Six spinel supergroup minerals have been found in the Kontozero volcano-plutonic complex rocks: chromite, ulvospinel, magnesioferrite, maghemite, and titanomaghemite, along with magnetite previously known here. Magnetite, chromite, ulvospinel, and magnesioferrite are connected by gradual transitions through a series of the intermediate compositions according to the isomorphic substitution schemes Cr3+ + Al3+ + Mg2+ ↔ 2Fe3+ + Fe2+ and Ti4+ + Fe2+ ↔ 2Fe3+. Maghemite and titanomaghemite were formed as a result of the low-temperature oxidation of magnetite and ulvospinel. These minerals, in turn, are replaced by hematite or an anatase–hematite assemblage.

Based on an original approach using geoinformation technologies, processing of Earth remote-sensing data, and structural–geomorphological, spatiogeometric, spatiodensity, and tectonophysical methods for the Tuyukan U cluster, specific features of the evolution of the fault framework are revealed and structural and tectonophysical criteria responsible for the location of ore mineralization within the area are formulated and spatially visualized. Using normalization and determination of weight coefficients of each criteria, a digital structural weight of evidence model was elaborated, the accuracy of which is 81% in comparison with reference ore objects. This model is an important basis for more accurate formulation of prospecting geological works, primarily for uranium, within sheet O-49-XII of the State Geological Map.

Ages of minerals of the Chudnoe deposit ores established by the isotope geochronology methods do not allow one to correctly estimate the time of formation of Au–Pd mineralization due to the lack of reliable signs of their syngenicity with gold. Based on linking isotope geochronological data with the history of the geological development of the Subpolar Urals and the entire complex of endogenous and exogenous processes that determined the features of its geological structure and minerageny, the Early Paleozoic mineralization age has been substantiated. The similar age of the metarhyolites hosting the mineralization suggests not only spatial, but also paragenetic relations between the ore mineralization and felsic volcanites. When studying the mineral composition and structural and textural features of ores, one should take into account the imposition of post-ore processes, especially the most powerful metamorphism manifested in the Subpolar Urals with the peak in the Upper Paleozoic (∼250 Ma).

Complex Au–Ir–Os placer deposits are associated with the Guli massif of ultramafic and alkaline rocks with carbonatites within the Maimecha–Kotui province in the north of the Siberian Platform. In contrast to Os and Ir minerals, which are genetically related to ultramafic rocks, the issue of the primary Au source is a matter of debate. We characterized for the first time the morphological and compositional peculiarities of Au minerals from Quaternary deposits of the Dunitovaya River in the southern part of the Guli massif. The native gold grains are subdivided into drop-shaped–round, lumpy, flattened–lumpy, and lamellar morphological types; the main morphometric parameters, the fineness of native gold, and the average statistical characteristics of chemical composition are determined. By inner structure, the studied native gold grains are subdivided on homogeneous, which mostly consist of homogeneous electrum, and heterogeneous, which contain (1) several minerals (e.g., electrum, tetraauricupride, and auricupride) or (2) electrum with a highly varying composition from Au-bearing silver to Ag-bearing gold. The first Cu isotopic composition of native gold of various morphological types of the Dunitovaya River is characterized by similar values of δ65Cu in a range of –0.59 to 0.11‰ (the average δ65Cu value = –0.30 ± 0.23‰, n = 5), indicating a primitive ore-matter source. Taking into account the geological setting of the riverbed and terrace deposits of the Dunitovaya River, insignificant transportation distance of placer gold (4–6 km), and similarity of Au minerals from the Dunitovaya River with those from calcite carbonatites, the rocks of the Maimecha–Kotui ijolite–carbonatite complex were the main source of the studied morphological gold types.

The U–Pb age of the Thunder Stone granite block, which is the pedestal of the Bronze Horseman monument to Peter the Great in St. Petersburg, is dated at ∼1595 Ma. This age was obtained from accessory zircons separated from the biotite flakes using a jeweler gravel. The study was carried out on an SIMS SHRIMP-IIe secondary ion microprobe (15 local U–Pb isotopic analyses, 12 zircon crystals) at the Center of Isotopic Research of the Karpinsky Institute (St. Petersburg). It is not yet possible to determine the source of the Thunder Stone, since granites of the same age have not yet been found either in the Vyborg batholith (1665–1615 Ma), in the Salmi batholith (1547–1535 Ma), or other granite intrusions located in the proximity of St. Petersburg. Thus, the Thunder Stone seems to confirm the historically established idea that it is unique and hints that it should be found among the manifestations of the yet unidentified phases of Early Riphean granitoid magmatism in the most closely located regions.

Results of the study of galena from the Berental gold ore system of the RIRGD (reduced intrusion-related gold deposit) type associated with the similarly named granite stock in the southeastern part of the Yana–Kolyma gold belt are reported. There is a trend to change from (i) the bismuth–sulfotelluride mineralization of the apical (intra-intrusive) zone to (ii) the sulfide–sulfoarsenide mineralization of the proximal zone and (iii) the silver–polysulfide mineralization of the distal zone as moving away from the Berental intrusive massif outcrop. Galena in the bismuth–sulfotelluride ores is characterized by the bismuth geochemical specialization caused by bismuthine (Bi2S3) microinclusions. In the sulfide–sulfoarsenide type, in addition to bismuth, the presence of silver is noted. It is caused by a solid solution of matildite (AgBiS2) in galena and, less often, by acanthite (Ag2S) microinclusions in it. In some areas, it contains gold (due to uytenbogaardtite (Ag3AuS2) or native gold microinclusions). Galena in the silver–polysulfide mineral mineralization type is characterized by increased concentrations of selenium (solid solution with clausthalite (PbSe)) and/or antimony and silver (due to miargyrite (AgSbS2) microinclusions).

Abstract Dating of the modern seafloor massive sulfides (SMS) is a complex task largely due to the multistage deposition of ore-forming minerals and the influence of changing physicochemical conditions on the isotope geochemistry during the interaction of hydrothermal fluids with host rocks and near-bottom seawater. Based on data obtained for the sulfide ores of the Semenov-5 field at the Mid-Atlantic Ridge (MAR), the possibilities and limitations of the 230 Th/U method are demonstrated, particularly concerning the formation of the radiometric system in environment above and below the paleo-seafloor level. New ages obtained for surface ores range from ~60 to ~8 thousand years. However, dating of subsurface sulfides was impossible due to the minimal input of near-bottom seawater within mound and its influence on the deposition of the sulfides. The study indicates that massive sulfides formed beneath the seafloor are of metasomatic origin, suggesting that the sulfide mineralization is not limited only by paleo-seafloor but also extends to the greater depths. This finding has significant implications for other sulfide deposits within the MAR as well and may lead to the revision of their resource potential. The established long-term character of hydrothermal discharge within the Semenov-5 field is comparable with longevity of other hydrothermal fields within the Semenov ore cluster. Obtained data indicate a long and complex evolution of hydrothermal systems related to the ultramafic rocks of the ocean core complexes in slow-spreading mid-ocean ridges.

The paper describes the occurrence of so-called “mustard gold,” which forms discrete grains and replacement rims on calaverite (AuTe2) in the adularia-quartz veins of the Evevpenta epithermal ore occurrence in Kamchatka, Russia. Four varieties of mustard gold were identified: (1) pure mustard gold, (2) mustard gold containing areas and veinlets of homogeneous native gold, (3) mustard gold with relicts of Ag(-Au) sulfides, and (4) mustard gold intergrown with oxygen-containing compounds of Fe and Mn. It is hypothesized that the mustard gold at Evevpenta formed through hypogenic replacement of calaverite (AuTe2) during late hydrothermal stages. We propose that the chemical composition of mustard gold may serve as an indicator for the gold–antimony orogenic and gold-telluride epithermal deposits.

Neyite Ag2Cu6Pb25Bi26S68 was identified in the wastes of the Yugo-Konevo tungsten deposit (Chelyabinsk oblast, Southern Urals) for a first time in Russia. This rare sulfosalt occurs as prismatic crystals up to 3 × 0.5 mm in fluorite–muscovite–quartz veins and is associated with aikinite, tetradymite, and pyrite. Reflectance spectra and coefficients of neyite are published for the first time. The electron microprobe composition of neyite (wt %, mean of seven analyses): Ag 1.75, Cu 3.59, Pb 35.01, Cd 0.12, Bi 42.59, S16.54, total 99.60. The empirical formula based on S = 68 apfu is Ag2.14Cu7.45Pb22.27Cd0.14Bi26.86S68. The crystal structure of neyite from Yugo-Konevo was refined based on the monocrystal, R1 = 3.43%, wR2 = 7.22%. The mineral is monoclinic, space group С2/m, a = 37.3900(6), b = 4.05500(10), c = 43.5821(7) Å, β = 108.740(2)°, V = 6257.5(2) Å3, Z = 2. The structure of neyite is based upon three different modules of archetypal structure of galena. (111)PbS blocks make up octahedral “columns” extended along the b direction, which alternate with (100)PbS blocks in the a direction. The resulting layers are alternated with (922)PbS layers along c. The main structural feature of neyite from Yugo-Konevo deposit that distinguishes it from previously described neyite from the type locality and cuproneyite is the disorder of the Me16 position and the presence of the additional Cu5 position. These features, along with analysis of the bond valence sums, suggest the presence of chains of CuS4 tetrahedra alternating with chains of BiS6 octahedra.