Geochemical Modeling of Water-Rock Interaction in Uppermost Regional Aquifer in Arar Area

Geochemical modeling technique was used to study the chemical evolution of the Upper most regional aquifer in Wadi Arar area. This aquifer composed from limestone, dolomite and some scattered or interbedded anhydrite and gypsum. Karstic terrains are highly developed in the area. Geochemical calculations showed that the studied groundwater are supersaturated and undersaturated with carbonate and sulfate minerals respectively. Four flow paths were selected to determine the main chemical reactions thought to be responsible for the variation of chemical composition of the system under consideration and also to evaluate the amount of mass transfer of selected mineral phases. Many reaction path models have been identified, mainly calcite precipitation, de-dolomitization and cation exchange of Ca for Na for paths 11 and 12 (eastern parts) and calcite precipitation, dolomitization and cation exchange of the Na for Ca for the western parts, flow paths 2 and 5.