Geochemistry of carbon dioxide mineral waters of the Choigan natural complex (northeastern Tuva)

Abstract

The abundance of various chemical elements (including trace, rare-earth, and radioactive) in the carbon dioxide mineral waters of the Choigan complex has been investigated. Three groups of waters are recognized according to the geochemical conditions and chemical composition: groundwaters of regional-jointing zone with oxidizing conditions; CO 2 -enriched groundwaters of regional-jointing zone with oxidizing conditions; and groundwaters of fault zones with reducing conditions. It is shown that water-rock interaction intensified by high temperature and carbon dioxide action is the main process determining the chemical composition of groundwaters.

Geothermometry and Isotope Geochemistry of CO2-Rich Thermal Waters in Choygan, East Tuva, Russia

“…The spring waters have been grouped into (I) "Higher" temperature (T > 23 • C) thermal CO 2 -rich waters; (II) "Lower" temperature (T < 23 • C) thermal CO 2 -rich waters; and (III) shallow (non-thermal) groundwaters. Data from our group [26] for samples previously collected from the same area in 2011 are also included for comparison. Chemical compositional difference between waters sampled in 2011 [26] and 2013 (this study) were generally insignificant or small, with observed differences in TDS of typically just 10-200 mg/L, fluorine (0.1-0.9 mg/L) and iron (0.1-1 mg/L); however, larger differences in TDS (400-500 mg/L) were observed in several springs, perhaps reflecting changes in weather and hydrological conditions impacting on mixing between groundwaters of whatever type and rainwater [41].…”

“…This iron may have been leached from biotite and pyroxenes contained in gneisses and crystalline schists in the subsurface. Piper diagram of spring water compositions in the study area (data for 2011 [26], 2013 this study). Open symbols are samples with SO4 > 0.4 meq/L.…”

“…Several samples also exhibit relatively elevated SO4 2− due to a different process, possibly the oxidation of iron sulphide minerals, such as pyrite. Piper diagram of spring water compositions in the study area (data for 2011 [26], 2013 this study). Open symbols are samples with SO 4 > 0.4 meq/L.…”

“…Located in the Eastern Sayan Mountains, Tuva, Russia, some of these springs are characterized by the bubbling of CO 2 -rich gases. Our group [26,27] have determined the dissolved gas [26], 222 Rn [26] and major and trace chemical compositions of these waters [28,29] (see also previous work summarized in [26,27] as well as making an assessment of the extent of thermodynamic equilibrium of these waters with various minerals [26]). These have enabled preliminary estimates of reservoir temperatures [30,31].…”

“…[4,9,22]). We use stable isotopes (δ 18 O and δ 2 H) to provenance the waters (cf., [1,26]) and to better understand underground flow paths. Lastly, this study aims to provide an improved conceptual circulation model of the Choygan hydrothermal system.…”