Nickel weathering ores are used to produce metallic nickel, stainless steels, and nickel sulfate, the main component of batteries. The global production of nickel from weathering ores is increasing and has surpassed production from sulfide magmatic deposits. The efficiency of the mining and processing of nickel ores from weathering rocks is determined by their mineralogical composition. The weathering crust profile of the Kempirsay ultramafite massif is divided into three zones—leached (kerolitized) serpentinites, nontronites, and final hydrolysis minerals (later referred to as “ochers”). The kerolitized zone consists of a mixture of Ni-bearing talc and saponites (later referred to as “kerolite”). During the geological mapping of the Donskoye, Buranovskoye, and Shelektinskoye deposits, the products of ultramafite hypergenic transformation into disintegrated and leached serpentinites, kerolites, nontronites, and ochers were selected and studied. For this purpose, 44 rock samples were studied via X-ray diffractometric and thermal analyses, supplemented with data from chemical, microscopic, and granulometric determinations. Based on the obtained numerical parameters of the crystalline structure of the weathering products, the thermochemical values were obtained. The hypergenic transformation of the initial minerals and their subsequent transformation were traced. The trace element distribution along the profile of the serpentinite weathering ores is related to the initial material composition of the ultramafites. The accumulation of nickel in industrial concentrations is associated with the nontronite–kerolite zone. X-ray diffractometric analysis can be used as a fast and reliable method for controlling the nickel content of ores and monitoring their mineralogical composition.

Various genetic and morphological types of voids in carbonate reservoirs make it difficult to diagnose them, which can be seen in the determination of reservoir properties in the northern marginal shear zone of the Caspian Syneclise. A macro- and microscopic study of rocks was carried out by staining carbonates in thin sections with alizarin (determination of the mineral composition, structure, texture, void and fracture spaces, rock genesis). Instrumental methods (X-ray, DTA—differential thermal analysis, TGA—thermo-gravimetric analysis, and probe microanalysis) established the composition of rocks, the nature of their diagenetic transformations, and the formation of void space. The elemental and oxide composition of a number of samples was carried out using the X-ray probe microanalysis method, and mineral formations with intermediate thermochemical properties were found. The results of X-ray, DTA, and TGA measurements and the data of probe microanalysis made it possible to reveal thermally inert formations of oxides of calcium, magnesium, silicon, iron, and other compounds in the composition of carbonates. A relatively low-cost express method was used to determine the material composition and the nature of epigenetic changes and to obtain data on the void space as a result of the development of tectonic fracturing and diagenetic processes of leaching and secondary mineral formation in bedded carbonate reservoirs.

The article deals with the issues of tectonic zoning of the Paleozoic and Mesozoic-Cenozoic structures of Kazakhstan. The principles of tectonic zoning are outlined, on the basis of which the zoning and indexation of tectonic units of the territory of Kazakhstan was carried out. For this, various data of complex geological and geophysical analysis of Paleozoids were used, including tectonic, structural, stratigraphic, lithological-paleogeographic, petrographic, geodynamic and other studies. A geological and tectonic scheme (model) is proposed that reflects the main tectonic units that make up the structural framework of the Paleozoids of Kazakhstan, consisting of a crystalline basement on which the formation of sedimentary oil and gas basins took place. The main tectonic units of the earth's crust of the territory under consideration are identified and characterized, and the mosaic-block structure of the complexes is shown. The characteristic of the complex multi-stage evolution of the paleozoids of Kazakhstan and its oil and gas regions is given.

Based on the analysis of stratigraphic, lithofacies, and geological and geophysical data, consideration is being given to the main stages in the formation of the basement and cover structures of the Alakol sedimentary basin. For this region, there was developed the substantiation of a scheme of tectonic zoning and there were proposed structural characteristics of faults and lithofacies features of the section. Evidence was found of a complex, multi-stage tectonic evolution. There were discovered potentially promising stratigraphic oil and gas complexes of the Late Paleozoic and Mesozoic. The deep-seated structure of the region is illustrated by a geological and geophysical section, spatially coincident with the "Turkestan" seismic profile. Based on the lithological and paleogeographic reconstructions, there were identified four major tectonic boundaries: Cambrian-Ordovician, Devonian-Carboniferous, Permian-Early Triassic, and Middle Triassic-Cretaceous. The correlation of the stratigraphic range of the hydrocarbon potential of the Alakol basin has been carried out. The criteria for forecasting hydrocarbon accumulations were substantiated.

The study of the material composition, textural, and structural features of skarns and magnetite ores is of great importance for increasing the efficiency of iron ore mining and its subsequent processing and enrichment. In the northwestern Balkhash region of Central Kazakhstan, there is a reserve iron ore region represented by a series of skarn contact-metasomatic deposits: Bapy, Zhuantobe, Karaulken, Akchagyl, Ushtobe, Kiyik, Taitobe, Tomashev, Kyzyl-Sayak, and others. The results of field investigations and laboratory analyses have enabled the characterization of the mineralogical and petrographic composition of the skarns, as well as their material composition and textural–structural features. All these specified characteristics of skarns reflect the stage-by-stage nature of the contact-metasomatic processes of iron ore formation. The skarn formation model at the Zhuantobe deposit developed over several stages: (1) the formation of skarns during granitoid intrusion and the establishment of conditions for contact metamorphism (resulting in iron-poor, barren diopside hornfels and marbles); (2) early skarn stage, during which anhydrous, dark-colored endo- and exoskarns composed of pyroxenes, magnetite, and hematite develop; (3) late fluid–hydrothermal stage, during which hornblende, epidote, calcite, and sulfides (pyrite, chalcopyrite, sphalerite, and galena) form; (4) oxidative supergene stage under near-surface conditions, during which limonite and iron hydroxides form. The conducted comprehensive analysis of the material composition and textural–structural features of iron ores of the Zhuantobe deposit made it possible to establish the influence of these parameters on the technological properties of ores. The performed studies make it possible to more accurately identify promising iron ore zones in skarns and predict the technological behavior of ore during processing.

Background: Carbonate rocks form subsalt hydrocarbon reservoirs in the Northwestern Margin Zone of the Pre-Caspian Basin. In this context, identifying and analyzing the causes of epigenetic alterations affecting the reservoir properties of carbonate formations is of particular importance, as these alterations influence the optimization of the hydrocarbon exploration and production. These factors underscore the scientific and practical relevance of the present study. Aim: To identify the causes of alteration and to quantitatively assess the reservoir properties of carbonate formations affected by secondary epigenetic transformations. Materials and methods: This study investigates subsalt carbonate reservoirs from oil and gas fields in the Northwestern Margin Zone of the Pre-Caspian Basin. The analysis involved both macroscopic and microscopic examination techniques, supported by a range of laboratory tools, including thermal analyzers, thermogravimetric instruments, and X-ray diffractometry. The method proposed in this paper relies on DTA data obtained during dynamic heating of dolomite, calcite and magnesite, focusing on their thermal decomposition behavior. Mineralogical and compositional control of the reservoir formations was carried out using X-ray phase analysis. Results: A thermal analysis–based technique was developed to quantify secondary calcite in carbonate reservoir formations from subsalt oil and gas fields in the Northwestern Margin Zone of the Pre-Caspian petroleum province. Thermal parameters associated with epigenetic transformations of the dolomite–calcite assemblage was established using representative carbonate samples. These transformations are characterized by the infilling of pore spaces with secondary minerals, leading to reduced porosity and permeability in the affected reservoirs. Conclusion: Accounting for the structural properties of sedimentary rocks described in this study can significantly improve the quality of hydrocarbon exploration. The proposed method provides detailed information on the mineral composition of the reservoir, their filtration-capacity characteristics of carbonate minerals, the crystallinity of their components, lattice properties, and the physical behavior of magnesium, calcium, and other trace elements. Secondary calcite formed through epigenetic alteration of the host rocks has a negative impact on the porosity and permeability of the reservoirs.