Carbonates and Evaporites (08912556)40(2)
The continental closed basin playas often serve as the discharge point of regional water flow systems and the evolution of brines and salts in these areas is a response to fluctuations in recharge or evaporation. This research discusses the geochemistry, brine type, and evaporite minerals of the Jandaq and Khur sabkhas located in the Great Kavir, Iran. The sabkhas consist of four main sub-environments: sand flats, mud flats, saline mud flats, and salt pans. Samples of brine, primary and secondary salt were collected and analyzed for their pH, major cations and anions, mineralogy. Brines of the sabkhas are moderately acidic and the low pH of the brines is likely due to the oxidation of Fe sulfides present in the green marl deposits. The quantities of Na+, Cl- and SO42- are lower in the brines than in the salts, while the amounts of Mg2+, Ca2+, K+ and Sr2+ are higher in the brines. The average contents of major cations in the primary salts are higher than those in the secondary dendritic salts, and the primary salts of the Jandaq sabkha have higher contents than those of the Khur sabkha. Halite is the primary mineral formed under natural conditions, and tachyhydrite may form during the final stages of concentration. The ionic strength and sum of Na+, K+, Ca2+, Mg2+, and Cl- quantities increase with evaporation, while pH decreases from the precipitation stage to desiccation stage. Carbonates in the pH range of the brines mostly exist as HCO3-. SO42- occurs in the secondary dendritic salts, primary salts, and brines, respectively, in order of abundance. The brine of the salt pan is of Na-(Mg)-Cl type. The brines are supersaturated with respect to calcite, aragonite, dolomite, and halite, indicating precipitation of these minerals. However, the brines are undersaturated with respect to barite, gypsum, sylvite, and celestite. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
