| Title | Geothermal Waters in Relation with Triassic Evaporitic Structures (North-Western Tunisia) |
|---|---|
| Authors | N. Inoubli, S. Bouri, M. Gouasmia and H. Ben Dhia |
| Year | 2005 |
| Conference | World Geothermal Congress |
| Keywords | Evaporite, Triassic diapirs, Hydrochemistry, Thermal water, North-Western Tunisia |
| Abstract | In North-Western Tunisia; mainly in the "diapirs zone", superficial and thermal waters occur in subsurface wells, springs showing sometimes very high salinity. A geological and hydrochemical investigation has been carried out, in the studied region, to improve our understanding of the origin of saline groundwater and its evolution within the framework of the complex geological history of the region. North-Western Tunisia has a complex geological evolution which is mainly controlled by halocinetic movements. Geological and structural studies show that thermal waters emerge through fractured limestones. It is obvious that the upcoming movement of the thermal saline and/or thermal groundwater, in North-Western Tunisia, is controlled by tectonics, mainly by the diapiric structures. The sampled waters have discharge temperatures ranging between 21 and 71?C and total dissolved solids (TDS) between 560 and 56 000 mg/l. They show a Na-Cl type of water with enrichment in Ca and HCO3 for few samples. The warm saline waters are undersaturated with respect to gypsum but oversaturated or around equilibrium with respect to calcite. Hydrochemical data provide evidence for water-rock interaction of thermal fluids with limestone aquifers and for dissolution of evaporite deposits of Triassic outcrops, mainly the halite component. Furthermore, several chemical diagrams were applied to have an idea about the original aquifer and the influence of the evaporitic levels on physico-chemical feature's evolution of the thermal waters. |