Gas geochemistry has been widely used over the last decades to investigate the origin of geothermal fluids and thus aid the understanding of reservoir processes, as well as in monitoring studies in tectonically and volcanically active regions. In this respect, the coupled systematics of CO2 and He, including both their relative abundances and isotopic compositions (3He/4He, δ13C), is a well-proven approach for defining volatile provenance in various tectonic settings (e.g., Hilton, 1996; Italiano et al., 2001; Kennedy and Truesdell, 1996; Marty and Jambon, 1987; O’Nions and Oxburgh, 1988; Sano and Marty, 1995; Van Soest et al., 1998).