Materiały konferencyjne SEP 2023

currently observed in the mine workings of Donbass (Donetsk coal basin) and Krivbass (Krivoy Rog iron ore basin). In the zone of transition of sedimentary rocks into metamorphic ones (at T > 570 0 K), a significant change in the structure of matter occurs, which is clearly seen in rock-forming quartz. This mineral is transparent and all changes in its structure or microstructure are reflected in its structure when side lighting is used. The technique of side illumination is successfully used to solve various geological problems [2]. If we take transparent quartz as an example and examine it at different stages of catagenesis, we can see the following. First, detrital grains of quartz are divided into blocks (Fig. 3a), then granulation is formed at the boundaries of blocks (Fig. 3b), and later, when sedimentary rock transforms into metamorphic, all detrital grains or their blocks pass into granular quartz, forming quartzites (Fig. 3c). Institute specialists established and described the phenomenon of fluid dissolution in detrital grains of quartz sandstones of the Donetsk coal basin [5]. A similar process has been traced in clastic quartz from other sedimentary basins. There are grounds to consider this process as a general regularity characteristic of sandstones of coal basins in different countries. It would be interesting and important to test this regularity in different sedimentary basins and countries. a b c Fig. 3. Division of clastic grain into blocks, medium catagenesis, magnification 100 X , sandstone of Donbass Institute specialists established and described the phenomenon of fluid dissolution in detrital grains of quartz sandstones of the Donetsk coal basin [5]. A similar process has been traced in clastic quartz from other sedimentary basins. There are grounds to consider this process as a general regularity characteristic of sandstones of coal basins in different countries. It would be interesting and important to test this regularity in different sedimentary basins and countries. Sandstone is one of the main hydrocarbon reservoirs for oil workers and the hardest rock for coal miners. It is in the sandstones that the miners build the main development workings in the mines in order to use them as long as possible. A negative factor is the increased gas content and outburst hazard of sandstones of coal deposits. One of the important lithological indicators of the formation of the sand stratum is the dimensionless coefficient of the relative thickness of paleoflows (Kr.t.p.). Schematic maps of equal thicknesses of sandstones (isopachs), reflecting the change in sandstone thickness, do not make it possible to identify core sections of paleoflows for polyfacies sandy complexes, since they do not take into account the time factor of sand material deposition (Fig. 4). The time of deposition of the terrigenous material correlates with the thickness of the studied stratigraphic interval containing the sandstone. The longer was the duration of the process of deposition of a