Izvestiâ Komi naučnogo centra Uralʹskogo otdeleniâ Rossijskoj akademii nauk

There are three geological-genetic types of primary diamond deposits as magmatic (kimberlite and lamproite), metamorphogenic and impact deposits. The authors carried out a comprehensive study of geological, petrophysical and petrographic features of kimberlite rocks, i.e. the main supplier of diamonds. The upper parts of weakly eroded kimberlite pipes are usually crowned with crater structures, transforming down the section into diatrems, which further turn into dikes. Kimberlite pipes have three-phase sections (crater, diatreme and root part), which differ in textural-structural and mineralogical-petrographic properties. The appearance and composition of different-facies kimberlites (porphyritic varieties, autolithic and kimberlite breccias, tuffs and tuff breccias) are largely determined by the material composition of the diatreme host rocks and the degree of their postmagmatic and hypergenic alterations. Mantle material in kimberlites is represented by xenoliths of ultrabasic, alkaline-ultrabasic and basic rocks and xenograins of minerals from them – diamond, pyrope, picroilmenite, chromospinelide, olivine, clinopyroxene, orthopyroxene, phlogopite, less zircon, apatite, titanoclinogumite and others. Mantle xenoliths in kimberlite pipes usually evidence different levels of the mantle, which are the source of deep matter that underwent diverse alterations during the diatreme formation. The southern part of the Siberian Platform includes high-magnesian garnet peridotites and pyroxenites. For kimberlite diatrems of the northern part of this craton, peridotites predominate in some areas and eclogites in others. Garnet-free peridotites and garnet-pyroxene rocks play a greater role here, which is not typical of kimberlites from the other platforms of the world. The paper underlines the importance of analysing the influence of different mantle rocks on the productivity of kimberlites. The obtained data on the typomorphic features of diamonds and their paragenetic satellites allow to improve both the diamond content criteria of kimberlite rocks and significantly influence the choice of promising territories and sites for forecasting and prospecting diamond deposits.

By the first conducted ⁴⁰Ar/³⁹Ar-isotope-geochronological studies of muscovite (345±4 Ma) and porphyroblastic microcline (347±14 Ma) in gneissogranites of the Evyugan complex of the Kharbey block of the Kharbey anticlinorium, these rock-forming minerals are synkinimatic and formed under the conditions of the Ural orogeny. The obtained ages practically coincide with the ages of glaucophane metamorphism (347±72 Ma) and eclogite exhumation (360 Ma) in the Polar Urals. New determinations of radiological U/Pb age of gneissogranites using the laser ablation method (494±2 Ma) with the dual nature of granite gneissic banding (relict and dynamic) contribute to the understanding the formation geology of the polygenic-rheomorphic Evyugan complex. The formation of gneissogranites of the Evyugan complex presumably matches with the period from the Late Cambrian to the Early Carboniferous.

By the analysis of foraminifera distribution in the Lower Cretaceous sections of the Luktakhskaya-4 well (Central Taimyr) and natural outcrops in the lower reaches of the Olenek River, we identified a sequence of five biostratons: Gaudryina gerkei, Trochammina rosaceaformis zone (KF1, middle Boreal Berriasian); Valanginella tatarica, Recurvoides obskiensis zone (KF2, uppermost Boreal Berriasian – Valanginian); Cribrostomoides infracretaceous, Cribrostomoides sinuosus zone (KF4, upper Lower Valanginian – lowermost Hauterivian); beds with Cribrostomoides concavoides, Trochammina gyroidiniformis (KF5, lower Hauterivian) (based on [1, 2]).

The paper presents the biofacial study results of the Early Cretaceous basin in the northern part of Central Siberia. The authors reconstructed foraminifer communities of the Boreal Berriasian ([1], =Ryazanian stage [3]), Valanginian and lower part of the Hauterivian of the Enisei-Khatanga Strait (Central Taimyr), and the southern end of the North Siberian Sea (lower reaches of the Olenek River). Their evolution mechanisms were discovered. The succession of bionamic zones was determined.

The article summarises new results, including unpublished data, obtained by the Applied Geomechanics Group of the Department of Mining and Construction Geotechnics at the Mining Institute of the Siberian Branch of the Russian Academy of Sciences while performing a series of works in the fields of geomechanics, geotectonics, and mining engineering. The discrete nature and serious deformations of geomaterials – participants of the studied processes – were unifying factors for the tasks these disciplines have to solve. With this in mind, the concepts of loose media mechanics and the modified method of discrete elements were used to study these issues. On the basis of this method, a computer program is developed, the efficiency of which is confirmed by the solving results of test activities. Numerically and on physical models, we have substantiated and confirmed by independent instrumental measurements the dependence between absolute values and orientation of elevated tectonic stresses in the area of mineral deposits and the tectonics of the surrounding endocircular structures. The work shows the relevance of this section of geotectonics from the point of the development of mineral reserves of the World Ocean bed. The following tasks are solved: increase of bearing capacity of ground anchors with flexible traction; decrease of peak loads on plate feeders of crushed ore of concentrating factories; increase of accuracy of volumetric dosers of continuous action for hard-to-flow materials; anti-erosion protection of pneumatic transport pipe bend; about the influence of cross-sectional shape and rotation speed of horizontal pipeline on the efficiency of pneumatic transport. The previously developed computer program for numerical simulation of the flow of broken ore during mining with sub-level caving and release under caved rocks has been improved and given to the mining organization. On the basis of the international cooperation results, the optimisation criterion of polydisperse media packing has been proposed.

The article is devoted to the analysis of the scientific activity of the candidate of geological and mineralogical sciences R. G. Timonina, a famous researcher of metamorphic rocks, who made a significant contribution to the study of the geological structure and history of geological development of the Subpolar Urals. She was the first to identify and characterize the main stages of regional metamorphism of formations in the Subpolar Urals. Her research is based on a detailed study of the petrography and petrochemistry of metamorphic rocks.

In the course of preparing the article, the author analysed published and archived works written by R. G. Timonina, who devoted more than 20 years of her life to studying the geology of the Northern Urals.

The significance of the topic is determined by an important historical and cultural event: Syktyvkar is expecting the unveiling of a monument to the President of the Academy of Sciences of the USSR academician A. P. Karpinsky in summer 2025. He visited Syktyvkar as head of the Pechora Brigade of the Academy of Sciences of the USSR in 1933 to evaluate the resources of the region. The article characterises the professional career and life journey of the radiochemist P. I. Tolmachev, a representative from the family of the Karpinsky mining engineers. It highlights the influence of a number of prominent scientists on the formation of his character, professional qualities, as well as his choice of occupation. For example, academician A. P. Karpinsky, who was an own grandfather of P. I. Tolmachev, had a principal impact on the formation of his character. The choice of profession was determined by academician V. I. Vernadsky, who shared the moral views of young Tolmachev. Academician A. E. Fersman submitted his article for publication in the reports of the Academy of Sciences of the USSR. Academician V. G. Khlopin appreciated P. I. Tolmachev’s diligence and extraordinary mental capabilities demonstrated in works on the radium deposits, published several co-authored papers and recommended to use the accumulated experience in radiochemical production in the Komi ASSR. Under the influence of his family, the scientific environment, and the planet-scale science development level, P. I. Tolmachev became a highly qualified research engineer. The industrial products from Ukhta, where Pavel I. worked for many years, contributed to the victory in the Great Patriotic War.