ABSTRACT
ABSTRACT: This paper reviews geochemical and isotopic studies carried out on hot and cold HCO3/Na/CO2-rich mineral waters issuing along a major regional NNE-trending fault (North Portugal). δ2H and δ18O values are similar to those of the local meteoric waters, indicating a meteoric origin for the mineral waters. δ13C values from CO2 gas and total dissolved inorganic carbon, and previously reported 3He/4He values, indicate that the carbon in these CO2-rich mineral waters is mainly derived from a deep-seated (upper-mantle) source. The low 14C activity measured in some of the cold CO2-rich mineral waters is incompatible with the systematic presence of
3H in those waters, indicating that total carbon in the recharge waters is being masked by large quantities of deep-seated (14C-free) CO2. Differences in the
87Sr/86Sr values presented by the thermomineral waters seem to be related with the existence of water-rock interaction with different granitic rocks.
