| Authors |
Clavero, J.; Pineda, G.; Mayorga, C.; Giavelli, A.; Aguirre, I. Simmons, S.; Martini, S.; Soffia, J.; Arriaza, R.; Polanco, E.; Achurra, L. |
| Abstract |
Tinguiririca geothermal project is located in the high Andes of Central Andes, ca. 150 km SW from Santiago within the main Andean range, on the western flank of Tinguiririca Volcanic Complex, a major eruptive center formed by at least three volcanic edifices aligned in NNE direction. The geology of the area consists mainly on Mesozoic and Cenozoic marine and volcanoclastic sequences, folded and thrusted according to major extensional and compressive deformation events. The Cenozoic volcanoclastic sequences consists mainly on large ignimbrites sheets and andesitic lavas, with some interbedded epiclastic units. Unconformably on top of these deformed units, a series of Lower to Middle Pleistocene subhorizontal lava units crop out, which also form themselves the basement of the younger volcanic edifices in the area. The latter, Tinguiririca, Fray Carlos and Montserrat volcanoes, are aligned in NNE direction, which is sub-parallel to the main faults in the area, suggesting the strong structural control on magmatic and fluid paths in the upper crust. Surface thermal manifestations are located mainly in two areas. The more distal ones at ca. 16 km to the south (with respect to Tinguiririca volcano) named Termas del Flaco, consist of Cl-rich waters (77ºC), with minimum geothermometer (Na-K) equilibrium temperatures of 220-240ºC. The other group consists on a series of hotsprings, fumaroles, mudpools and steam soils located on the western flanks of Tinguiririca and Fray Carlos volcanoes, in an area of about 40 km2. These thermal waters, interpreted as steam heated, are sulfate-rich (up to 90.6ºC, close to boiling temperature at this elevation, ca. 2,700 m asl). He-isotope data from these manifestations give a R/Ra ~2.7-2.9. Preliminary gas geothermometry gives minimum temperatures of ~230ºC. Aeromagnetic, gravity and MT/TDEM surveys have been carried out in the area, showing a major conductivity anomaly on the southwestern flank of the volcanic complex, evidencing the existence of a geothermal reservoir at depth. A first slim hole well was drilled in the summer of 2011 with excellent results that will be presented at the meeting. |