Ion-exchange adsorption processes in hydrostratisphere

Abstract

On the basis of field and experimental lithological and hydrochemical investigations carried out in the Volga-Ural sedimentary basin, a number of important provisions related to the mechanism and kinetics of cation exchange in a heterogeneous system of water-rock have been done. It has been established that they are zonal and differentiated by the depth of the basin. The most significant ion-exchange interaction is in the top of the supergene zone (up to 300 m) with Upper Permian argillaceous sediments with high adsorption properties. Here a radical metamorphic composition of underground fluids and formation of fresh sodium bicarbonate and sodium sulfate salty waters are marked. In areas of catagenesis and metagenesis at the depths greater than 1000-1500 m as a result of the restructuring of the clay minerals in the series of montmorillonite-hydromica-chlorite, the absorption capacity of the adsorption complex of clastic formations of Paleozoic and Late Proterozoic is sharply reduced. Exchange adsorption loses its geochemical significance and plays no significant role in the formation of calcium chloride brines. Their origin is associated with the processes of epigenetic dolomitization of limestone under the influence of density convection of the sodium chloride and magnesium brines from the Permian evaporate paleobasins.