismuthite → rucklidgeite solid solution. Three telluride generations were highlighted: (1) primary hydrothermal tellurides in fragments of chalcopyrite and sphalerite of chalcopyrite-rich black smoker chimneys; (2) authigenic tellurides in pseudomorphic chalcopyrite and chalcopyrite veins after fragments of colloform and granular pyrite; and (3) authigenic tellurides in pyrite nodules. Authigenic tellurides are widespread in pyrite-chalcopyrite turbidites. Primary hydrothermal and authigenic tellurides are less common in sulfide turbidites and gritstones with fragments of sphalerite-pyrite, pyrite-sphalerite paleosmoker chimneys and clasts of colloform and fine-grained seafloor hydrothermal crusts. Siliceous siltstones intercalated with sulfide turbidites contain pyrite nodules, whose peripheral parts contain inclusions of epigenetic tellurides. It is assumed that Te for authigenic tellurides originated from fragments of colloform pyrite and hydrothermal chalcopyrite of pyrite-chalcopyrite chimneys, which dissolved during the postsedimentation processes. The main Te concentrators in clastic ores include pseudomorphic chalcopyrite, which inherits high Te, Bi, Au, Ag, Co, Ni, and As contents from the substituted colloform pyrite, and varieties of granular pyrite containing microinclusions of tellurobismuthite (Bi, Te), petzite (Au, Ag, Te), altaite (Pb, Te), coloradoite, and hessite (Ag, Te).

espanolLa mina La Herradura, en Sonora, constituye uno de los distritos de oro mas importantes de Mexico, con una produccion a la fecha superior a 5.5 millones de onzas de oro durante 17 anos. Forma parte de un cinturon de yacimientos de oro orogenico que se extiende en direccion noroeste-sureste por mas de 300 km de largo y 50 km de ancho. La mineralizacion consiste en vetas y enrejados de vetillas de cuarzo formadas en un ambiente geologico ductil-fragil, que se hospeda en gneises cuarzo feldespaticos del Proterozoico. Los cuerpos mineralizados, definidos por una ley minima de corte (cut off) de 0.3 g/t de Au tienen formas tabulares y alcanzan hasta 1 km de largo, 1 km de profundidad y 100 m de ancho. El control visual de la mineralizacion es la constancia de vetas y vetillas de cuarzo y una alteracion hidrotermal sericitica persistente. Para este trabajo se utilizaron diferentes tecnicas, poniendo enfasis en el programa Mineral Liberation Analizer (MLA), con el objeto de probar la posibilidad de predecir el oro recuperable en la mina, para la zona de sulfuros primarios. Se definieron 3 zonas geometalurgicas (Zonas A, B y C) de las cuales se hicieron compositos y concentrados gravimetricos. La composicion modal de los concentrados es de cuarzo, feldespato y muscovita (sericita) y una mineralogia metalica de pirita, esfalerita, galena, magnetita, oro y telururos de oro y plata. El oro se identifica como inclusiones en pirita o en diversas gangas como cuarzo, albita, ortoclasa o ankerita, asi como en peliculas en el borde pirita. La composicion del oro es electrum con 74 % de Au y 26 % de Ag; tambien se identifico la presencia de petzita (Ag3AuTe2) y stutzita (AgTe). Se calcularon constantes de recuperacion para cada zona geometalurgica las cuales, incorporadas al modelo informatico de recursos calculados en mas de 14 millones de onzas de oro, indicaron rangos de error en oro recuperable de menos de 4 % para la Zona A, 6 % para la Zona C y 13 % para la Zona B, en relacion con calculos tradicionales efectuados con datos experimentales. Los resultados son aceptables para aplicar esta metodologia al deposito. El rango de error mas acusado en la Zona B se interpreta como causado por un “efecto pepita” muy comun en este tipo de yacimientos. Se concluye tambien que un proceso de remolienda, incorporado actualmente a la planta de beneficio, es probablemente innecesario, lo cual implicaria un ahorro notable en energia y en la economia de la mina. EnglishLa Herradura mine in Sonora is one of the most important gold districts in Mexico producing more than 5.5 million ounces of gold over 17 years. It is part of an orogenic gold deposits belt with a northwest-southeast direction for 300 km long and 50 kmwide. The mineralization consists of veins and quartz networks veinlets formed in a brittle-ductil geologic environment and it is hosted in Proterozoic quartz-feldspar gneisses. The ore bodies, defined by a 0.3 g/t Au cut-off grade, have tabular forms up to 1 km in length, 1 km in depth and 100 m in width. The visual control for mineralization is the abundance of quartz veins and veinlets, and a persistent sericitic hydrothermal alteration. Different techniques were used in this work with special focus on the Mineral Liberation Analizer (MLA) program to prove the possibility of predicting recoverable gold in the mine for the primary sulphide zone. Three geometallurgical zones (Zones A, B and C) were defined by ore composites and gravimetric concentrates from the same composites. Modal composition of the concentrates is quartz, feldspar and muscovite (sericite), and a metallic mineralogy of pyrite, sphalerite, galena, magnetite, gold and tellurides of gold and silver. Gold is identified as inclusions in pyrite or in gangue minerals like quartz, albite, orthoclase or ankerite, as well as coating pyrite crystals. The gold composition is electrum with 74 % Au and 26 % Ag; the presence of petzite (Ag3AuTe2) and stutzite (AgTe) were also identified. Recovery constants were calculated for each geometallurgical zone, which were introduced to the resource model of more than 14 million ounces of gold, indicating that error range in recoverable gold is less than 4 % for Zone A, 6 % for Zone C and 13 % for Zone B, in relation with gold recovery calculated with traditional methods. These results could be acceptable to applicate this methodology to La Herradura deposit. The most important error range in the Zone B is interpreted as due to a nugget effect, which isvery common in such mineral deposits. It is also concluded that the secondary milling process currently incorporated to the metallurgical plant is probably unnecessary, so its removal would result in a significant saving in energy and therefore in the economy of the mine.

Gold ore deposits of Uzbekistan are confined to the South Tien Shan orogenic belt. They are located in black shales (Muruntau, Amantaytau, Daugyztau), terrigenous sedimentary (Kokpatas), volcanic (Balpantau), and intrusive (Zarmitan, Guzhumsai) rocks. Their age is 280—290 Ma and coincides with the age of post-collision granitoid magmatism. The deposits form Kyzylkum and Nurata mining districts. Gold forms micro-nanoparticles and is incorporated into diversified compounds with Bi, Sb, As, Te, Se, S, Ag, Hg in primary quartz-sulfide and sulfide ores. Seven mineral and geochemical types of ores are recognized: Au—W with scheelite and molybdenite; Au—Bi—Te with maldonite, tellurides, bismuth sulpho-tellurides; Au—As with pyrite, arsenopyrite, Ni—Co minerals; Au—Ag—Te with calaverite, petzite, hessite, etc.; Au—Ag—Se with fichesserite, acanthite, freibergite, agvilarite, petrovskite, etc.; Au—Sb—Ag with aurostibite, boulangerite, burnonite, cincenite, chalcostibite, tetrahedrite, etc.; Au—Hg with cinnabar, consbergite, Hg-bearing native gold. Recoverable resources are determined by 2—3 types of ores. Three main types of gold deposits are proposed on the base of outlined mineralogical and geochemical types: Au—W—Bi—Te (Muruntau, Myutenbay, Zarmitan); Au—As—Sb—Ag (Amantaytau, Kokpatas, Daugyztau); Au—Ag—Sb—Se (Kosmanachi, Okzhetpes). The emphasis on the nanomineral approach in the study of gold, its compounds, and micro-nano ensembles increases the efficiency of searching, typifying and evaluating the prospects of hidden mineralization, and is favorable to determine the conditions of formation and technological properties of gold ores.

The published and original data on the tellurium mineralization of gold ore deposits of the Aldan Shield are systematized and generalized. The gold content is related to hydrothermal-metasomatic processes caused by Mesozoic igneous activity of the region. The formation of tellurides occurred at the very late stages of the generation of gold mineralization of all existing types of metasomatic formations. 29 tellurium minerals, including 16 tellurides, 5 sulfotellurides and 8 tellurates have been identified. Tellurium minerals of two systems predominate: Au-Bi-Te and Au-Ag-Te. Gold is not only in an invisible state in sulfides and in the form of native gold of different fineness, but also is part of a variety of compounds: montbrayite, calaverite, sylvanite, krennerite and petzite. In the gold deposits of the Aldan Shield, three mineral types are distinguished: Au-Ag-Te, Au-Bi-Te, and also a mixed one, which combines the mineralization of both systems. The decrease in the fineness of native gold is consistent with the sequence and temperatures of the formation of Te minerals and associated mineral paragenesis from the epithermal–mesothermal Au-Bi-Te to epithermal Au-Ag-Te. The conducted studies allowed us to determine a wide variety of mineral species and significantly expand the area of distribution of Au-Te mineralization that indicates its large-scale regional occurrence in the Aldan Shield.

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.

Object . The zonal pyrite nodules and metacrystals from siliceous siltstones of ore-bearing horizon of the Second ore body from the Yubileynoe massive sulfide deposit are studied. Materials and methods . We used 9 samples and 15 polished sections of siliceous siltstones with pyrite mineralization. Analysis of chemical composition minerals was determined by Tescan Vega 3 with an energy dispersive microprobe Oxford Instruments X-act (Institute of Mineralogy UB RAS, Miass). Quantitave LA-ICP-MS analysis of pyrite for major and trace elements was carried out using New Wave Research UP-213 laser microprobe coupled to an Agilent 7500 quadrupole ICP-MS housed (University of Tasmania, Australia). Results. Microtopochemistry was established that the diagenetic core of the nodule is characterized by trace elements of typical poikilites of quartz (Si) and alumosilicates (Si, Al, Mg, V, Cr, K, Na, Ca), rutile and titanite (Ti), inclusions of chalcopyrite (Cu), sphalerite (Zn), galena (Pb, Sb, Bi), tetrahedrite-tennantite (As, Sb), native gold, petzite, hessite (Au, Ag, Te), tellurobismuthite, altaite, and coloradoite (Te, Bi, Pb). Cobalt and Ni substitute for Fe 2+ . The rim of subhedral pyrite is depleted in most trace elements except for Ni and As. Subhedral pyrite became rich in chalcophile (Au, Ag, Sb, Bi, Cu, Zn, Hg) and lithophile (Ca, K, Na, Cr) elements at the final stage of growth of the nodule. Similar mineralogical and geochemical zonation is typical of the pyrite metacrystals, where a micro-grained core concentrates Pb, Bi and Te, and a rim of subhedral pyrite is depleted in most trace elements. Similarly to the nodules, the outer rim of pyrite metacrystals is enriched in most trace elements (Pb, Au, Ag, Sb, Cu, As, Mo, Cr, etc.). The nodules and metacrystals were formed from diagenetic micronodule of poikilite pyrite. Conclusions. It is suggested that mineralogical and geochemical differences in pyrite metacrystals and nodules are caused by the greater degree of development of rims of subhedral pyrite.

The Au-Ag-Pb-Zn-Cu epithermal deposit Banska Hodrusa of intermediate-sulphidation type is located in the Middle Miocene Stiavnica stratovolcano on the inner side of the Carpathian arc in Slovakia. This deposit represents an unusual subhorizontal multi-stage vein system, related to processes of underground cauldron subsidence and exhumation of a subvolcanic granodiorite pluton. Veins are developed on a low-angle normal shear zone, possibly representing a detachment zone in andesitic wall rocks that formed during emplacement and exhumation of the granodiorite pluton. The deposit consists of two parts, separated by a thick sill of quartz-diorite porphyry. The eastern part is currently mined, and the western part has already been depleted. The Banska Hodrusa mineralization was formed during four stages: (1) low-grade silicified breccia at subhorizontal structures at the base of the deposit; (2) stockwork of steep veins with rhodonite-rhodochrosite, quartz-sulphide-carbonate and quartz-gold assemblages; (3) thin quartz-gold veins with medium dip in tension cracks inside the shear zone and complementary detachment hosted quartz-base metals-gold veins; (4) Post-ore veins. Gold and electrum (920–730) occur as intergrowths with base metal sulphides or hosted in quartz and carbonates, accompanied by Au-Ag tellurides (hessite, petzite). Rare Te-polybasite and Cu-cervelleite result from re-equilibration of early Te-bearing minerals during cooling. Sulphide minerals include low Fe sphalerite (~ 1.25 wt%), galena, chalcopyrite, and pyrite. The wall rock alteration is represented mostly by adularia, illite, chlorite, quartz, calcite and pyrite. Precipitation of gold, Au-Ag tellurides, Mn-bearing minerals and adularia resulted from boiling of fluids due to hydraulic fracturing, as well as opening of dilatational structures within the shear zone.

Mineral assemblages and formation conditions of precious metals (Au, Ag, PGE) in ores of the Mikheevskoe porphyry copper deposit (South Urals) are the subject of our study. Three mineralization types can be distinguished: (1) Gold-silver-telluride mineralization overlapping porphyry-style bornite-chalcopyrite ores includes native gold (fineness 863–873), electrum (fineness 593–672), galena, hessite, coloradoite, and, more rarely, petzite, stutzite, Au-Ag ditellurides, native tellurium, tellurobismuthite, tetradymite–kawazulite, altaite, and extremely rare melonite NiTe2, merenskyite PdTe2, and sopcheite Ag4Pd3Te4; (2) Gold-arsenopyrite-base-metal mineralization within quartz-tetrahedrite-sphalerite veinlets cutting porphyry-style mineralization; (3) Gold-telluride mineralization with argillic alteration and mineralogically similar to that of type (1) but distinct because of the presence of Au-Ag, Ag, and Pb selenides. Textural relationships supported by fluid inclusions data and chlorite geothermometry provide evidence that occurrence of precious metals minerals at the Mikheevskoe deposit is mostly linked to epithermal overprint of the porphyry mineralization and was deposited at ca. 300–200 °C from moderately saline fluids (ca. 5–10 wt%-eq.NaCl). It is suggested that the observed variability in Au and Ag minerals results from small fluctuations of S2 and/or Te2 fugacity.

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 Betare Oya district has a substrate composed of the Neoproterozoic metavolcanic-metasedimentary rocks of the Lom Belt in eastern Cameroon. The district is well-known for alluvial gold mining activities, however, the primary gold mineralization has received little attention. In the current study, we newly report geological, ore mineralogy, fluid inclusion microthermometric, laser Raman spectroscopy, and stable isotope data from auriferous veins of the Lom Belt to characterize the style of gold mineralization and to constrain the origin of the ore-forming fluids. The auriferous quartz veins are laminated, fractured, N- to NE-trending, and spatially associated with the Betare Oya Shear Zone. Fieldwork coupled with microscopic examination and the textural relationships of ore minerals revealed two stages of mineralization. The first stage is characterized by the presence of pyrite, sphalerite, galena, chalcopyrite, pyrrhotite, hematite, petzite, hessite, wolframite, electrum, and gold, while the second stage is characterized by the presence of a later deposition of galena and pyrite, as well as minor greenockite. The gangue minerals are quartz, sericite, muscovite, chlorite, calcite, ankerite, and barite, whereas the supergene assemblage (stage 3) includes goethite, hematite, covellite, and enargite. Two fluid inclusion assemblages containing three types of inclusions are identified in mineralized quartz veins. Assemblage 1 consists of gold-related types 1 and 2 with daughter minerals consisting of nahcolite, magnesite, and arsenolamprite (black native arsenic), whereas assemblage 2 consists of post-gold type 3 fluid inclusions. Type 1 has H2O-NaCl-CO2±N2±CH4 primary fluid inclusions (FI), with a TmCO2 ranging from −59.8 to −56.6 °C, salinities from 0.5 to 10.8 wt% NaCl eq., densities from 0.87 to 1.00 g.cm−3, and total homogenization temperatures between 280 and 360 °C. Type 2 contains CO2 (±H2O-NaCl)±N2±CH4 FI that exhibit TmCO2 ranging between −60.0 and −56.7 °C, ThCO2 from 13 to 25 °C, and densities between 0.73 and 0.85 g.cm−3. Type 3 shows H2O-NaCl FI with salinities between 0.2 and 10.1 wt% NaCl eq., densities between 0.82 and 0.98 g.cm−3, and total homogenization temperatures from 160 to 235 °C. Measured δ18O for gold-bearing quartz (+11.5 to +16.0‰), δD from FI (−50.6 to −21.8‰), δ13C from FI (−5.8 to −5.5‰), and δ34S from galena and pyrite grains (+5.3‰ and +8.2‰, respectively) suggest a metamorphic source as most likely for the ore-forming fluids and sulfur, although a mantelic CO2 contribution cannot be ruled out. The gold deposition probably took place by fluid-rock interaction and fluid unmixing at ∼310 °C and at a depth of about 6-9 km. The ore-forming fluid was a low salinity (∼6.2 wt% NaCl eq.) H2O-NaCl-CO2±N2±CH4 solution. These data revealed that the Lom Belt gold mineralization is best classified as a mesozonal orogenic gold deposit.

Our paper reviews a series of relatively low-grade gold deposits and prospects hosted by granitoid intrusions within the southeastern East Sayan in the Altaid Belt (northern Central Asian Orogenic Belt, Russia). The studied deposits/prospects are characterized by the presence of Te-, Sb- and Bi-bearing minerals. However, they differ in their main gold-associated mineral assemblages, which permits to distinguishing four mineralization assemblages: 1) gold-telluride; 2) gold-tetradymite; 3) gold-stibnite; and 4) gold-bismuth sulfosalt. The gold-telluride mineralization (1) is represented by the Tainskoye deposit, and the Khoringolskoye and Sagangolskoye prospects which are defined by paragenesis of native gold with Au-Ag-Bi-Pb-Ni tellurides, such as hessite, petzite, altaite, wehrlite, calaverite, melonite, altaite, and tellurobismuthite. The gold-tetradymite mineralization (2) which is represented by the Konevinskoye deposit, is hosted by the Saylag granitoid pluton, and contains tetradymite as one of the principal minerals associated with native gold. The gold-stibnite mineralization (3), represented by the Tumannoye prospect, is also hosted in a granitoid complex consisting of granodiorite and leucogranite. The gold-bismuth-sulfosalt mineralization (4) is documented at the Pogranichnoye prospect, where native gold is associated with the bismuth-bearing minerals: bismuthinite, galeno-bismuthite, lillianite, and native bismuth. Estimated δ18O values of ore-forming fluids from intrusion-hosted deposits range from 5.7 to 7.4‰, indicative of a magmatic origin; δ34S values of sulfides vary from −4.2 to 4.5‰, which corresponds to magmatic sulfur. The geological setting, element geochemistry of host granitoids, stable isotope ratios, and mineralogy of the studied deposits are consistent with a magmatic origin of the mineralizing fluids. The studied deposits are spatially associated with either Neoproterozoic or Early Paleozoic granitoids, belonging to the two main orogenic stages of the East Sayan geodynamic evolution. At ∼850 Ma, during the Neoproterozoic stage, deposits with dominant gold-telluride assemblages, formed in association with granitoids characterized by geochemical features of island arc granites. During 458–439 Ma, in the Early Paleozoic stage, gold-tetradymite, gold-stibnite, gold-telluride and gold-bismuth-sulfosalt assemblages were formed that are spatially associated with orogenic granites with different geochemical compositions. Most gold-bearing mineral assemblages are intersected by post-mineral Late Paleozoic dykes. The origin of these different gold-sulfide-telluride assemblages is explained with their genetic association with granitoid intrusions of different ages and compositions.

The Dayingezhuang gold deposit in the Jiaodong district, eastern margin of the North China Craton is hosted in Mesozoic granitic rocks and consists of quartz-sulfide veins/veinlets and sulfide disseminations in alteration envelopes. Previous studies mainly focused on the geochronology, sources of ore-forming fluids and metals to investigate the ore genesis. However, enrichment mechanism of Au and other associated trace metals remain unclear. In this study, we present detailed textures and in-situ LA-ICP-MS trace-element compositions of different generations of pyrite, as well as EMP analysis of Au-bearing minerals to discuss the occurrence and enrichment mechanism of Au at this deposit. Three generations of pyrite (Py1, Py2 and Py3) formed during three hydrothermal ore stages (I, II, and III) at Dayingezhuang. Py1 occurs as disseminations in sericitic alteration assemblages and is characterized by low Au (mean 0.15 ppm), Ag, As and Te contents. The time-resolved depth-concentration profiles indicate that Au in Py1 mainly occurs as nanoparticles and/or micron-sized inclusions. Py2 can be further divided into the early undeformed Py2a and later Py2b, which is the product of deformed Py2a with different degrees of brittle to plastic deformation and recrystallization. Py2a in pyrite-siderite-quartz veins is relatively enriched in invisible Au (mean 0.41 ppm), Ag, As, and Te compared to Py1, and contains numerous micron-sized Au inclusions. In contrast, Py2b contains lesser invisible Au (0.21 ppm) and host abundant gold minerals along the grain boundaries and microfractures. Py3 in polymetallic sulfide veins has little Au. As a whole, Au in pyrite is positively correlated with Ag and Te, which is consistent with the results of EMP analysis showing the occurrence of Au as electrum, native gold and minor petzite in pyrite. Such evidences show that the deformation and recrystallization of auriferous Py2a potentially caused local remobilization of Au (mainly as micron-sized inclusion Au) via solid-state ductile flow and subsequent reconcentration of Au in microfractures of Py2b. The pyrite deformation and Au remobilization events were suggested to be related to the continuous reactivation of the regional Zhaoping Fault contemporaneous with gold mineralization. Our study highlights the importance of remobilization and reconcentration of Au triggered by syn-ore tectonic activities at Dayingezhuang and possibly other Au deposits in the Jiaodong district.

The Podgolechnoe deposit, which belongs to the alkalic-type (A-type) epithermal gold-ore deposits, lies in the Central Aldan ore district (Russia). Gold-ore mineralization is associated with a volcano-plutonic complex made of rocks of the monzonite-syenite formation (J3–K1). The ore bodies are localized in the crushing zones developed after crystalline schists, gneisses, and granites of the crystalline basement complexes (Ar–Pr). Metasomatic alterations in host rocks have potassic specialization. Vein ore minerals are adular, fluorite, roscoelite, sericite, and carbonate. Ore minerals are pyrite, galena, sphalerite, cinnabar, brannerite, monazite, bismuth telluride, stutzite, hessite, petzite, montbraite, and native gold. The deposit has been explored as a gold-ore deposit, however, due to complex composition of ores there is a need to reveal the possibilities of the integrated development of this deposit. This could provide for a reserve increment and an increase in the gross recoverable value of ores due to the extraction of associated components.

An investigation into the factors inhibiting the leaching of precious metal tellurides in cyanide solutions and initial testing of possible methods to improve leach performance were conducted. Petzite (Ag 3 AuTe 2 ) was the principle mineral examined, along with calaverite (AuTe 2 ) and hessite (Ag 2 Te). Both electrochemical measurements and batch leach experiments were employed to verify findings. It was found that tellurium is not readily oxidised under standard cyanidation conditions and thus was impeding the extraction of the precious metal elements. While this appears to be the primary problem to be overcome in leaching telluride minerals (particularly calaverite and hessite), evidence of passivation (previously noted in multiple studies) by a Te-rich layer was also observed in leach tests. Both established and new approaches to improve the telluride mineral leaching were tested to examine their effectiveness and better understand the fundamental chemistry involved. While elevated pH remains the most effective approach, actually leaching tellurides faster than pure gold, small proportions of citrate improved recovery from the gold-bearing tellurides.

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.

Petzite, Ag3AuTe2, crystallizes in the space groupI4132, which is a Sohncke type of space group where chiral crystal structures can occur. The structure refinement of petzite reported long ago [Frueh (1959).Am. Mineral.44, 693–701] did not provide any information about the absolute structure. A new single-crystal X-ray diffraction refinement has now been performed on a sample from Lake View Mine, Golden Mile, Kalgoorlie, Australia, which has resulted in a reliable absolute structure [a Flack parameter of 0.05 (3)], although this corresponds to the opposite enantiomorph reported previously. The minimum Te–Te distance is 3.767 (3) Å, slightly shorter than the van der Waals bonding distance, which suggests a weak interaction between the two chalcogens. XANES spectra near the Au and TeLIIIedges suggest that the chemical-bonding character of Au in petzite is more metallic than in other gold minerals.

Gold–(silver) telluride minerals constitute a major part of the gold endowment at a number of important deposits across the globe. A brief overview of the chemistry and structure of the main gold and silver telluride minerals is presented, focusing on the relationships between calaverite, krennerite, and sylvanite, which have overlapping compositions. These three minerals are replaced by gold–silver alloys when subjected to the actions of hydrothermal fluids under mild hydrothermal conditions (≤220 °C). An overview of the product textures, reaction mechanisms, and kinetics of the oxidative leaching of tellurium from gold–(silver) tellurides is presented. For calaverite and krennerite, the replacement reactions are relatively simple interface-coupled dissolution-reprecipitation reactions. In these reactions, the telluride minerals dissolve at the reaction interface and gold immediately precipitates and grows as gold filaments; the tellurium is oxidized to Te(IV) and is lost to the bulk solution. The replacement of sylvanite is more complex and involves two competing pathways leading to either a gold spongy alloy or a mixture of calaverite, hessite, and petzite. This work highlights the substantial progress that has been made in recent years towards understanding the mineralization processes of natural gold–(silver) telluride minerals and mustard gold under hydrothermal conditions. The results of these studies have potential implications for the industrial treatment of gold-bearing telluride minerals.

Seven mineralogical-geochemical types of ores have been identified in the gold orogenic deposits of Uzbekistan: /Au-W/Au-Bi-Te/Au-As/Au-Ag-Te/Au-Ag-Se/Au-Sb/Au-Hg/. Non-industrial are Au-W and Au-Hg. For each industrial type, certain gold compounds are characteristic: maldonite, Au-arsenopyrite and Au-pyrite, petzite, physhesserite, petrovskaite, aurostibite, which form regular micro- nanoensembles with the corresponding minerals Bi, Te, Se, S, As, Sb. They are direct indicators of the type and technological properties of ores. Pyrite and arsenopyrite are preserved in the processing wastes of Au-Bi-Te and Au-As ores, in which gold (901‰), maldonite (Au2Bi), headleyite (Bi7Te3) and others were detected, 300–700 nm in size. Waste is suitable for the secondary extraction of gold.

The Gedabek Au-Ag-Cu deposit located in the western part of Azerbaijan is hosted by quartz porphyry which is situated at contact between Middle Jurassic andesitic tuff and Late Jurassic-Early Cretaceous Gedabek intrusive rocks consisting of granodiorite, diorite and gabbro. Geochemical investigations for the Gedabek intrusive rocks indicate that these are calc-alkaline, and probably developed pre-collisional regime. The Gedabek Au-Ag-Cu deposit, mainly observed in the advanced argillic alteration, is composed of native gold, electrum, hessite, petzite, chalcopyrite, sphalerite, galena, molybdenite, pyrite, arsenopyrite, fahlore, enargite, bornite, hematite, barite, jarosite, adularia, covellite, chalcocite, malachite and azurite. The Gedabek Au-Ag-Cu deposit predominantly comprises Au, Ag, Cu, Zn, Pb, Fe, As, and S for the ore-bearing samples. Homogenization temperatures and salinities of fluid inclusions (FIs) trapped in quartz and sphalerite range from 134 to 371 °C and 227 to 410 °C; 3.4 to 15.2 wt% NaCl equivalent and 4.0–12.0 wt% NaCl equivalent, respectively. The δ34SH2S values (2.0–5.9‰) of sulfides (chalcopyrite, pyrite and sphalerite) from the Gedabek Au-Ag-Cu deposit indicate a magmatic origin for the ore-forming fluids. The geological, mineralogical, geochemical, isotopic, and microthermometric data for the Gedabek Au-Ag-Cu deposit suggest a high sulfidation epithermal deposit associated with porphyry system.

The crystal structure of the mineral uytenbogaardtite, a rare silver-gold sulfide, was solved using intensity data collected for a crystal from the type locality, the Comstock lode, Storey County, Nevada (USA). The study revealed that the structure is trigonal, space group R3̄c, with cell parameters a = 13.6952(5), c = 17.0912(8) Å and V = 2776.1(2) Å3. The refinement of an anisotropic model led to an R index of 0.0140 for 1099 independent reflections. The structure consists of a sub-lattice of sulfur atoms forming a distorted body-centred cubic arrangement. The structure contains distinct tri-atomic linear groups (S–Au–S) and Ag atoms bonded to four S atoms (from four different linear groups) in a distorted tetrahedral arrangement. On the basis of information gained from this characterization, uytenbogaardtite is here definitively proved to be structurally different from petzite, Ag3AuTe2 and fischesserite, Ag3AuSe2. By use of high-quality single-crystal diffraction data, the symmetry of the mineral was found to be trigonal, and not tetragonal as erroneously supposed. A revaluation of the powder diffraction data listed in the scientific literature for uytenbogaardtite according to the structural results obtained here leads to an excellent agreement. Crystal-chemical features of uytenbogaardtite, Au2S, petrovskaite AgAuS, uytenbogaardtite–fischesserite series Ag3Au(S2–xSex) and acanthite–naummanite series Ag2(S1–xSex) are compared.

Gold- and silver-containing pyrites of the Tikhii area at the Julietta deposit (Engteri ore cluster, Magadan Region) were studied by optical and scanning electron microscopy and electron probe microanalysis. One- or two-phase rounded microinclusions consisting of electrum (450–680‰) and/or galena or of petrovskaite and/or uytenbogaardtite, galena, and sphalerite have been found in early pyrites. Later As-pyrites (up to 2.6 wt.% As) contain multiphase xenomorphic microinclusions of acanthite, uytenbogaardtite, freibergite, argentotetrahedrite–tennantite, naumannite, petzite, selenopolybasite-selenostephanite, tellurocanfieldite, and other ore minerals localized in pores, cracks, and interstices. Pyrites that underwent hypergene alterations have rims and veinlets formed by acanthite, goethite, anglesite, plattnerite, and native silver. The presence of rounded ore mineral microinclusions and large pores in the early pyrites suggests the participation of volatiles in the mineral formation and the uptake of large amounts of impurities by pyrite under high-gradient crystallization conditions. The thermobarogeochemical studies of fluid inclusions in quartz have shown that the ore zone formed under boiling-up of hydrothermal medium-concentration NaCl solutions at 230–105 °C. The results of thermodynamic calculations evidence that Ag–Au–S–Se minerals formed under decrease in temperature and fugacity of sulfur (log10fs2 = –22 to –9) and selenium (log10fse2 = –27 to –14) and change of reducing conditions by oxidizing ones in weakly acidic to near-neutral solutions.

Raisaite, CuMg[Te 6+ O 4 (OH) 2 ] · 6H 2 O, is a new mineral found at the Sentyabr’skoe deposit, Ilirney ore district, Western Chukotka, North-Eastern Region, Russia. It is associated with gypsum, malachite, azurite, cerussite, anglesite, brochantite, linarite, posnjakite, chlorargyrite, acanthite, gold, brucite, goethite, coronadite, paratellurite, and xocomecatlite in the oxidation zone of quartz veins with calcite, dolomite, ankerite, muscovite, pyrite, chalcopyrite, galena, sphalerite, hessite, petzite, altaite, primary acanthite and gold, etc . Raisaite occurs as prismatic crystals (up to 0.1 × 0.6 mm), as groups or crusts (up to 0.4 × 0.6 mm) and as dense roundish clusters (up to 0.2 mm in diameter) forming botryoidal aggregates (up to 1 mm across). Raisaite is transparent, light blue to bright sky blue, with a vitreous lustre. Its Mohs’ hardness is ca. 2. Cleavage is imperfect, probably on (100), the fracture is uneven. D meas = 2.82(1), D calc = 2.828 g cm −3 . Raisaite is optically biaxial (+), α = 1.626(3), β = 1.642(5), γ = 1.665(3) and 2 V meas = 80(10)°. The IR spectrum is reported. The chemical composition (average of 7 analyses, H 2 O by difference) is: MgO 10.68, CuO 18.09, SO 3 0.44, TeO 3 41.19, H 2 O calc 29.60, total 100.00 wt%. The empirical formula calculated on the basis of 12 O apfu is: Cu 0.96 Mg 1.11 Te 0.99 S 0.02 O 4.20 (OH) 1.80 ·6.00H 2 O. Raisaite is monoclinic, C 2/ c , a = 9.9078(2), b = 10.1325(3), c = 9.8375(2)A, β = 91.839(2)°, V = 987.09(4)A 3 and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [ d ,A( I )( hkl )] are: 7.088(100)(110), 5.815(35)(−111), 5.690(23)(111), 4.949(91)(200, 002), 4.507(50)(021), 3.533(17)(−202, 022), 3.358(17)(−221), 3.310(21)(221) and 2.694(29)(−132). The crystal structure (solved from single-crystal X-ray diffraction data, R = 0.0186) is unique. It is based on heteropolyhedral zig-zag chains built by alternating edge-sharing Te 6+ O 4 (OH) 2 and CuO 4 (H 2 O) 2 octahedra. Mg(H 2 O) 6 octahedra are connected with the chains from two sides via common O vertices. Adjacent chains are bound by H-bonding forming “layers” which are connected with each other by a system of H-bonds. The mineral is named in honour of the Russian mineralogist Raisa A. Vinogradova (born 1935), Moscow State University. Both the new mineral and its name have been approved by the IMA CNMNC (IMA2014-046).

Honeaite, ideal formula Au3TlTe2, is a new mineral from the late Archaean Karonie gold deposit, Eastern Goldfields province, Western Australia. Honeaite is found with native gold, tellurobismuthite, petzite, hessite, calaverite, melonite, mattagamite, frohbergite, altaite, pyrrhotite and molybdenite. These minerals are concentrated in microvughs and microfractures mainly within areas of prehnite alteration of amphibolite. The mineralisation appears to have been deposited under greenschist-facies conditions at lower temperatures than most gold deposits in the Eastern Goldfields. Single-crystal X-ray studies identified the structure of honeaite as orthorhombic, space group Pbcm , with a = 8.9671 (4) A, b = 8.8758(4) A, c = 7.8419(5) A, giving V = 624.14(6) A3 with Z = 4. The strongest reflections of the calculated powder X-ray diffraction pattern are [ d in A (Irel)( hkl) ]: 2.938(100)(022), 2.905 (39,8)(322, 411), 2.989 (31)(300), 2.833 (23)(310), 1.853 (17)(332). Electron-microprobe analysis (EDS mode) gave (wt%) Au 56.33, Tl 19.68, Te 24.30, total 100.31, leading to an empirical formula (based on 2 Te apfu ) of Au3.00Tl 1.01Te 2.00. Honeaite is black with a metallic lustre and no observed cleavage. The calculated density is 11.18 g/cm3. In reflected plane-polarized light it is slightly bluish grey. Between crossed polars it is weakly anisotropic with dark brown to dark blue rotation tints. Reflectance values in air and in oil are given. Honeaite is named after the late Russell M. Honea (1929–2002).

Mahd Adh Dhahab polymetallic Au-telluride mine in Kingdom of Saudi Arabia is a world-class deposit. The mineralization is hosted by subalkaline bimodal rhyolite-basalt arc succession part of the late Proterozoic Mahd group. The mineralized quartz veins mostly occupy fractures that formed in response to local folding of the Mahd volcanic-sedimentary sequence. The ore predominantly consists of massive sulfides (sphalerite, chalcopyrite, pyrite, and galena) and a diverse range of Au-(Ag)-tellurides (sylvanite, petzite, hessite, tetradymite, tellurobismuthite and altaite). Gangue mineral assemblage comprises chlorite, epidote, sassurite and quartz. Tellurides occur as subhedral grains dispersed within chalcopyrite, sphalerite and Fe-rich chlorite. Geological, structural and mineralogical observations support a model invoking a multi-stage process of mixed magmatic-meteoric fluids and boiling as a cause of telluride precipitation. The metal-bearing magmatic fluid was exsolved from a crystallizing arc alkaline melt produced by partial melting of a subducted slab containing ocean floor sediments. Precipitation from solution occurs as a result of the condensation of Te-rich vapor phase and mixing of auriferous fluids with cooled oxygenated meteoric water at a shallow depth.

Microporous gold is common in many Te-Au deposits. Experimental formation and textures of microporous gold have recently been studied. However, few studies have worked on naturally occurring microporous gold. At the Dongping gold deposit, which is one of the most studied Au-Ag-Te deposits in China natural microporous gold is widely distributed in both primary and oxidized ores. This provides a good opportunity to study the textures and the formation of microporous gold in nature. This gold is pseudomorphous in addition to being porous, indicating that it formed via interface coupled dissolution-reprecipitation (ICDR) reactions. Four textures that were not described previously in experiments were observed in samples from this deposit. (1) A hackly interface between the microporous gold and parent calaverite. Te content shows a decreasing trend with increasing distance from the interface. This texture may result from diffusion of excess surface energy as the ICDR reaction moves towards equilibrium. (2) A less-porous band exists in the microporous gold. The band has fewer pores, smaller crystal sizes and similar chemical composition with the surrounding microporous gold. It likely formed due to the fluctuation of the fluid physicochemical conditions (including decreasing temperature, αO2(aq) and increasing pH) that changes the dissolution rate of calaverite. (3) Microporous gold precipitated between quartz and calaverite. As well, gaps developed between gold and remnant calaverite. This texture is derived from catalytic effects of a heterogeneous nucleation or recrystallization process. It is helpful for extraction and aqueous processing of Au-Te ores, and accounts for the phenomenon that quartz can accumulate gold in some hydrothermal gold deposits. (4) Petzite coexists with Ag-bearing microporous gold, indicating that petzite may also decompose to microporous gold under hydrothermal conditions. Calaverite could be dissolved without altered pyrite at high-temperature (>200 °C) conditions, but under weathering conditions, pyrite would be altered first. In primary ores, microporous gold coexists with pyrite and baryte, indicating that it was formed during the late-stage mineralization. In oxidized ores, microporous gold coexists with limonite and baryte, indicating it may have generated during late-stage mineralization and then altered by weathering. Hydrothermal fluids derive from late-stage mineralization may play the main role in the formation of microporous gold compared to weathering processes. This observation also leads us to reappraise the importance of hydrothermal fluids in the weathering dominated ICDR geological processes.

Numerous limestone–hosted vein–type Au deposits (12 million tonnes at 5.0 g/t Au) are located peripheral to Cu–Au skarn deposits around the Late Jurassic granodiorite intrusions in the Fengshan area, Middle–Lower Yangtze River metallogenic belt, Eastern China. Both the Cu–Au skarn and distal vein–type Au deposits have a complex mineral assemblage, consisting of base metal sulfides, sulfosalts and Au–Ag–(Tl) telluride minerals. In the Cu–Au skarn deposits, grains of electrum, Au–Ag tellurides (hessite and petzite) coexist with Bi–Te minerals (native bismuth, tetradymite, Phase C, and aikinite), sulfides (chalcopyrite, sphalerite, and galena), occurring as grain aggregates or veinlets. In the distal vein–type Au deposits, fine–grained Au–Ag–Tl tellurides (calaverite, petzite, hessite, and Tl–bearing Au telluride) occur as ore minerals in assemblages of sulfides, and carbonate minerals. The mineralogical Bi–Te signature characterizes the skarn assemblages, while the Te–Tl signature is typical of the distal vein–type Au mineralization. Textural relations and mineral assemblages allow the recognition of five generations of hydrothermal carbonate: (1) Cu sulfides and tellurides–bearing calcite assemblages; (2) sphalerite, galena and tellurides–bearing dolomite assemblages; (3) sericite, quartz and tellurides–bearing carbonate veinlets; (4) realgar and fluorite–bearing carbonate veinlets; (5) pure calcite veinlets. Electron microprobe analysis indicates that the tellurides–bearing, ore–related carbonate contains variable Mn content (up to 80 mol.% MnCO3). The C–O isotope compositions of carbonate from the Cu–Au skarn mineralization, to the carbonate–replacement Pb–Zn and distal vein–type Au mineralization, and to the post–ore, realgar–bearing veinlets in the country rocks display a tendency towards heavier isotopic compositions with time, which could be best interpreted as the effect of fluid–rock interaction between magmatic fluid and the Triassic carbonate host rocks. New S isotope data on sulfate minerals (anhydrite, gypsum, and celestite), and C–O isotopic data suggest a common magmatic fluid source for both skarn and distal vein–type mineralization.

Porphyry copper-molybdenum deposits (PCDs) are the world’s most important source of copper, molybdenum and rhenium. Previous studies have reported that some PCDs can have sub-economic to economic grades of critical metals, i.e., those elements that are both essential for modern societies and subject to the risk of supply restriction (e.g., platinum group elements (PGE), rare earth elements (REE), In, Co, Te, Ge, Ga, among others). Even though some studies have reported measured concentrations of Pd and Pt in PCDs, their occurrence and mineralogical form remain poorly constrained. Furthermore, these reconnaissance studies have focused predominantly on porphyry Cu-Au deposits, but very limited information is available for porphyry Cu-Mo systems. In this contribution, we report the occurrence of critical metal (Pd, Pt, Au, Ag, and Te) inclusions in copper sulfides from the world’s largest PCD, the supergiant Río Blanco-Los Bronces deposit in central Chile. Field emission scanning electron microscope (FESEM) observations of chalcopyrite and bornite from the potassic alteration zone reveal the presence of micro- to nano-sized particles (

Epithermal Au-Ag deposits of the La Carolina district, in the San Luis metallogenetic belt (Argentina), are related spatially and genetically to Mio-Pliocene volcanism. In this district, mineralization in the Cerro Mogote and Puesto La Estancia prospects occur as disseminations, veins and fracture/cavity infillings in volcanic/pyroclastic rocks, metamorphic basement and hydrothermal breccias. The gangue assemblage is dominated by carbonates (siderite, rhodochrosite, kutnahorite, dolomite). The main sulfides are pyrite, sphalerite, galena and chalcopyrite. Pyrite and sphalerite have compositional zoning, the former with As-rich cores and Cu-rich overgrowths, the latter with Fe-rich and Fe-poor bands. Sphalerite shows variable contents of Mn, Cu, In, Ga, Ge and Ag. The In-richest sphalerite hosts up to 5940 ppm In but also contains elevated concentrations of Cu, Ag, Ga and Ge, suggesting a coupled substitution mechanism resulting in enrichments in monovalent (Ag+, Cu+) and trivalent-tetravalent cations (Ga3+, In3+, Ge4+). The main precious metal minerals are Ag-rich tetrahedrite, acanthite, argyrodite, pearceite–polybasite and Au-Ag alloy. Locally, Se and/or Te-enriched minerals include galena Pb(S0.9–1Se0.1–0), hessite Ag2(Te0.9–1Se0.1–0), Se-rich cervelleite Ag4(Te1.3–0.9S1–0.5Se0.5–0.2), and also alburnite [Ag8GeTe2S4] and benleonardite [Ag15Cu(As,Sb)2S7Te4]. Pearceite contains Te (3.6–4.3 wt.%) and Se (1–2.3 wt.%) substituting for S, which are unusually high concentrations for this mineral. The Puesto La Estancia deposit contains various tellurides including sylvanite, petzite, stutzite, altaite, tellurobismuthite and volynskite. This study shows that the chemistry of the fluids fluctuated during ore deposition suggesting different fluid pulses (system rejuvenation and/or boiling). The enrichment in Te, Se and Bi enrichment is supportive of a magmatic contribution to the ore fluid, while graphite in the metamorphic basement could be the source of germanium, although a magmatic source cannot be ruled out.

Northeastern China is characterized by widespread Mesozoic volcanic rocks and Au–Cu–Mo mineral deposits with a total gold reserve of > 2000 t. Amongst those gold deposits, the newly discovered Sandaowanzi has a total reserve of ≥ 25 t of Au and an average grade of 15 g/t. This deposit is important because it is the first reported case of a dominantly Au(± Ag)-telluride deposit containing economically valuable bonanza Au- and Ag-telluride ores in the region. The Sandaowanzi quartz vein system and associated Au–(± Ag)-telluride mineralization are mainly hosted by trachyandesites and andesitic breccias. Native gold is closely associated with abundant tellurides including petzite, sylvanite, calaverite, hessite, and altaite. Twelve pyrite samples from the alteration zone yield a well defined Rb–Sr isochron age of 119.1 ± 3.9 Ma, which is in agreement with a robust Rb–Sr isochron age of 121.3 ± 2.6 Ma derived from 10 auriferous quartz samples. The obtained isochron age of ~ 120 Ma represents the formation of the Sandaowanzi gold-telluride epithermal system, which is much younger than the host trachyandesite with a zircon U–Pb age of 312.5 ± 0.5 Ma and the spatially associated monzogranite with a zircon U–Pb age of 182.2 ± 1.1 Ma. Dating results indicate a close relationship between the local Au–Ag–Te mineralization and a magmatism episode in the Early Cretaceous. Noble gas (He and Ar) isotopes obtained from telluride, sulfide and quartz and sulfur isotopes determined from sulfides including chalcopyrite, sphalerite and pyrite demonstrate clear mixing trends between crustal and mantle-derived components, confirming a significant contribution of fluid produced from mantle-derived magmas into the epithermal system. Like many Mesozoic porphyry Cu–Mo ± Au deposits, the coeval epithermal Au–Ag ± Te deposits in the region are genetically related to magmatism triggered by the subduction of the Pacific oceanic plate beneath the Eurasian continent at the time.

The Dongping gold deposit is a mesothermal lode gold deposit hosted in syenite. The ore petrography and chemistry of the tellurides from the alteration zone of the deposit have been studied in detail using optical microscopy, scanning electron microscopy, electron probe micro-beam and X-ray diffraction facilities. The tellurides, consisting mostly of calaverite, altaite, petzite tellurobismuthite and tetradymite, are hosted irregularly in pyrite fractures and voids. In the ore bodies, the species and quantity of tellurides decrease from the top downwards, accompanied with lowering of gold fineness, and the existence of tellurides exhibits a positive correlation with gold enrichment. Mineral paragenesis and chemical variations suggest that during evolution of the ore-forming fluids Te preferably incorporated with Pb to form altaite, followed in sequence by precipitation of petzite, and calaverite when Ag has been exhausted, and the residue fluids were enriched in Au, giving rise to formation of native gold. Calculation with reference of the fineness of native gold coexisting with the tellurides indicates that at 300 °C, log f (Te 2 ) varied between − 8.650 and − 7.625. Taking account of the Au–Ag–Te mineral paragenesis, it is inferred that log ƒ (Te 2 ) varies from − 9.12 to − 6.43, log ƒ (S 2 ) − 11.47 to − 8.86. In consideration of the physicochemical conditions for formation of tellurides, with comparison to some known telluride deposits, it is suggested that high log ƒ (Te 2 ) is a key factor for high fineness of native gold as well as precipitation of abundant tellurides.

The newly discovered Bellerophon-Nelson telluride-bearing gold deposit at the St. Ives camp, Western Australia, is hosted by meta-sedimentary rocks of the lower Black Flag Group and alkaline intrusions. Four stages of mineralization are recognized; from oldest to youngest these are: quartz-carbonate veins (Stage I), quartz-albite-carbonate-pyrite veins and sericite-pyrite seams (Stage II), quartz-pyrite veins (Stage III), and carbonate ± chlorite veins (Stage IV). Stages II and III contain economic gold mineralization, and the gold grains are strongly associated with pyrite. Intense albite and hematite alteration surround the mineralized veins, and trace amounts of gold precipitated in these altered rocks. The albite and hematite alterations are synchronous and derived from the same oxidized fluid as the auriferous veins. The occurrence and absence of hematite within the alteration zone reflects variable amounts of magnetite in the precursor rocks. Thirteen species of telluride and sulfosalt minerals have been identified in Stages II and III. The most common telluride minerals include calaverite, petzite, tellurobismuthite, and altaite, and these minerals have similar occurrences to native gold. In addition to native gold, telluride and sulfosalt minerals are also major Au carriers and account for at least 15% of the gold in this deposit. The mineral associations of PbCl(OH)–Pb2Cl3(OH)–Te–TeO2 and BiOCl–BiO(OH,Cl)–Te–TeO2 were formed as replacement of earlier telluride minerals as the result of reactions with Cl-bearing fluids. The intergrowth between native gold and Cl-bearing minerals + native Te/Te-oxide indicates that Au in telluride minerals was remobilized and re-deposited. The phase diagram for the telluride and sulfosalt mineral association suggests that during Stage II logƒS2 decreased from −8 to −11, and that logƒTe2 increased from −8 to the level required for the formation of Te-oxide. The values of logƒTe2 and logƒS2 in the Stage III veins were −8 to −11 and −9 to −11.5, respectively. The highly oxidized, tellurium-enriched hydrothermal fluid, which formed the Bellerophon gold telluride deposit, is consistent with the involvement of magmatic fluid, and sulfidation is the likely cause of gold precipitation.

The Dahu Au-Mo deposit is located in the Xiaoqinling region and belongs to the Qinling-Dabie orogen of central China. The quartz vein-style Dahu Au-Mo deposit (31 t Au, average grade: 4.7 g/t; 30,000 t Mo, average grade: 0.13 %) formed in four stages, i.e., an early quartz-K-feldspar stage (I), a pyrite-molybdenite stage (II), a sulfide-telluride-sulfosalt-gold stage (III), and a late carbonate-barite stage (IV). Abundant tellurides and sulfosalts occur in stage III: altaite, tellurobismuthite, buckhornite, hessite, petzite, calaverite, aikinite, kupcikite, lindstromite, salzburgite, wittichenite, and tetradymite. The system is characterized by carbono-aqueous fluids of low to moderate salinity and high oxygen fugacity. Total homogenization temperatures of the H 2 O-CO 2 fluid inclusions in stage I and stage III quartz range from 230° to 440°C and 198° to 320°C, respectively. The variation in CO 2 /H 2 O ratios and microthermometric data of the H 2 O-CO 2 fluid inclusions results from a combination of fluid unmixing and sequential trapping of fluid inclusions, but also from postentrapment reequilibration. Abundant minerals are present as solid phases in H 2 O-CO 2 fluid inclusions in stage I quartz: Cu 1.65 S, covellite, chalcopyrite, bornite, molybdenite, pyrite, colusite, anhydrite, and celestine. δ 18 O quartz values of stage I quartz range from 10.2 to 12.0‰, with calculated δ 18 O fluid values ranging from 5.6 to 7.4‰. The δ D values of fluid inclusion waters (thermal decrepitation) in stage I quartz range from −117 to −54‰. The low and scattered δ D values reflect a mixture of ore-forming fluids trapped by the H 2 O-CO 2 fluid inclusions at deep crustal levels and postmineralization fluids, possibly meteoric waters, trapped by secondary aqueous fluid inclusions at higher crustal levels during uplift of the Xiaoqinling core complex. Four molybdenite samples yield an Re-Os isochron age of 206.4 ± 3.9 Ma (MSWD = 0.88), suggesting ore formation in the Late Triassic. Metal signature, mineral association, fluid characteristics, and isotope data of the Dahu deposit, together with the tectonomagmatic setting, imply that the ore-forming fluids were derived from an unexposed and oxidized magmatic system, which likely stems from partial melting of enriched lithospheric mantle beneath the North China craton in a postcollisional extensional setting.