In this study, sulphate efflorescent minerals covering the surface of the Donnoe and Dachnoe fields of the Mutnovsky volcano are described. The minerals were precipitated on the argillic facies as the result of water–rock interaction and fumarole emission. A chemical composition of Ca, Ba, (NH₄)⁺, Na-Fe³⁺, (NH₄)⁺-Al, (NH₄)⁺-Fe³⁺, Na-Al, K-Al, and K-Fe³⁺ sulphates was reported. Elements such as Sr, Mg, Co, Ni, Ti and P were found as isomorphic impurities. Ammonia species were concentrated around fumaroles. The mineral assemblage described herein is unique in relation to other geological settings and reflects the process of low-temperature mineral formation associated with volcanism. The thermal water contains cations such as H, Na, K, NH₄, Ca, Mg, Fe²⁺, Fe³⁺, and Al in different proportions with pH ranging from 2.4 to 6.5 and the dominance of acidic waters. The gas condensate bears such cations as (NH₄)⁺, Ca, and Mg and has a pH of ~5. Thus, the rest of the main cations are derived from the leaching of the host rocks. Among the identified phases, the alunite-supergroup minerals are more prone to isomorphism. The Ti, Co, and Ni impurities mark the unique geochemistry of thermal water at the Mutnovsky volcano. We postulate that the chemical composition of alunite-supergroup minerals reflects the types of hydrothermal occurrences and contains important information on the geochemistry of the hydrothermal process.

This paper reviews and summarizes the available information on the composition of palladian gold with various contents and sets of isomorphic impurities (Ag, Cu, Hg) at 50 deposits and ore occurrences with Au-Pd mineralization. It is revealed that Palladian gold is represented by the systems Au–Pd, Au–Pd–Hg, Au–Pd–Cu, and Au–Pd–Ag–Hg, but more frequently corresponds to Au–Pd–Ag, Au–Pd–Ag–Cu, and Au–Pd–Ag–Cu–Hg. Objects with palladian gold belong to different types of gold deposits and to the deposits at which the main components of ores are PGE, Cr, Cu, Ni, V, and Ti. We propose a classification of the types of deposits with palladian gold: (1) PGE ore deposits related to mafic–ultramafic magmatic complexes (two subtypes—(a) low-sulfide-grade (less than 2%–5% sulfides) Alaskan, and (b) high-sulfide-grade (more than 5% sulfides) Norilsk); (2) orogenic gold deposits (OG); (3) epithermal (porphyry) gold–copper deposits (EPGC); (4) iron oxide copper gold deposits (IOCG); (5) ferruginous quartzite deposits; (6) volcanic exhalation; and (7) gold-PGE placers of five subtypes corresponding to the types of 1–5 primary sources. Physicochemical conditions of the formation of palladian gold at some deposits of type 1 cover two areas—magmatic high-temperature and hydrothermal low-temperature. At the majority of deposits of types 2–4, its formation proceeds with the participation of hydrothermal fluids (300–60 °C) of various salinities (0.2–30 wt.% NaCl eq.). Palladian gold is mainly high-fineness (910‰–990‰), is less frequently medium-fineness, and contains Ag and Cu, but does not contain Hg at the deposits of types 1, 3, and 4. The only exception is the Au-Pd-Hg Itchayvayam ore occurrence (Kamchatka, Russia), for which two varieties of Pd,Hg-bearing native gold (fineness 816‰–960‰ and 580‰–660‰) are determined. Low-fineness palladian gold with the major content of Ag is typical of OGD deposits. Medium-fineness palladian gold occurs at ferruginous quartzite deposits and in volcanic exhalations. Hg, Ag, Cu-bearing high-fineness palladian gold is present mainly in placer deposits (type 7). The most common minerals in association with palladian gold are arsenides, stibioarsenides, sulfides, stannides, bismuthides, tellurides, and selenides of Pd and Pt. These are typical of deposit types 1 and 7. The minerals of Au, Ag, and Cu (tetra-auricupride, aurostibite, chalcopyrite, bornite, chalcocite, eucairite, etc.) are in association with palladian gold at OG, EPGC, and IOCG deposits. Hg minerals (cinnabar, tiemannite, coloradoite, potarite) are at some deposits (types 1, 2, 7-1, 7-4). Cu, Fe, and Pd oxides (tenorite, hematite, magnetite, PdO, (Pd,Cu)O) and Fe and Pd hydroxides (goethite, (Fe,Pd)OOH) occur at the deposits of the 3, 4, and 7 groups and indicate the highly oxidizing conditions of ore formation. The most common minerals among host minerals are quartz and muscovite, including fuchsite (Cr-Ms), chlorite, albite, K-feldspar, hornblende, and carbonates (calcite, siderite, etc.). The fineness, content, and set of impurities in palladian gold and minerals in association with it reflect the mineralogy of Au-Pd ores and allow them to be used as indicators for the deposit types.

The unique minerals of the Au-Pd-Hg system in gold grains from heavy concentrates of the Itchayvayam placers and watercourses draining and ore samples of the Barany outcrop at the Itchayvayam mafic–ultramafic complex (Kamchatka, Russia) were investigated. Gold grains from watercourses draining and heavy concentrates of the Itchayvayam placers contain substitution structures formed by Pd,Hg-rich low-fineness gold (Au_0.59–0.52Pd_0.24–0.25Hg_0.17–0.23, 580‰–660‰) and Pd,Hg-poor high-fineness gold (Au_0.94–0.90Pd_0.02–0.04Hg_0.03, 910‰–960‰). Potarite (PdHg) without and with impurities (Au < 7.9, Cu < 3.5, Ag < 1.2 wt.%), Ag-poor high-fineness gold (Au_0.91Ag_0.09, 950‰), Ag,Pd,Hg-bearing middle-fineness gold (Au_0.75Ag_0.08Pd_0.09Hg_0.08—Au_0.88Ag_0.09Pd_0.02Hg_0.01, 820‰–930‰), and Pd,Hg-rich low-fineness gold with minor contents Ag and Cd (Au_0.51–0.55Pd_0.25–0.22Hg_0.21–0.16Ag_0.03–0.06Cd_0.01, fineness 580‰–630‰) were observed as individual microinclusions in the ore samples of the Barany outcrop. XRD and EBSD study results show that the Pd,Hg-rich low-fineness gold is isotypic to gold and has the same structure type, but different cell dimensions. According to data obtained for the Itchayvayam and some deposits and ore occurrences with Pd,Hg-bearing gold, the stable ternary phases and solid solutions of the following compositions in the Au-Pd-Hg system have been identified: Pd,Hg-poor gold (Au_0.94–0.90Pd_0.02–0.04Hg_0.03), Pd,Hg-rich gold (Au_0.59–0.52Pd_0.24–0.25Hg_0.17–0.23), Au-potarite (PdHg_0.62Au_0.38—Pd_1.04Hg_0.96—Au_0.80Pd_0.68Hg_0.52), and Au,Hg-bearing palladium (Pd_0.7Au_0.3Hg_0.1). The genesis of Pd,Hg-rich gold is insufficiently studied. We supposed that the meteoric waters or low-temperature hydrotherms rich in Pd and Hg could lead to the replacement Pd,Hg-poor gold by Pd,Hg-rich gold. High concentrations of Pd in Pd,Hg-bearing gold indicate a genetic relationship with mafic–ultramafic rocks.

The relevance of this study is determined by lack of information of the behavior and accumulation of non-conventional metals (-oids), such as tellurium, bismuth, selenium (TBS-microelements), involved in modern industries, as well as the limited information about deposits, in which they are able to accumulate significant concentrations, including in association with native gold. Such objects are represented by some epithermal deposits. Russia's share in the total balance of these deposits accounts for a negligible number, although in some regions, such as the Arctic, Siberian and Far East, they have a significant role. The key task of this research is to investigate the material composition and conditions of gold and TBS-microelements formation in an exotic for the low sulfidation type «copper mineral association» of the Baranyevskoe Au-Ag epithermal deposit (Central Kamchatka). The objects of the research are ores and their host altered rocks in the form of core-, hand-and-chip-samples. Research methods. Minerals, ores, and host altered rocks were studied by electron and optical microscopy, as well as by X-ray diffraction analysis, microthermometry, Raman and infrared spectroscopy. To determine the temperatures of phase transitions, salinity and composition of gas-liquid inclusions, microthermometry and Raman spectrometry of bipolished plates were carried out. It was established that the main volume of the «copper mineral association» with gold enriched in tellurium, selenium, bismuth is associated with illite-muscovite quartz formed in modern altered rocks of late Miocene–Holocene age. The composition of copper mineralization is represented by copper sulfides (geerite (Сu8S5), sometimes with impurities of Pd (up to 0,8 wt. %) and Te (up to 1,9 wt. %), chalcopyrite, bornite, tetrahedrite fahlore with Bi impurities (up to 11,16 wt. %), wittechenite (Cu3BiS3), emplectite (CuBiS2), miharaite (PbCu4FeBiS6), aikinite (CuPbBiS3), finegrade gold (Au 920–980), gold and silver tellurides, telluro-selenides Bi and Pb, including non-stoichiometric (unknown), to a lesser extent, pyrite sporadically enriched in Cu (up to 0,9 wt. %), galena enriched in Se (up to 8,5 wt. %). As a result of the data obtained, it was established that the gas-liquid inclusions in quartz and calcite, the hydrothermal-ore process proceeded at temperatures of 250…305 °C at a salinity of 0,5…1,2 wt. % NaCl equiv. As a result of studying the material composition of ore and vein mineralization, it is assumed that aqueous H3TeO3+ and H2TeO3, chloride BiCl3(aq) (III) solutions, and carbon dioxide participated in ore formation. Актуальность настоящего исследования обусловлена дефицитом информации о поведении и формах нахождения нетрадиционных видов полезных ископаемых в качестве рассеянных металлов (-идов), таких как теллур, висмут, селен (TBS-микроэлементов), задействованных в современных отраслях промышленности, а также ограниченностью сведений об объектах, в которых они способны концентрироваться в промышленно-значимых объемах, в том числе совместно с золотом. Одним из вариантов таких важных и перспективных объектов являются эпитермальные (низкотемпературные) Au-Ag месторождения. При этом на долю России в общем балансе эпитермальных месторождений в настоящий момент приходится небольшая часть, хотя в отдельных регионах, таких как Арктический, Сибирский и Дальневосточный, они приобретают промышленно-важное значение. Целью проведенного исследования является изучение вещественного состава и условий формирования золота и TBS-микроэлементов в «медной минеральной ассоциации» эпитермального Бараньевского Au-Ag месторождения (Центральная Камчатка). Объектами исследования являются руды и вмещающие их метасоматические породы в виде керновых, штуфных и сколковых проб. Рудная минерализация и вмещающие ее метасоматиты проанализированы методами оптической и электронной микроскопии c энергодисперсионной спектроскопией, а также методами рентгено-дифракционного анализа, микротермометрии, рамановской и инфракрасной спектроскопии. Полученные результаты исследования свидетельствуют о том, что основной объем «медной минеральной ассоциации» с золотом, обогащенной теллуром, селеном, висмутом связан с иллит-мусковитовыми кварцитами, образованными в современных околорудных метасоматитах плейстоцен-плиоценового возраста. Медная минерализация представлена сульфидами меди (гееритом (Сu8S5), иногда с примесями Pd (до 0,8 мас. %) и Te...

The Evevpenta ore occurrence is situated in the northeastern part of the Central Kamchatka volcanic belt (Kamchatka Peninsula, Russia), and lies among andesitic volcanic complexes of the Neogene age. The ore bodies are veins, zones of quartz streaks, and hydrothermal breccias, accompanied by aureoles of argillization which transition into propylites at the periphery. The formation of noble-metal mineralization occurred through two phases: the hypogene (hydrothermal) phase and the hypergene phase. For the hypogene phase we have identified two mineral associations related to noble-metal mineralization: the Central area contains gold—telluride–quartz mineralization, while the Northern area hosts telluride–sulfide–quartz mineralization. The hypergene mineral association with native gold occurs within the Central area only. Based on data relating to the material composition of the ores we show that the Evevpenta ore occurrence is a typical member of epithermal reduction-alkaline or low sulfidation deposits.

Новые данные о составе и возрасте долеритов оюского комплекса хр. Ямб-Пэ, Северо-Западный Пай-Хой