Desalting of sodium and potassium chlorides at the final stages of halogenesis: Evidence from the Gremyachinsk potash deposit in the Caspian basin

The study of “productive” intervals of the Gremyachinsk potash deposit showed that the precipitation of potassic and potassic–magnesium salts was accompanied by large-scale desalting of sodium chloride owing to the interaction of concentrated solutions from the given part of the saliferous basin with diluted solutions. The constant influx of diluted brine was characterized by the high content of sodium chloride, which led to the large-scale precipitation of halite as lenses, crusts, and accumulations of random morphology. Based on the ultramicrochemical analysis of the composition of brine inclusions in halites of different stages of densification, it is suggested that this process was accompanied by the growth of K ion concentrations in the brine and the subsequent desalting of potassium chloride in the carnallite stage brine with the formation of rocks of the carnallite–sylvinite paragenesis.