A model of basin evolution in the Qa’ Al-Azraq, Jordan using sulfur isotope analysis to distinguish sources of sulfur and gypsum

Abstract

The closed basin of the Qa’ Al-Azraq, Jordan records gypsum and sulfur depositions. Analysis of the cored sediments used smear slides, isotope geochemistry of gypsum and sulfur, XRD, and SEM. This study distinguishes the sources of gypsum and sulfur in the basin from four different processes. Algae production was responsible for the presence of laminated sulfur at a depth of 48 m where paleolake levels were at a high stand. Primary gypsum, represented by laminated, thick massive beds, records sulfur isotope values of +15.7‰. This period of the paleolake indicates evaporation processes exceeded precipitation, leading to the deposition of thick, massive bed of gypsum. Other sources of gypsum originate from pyrite oxidation, indicated by the overlapping of sulfur isotope values of gypsum and pyrite at −0.7‰. Bassanite and anhydrite identified in this section resulted from dissolution and recrystallization processes. The application of sulfur isotopic analyses identifies environmental distinct formation processes of sulfate minerals in the Al-Azraq basin. This provides the basis for a model of basin evolution and associated changing climates. Finally, this research considers the effect of sulfate minerals on Al-Azraq basin groundwater.