Estimation of the Real Subsurface Temperature for Mineral Water Circulated within the Essentuki Spa, Caucasian Mineral Waters Region

Abstract

This paper estimates the deep heating temperature of the mineral waters of the Essentuki field by ionic geothermometers. The water is extracted from four productive aquifers (Danian–Selandian, Cenomanian–Maastrichtian, Aptian–Lower Albian, and Tithonian–Valanginian). The study shows that the most adequate deep temperatures, from 64 to 97°C, are provided by a SiO₂ geothermometer; the Na–K geothermometer overestimates and the Mg–Li and chalcedony geothermometers underestimate this temperature. The water penetration depth is assessed at 1.2–1.8 km for the Danian–Selandian, Cenomanian–Maastrichtian, and Aptian–Lower Albian aquifers and at more than 2 km for the Tithonian–Valanginian aquifer.