Peculiarities of Compositions and Formation Environments of Potassium and Potassium-Magnesium Rocks From the Pogozhskaya Rhythmic Member in The Northwestern and the Northeastern Parts of the Caspian Slope Zone

The paper presents the results of composition examination of the uppermost of the Pogozhskaya rhythmic member from the northern near-slope fringes of the Caspian Region. The potassium-bearing horizon encountered there is determined to have resulted from the demineralization stage overlapping the carnallite and the bischofite stage deposits. In potassium salt accumulation, the major importance is attributed to the process of potassium ion concentration during the large-scale precipitation of salt-out halite associated with inflowing brine condensed to halite stage.

Environment of Texture and Structure Formation in Potassium, Potassium-magnesium and Magnesium Salts within the Caspian Halogenic Basin

The paper deals with the role of the factors that determine the texturalstructural peculiarities of potassium, potassium-magnesium and magnesium salts in the Caspian halogenic basin. Special reference is made to the role of highly concentrated brine preservation in certain basin water areas, importance of constant inflow of low condensed brine, salting-out of sodium and potassium chlorides, basin bottom morphology, the influence of two types of sedimentation rhythmicity (halogenic and terrigenous) and secondary processes of mineral formation.

Main Features of the Permian Halogenesis Hydrochemistry in the Caspian Region

In 1960–1980, the Elton and the Gremyachka deposits of potassium salts were discovered within the Permian halogen sequences in the Lower Volga Region, bischofite presence was recorded in the Privolzhskaya monocline, the conditions of halogen-bed formation were defined as those peculiar for typical evaporites. But in 1980-2010, halogenesis hypotheses emerged that denied the principal importance of climatic factor and the dominant role of oceanic waters in the brine composition of the salt-generating basin.

On the Role of the Salting-out Processes at the Final Stages of Halogenesis (the Case of the Gremyachinskoye Potassium-Salt Field)

Investigation of the ≪productive≫ intervals in the Gremyachinskoye potassium-salt field shows the potassium and potassium-magnesium salt settling to have been accompanied with large-scale salting out of sodium chloride due to interaction of highly concentrated solutions from that part of the salt-generating basin with the low concentrated ones. The constantly arriving low concentrated brine was peculiar for high contents of sodium chloride. That has resulted in large-scale salting-out of halite as lenses, crusts and randomly shaped clusters.