The Role of Density-Driven Convection in the Formation of Hydrogeochemical Zonality in Artesian Basins.

The main types of mass transfer in the subsurface hydrosphere are considered. Specific features of vertical hydrogeochemical zonality in the Volga–Ural Artesian Basin are discussed, and the history of its hydrogeological development is considered. The principal role in the formation of the zone of different-composition brines, dominating in the sedimentary cover, is shown to belong to the processes of halogenesis in the Early Permian and density-driven convection of mother brine from evaporite paleoreservoirs into underlying terrigenous–carbonate Paleozoic strata. The problems regarding the mechanism and lithologic–hydrogeochemical consequences of the density-driven convection in the subsurface hydrosphere in a sedimentary basin are considered. [ABSTRACT FROM AUTHOR]