The Role of Stable Bromine Stable Isotopes in Determining the Origin and Evolution Model of the Abu Dhabi Costal Sabkha (UAE)

Recent studies of the Abu Dhabi coastal sabkha system that included hydrological, geochemical and isotopic evaluations suggested a new model (ascending brine) to explain the formation process of this Sabkha. The investigations also revealed that the system is chemically open, especially, for sodium, chloride and bromide, where a large amount of these ions are lost from the system.

Bromine stable isotopes in conjunction with the available geochemical and isotopic data were used to examine the three formation models; the seawater flooding model, the evaporative-pumping model and the brine-ascending model in order to determine the origin of the solutes of the sabkha and investigate the solute transport mechanisms.

In this study waters from the sabkha and potential end members (seawater, fresh water, tertiary brines) were analyzed for bromine stable isotopes. The δ⁸¹Br values ranged over 2 ‰ and showed that the different waters are isotopically distinct. The isotopic results obtained from the sabkha brines suggested that the solutes mainly originate from the continental brines ascending from the deep underlying Tertiary carbonate formations. The results also favor the ascending-brine mechanism over the classical processes (seawater flooding and evaporative-pumping).

The evaluation of these processes is an important issue not only to understand the origin of the solutes and the formation model; but also to study some of the proposed processes used in explaining the loss of major ions.