Home – Home – Jornals – Russian Geology and Geophysics 2026 number 6

This article presents data on active fault-related deformation of the Kamchatka Peninsula (Kamchatka, Russia), located between the converging Aleutian and Kamchatka Island arcs. It is shown that convergence of the arcs results in shortening of the Earth’s crust of the Kamchatka Peninsula in a direction transverse to the peninsula. The convergence is accomplished by underthrusting of the colliding blocks: the Aleutian Arc is underthrusting beneath the Kamchatka Peninsula, and the Kamchatka Peninsula is, in turn, underthrusting beneath Kamchatka. It is demonstrated that this mode of convergence is also characteristic of larger-scale collision zones, as in case of those between the Indian and Arabian plates with the Eurasian Plate. In all cases, the plate (block) that underthrusts is the one whose hinterland contains the driving source of motion.

Massifs of alkaline granitoids and nepheline syenite are widespread in Eastern Tuva and are frequently associated with rare-metal deposits and occurrences, which formed mainly during the Late Carboniferous and Permian. The Naryn massif comprises nepheline syenite of the main phase, rocks of the contact zone, and a complex of three types of foidite microsyenite dikes. Zircon U-Pb geochronology yields ages of (SIMS - 315 ± 3 Ma) for the main phase and (CA-ID-TIMS - 318 ± 1 Ma) for the microsyenite-1 dikes, indicating that the massif was emplaced during the Middle Carboniferous. The mineralogical, geochemical, and Nd isotopic characteristics of the massif rocks suggest that their diversity results from the differentiation of a single parental magma, a process that occurred at different hypsometric levels. Crystallization of biotite-pyroxene-amphibole nepheline syenite of the main phase and feldspar liebnerite syenite of the marginal zone occurred at the upper level. Dikes of apo-amphibole nepheline microsyenite-1, pyroxene-biotite microsyenite-2, and biotite nepheline microsyenite-3 were emplaced sequentially from a deeper chamber containing the differentiating melt. The evolution of the melts at both levels was driven by the fractionation of mafic minerals (amphibole), apatite, and feldspar. As melt alkalinity increased, rare elements such as Zr, Nb, Ta, and REE accumulated, eventually forming their own mineral phases during the late stages of crystallization. These findings indicate that the widespread foidite-series rocks of Eastern Tuva may be potentially ore-bearing, and the Middle Carboniferous should be considered as a distinct phase of alkaline magmatism within the East Sayan rare-metal metallogenic zone. The Nd isotopic composition of the Naryn massif rocks (ε_Nd( T ) = 6.3-7.1) precludes significant involvement of continental crust in their source. Therefore, sublithospheric alkaline basaltoid magmas are interpreted to be the parental magmas for all rocks of the Naryn massif.

A model sample of ore pyrite from the Degdekan gold deposit (Northeastern Russia) is used to demonstrate the application of different variants of inductively coupled plasma mass spectrometry for the purpose of determining the ratio of surface-bound and structurally bound trace elements in pyrite. Despite the differing physicochemical principles of the analytical methods, namely, the decomposition of crystals of varying sizes and data processing using the statistical sample of analytical data for single crystals (SSADSC) and direct surface scanning with a laser beam of varying power using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), a number of elements show a tendency to be enriched in the surface layer of pyrite crystals. The ratio of the trace element content in the surface layer to that in the volume (structure) of the crystal is defined as the selectivity of surface phases for a given element. The selectivity (S) values obtained by the first method are as follows: 3.9 (Mn), 3.3 (Ag), 6.4 (Pd), 6.4 (La), 0.3 (Pr), 0.8 (Tb), 2.6 (Ho), 0.5 (Er), and 1.0 (Lu). The LA-ICP-MS results yield the following values: 3.9 (Mn), 1.4 (Co), 6.2 (Ni), 1.6 (Cu), 0.9 (Sb), 0.2 (Au), 0.3 (As), 6.8 (Ag), 18 (La), 46 (Ce), 5.2 (Pr), 11 (Nd), 1 (Eu), and 0.6 (Dy). A comparison with experimental selectivity values for Mn, Pd, and Ag shows a reasonable agreement. Most of the studied trace elements show a direct correlation between selectivity and the difference in the ionic radii of the element and Fe, confirming the relationship between selectivity and the incompatibility of the impurity element in the FeS₂ structure. High correlation coefficients are observed among light rare earth elements on the surface, whereas correlations between light and heavy rare earth elements are either absent or negative. Despite the preliminary nature of these results, they warrant practical consideration as a foundation for developing technologies to extract critically important rare earth elements as byproducts during the processing and beneficiation of pyrite ore and concentrate.

New data on the composition and distribution of polycyclic aromatic hydrocarbons (PAHs) in thermal waters and host rocks in the Baikal Rift Zone have been obtained. It is shown that the total concentration of all identified compounds is 0.17-1.15 μg/L in the thermal springs and 0.021-1.19 μg/kg in the host rocks. Naphthalene, phenanthrene, and dibenzo[a,h]anthracene predominate in the waters. Phenanthrene, fluoranthene, and dibenzo[a,h]anthracene prevail in the rocks. It has been established that the total PAH concentration increased with TDS of water and with N₂ and He concentrations in released gases. The calculated coefficients of technogenic load show a low level of pollution for all the studied thermal springs. The PAH origin was determined based on indicator ratios. On the one hand, PAHs are petrogenic in the thermal waters; they resulted from the geochemical transformations of organic matter at high temperatures, pressures, and microbial activity and were transported with aqueous and gas condensate solutions along faults and fractures. On the other hand, some compounds are pyrogenic; the pyrolysis products get into thermal waters under near-surface conditions or during the mixing of thermal water with cold groundwaters. The results obtained give detailed insight into the composition of thermal waters and the genesis of organic matter. They can be used to propose a conceptual model for the formation of thermal water composition in the region under study.

We propose a comprehensive field method for assessing the accuracy of the Earth’s magnetic field models. Our approach involves instrumental determination of the geomagnetic field vector elements at specific locations. The measurement complex includes aeromagnetic surveys using unmanned aerial vehicles and ground-based surveys comprising areal pedestrian magnetometry and absolute measurements of magnetic declination and inclination. The developed method enables the determination of the Earth’s magnetic field in regions with insufficient coverage by permanent ground-based geomagnetic observatories. We present the results of applying this method in the central part of the West Siberian Platform. These results confirm the effectiveness of the proposed approach for conducting high-precision measurements within time intervals constrained by seasonal and weather conditions. The resulting data exhibit high accuracy and demonstrate the potential of this method for determining the secular variation of the Earth’s magnetic field in arbitrary regions.

When conducting seismic surveys on the ground, it is usually not possible to placereceivers with a uniform sufficiently frequent step over the area of observation. Interpolation (regularization) is an effective tool for generating additional seismic records without changing the spectral composition of data over time and with expansion of the spectral composition over space. This paper considers the optimization of a regularization algorithm based on iterative application of discrete Fourier transform (DPF) over a space known as ALFT (Anti-leakage Fourier transform). The proposed modification of ALFT is a way to reduce the set of sample wave numbers when performing DPF. The effectiveness of the proposed algorithm was confirmed by processing both synthetic and field data. The calculation time was reduced several times compared to the original algorithm, and the results of restoring missed traces did not worsen. The results are valuable from a practical point of view and can be applied in future to the processing of ground-based seismic data on an industrial scale.

This paper provides a brief review of methods based on the analysis of natural microseismic ground vibrations - collectively known as passive seismic methods. These include spatial autocorrelation, seismic interferometry, and the spectral ratios of seismic noise components. Their application for studying the structure and properties of the shallow subsurface in the Arctic is discussed. The shallow section across frost mounds in the Arctic is analyzed and interpreted using the spectral ratios of seismic noise components. The resulting two-dimensional sections reveal a horizontally bedded structure, with four main beds distinctly identifiable on the profiles. These beds are interpreted as an upper sedimentary bed, a basement, and two intermediate beds distinguished by their velocity characteristics. The section is disrupted by vertical and inclined heterogeneities that extend from the basement faults to the surface, exhibiting high anisotropy and reduced rigidity. The spatial correlation between these subvertical heterogeneities and the surface locations of frost mounds suggests that these areas represent zones of weakness, possibly fault zones or fluid migration pathways. A review of scientific publications suggests that the results obtained using passive seismic methods are reliable, as also confirmed by other independent geophysical techniques. Passive seismic methods prove highly effective in hard-to-reach areas like the Arctic because they do not require long-term deployment of an observation network. Furthermore, spectral ratio methods do not necessitate a large number of seismic stations. These methods are particularly useful for studying hard-to-recover hydrocarbon reserves characterized by a complex shallow structure (several meters). They enable rapid investigation of the upper section at depths ranging from a few meters to tens of kilometers during reconnaissance work, with minimal financial and labor investment. From an environmental standpoint, passive seismic methods are the least intrusive, as they are non-invasive and non-destructive.