pdf № 362, February

DOI: 10.19110/geov.2025.2.1

The article provides a novel detailed mineralogical and petrogeochemical description of the Sharip group porphyries. They are visually divided into 4 main type by color, quantity and composition of inclusions, but in general have a similar mineral composition, being members of a single trachyandesite-trachyte association. The most important mineral determining the conditions of rock formation is amphibole, corresponding to pargasite and magnesiohastingsite (Mg# varies from 0.80 to 0.35). Amphibole crystallization began at a temperature of about 842—973 °C. Amphibole fractionation in trachyte magma caused petrogeochemical variations in the rocks, expressed in the distribution of the main petrochemical components and the level of accumulation of a number of incompatible elements. Geochemically, the Sharip porphyries are close to adakites (high Sr/Y, La/Yb ratios), and their sources could have been rocks of the lower crust of the Southern Urals (including ultramafic-mafic rocks of the Main Ural Fault and Riphean sedimentary-metamorphic formations).

Keywords: Sharipovo group, Balbuk complex, mineralogy, amphibole, geochemistry, adakite-like porphyries

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DOI: 10.19110/geov.2025.2.2

The distribution of the main chemical elements of the ore association identified by the results of correlation and factor analysis and their mutual arrangement was considered at the Nezhdaninskoye large gold ore deposit. Maps of factor loads for the groups of such elements are constructed: As-Cd-Au; Ag-Pb-Sb; Ni-Co-Cu-Be-Zn; Ba-Ce. Zoning coefficients of the upper- and lower-ore elements as well as the relationship between Cd and Zn within the ore field of the Nezhdaninskoe deposit were studied. Assumptions about a possible source of cadmium anomalies within the gold ore zones were made: decomposition of sphalerite under the influence of hypergene processes or introduction into the ore deposition zone by hydrothermal solutions along with lead and gold.

Keywords: Nezhdaninskoye deposit, geochemical zoning, gold, cadmium

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DOI: 10.19110/geov.2025.2.3

The objects of the study are rocks and soils of the Valaam Archipelago. The archipelago is composed of igneous rocks of basic composition and Quaternary sediments, which caused the unique diversity of natural complexes on its territory. Due to a very weak expression of technogenic pollution, the study of the chemical composition of Valaam soils becomes especially relevant, as it allows tracing the connection between the geochemical composition of the upper soil horizons and rocks. The composition of the upper horizon (0—10 cm, 141 samples) and 141 samples of parent materials was analyzed by X-ray spectral analysis. Additionally, the geochemical composition of the main soil types was analyzed by genetic horizons of the profile. A database of the chemical composition of soils on Valaam Island was made. Information on the composition of the soil-forming rock, soil type, relief character and agricultural use was included for each sample. The data were processed using Statistica-5. We found that the type of parent material was one of the main factors determining the geochemical properties of the upper soil horizon. According to the associations of chemical elements, the island soils were divided into 4 groups: formed on gabbro-diabases, monzonites, lake-glacial clays and sands. Associations of chemical elements inherited by soil from bedrock, depending on relief and characteristic for different types of soils, were revealed.

Keywords: Valaam sill, gabbro-diabases, monzonites, ferruginous-metamorphic soils, soil geochemistry

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DOI: 10.19110/geov.202.2.4

The relevance of the study is underscored by the fact that the active development of mineral deposits in the north of the Komi Republic provokes various seismic events. Most of them remain unnoticed and unexplored. The study aimed at reconnaissance seismic observations of the northern regions of the republic. To clarify the actual seismic situation in the territory of the Vorkuta coal mining region and the mountain-dynamic processes occurring here, expeditionary seismological work was organized in the Polar Urals in the summer of 2023. Similar short-term observations in the Subpolar Urals were also carried out in 2021 and preceded the installation of a stationary seismic station in the city of Inta.

Field work was carried out in 3 stages: at the Yun-Yaga limestone quarry, in the southern pericline of the Enganepe massif and in the southern part of the Niyakhoy ridge. Seismic records were characterized by low and medium noise levels compared to the new Peterson noise model. In total, more than 100 local seismic events with the energy class according to T. G. Rautian KR = 3.8—8.9 and magnitude ML from –0.2 to 2.8 were registered. The spatial distribution of seismic events showed that they were mainly concentrated around the city of Vorkuta and, accordingly, mine fields. The study of mining activity, as well as the analysis of the wave pattern allowed identifying differences in the wave forms of mine dynamic phenomena and industrial explosions and establishing the nature of seismic events. Most of the events are dynamic phenomena in coal mines. We constructed a recurrence graph characterizing features of seismic processes. Based on the law of recurrence, we concluded that temporary observations in the Polar Urals recorded precisely man-made seismicity within the Vorkuta coal mining region.

Keywords: temporary seismic station, microseisms, man-made seismicity, rock burst, coal mine

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DOI: 10.19110/geov.2025.2.5

The essay is dedicated to the outstanding Russian-German physical chemist Wilhelm Ostwald, Nobel Prize Laureate in Chemistry in 1909. His scientific and organizational activities, which began at the University of Dorpat, continued at the Riga Polytechnic, and were most fruitful at the Leipzig Physicochemical Institute, are briefly reviewed. Ostwald's name is associated with the revolution in chemistry that occurred at the turn of the 19th and 20th centuries. Particular attention is paid to his world-famous scientific school and its lessons. Ostwald's denial of atoms as material objects, which surprised his contemporaries, is discussed. The phenomenon of «Ostwald ripening» — the enlargement of crystals in a polydisperse system — which is widespread in crystallogenesis, is also discussed.

Keywords: Wilhelm Ostwald, the formation of physical chemistry, Ostwald's scientific school, antiatomism, energetics, Ostwald ripening of crystals, University of Dorpat, Riga Polytechnic, Leipzig University

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DOI: 10.19110/geov.2025.2.6

In this paper we present an experimental evaluation of the applicability of the stereological principle (equality of area and volume ratios) for low contents of the studied phase and various textural and structural parameters. This principle works well for uniformly distributed ellipsoidal particles. In other cases, it is necessary to apply a correction factor to the average values of the phase ratios determined from sections. This factor depends on textural and structural characteristics.

Keywords: stereological principle, phase ratio, thin sections, polished sections, three-dimensional modelling

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