World Geothermal Congress 2020+1
March - October, 2021

Geochemistry of Nitric Thermal Springs from Khoja-Obi-Garm Thermal Area (Pamir-Tien Shan Region)

Natalia KHARITONOVA, Ivan BRAGIN, George CHELNOKOV, Vasiliy LAVRUSHIN, Anna KORZUN, Farid SALIKHOV, Anna DEMONOVA, Victoria FUNIKOVA

[Lomonosov Moscow State University, Russia]

This paper presents data on the composition of the low-enthalpy thermal waters from the unique Khoja-Obi-Garm field located at the central part of the southern slope of the Gissar Range, in the gorge of the Khoja-Obi-Garm River, at an altitude of 1740-1960 meters. In this place, the eponymous SPA-center was built. Groundwaters from springs and boreholes of Khoja-Obi-Garm thermal area have temperatures from 57 to 93 °C, high pH (up to 8) and low TDS (less than 0.5 g/l). These waters belong to Na–SO4–HCO3 type with high content of H2SiO3 (~140 mg/l), F (up to 18 mg/l) and Rn (up to 814 Bq/l). The specific feature of these thermal waters is a predominance of N2 in the gas phase (up to 83-98 vol.%), while other gases (O2, CO2, Ar, Кr, Хе, Не and Ne) are nonessential. Gas content at Khoja-Obi-Garm spa waters is usually not high, does not exceed 30 ml/l. We prove that N2 and O2 are atmospheric gases, but CO2 is biogenic gas (δ13CTIC -30‰ – -22 ‰). The estimated subsurface temperature is 193-197 °C based on the silica and K/Na geothermometer. Thermodynamic speciation indicate that these groundwaters are supersaturated with clay minerals and lowtemperature zeolites and undersaturated with carbonate and aluminosilicate minerals.

        Topic: Geochemistry Paper Number: 14087

         Session 8P: Poster 2 [Tuesday 11th May 2021, 11:00 pm] (UTC-8)
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