Lithochemical features of the rocks of the Hrushka Formation of the lower vend of the Podillya structural-facies zone

Silicate analyzes of siltstones, argillites, sandstones, gravelites, and conglomerates were used to examine the lithochemical features of the clastic rocks of the Hrushka Formation.Lithochemical data indicate a preference in places of paleowatersheds during the formation of sedimentary associations of the Lower Vendian of igneous rocks of acidic and medium composition with one or another role of sedimentary formations.The CIA chemical weathering intensity index for all samples analyzed ranges from 53.80 for sandstones to 82.79 for mudstones, showing a wide range of chemical weathering intensity from early to late stages, with most samples belonging to the intermediate stage of silicate weathering. The application of additional chemical weathering indices, such as CIW, PIA, WR, WI-2 and the plot of CIA versus Al2O3 jointly demonstrate the moderate intensity of chemical weathering of rocks in the area of the wear source.The degree of chemical weathering, determined by weathering indicators, played an important role in the reconstruction of paleoclimatic changes. The prevailing climatic conditions for the formation of rocks in the source of erosion can be considered the alternating conditions of an arid desert with short-term episodes of a warm, humid climate. The presence of climate indicators corresponding to glaciogenic formations for some samples of sandstones and gravelites may be an echo of the Marinoan glaciation, which preceded the Ediacaran period.Several indicators of the ICV maturity index of siltstones and sandstones of the Hrushka Formation have high ICV values (>1), which indicates tectonically active conditions of rock formation in sources of erosion.The rock sequences of the Hrushka Formation were formed by the continuous deposition of material from crystalline parent rocks into the basin of sedimentation, as well as material that underwent several cycles of sedimentation at a small distance and time from mobilization to the final burial of clastic material.Geochemical characteristics and parameters of discriminating tectonic diagrams reflect the formation of sandstone in the conditions of active continental margins and oceanic island arcs, which is associated with the mixing of clastics from various sources of erosion, including volcanic ones.A complex lithologic-geochemical analysis using a number of indices and charts made it possible to consider the origin, composition of the parent rocks of the erosion areas, geodynamic conditions, climate, degree of chemical weathering, geodynamic conditions, degree of maturity of the rocks of the Hrushka Formation of the Volyn Group, which are the basal formations of the Ediacaran period and the most ancient deposits sedimentary cover on the territory of Podillya structural-facies zone.