Geochemistry of fresh groundwater in the Altai–Sayan folded area and adjacent areas of the West Siberian plate

This study investigates the regional geochemical features of groundwater in the hypergenesis zone of the Altai–Sayan fold zone and in the adjacent structures of the West Siberian plate (hereafter simply called the Region). The hypergenesis zone of the Region contains widely spread freshwater and (to a lesser extent) low-saline waters. The patterns of changes in the water composition, the migration forms of various macro- and micro-components, and the equilibria of waters with various minerals, are analysed. The hypergenesis zones of the Altai–Sayan folded area and the adjacent structures of the West Siberian plate are characterised by high-altitude and latitudinal hydrogeochemical zonality, respectively. The total salinity of the groundwater increases with the lowering altitude conditions and changing landscape conditions in the Altai–Sayan region, and with the latitudinal changes of landscape in the adjacent structures of the West Siberian plate. In the same sequence, the contents of most mobile chemical elements and the role of complex forms of element migration increases, and the variety of minerals in equilibrium secondary formations expands. The main parageneses (geochemical water types and the associations of secondary newly-formed minerals) in the Region are oxide-hydroxide-forming, aluminosilicate forming, carbonate forming, and sulphate-forming. The parageneses are formed in genetic unity.