| Title | Geochemical Study of Thermal Waters in the Tutupaca Geothermal Zone, Tacna, South of Perú |
|---|---|
| Authors | Vicentina CRUZ, Koji MATSUDA |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | geothermometers, geothermal waters, Tutupaca, Peru |
| Abstract | In this study, representative samples from hot springs were chemical analyzed and geothermometers were used to calculate the deep temperatures of geothermal reservoirs on the basis of water mineral equilibrium. In all cases, the chemical components are not in equilibrium with the minerals in the reservoir, due to the fact that most of these waters are acids. Geothermal manifestations in the Tutupaca zone are evidenced by the presence of hot springs, mud pools and fumaroles of high temperatures up to 90°C the pH values of 2.90 to 6.9 and conductivity 800 to 2900 µS/cm. The geochemical interpretation according to Cl-SO4-HCO3 ternary diagram shows that thermal waters are classified into sulphate, sulphate-chloride and bicarbonate waters. In B-Cl binary diagram the waters of the Tutupaca area are reacting in deep levels with marine sedimentary rocks, which probably have relatively high porosity and permeability with abundant fractures. The Na-K-Mg triangular diagram is also used to evaluate equilibrium between water and reservoir rocks, indicating a linear trend pointing an equilibrium temperature Na/K of 200 ° C in the reservoir either by dilution or mixing. For this reason the isotopic of δ2H and δ18O diagram shows that thermal waters originate mainly from meteoric water. According to the geological and geochemical exploration a hydrogeochemical conceptual model has been processed for the Tutupaca zone. This model shows a geothermal system associated to magmatic sources where the geothermal fluids emerge. There is a structural trend which allows the deep circulation of the waters between 2 and 3 km. The chemistry of these thermal waters would be explained by the interaction between the thermal fluid with sedimentary and volcanic rocks. |