Isotopic-geochemical features of thermal water of the Kyndyg deposit (Republic of Abkhazia)

Abstract

Subject. The aim of the work is to study the mechanism and sources of water formation, as well as the peculiarities of carbonate mineralization in the aquifer of the Kyndyg thermal water deposit. Materials and methods. The samples of water (8) and deposited carbonates (15), collected at different seasons at three sites, characterized by different temperatures and dis-tances from the source, were investigated. pH, Eh, and electrical conductivity were determined by an electrochemical me-thod. For the determination of HCO3–, Cl– 2–, SO4, titrimetric, mercurymetric and turbidimetric methods were used. Trace element composition was determined by ICP-MS (NexION 300S); strontium isotopic composition – by MC-ICP-MS (Nep-tune Plus) using the bracketing technique after Sr chromatographic separation. Results. The chloride-calcium hydroche-mical type prevails in the studied waters. A number of trace elements in water exceeds the clarke concentrations for ground-water in the supergene zone of mountain landscapes.87Sr/86Sr isotope ratios (0.7065–0.7072) in thermal waters suggest that their composition is determined rather by the isotopic characteristics of the rocks through which water drains than by the influence of sea water. Among the newly formed carbonates, aragonite prevails. In contrast to thermal water, the concentrations of most metals in carbonates are below the clarke values; only Sr and Se are increased, which content is significantly increased in water as well. Deposited carbonates are characterized by87Sr/86Sr values (0.7028–0.7074), which are lower than in the source thermal waters. Conclusions. On the basis of hydrogeological, hydrochemical and geochemical data, it can be assumed that the waters of this aquifer complex are formed mainly due to fresh fractured karst waters of lower Cre-taceous limestones with submerged monocline dipping into the zone of slow circulation and mixing with sedimentogenic sodium chloride waters. The geochemical data and the presence of scandium anomaly suggest that the underlying Jurassic volcanogenic rocks also participate in water exchange. © 2020, AN Zavaritsky Institute of Geology and Geochemistry. All rights reserved.