Geochemistry and isotopic analysis of brines in the coastal sabkhas, Eastern region, Kingdom of Saudi Arabia

Abstract Several solute-source models have been proposed to elucidate the origin of the solutes in the Gulf coastal sabkhas. The Ascending Brine hydrogeologic model has been shown to be a viable explanation for the origin of solutes in the Arabian (Persian) Gulf coastal sabkha in the UAE (United Arab Emirates). A coastal sabkha approximately 500 km northwest of the UAE sabkha and 40 km northwest of Dhahran, Kingdom of Saudi Arabia was selected to test the general applicability of this conceptual model. The Cl and Br relationship was used to assess the source of solutes in combination with the activities of 226Ra, and bromine isotopes δ81Br. The possible origin of water in the system was constrained using isotopes of δ18O, δ2H, and activity of 3H. The analyses of Cl−/Br−, 226Ra activity and bromine isotopes δ81Br indicate solutes are consistent with the Ascending Brine model and incompatible with seawater based models. Isotopes of δ18O, δ2H, and activity of 3H suggest most of the water is from local precipitation. Whereas the geology, solute chemistry, and mineral sequence is different in both sites, water and solute isotopes at this site are consistent with the proposed Ascending Brine model.