Nature of chemical composition diversity of the East Ttransbaikalia salt lakes (Russia)

Abstract

We have developed a new concept for the formation of geochemical types of salt lakes which explains the nature of their different chemical composition under close landscape-climatic and geological-geochemical conditions. The extensive field hydrogeochemical material and thermodynamic calculations demonstrate that in addition to evaporation, the interaction with rocks plays a great role in the formation of the composition of lakes. This interaction begins in the catchment area of a particular lake and continues directly in the lake. Such processes are most widespread in soda lakes, which is confirmed by the presence of the highest pH values (9.0-10.7). Besides, one of the most important processes is sulfate reduction, which results in hydrogen sulphide in lakes fundamentally changes the geochemical environment from oxidizing to reducing one and leads to a change in the oxidation state of many elements, changing their migration ability and, therefore, the ability for concentration or binding by secondary minerals. The presence of an oxidizing environment and sulphides in rocks gives additional sources for sulfates, which ensures the formation of sulfate-type lakes.