Conference abstractOpen access
Hydrogeochemistry of thermal waters in the intermountain basin of the Tien Shan Region
- Lomonosov Moscow State University, Moscow, Russia
- Geological Institute, Russian Academy of Sciences, Moscow, Russia
https://doi.org/10.5194/egusphere-egu25-10533
Highlights
- Water temperature at the sampling sites 16.2–52.3 °C.
- Total dissolved solids: 0.3–0.5 g/L in CO₂-rich waters of fractured rocks; 2.0–35.0 g/L in CO₂–N₂ and N₂–CH₄ waters under thick sedimentary cover.
- δ¹⁸O −13.9‰ to −8.5‰; δD −95.8‰ to −66.0‰.
- Ion-salt geothermometer temperatures at depth 21.4–144.8 °C.
Abstract
This study presents new data on the chemical composition, content, and distribution patterns of stable oxygen and hydrogen isotopes in natural waters from the Issyk-Kul intermountain artesian basin. This area has significant balneological potential due to the abundance of mineral waters with diverse temperatures, chemical and gas compositions, and total dissolved solids (TDS). The uniqueness of this region lies in the coexistence of two distinct types of mineral waters: fissure-pore waters confined to intermountain artesian basins and fissure-vein waters associated with tectonic fault zones in rock massifs. The study is based on field research conducted in the Issyk-Kul basin, located in the Tien Shan region. The temperature of mineral waters at the sampling sites varies widely (16.2-52.3°C), as does TDS, which depends on the hydrogeological structure. CO₂-rich waters with low TDS (0.3-0.5 g/L) form within rocks and open fractures, while carbon dioxide-nitrogen or nitrogen-methane waters with TDS ranging from 2.0 to 35.0 g/L are associated with significant sedimentary cover thickness. A common pattern in anion composition is observed, as all mineral waters contain sulfate (SO₄²⁻) and chloride (Cl⁻) ions. Sodium (Na⁺) consistently predominates in the cationic composition. The content of stable isotopes of oxygen (δ18O) and hydrogen (δD) in the studied waters also varies significantly, from -13.9‰ to -8.5‰ for δ18O and from -95.8‰ to -66.0‰ for δD. Most data points on the δ18O-δD binary diagram align with the global meteoric water line, indicating an infiltration origin with a pronounced altitude effect. It was also established that the trace element composition of thermal waters serves as a marker for the hydrogeological conditions of their formation and circulation: waters from the sedimentary cover of intermountain artesian basins are enriched with Sr, Ba, Mn, B, Mo, and U, whereas waters from rocky massifs contain elevated concentrations of F, Rb, W, and Sc. The calculation of the water migration coefficient revealed a dependence of the accumulation rate of trace components on the type of host formation and the hydrogeological conditions of water formation. Ion-salt geothermometers were applied to estimate the deep formation temperatures of the mineral waters, revealing a broad range of values (21.4-144.8°C). These results reflect diverse formation conditions for the studied waters.
Abstract from the EGU General Assembly 2025 programme. The authors’ abstract, reproduced under CC BY 4.0.
In plain English
Ekaterina Baranovskaya and Natalia Kharitonova of Lomonosov Moscow State University and George Chelnokov of the Geological Institute of the Russian Academy of Sciences present new data on the chemistry and the stable oxygen and hydrogen isotopes of natural waters in the Issyk-Kul intermountain artesian basin of the Tien Shan, from field work in the basin. Two types of mineral water occur there together: fissure-pore waters of the artesian basin and fissure-vein waters of fault zones in rock massifs. Mr. Chelnokov and Ms. Kharitonova are also authors of a wider study of thermal and cold mineral waters of the Tien Shan and the Pamir.
Water temperatures at the sampling sites range from 16.2 to 52.3 °C. CO₂-rich waters with low total dissolved solids (0.3–0.5 g/L) form in rocks and open fractures, while carbon dioxide–nitrogen and nitrogen–methane waters with 2.0–35.0 g/L occur where the sedimentary cover is thick. All the mineral waters contain sulphate and chloride, and sodium always dominates the cations. δ¹⁸O ranges from −13.9‰ to −8.5‰ and δD from −95.8‰ to −66.0‰. Most samples lie on the global meteoric water line, which shows that the water is infiltrated precipitation, with a marked altitude effect.
Trace elements mark where the water formed and circulated: waters from the sedimentary cover of the artesian basins are enriched in Sr, Ba, Mn, B, Mo and U, and waters from rock massifs in F, Rb, W and Sc. Ion-salt geothermometers give deep formation temperatures of 21.4–144.8 °C.
How to cite
Ekaterina Baranovskaya, Natalia Kharitonova and George Chelnokov (2025). Hydrogeochemistry of thermal waters in the intermountain basin of the Tien Shan Region. EGU General Assembly 2025, Vienna, 27 April–2 May 2025, EGU25-10533. https://doi.org/10.5194/egusphere-egu25-10533