HYDROCHEMICAL ANOMALY OF PORE SOLUTIONS OF LOW-PERMEABILITY CLAYEY ROCKS OF PLATFORM ARTESIAN BASINS OF UKRAINE

Abstract

This paper presents the results of the study of hydrochemical anomalies of pore solutions of low-permeability clayey rocks of platform artesian basins of Ukraine on the example of two basins – Dnipro and Black Sea. As a result of vertical flow, artesian waters can change their chemical composition and form pore water horizons of anomalous composition in relation to aquifers and complexes. Such anomalous water composition has been recorded in the pore solutions of the northwestern part of the Dnipro artesian basin, in the pore solutions of the Palaeogene clay beds in the southern and central parts of the Dnipro artesian basin , and in the pore solutions of the Palaeogene clay-marl rocks of the Dnipro artesian basin. A number of pore solutions of Jurassic clay in the eastern part of the Dnipro artesian basin can also be classified as anomalous. Anomalous pore solutions of clay rocks in the Black Sea artesian basin differ from those in the Dnipro artesian basin in terms of higher mineralisation and chloride anionic composition, which is associated with their sedimentogenic origin and close connection with sedimentogenic marine waters. They are found in both Quaternary and Paleogene clayey rocks. It has been shown that a separate group of anomalous pore solutions consists of pore solutions with an increased concentration and specific composition of microcomponents. The increased concentration of biogenic microcomponents is typical for pore solutions of bottom sediments of water bodies – lakes, rivers, reservoirs, and estuaries. In the zone of intensive water exchange of platform artesian basins, pore solutions with anomalous content of biogenic elements, such as ammonium, silicon and phosphorus, are also found in certain layers of clay rocks (especially Jurassic). In general, the analysis of anomalous pore solutions of poorly permeable layers indicates the complex nature of hydrogeochemical development of continental artesian basins in Ukraine.