Caratteri idrogeochimici e origine della composizione chimica di acque sotterranee carbonatiche

HYDROGEOCHEMICAL PATTERNS AND ORIGIN OF THE COMPOSITION OF CARBONATE GROUNDWATERS The present contribution deals with the hydrogeochemical patterns and the types of groundwaters at Cuba which drain carbonate deposits. The samples analyzed in this study derive from Miocene sediments of the Matanzas province, Jurassic marbles from Isla de la Juventud, and carbonate deposits of the Cretaceous massif of Las Tunas. Water flows in these sediments have hydrogeochemical characters typical of bicarbonate-calcium or cal- cium-magnesian waters, depending upon the calcite-dolomite relation within the aquifer. Other characters reflect the effect of sea water intrusion or the salinity of the recharge area of the aquifer. The geochemical processes which may explain the water composition are: dissolution of calcite and dolomite where there is no contact with sea water; on the other hand, processes of dissolution or precipitation of calcite and dolomite, ionic interchange and oxidation of pyrite or anaerobic reduction of sulfates, predominate in the coastal aqui- fers with sea water intrusion.