The chemical, gas, and isotopic compositions of nitric thermal waters in the Baikal Rift Zone are considered. It is shown that the behavior of sulfate and carbonate ions in hydrothermal systems is different, which indicates that they are of two different origins. The studied thermal waters are of five chemical types formed in different geologic conditions. Special attention is given to the genesis of hydrotherms, the geologic and geomorphologic conditions of their recharge, and their equilibrium with rocks. It has been established that most of chemical elements of the waters migrated from rocks, but a significant portion of them is bound by secondary minerals, which results in their deep differentiation, accumulation, or precipitation. Thus, the so-called redundant elements appear, which were earlier considered to be of mantle origin.
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