New insight from noble gas and stable isotopes of geothermal/hydrothermal fluids at Caviahue-Copahue Volcanic Complex: Boiling steam separation and water-rock interaction at shallow depth

The layered model of the Copahue geothermal reservoir, Argentina

“…In addition, the development of vapor zones could be overlaid by shallow steam-heated waters, so a sealed upper boundary may not be essential (Ingebritsen and Sorey 1988;Hochstein and Sudarman 2000). This setting is consistent with the isotopic signature of the fumaroles at the western margin of the Copahue reservoir given the interaction inferred between deep geothermal fluids and the shallow steam-heated water table (Chiodini et al 2015;Roulleau et al 2016).…”

“…4 Chemical features of the geothermal manifestations (red patches) at Copahue geothermal field overlying a 3D view of the topography (blue-red colormap; Shuttle Radar Topography Mission data). Chemical and isotopic data from Chiodini et al (2015) and Roulleau et al (2016). Hydrothermal soil composition from Mas et al (1996) opal + alunite + kaolinite + pyrite (Pirajno 2009), as the alteration showed by the soils of Copahue (Fig.…”

“…A complementary approach is supported by elementary abundances of noble gases that are fingerprints of physical changes in the geothermal reservoir (Ozima and Podosek, 2002;Pinti et al 2013). Roulleau et al (2016) analyzed noble gases and stable isotopes of several geothermal fluid samples of Copahue and showed that the R/Ra values are constant with the increase of normalized 132 Xe (Fig. 8).…”

“…These authors concluded Fig. 8 Boiling and steam separation model based on the isotopic variations of helium and elemental abundance of atmospheric noble gases of the fumaroles at Copahue (modified from Roulleau et al 2016) that (a) strong elemental fractionation due to boiling and the steam separation of a deep liquid-dominated reservoir at temperatures between 250 and 300 °C modified the original composition and (b) increasing participation of the meteoric water during the boiling, and a steam separation at shallow levels at marginal fumaroles are both occurring. The latter suggests that the steam cap has variable thickness and that the thicker zones correspond to Termas de Copahue, Máquinas, and Maquinitas geothermal zones.…”

Noble Gas and Carbon Isotope Systematics at the Seemingly Inactive Ciomadul Volcano (Eastern‐Central Europe, Romania): Evidence for Volcanic Degassing

“…Gas emissions are often associated with active or dormant volcanic areas and regions affected by extensional tectonics (e.g., O'Nions & Oxburgh, 1988;Oppenheimer et al, 2014). Monitoring of fluids (chemical and isotopic compositions and physical properties) in volcanic regions provides important information concerning the processes occurring at depth (e.g., Agusto et al, 2013;Barry et al, 2013Barry et al, , 2014Caliro et al, 2015;Christopher et al, 2010;Edmonds, 2008;Fischer, 2008;Mazot et al, 2011;Roulleau et al, 2016;Ruzié et al, 2012;Tassi et al, 2010Tassi et al, , 2011Tassi et al, , 2016Wei et al, 2016). The chemical and isotopic composition of the emitted fluids in active volcanoes is primarily controlled by magmatic processes, such as the injection of new magma into the plumbing system or degassing of deep mafic magma in the lower crust, or interaction with the volcanic hydrothermal systems, among others (e.g., Caracausi et al, 2003Caracausi et al, , 2013Christopher et al, 2010;Edmonds, 2008;Paonita et al, 2012Paonita et al, , 2016Sano et al, 2015).…”