A MULTI ISOTOPE (δ81BR, δ37CL AND 87SR/86SR) APPROACH SUPPORTS THE ASCENDING BRINE CONCEPTUAL MODEL FOR SOLUTES IN THE COASTAL SABKHA OF ABU DHABI (UAE)

The ascending brine conceptual model for the origin of solutes in the coastal sabkha system of the Emirate of Abu Dhabi proposes that the nearly 90% of the solutes are derived from the upward flux of underlying geologic brines. This contrast to earlier conceptual models that suggested that seawater was the major source of solutes in this system. The ascending brine conceptual model was based on two independent but secondary lines of evidence (solute ratios and solute fluxes).

δ⁸¹Br, δ³⁷Cl and ⁸⁷Sr/⁸⁶Sr isotopic data were employed as a multi isotope approach in conjunction with the available geochemical and water isotopic (δ¹⁸O, δ²H) data to evaluate the ascending brine conceptual model for solutes in the coastal sabkha of Abu Dhabi. In this study waters from the sabkha and potential end members (seawater, fresh water, tertiary brines) were analyzed for δ⁸¹Br, δ³⁷Cl and ⁸⁷Sr/⁸⁶Sr signatures. The obtained data shows that a primary line of evidence of their origin can be gained through isotopic data as different solute histories of geologic brines and ocean solutes, can uniquely distinguish between the two possible sources. The results provide compelling primary evidence supporting the suggestion that the dominate source of solutes observed in the sabkha system is from geologic brines not seawater.

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 processes used in explaining the loss of major ions.