Research subject. Geochemistry and mineralogy of chromium in the Paleozoic carbonate rocks of the Northern Urals. A recent review of these data, published more than half a century ago during the flourishing of Russian geology (1980– 1997), showed that these data were undeservedly forgotten.
Materials and methods. The generalisation of all the results of previous work on the Northern Urals region, as well as the compilation of the World’s data on the chromium content in the stratosphere.
Results. The previous studies retain their acute relevance not only in their narrow specialised sense, but also more broadly for the solution of a number of major geological issues in this region, far beyond the scope of geochemistry or mineralogy alone. One of the important results is the statement about the wide development of ultramafic magmatism in the ancient sequences of the Northern Urals.
Conclusion. The article formulates current unresolved issues and suggests the methods for solving them. That unconventional approach promises great progress in deciphering the Paleozoic facies and paleogeography of the Northern Urals region.

Research subject. Conodont-based biostratigraphic subdivision of the monotonous siliceous-terrigenous sequence stratigraphically underlying the Famennian Zilair Formation.
Materials and methods. Conodont imprints on the bedding planes from our own collections along with the data from other researchers were used for dating and subdivision of siliceous formations.
Results. Our study of conodonts from the deposits underlying the Zilair Formation at a number of intersections on the eastern side of the Zilair synclinorium showed that the stratigraphic scale of the straton, previously recognised as the “Betrinskaya Formation”, should be revised. Numerous collections from well-known and many new localities have proved that the terrigenous-siliceous deposits occurring stratigraphically below the graywackes of the Zilair Formation, in fact constitute the sequence of the entire Devonian section and include characterised by conodonts intervals of the upper Pragian and Emsian stages of the Lower Devonian, the Eifelian and Givetian stages of the Middle Devonian, and the Frasnian stage of the Upper Devonian. These deposits compose a lithologically homogeneous straton – the Novousmanovo succession with siliceous rocks prevailing in its section. The isolation of indicative siliceous members, in particular the Ibragimov horizon, is inexpedient due to the lithological uniformity of the succession as a whole, and its facies variability along the lateral. The limestone members included in it are dated by conodonts. They belong to different stratigraphic intervals and occur in situ in the section.
Conclusions. The sediments stratigraphically underlying the Zilair Formation and fully comparable with the identified Novousmanovo succession are developed in the Kuragan-Sakmara zone (Akchura (D1), the remote facies of the Utyagulovo (D2 ef) and Sarbai (D2-D3f) Formations). In the West Magnitogorsk zone in the Voznesenka-Sakmara subzone below the Zilair Formation in a similar siliceous succession, a sequence in conodont zones of stratigraphic intervals of the Eifelian and Givetian stages (D2) and Frasnian stage (D3) united into the Aktau Formation are revealed.

Research subject. The composition and distribution patterns of lattice defects in the clastic quartz of sedimentary rocks.
Material and methods. Quartz collected from the core of two wells uncovering the Neogene, Paleogene and Cretaceous deposits in the rocks of the Central Kyzylkum. The registration and determination of the concentrations of lattice defects in detrital quartz were carried out by the EPR spectroscopy. Their stability in quartz under natural conditions was evaluated by comparing the concentrations of lattice defects in the near-surface and deep zones of quartz grains. The etching of quartz grains in HF was used to study the spatial location of lattice defects in the mineral. The genetic analysis of detrital quartz was carried out using the methods tested in the study of quartz from crystalline rocks.
Results. The presence of substitutional Al, Ti, and Ge impurities, radiation induced E1-, Al–O−- and Ti-centers, as well as other paramagnetic centers possessing genetic information was found in quartz. The distribution of substitutional impurities in clastic quartz is close to their original distribution formed at the time of the mineral formation. This creates the prerequisites for identifying genetically similar quartz samples and attributing them to the certain provenance. The formation of sedimentary rocks of the Central Kyzylkum occurred due to two main provenance sources of terrigenous material. The expediency of using radiation induced centers with different thermal stability for studying the radiation prehistory of quartz and the conditions for the formation of uranium deposits is demonstrated.
Conclusion. The clastic quartz of sedimentary deposits retains the main part of the genetically significant lattice defects formed during crystallisation. The most important of them are Al, Ti, and Ge isomorphic impurities. The regularities of their distribution, along with the distribution of radiation induced lattice defects in quartz, are able to carry information about the provenance of detrital material and the conditions of sedimentation and associated formation of mineral deposits.

Research subject. Composition and isotopic parameters of zircons and their host granites of the Bitim complex, localised in the eastern part of the Ufaley block (Middle Urals).
Materials and methods. The determination of trace element composition and Lu-Hf isotope system in zircons was carried out by LA-ICP-MS (the “Geoanalitik” shared research facilities of the IGG UB RAS, Ekaterinburg).
Results and conclusions. The images and geochemical features of the main zircon population from granites confirm their magmatic genesis and minimal alteration, which proves previously defined Vendian- Cambrian (520 ± 9 Ma) age for the granites. Younger zircons (401–459 Ma) differing in composition from the older ones, were formed during subsequent tectonic-thermal activity, possibly under the fluid action. The mixed mantle-crustal nature of substrate for the granite melting is indicated by specific isotopic parameters (87Sr/86Sr = 0.703389, εHf(t)aver = +6.3) and a number of characteristic ratios for zircons and granites. The geodynamic concepts of the granite formation settings of the Bitim complex are corrected: in the Vendian–Early Cambrian, a transform-type margin has developed in this sector, the divergent movements on which have been accompanied by a break in the continuity of the crust and the intrusion of a deep mantle diapir; the participation of the slab substance in the magma generation might also be assumed.
Conclusions. The results obtained can be used for the geological mapping and correction of a general geodynamic scheme for the junction zone between the Ural Mobile Belt and the East European platform.

Research subject. Upper Silurian (Lower Ludfordian) slope deposits of the Lyagadin section (Ilych River, Northern Urals).
Materials and methods. The composition and structure of 40 rock samples collected across the section during fieldworks in 2019 were studied. Thin sections were examined under a polarising microscope. Eight samples were investigated by silicate analysis, and clay minerals from 2 samples were determined by X-ray diffraction analysis of oriented samples.
Results. The Lyagadin section with a visible thickness of 70 m is represented by an uneven alteration of clayey-siliceouscalcareous schists, micro-grained limestones with burrows, micro-fine-grained layered limestones, fine lime sandstones, coarse- and medium-grained lime sandstones, lime conglogravelites and lime conglobreccias. Clayey-siliceous-calcareous schists and micro-grained limestones with burrows characterise the background periplatform clayey-carbonate deposits. The part of micro-fine-grained layered limestones (their horizontally layered varieties) are bottom current sediments. Gravity flow deposits are represented by clastic rock assemblage. The most characteristic of them is the assemblage composed of lime conglogravelites with an erosional bottom, which pass into gradational-layered lime sandstones, first coarse- and medium-grained, and further the into their fine-grained varieties. They are covered, in turn, with micro-fine-grained limestones with cross or convolute stratifications. That association is interpreted as calciturbidites. Calcidebrites are characterised by lime conglobreccias. The deposits of grainy flows (?) are represented by the layers of lime sandstones not revealing the characteristic features of the Bouma sequence.
Conclusion. The reconstructed background sedimentation on the continental slope during Early Ludfordian was characterised by the accumulation of hemi-pelagic clay deposits together with a certain amount of microscopic quartz, orthoclase and organic matter. Periodically appearing thin layers of micro-grained limestones with burrows correspond to the periods of increased supply of carbonate material, which could be attributed to “marine snow”. The irregular nature of the distribution of gravity flow deposits in the Lyagadin section suggests that the studied slope deposits are, most likely, the formation of the outer apron of slope bottom, rather than calciclastic fans.

Research subject. Several gold deposits, including superlarge (Natalka), large (Pavlik and Degdekan) and a number of smaller ones are located in the Central Kolyma ore region, near the Ten’kinsky deep fault. The similar position in the recumbent fault flank and confinement to upthrust-thrust plumage faults are characteristic of these objects. The differences are in the position at the different levels of the Permian section, the scale of mineralisation, and some characteristics of the material composition.
Materials and methods. An analysis of the spatial characteristics of ore-bearing disturbances was carried out taking into account the change in the angles of their incidence along the section of the enclosing strata. In addition, the composition of the ores, the parameters of fluids and the regular changes in their thermodynamic characteristics were studied.
Results. The additive hydrothermal column is restored, in the lower part of which the Rodionovskoye deposit is located, followed by the Degdekan and Natalka deposits, and ending in the upper part by the Pavlik deposit. The total vertical span of such a column is more than 5 km. This structural model explains the trends in the material characteristics of ore-forming fluids, reflecting the variability of the P-T characteristics from bottom to top in the hydrothermal column.
Conclusions. The occurrences located directly in the zone and near the ore-supplying Ten’kinsky fault are relatively small in scale; the feathering ore-bearing reverse-thrust structures at a distance of 2–5 km from it are more favourable. Based on this model, a large-volume deposit similar to the Natalka might be located below the Pavlik deposit, which is the upper part of the column.

Research subject. SThe geophysical fields and physical properties of altered gold-bearing rocks within the Belogorskoye ore field and the Belaya Gora gold deposit located in the Khabarovsk Krai.
Materials and methods. Magnetic field and the distribution of electrical resistivity and polarisability obtained during land-based surveys as well as magnetic susceptibility, apparent electrical resistivity and polarisability of the samples from trenches and drilling cores have been studied. The analysis of the spatial correlation of the features of geophysical fields and gold mineralisation has been carried out. The physical properties of rocks are analysed depending on the intensity and type of superimposed hydrothermal alterations and gold content.
Results. A significant decrease of magnetic susceptibility for all types of altered rock is indicated. Differences in electrical resistivity and polarisability are observed for hydrothermally altered rocks of the pre-ore stage and ore-bearing metasomatites. The former, with a relatively increased electrical resistance, have the highest polarisability (within the ore field), while the latter are characterised by an even higher resistance, but with the significant decrease in polarisability, which remains slightly elevated relative to unaltered rocks. These patterns also determine the geophysical characteristics of the ore field and deposit. The gold ore field is characterised by a significant decrease in the magnetic field intensity, an areal anomaly of increased polarisability, and, in general, an increased apparent electrical resistance. The deposit itself, as an area covering ore bodies, is generally characterised by an even more intensive increase in apparent electrical resistivity and a relative decrease in polarisability against its generally high background.
Conclusions. Based on the performed research, a geophysical model of the Belaya Gora gold deposit is proposed, which may be used as a reference during the planning of geophysical works and the interpretation of geophysical data during the exploration works for epithermal gold mineralisation within the volcanic-tectonic structures in the Nizhne-Amursky region.

Research subject. The processing waste of the slag from the Sredneuralsk copper smelter (“SUMZ technical sand”) is a finely dispersed (particle size less than 0.05 mm) material, mechanically activated by crushing cast slag and containing high concentrations of copper, zinc and other chalcophilic elements. Fayalite and ferrous glass predominate in its phase composition.
Materials and methods. An outdoor experiment to study the elemental migration from waste into the soilplant system was conducted on the territory of the Institute of Geology and Geochemistry, Ural Branch of RAS (southwestern part of the Ekaterinburg, Sverdlovsk region). The soil substrate was prepared from lime-neutralised ombrotrophic peat (pH 6.6) with the addition of “technical sand” of 5, 10 and 20% by weight. Lawn grass mixture was grown on trial plots (1 m2). The samples of lawn grass (without separation by species), together with the root part and peat, were collected after the growing season by the “envelope” method, dried at room temperature until constant weight, and powdered. The chemical analysis of the samples was performed at the “Geoanalitik” shared research facilities of the Institute of Geology and Geochemistry, Ural Branch of RAS. The analyses were performed by inductively coupled plasma massspectrometry using the NexION-300S ICP mass-spectrometer.
Results. The mobilisation of elements from the “SUMZ technical sand” into ombrotrophic peat during the summer was investigated, the distribution of elements in the underground and aboveground parts of lawn grasses was demonstrated, and accumulation coefficients were calculated. The content of most elements in all soil substrates containing waste decreased by autumn, for example, 2–3 times for Zn, Cu, Co, S, As, Pb, and Mo. The aboveground part of lawn grass had a lower concentration of the elements considered as compared to the roots, the greatest difference was observed for Co, Cd, Cu, and W. The lawn grasses grown on soil substrates with the different ratios of “SUMZ technical sand” had lower coefficients of accumulation of heavy metals compared to plants grown on the peat. The coefficients of Na, Ba, Mo, As, Cd, and Pb decreased with an increase in the proportion of waste, and for Li and Rb increased.
Conclusion. The results of the research contribute to the study of the migration of elements from non-ferrous metallurgical waste into soil and plant systems.