Origin, hydrogeochemistry and evolution of Meighan Playa brine, Arak province

Meighan Playa is a sedimentary inland closed basin which is located in 15 km northeastern part of Arak. In this playa water-level is controlled by the amount of rainfall, evaporation and groundwater input. To study brine origin and evolution 19 water samples from three transects were collected by digging holes with specified intervals of 2 km. By doing chemistry experiments on the brine and X-Ray diffractometer analysis on the sediments, the ions concentrations of brine and mineralogical composition of sediments were identified. Major cations, according to their abundance, are Sodium, Magnesium, Calcium and Potassium and anions include Chloride, Sulfate, and Bicarbonate, respectively. Dominant evaporative minerals in sediments are Calcite, Gypsum, Halite, Glauberite, Thernadite and Mirabilite. Chemical analysis studies of input water indicates that the water has molar ratio of HCO3 <