Chemical and Isotopic Features of a High pCO2 Natural Mineral Water from Essentuki Field (Caucasian Mineral Water Region, Russia)

Abstract

This article presents the new data on the chemical and gas composition, the content of stable isotopes of oxygen, hydrogen, carbon, and sulfur in natural mineral waters of the Essentuki field. A detailed study of the geological and hydrogeological features of the water circulation area, its major chemical composition, the content of organic matter in water, temperature conditions and δ18OSMOW, δDSMOW, δ13CDIC, δ18ODIC, δ34SVCDT, δ13CCO2, δ13CCH4, δ15N values made it possible to specify the genesis of water, gas, and solute components of the Essentuki CO2-rich mineral water field. The stable isotopes values (δ18OSMOW and δDSMOW) in the water phase ranges from −13.75 to −9.69‰ and from −101.08 to −74.34‰, respectively. They correspond to GMWL, which indicates their predominantly infiltration genesis. The values of δ13CDIC in mineral waters of the Essentuki field vary widely from −14.43 to +8.59‰ and indicate their mixed genesis. δ15N gas values in mineral waters of the Essentuki field vary quite widely from −2.31 to 2.50‰ indicating a different source of this gas. Obtained data prove that all mineral waters in the Essentuki field are infiltration waters, and the heterogeneous component composition of waters circulating in different aquifers reflects the lithological composition of water-bearing strata, the rate of openness/closure of faults and the intensity of reactions in the «water-rock-gas-organic matter» system.