Chlorine Geochemical and Isotopic (37 Cl/35 Cl) Signatures of CO2-Rich Mineral Waters (N-Portugal): Revisited

Abstract

The CO2-rich mineral waters from Vilarelho da Raia, Chaves, Vidago and Pedras Salgadas region (N-Portugal) were analyzed for37 Cl/35Cl, Cl and other major elements. Local rain and shallow cold dilute waters were also studied. The main objective of this study was to use Cl geochemical signatures together with Cl isotope geochemistry to improve our knowledge on the origin of Cl in the hot ( . 76 °C) and cold ( . 16 °C) Na-HCO3-CO2-rich mineral waters that discharge in the region. Chlorine, a good tracer of water-rock interaction, presents a strong correlation with sodium (dominant cation) indicating that Cl− present in the mineral waters originates from water-granitic rock interaction. d37 Cl isotope signatures indicate that i)37 Cl/35 Cl in the studied mineral waters can also be explained by water-granitic rock interaction and ii) the contribution of a deep-seated (upper-mantle) Cl component should not be excluded.