SHALLOW MAGNETOTELLURIC IMAGES OF THE GOLLETE GEOTHERMAL AREA IN VALLE DEL CURA, MAIN ANDES CORDILLERA OF SAN JUAN

H. BARCELONA; V. PERI

San Juan

Congreso; XXVI Reunión Científica de la Asociación Argentina de Geofísicos y Geodestas; 2014

Asociación Argentina de Geofísicos y Geodestas

The Valle del Cura basin is located at the avolcanic Pampean flat-slab segment (Fig. 1a), where very important mineralization and strong hydrothermal evidences (Kay et al., 1999) are related to the intense magmatic episodes carried out between Oligocene-Miocene ages (Maksaev et al., 1984; Bissig et al., 2001). Lack of recent volcanic activity contrasts with the various hydrothermal manifestations present in the Valle del Cura. A total of seven main thermal zones scattered 60 km long through N-S trend were identified in the literature. They are constrained along the Zancarrón and La Brea ridges, where outcrops the Oligocene-Miocene volcano-sedimentary rocks and the Cretaceous basement rocks by a set of west tectonic vergent thrust faults (Malizia et al., 1997; Litvak, 2009; Winocur et al., 2014). Pesce and Miranda (2003) compiled geochemical information about the thermal zones, giving temperature estimations ranging from 180-200°C, but no extended data analysis or complementary studies were carried out. Only the middlemost geothermal zone, called Despoblados, was partially studied and a local geothermal model was recently proposed (Barcelona et al., 2014). Here we report partial results of a shallow magnetotelluric (MT) study that was focused on the Gollete Valley (Fig. b,c), the southernmost thermal zone. A total of nineteen MT sites approximately 500 m apart were collected using Geometrics Stratagem data logger by standard procedure (Fig. d). The registered frequency band ranged from 1 Hz to 1000 Hz in all sites, but depending on the curve features obtained the range increased to 3000 Hz-0.3 Hz. Single-site multi frequency analysis was performed and the regional strikes were calculated through the Strike code of McNeice and Jones (2001). The 2-D electrical resistivity models of the Gollete Valley were inverted by the same parameters to facilitate the geoelectric structures correlation between them. Through the models, the valley shows a southward progressive simplification of the electrical resistivity distribution, increasing size and decreasing in number the conductive anomalies (