[Formation and extent of peloid deposits in the Caspian Plain].

Main mud resources of brine lakes for balneological purpose form and accumulate in the zone of steppes and semi-deserts in the south and south-east of Russia (for example, in the Caspian Lowland). The main genetic types of peloids in the zone of steppes and semi-deserts are: 1) sulfide silt muds; 2) sapropels; 3) freshwater clayey silts. Sulphide silt muds form in the areal extent of salt-dome tectonics of the Caspian Lowland. According to the salt ionic composition of slush, the peloids of the lakes of the Caspian Lowland are sodium chloride, magnesium, magnesium-sodium; sulphate-chloride magnesium-sodium (less often sodium); the sodium bicarbonate chloride peloids are less common. Slush mineralization varies between 73 and 328 g/dm. The deposits of the Inder, Botkul, Elton, and Baskunchak Lakes and a number of shors are an example of highly mineralized sulfide muds. Black muds are oily to the touch. The silt deposits of lakes and shors are those of (bromine) salt saturated peloids - from weakly sulfide to strongly sulfide. They belong to promising or unpromising deposits due to the low power of the layers. The balneological resources of lakes, mud, and brine are a multipurpose product and can be comprehensively used in the national economy and in the improvement of the population's health.