| Title | Detailed Geochemical Study of Alkaline Thermal Waters: A Geothermal Evaluation in the Pyrenees Range, Southern France |
|---|---|
| Authors | Vuataz, Francois-D.; Criaud, Annie; Fouillac, Christian |
| Year | 1985 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Brine Technology; Exploration; France; Pyrenees Range; Hydrothermal; Geothermometers; Chemistry; Base |
| Abstract | Alkaline thermal waters occur from faults in granitic rocks along the Pyrenees Range. About 30 thermal zones, extended over 200 km, display very similar geochemical features: a very low mineralization, an alkaline pH, a sodium sulphurated composition and an extremely low magnesium content. In case of dilution with superficial waters, the alkaline cations, silica and sulfphide decrease, whereas earth alkaline and sulfate increase. The oxidation processes were studies by on site analyses of sulphur, under its various forms form the most reduced to the oxidized species. Chemical modeling allowed to compute the non ionized form of silica in order to estimate the equilibrium temperature with respect to chalcedony and quartz. Results of the Na/Li and Na/K geothermometers give a good agreement for most thermal zones. The homogeneous deep temperatures evaluated with the chemical geothermometers yield and average of 100 =/- 20°C for the study area. Exploration drilling would be needed now to assess the size of this low to moderate temperature geothermal resource. |