Geochemical Modeling of Water-Rock Interaction in UppermostRegional Aquifer in Arar Area

Abstract

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.