The Annenskiy thermal waters as the certain stage of the water-rock interaction (Far East, Russia)

Abstract

Chemical composition and saturation degree of the Annenskiy thermal waters to minerals of water-bearing rock have been considered in the manuscript. It is shown that the thermal waters are low mineralized, alkaline and belong to HCO3-Na type. The thermal waters-rock system is equilibrium-nonequilibrium. It means that the waters dissolve primary minerals continuously, never reaching saturation (anorthite, K-field spar and etc.), and form new secondary mineral phases simultaneously, reaching saturation (gibbsite, montmorillonite, albite and etc.). Besides, peculiarities of the equilibrium with minerals of water-bearing rocks for surface and ground waters of the studied region was considered. It is established that the thermal waters are ahead of surface and ground waters and represent the certain stage of the water-rock system evolution. The stage is characterized by the certain chemical composition (TDS=148-317 mg/L, HCO3-Na, SiO2=9-80 mg/L), complex of secondary minerals (calcite, albite, laumontite and etc.) and special geochemical environment (pH 8.2-8.6).