Hydrogeochemical characteristics and sources of mirabilite in the high saline system of Sabkha Oum El Khialate, Southern Tunisia

Abstract

Using hydrogeochemical approaches and geochemical modeling, integrated with data from 83 samples, including brines and fresh water, the main factors controlling the evolution of brine in the Sabkha Oum El Khialate catchment area in southeastern Tunisia are determined. Samples with high total dissolved solids (TDS), in the continental saline depression, are consistently dominated by Na–SO4 and Na–SO4–Cl water types while Ca–SO4–HCO3 and Ca–HCO3–SO4–Cl are the dominated facies in the catchment area of the sabkha. The PHREEQC geochemical modeling using PITZER database shows that most samples of the saline depression are oversaturated with respect to (sulfate minerals) thenardite, bloedite, glauberite, gypsum, and mirabilite and undersaturated with respect to calcite, halite, and dolomite. The most important hydrogeochemical processes that affect brine evolution in the Sabkha along the flow path are evaporation, gypsum dissolution, and the cationic exchange on clay minerals.