Carbogaseous spring waters, coldwater geysers and dry CO2 exhalations in the tectonic window of the Lower Engadine Valley, Switzerland

Abstract

In the region of Scuol-Tarasp in the Lower Engadine Valley in the Eastern Swiss Alps, there are a variety of phenomena related to a geogenetic CO2 production, including carbogaseous mineral springs, previously active coldwater geysers and dry gas exhalations from the ground via mofettes. Previous isotopic studies revealed that the CO2 originates from the metamorphic decomposition of carbonate rocks in the crust. This paper presents an inventory of the springs, geysers and mofettes, and proposes a conceptual model on the regional gas and water circulation. Based on hydrochemical criteria, it was possible to identify six main groups of spring waters, three of which are carbogaseous mineral springs. Most of the carbogaseous springs and gas exhalations are bound to the Bündnerschiefer fractured aquifer. The different water types originate from mixing of groundwater and highly mineralised carbogaseous fluids from depth. Near-surface degassing of CO2 from the fluid phase creates the dry gas exhalations. CO2 and radon measurements in 178 soil boreholes suggest that the gas exhalations occur at a limited number of point-like anomalies, and there is no evidence for regionally important diffuse CO2 discharges from the ground. RESUMAZIUNEn la regiun da Scuol-Tarasp en l'Engiadina bassa, en l'orientala part dallas alps svizras cumparan antgins fenomens, che coreleschan cun la producziun da CO2 en la profunditad. Ei dat fontaunas mineralas carbonicas, antruras geisirs activs d'aua freida e sortidas da gas schetg da mofettas. Anteriuras retschercas d'isotops han mussau, ch'il CO2 deriva dalla decumposiziun metamorfosa da caltschina en la crusta dalla tiara. Questa lavur presenta in inventari da fontaunas, geisirs e moffettas e fa ina proposta per in model concepziunal per la circulaziun regiunala da gas ed aua. Sin fundament da criteris hidrochemics han sis gruppas da fontaunas saviu vegni identificadas, dallas qualas treis gruppas cumprendan fontaunas mineralas carbonicas. Las pliras fontaunas carbonicas neschan egl aquifer dil sfendaglius platter Grischun. Ils differents tips d'aua da fontauna resultan entras la mischeida da liquidas profundas carbonicas fetg mineralisadas cun auas sutterranas giuvnas. Degasaziun dil CO2 ord la fasa d'aua damaneivel da la surfatscha meina tier l'exhalaziun da gas. Mesiraziuns da CO2 e radon en 178 ruosnas indicheschan, che l'exhalaziun da gas serestrenscha sin paucas anomalias punctualas. Ei dat negins indezis per ina impurtonta sortida regiunala da CO2.

The Fascinating and Complex Dynamics of Geyser Eruptions

“…There is interest in CO 2 -driven geysers because they capture some of the processes that would arise if CO 2 leaked into faults and wellbores during geological carbon sequestration and storage. All of the reported cold geysers are wells that were drilled into carbonate units (e.g., Glennon & Pfaff 2004, Bissig et al 2006, Watson et al 2014. For example, the CO 2 discharged from Crystal and Tenmile geysers in the northern Paradox Basin near Green River, Utah, originates from thermal decomposition of marine carbonates (Watson et al 2014).…”

Revisión: Recursos de aguas termales en acuíferos de rocas carbonáticas

“…There are three principal origins Fig. 3 Schematic diagrams illustrating geochemical processes contributing to hypogenic speleogenesis: a mixing corrosion-mixing of two waters (A, B) saturated with respect to calcite results in a mixture (M) that is undersaturated (Bögli 1964); b dissolution kinetics-when calcite-saturation exceeds 75%, dissolution rate drops to very low levels, thus allowing undersaturated waters to penetrate great depth (Plummer et al 1978;Dreybrodt 1990); c other acids-oxidation of H 2 S to H 2 SO 4 boosts karstification (Palmer 1991); d retrograde solubility-in a closed system, calcite solubility increases with decreasing temperature, allowing for karstification by cooling of upward flowing fluids (Andre and Rajaram 2005) of geogenic carbon dioxide: transformation of organic matter during oil, gas and coal formation; metamorphism of carbonatic rocks in the crust; or degassing of the Earth's mantle, often associated with volcanic activities (Palmer 1995;Bissig et al 2006).…”

“…The pumping rate of large geothermal installations can reach 150 L/s (Table 1). Natural carbogaseous waters often include several g/L of CO 2 (Bissig et al 2006;Ufrecht 2006b). On this basis, it is estimated that, for the purpose of sequestration, 1-10 g/L of CO 2 could be mixed with the water and pumped into the aquifer via the injection well, although feasible CO 2 concentrations critically depend on pressure-temperature conditions and technical aspects, which would require further investigation.…”

Properties of geothermal fluids in Switzerland: A new interactive database

“…For example, the thermal springs of Combioula emerge from Triassic formations but circulate partly in crystalline rocks found below these sediments. The deep borehole of St-Moritz contains strongly mineralized thermal water (TDS > 13 g/L), which is believed to be due to high levels of CO 2 favoring rock dissolution (Aemissegger, 1993;Bissig et al, 2006).…”