| Abstract |
The Copahue geothermal field is located in a volcanic complex that has suffered a strong influence of tectonic movements from the beginning of its evolution. Regionally, it is possible to recognize two predominant fracture systems, the main system has a N55W direction and the other one has a N15W direction. According to these fracture systems, it is possible to define the strength direction that affected the NeuquÈn basin since pre-Jurassic times. The tectonics of the studied area is characterized by a fracture system associated to the evolution of the volcanic complex. Circular faults that constitute the borders of a big caldera were formed in the first stage of the volcanic evolution, developing a radial fault system, observable in the external part of the caldera. The second stage of the Copahue volcanic complex is represented by a group of several effusive centres: Las Mellizas, Trolon, Bayo and Copahue. Las Mellizas Centre has the largest area. It covers the bottom of the great caldera (15 x 20 km). Trolon, Bayo and Copahue effusive centres are located on the border of this caldera. There is a fault system that affected this volcanic complex, which main direction is N55W and their associated directions are N55E, EW and N40W. The geothermal reservoir is located predominantly in zones of secondary permeability, in calc-alkaline lavas and pyroclastic rocks of Las Mellizas Formation, and contains overheated steam. This work was performed with the data obtained from 12 wells drilled for this purpose, with depths that ranged from 50 to 200 meters. A Heat Flow Map was prepared, that shows the distribution of this parameter in an area of about 100 Km2, with values above the world average of 60 mW m-2. These data indicate that the thermal anomaly is significant, with peak values six times the world rate. The comparative analysis of the heat flow distribution with the tectonic scheme of this area, shows the correlation that exists between the axe of the elongated area with the highest heat flow values, with the main structural lineament of this zone, recognized by geology and remote sensing evaluation. |