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A detailed description of alkali water springs (pH > 10) found within the ultrabasic massif of Mount Soldatskaya in the Kamchatsky Mys Peninsula in Kamchatka is presented for the first time. The chemical composition of the springs and the dependence of the ratios and concentrations of some components on pH are indicative of the fact that these waters were involved in the present-day serpentinization of ultrabasic rocks. The springs with the highest alkali levels (pH 12.3) contain dissolved hydrogen at a concentration of about 0.6 mmol/l. The isotopic composition behavior of carbonate travertines deposited from these springs (δ 13 C and δ 18 O) differs from the known trend of “meteogenic” travertines related to serpentinization of ultrabasic rocks in Oman and California. The age of travertines determined by the radiocarbon method is close to modern.

— Mineral associations and compositions of sulfoselenides and other silver chalcogenides from epithermal deposits of the Okhotsk–Chukotka volcanic belt (Northeast Russia)—Rogovik, Lunnoe, Julietta, Valunistoe, Corrida, and Pepenveem—have been studied. Different types of relationships between S–naumannite and Se-acanthite in the ores of the study deposits have been established. It is shown that the replacement of S–naumannite and Se-bearing minerals (Se–galena, Se–stephanite) of early parageneses by Se-acanthite or acanthite at later stages is a general pattern in the sequence of formation of silver chalcogenides. Based on the results of thermodynamic calculations and data on the composition of the main productive mineral associations, the physicochemical parameters (T, ƒS 2 , ƒSe 2 , ƒO 2 , pH) of ore formation at these deposits were reconstructed.

The paper presents geological and genetic typification of orogenic gold-ore deposits of Taimyr–Severnaya Zemlya province, associated with accretionary processes in the Precambrian and collisional ones in the Late Paleozoic. Gold-bearing mineral associations of gold-quartz and gold-sulfide-quartz deposits of accretionary formations of the Precambrian Shrenk–Faddei (Yasnensk, Malinovsk) and collisional Mininsk–Bolshevik (Nizhnelitkenskoe, Vidimoe, Nerpichye, Konechninskoe) mineragenic zones have been studied. Studies of fluid inclusions have made it possible to establish the main PTX parameters of gold-ore mineralization formation. The greenschist regional-dislocation metamorphism was the main ore-generating processes during the orogenic-accretionary epoch; plutonogenic-metamorphogenic and plutonogenic granitoid magmatism—during the orogenic-collisional epoch. The obtained data indicate the possibility of identifying two new geological and economic regions in the central sector of the Russian Arctic.

An Erratum to this paper has been published:

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070097

A detailed description of alkali water springs (pH > 10) found within the ultrabasic massif of Mount Soldatskaya in the Kamchatsky Mys Peninsula in Kamchatka is presented for the first time. The chemical composition of the springs and the dependence of the ratios and concentrations of some components on pH are indicative of the fact that these waters were involved in the present-day serpentinization of ultrabasic rocks. The springs with the highest alkali levels (pH 12.3) contain dissolved hydrogen at a concentration of about 0.6 mmol/l. The isotopic composition behavior of carbonate travertines deposited from these springs ([delta].sup.13C and [delta].sup.18O) differs from the known trend of \"meteogenic\" travertines related to serpentinization of ultrabasic rocks in Oman and California. The age of travertines determined by the radiocarbon method is close to modern.

Samples of siliceous rocks of the Southern Kambalny Central Thermal Field (SKC) containing a unique ore mineralization were studied. Optical microscopy, scanning electron microscopy, X-ray microanalysis, X-ray diffraction, ICP-MS, and Raman spectroscopy were used in this study. High concentrations and a wide range of rare and rare-earth elements were found in siliceous rocks. Silicates (quartz, moganite, and opal-crystobalite/tridymite opal), oxides (hematite and anatase), hydroxides (goethite), carbonates (calcite with Fe and Mn impurities), sulfates (barite with Sr impurity and gypsum), sulfides (pyrite, marcasite, chalcopyrite, and chalcocite), phosphates (xenotime-Y, YPO 4 with impurities of lanthanides, S, Ca, and As; berlinite, AlPO 4 with the V impurity), and apatite were identified. Structures of anatase replacement by quartz often in association with pyrite were identified. The mineralization of SKC siliceous rocks reflects the physicochemical specificity of deep metal-bearing solutions.

The supergene Au in weathering crusts of both the Suzdal and Raygorodok deposits is characterized by enhanced fineness, grain size, crystallinity, and the appearance of botryoidal aggregates of crystals. In the weathering crust of the Suzdal deposit, the exogenous Au is associated primarily with scorodite and carbonates; for Raygorodok, with chalcocite, bornite, hydrocarbonates and Cu hydrosulfates. The difference in the mineral associations of supergene Au at the deposits is determined by the occurrence of various mineral concentrators of Au in the primary endogenous substrate: arsenopyrite and pyrite at the Suzdal deposit and chalcopyrite with pyrite at the Raygorodok deposit. Due to the much greater mobility of Ag in the supergene zone, the weathering crusts are likely to contain submicron microinclusions of Ag minerals beyond the zones of Au concentration.

The composition of a reduced C–O–H fluid was studied by the method of chromatography–mass spectrometry under the conditions of 6.3 GPa, 1300–1400°C, and f O 2 typical of the base of the subcratonic lithosphere. Fluids containing water (4.4–96.3 rel. %), methane (37.6–0.06 rel. %), and variable concentrations of ethane, propane, and butane were obtained in experiments. With increasing f O 2 , the proportion of the CH 4 /C 2 H 6 peak areas on chromatograms first increases and then decreases, whereas the CH 4 /C 3 H 8 and CH 4 /C 4 H 10 ratios continually decrease. The new data show that ethane and heavier HCs may be more stable to oxidation, than previously thought. Therefore, when reduced fluids pass the “redox-front,” carbon is not completely released from the fluid and may be involved in diamond formation.

The forms of Au and Ag occurrence in the crystallization products of melts in the Fe–S–Ag–Au system depending on the proportions of Fe/S and Ag/Au have been studied at (Fe + S)/(Ag + Au) = 0.1. It is shown that the S-rich systems with S/Fe = 2 contain Au–Ag sulfides and Au–Ag alloys. The systems depleted in S with S/Fe = 1 contain only Au–Ag alloys. The results of XPS provide evidence for the sulfide and metallic components of Au and Ag among the crystallization products of melts in the system studied at S/Fe = 2 and a metallic component with S/Fe = 1. According to the data of electron microprobe analysis, the content of “invisible” forms of noble metals in pyrite and pyrrhotite is < 0.024 wt % for Au and <0.030 wt % for Ag; the contents of “invisible” Au and Ag in troilites are 0.040 ± 0.013 wt % Au and 0.079 ± 0.016 wt % Ag.