δc, CO2/3and 3He/4He ratios reveal the presence of mantle gas in the CO2-rich groundwaters of the Ardennes massif (Spa, Belgium)

Although natural CO2-rich groundwaters of eastern Belgium have been known for centuries, the exact origin of their gas is still unclear. This paper presents the results of a sampling campaign in Belgium (Spa, Stoumont, Malmedy): 30 samples of both carbogaseous and non-carbogaseous groundwaters were analyzed for major elements, CO2 content and carbon isotopic composition. Among them, 13 samples were also analyzed for 3He/4He and 4He/20Ne ratios. The combination of δC (between ca.-9‰ĝ€¯VPDBVienna Pee Dee Belemnite and-2‰ĝ€¯VPDB), CO2/3He ratio (between 1.9×108 and 2.9×109) and 3He/4He (between 0... Mehr ...