| Title | Geochemical and Isotopic Features of Hot and Cold CO2-Rich Mineral Waters of Northern Portugal: a Review and Reinterpretation |
|---|---|
| Authors | Jose Marques, Luis Ares-Barros & Rui Graca |
| Year | 1999 |
| Conference | European Geothermal Conference |
| Keywords | Geochemistry, isotopes, hot and cold COz-rich mineral waters, flowpaths, Chaves geothermal area, Portugal |
| Abstract | During past few years we have been mainly focused on the study of the relation among the hot (76?C) and cold (17?C) COz-rich mineral waters discharging, in the northern part of Portugal. All mineralised waters belong the HCOfld COz-rich type. The results of SOz, Na-K-Ca, Nan< and NaLi geothermometers are not generally compatible. Using the diagrams log (bSi0,) vs log (NdK) and log (Can<') vs log (NdK) we have concluded that most of the studied COz-rich waters are far from equilibrium. These results are in good agreement with those obtained by the graphical evaluation of water-rock equilibration temperatures using the Nd400, W10 and Mg'" concentrahons. Vilarelho da Raia cold mineral waters have S180 and SD values similar to Chaves hot waters suggesting a common origin for these waters. The heavier S"0 and SD values found in Vidago and Pedras Salgadas cold mineral waters could be attributed to different recharge altitudes. The high mineralization, low tritium activity and a positive I80-shift found in Vidago AC18 cold mineral waters could be faced as signatures of a long residence time at depth as the result of a regional circulation (as indicated by the lighter SD values). |