Geophysical Characterization of Medium and Low Temperature Geothermal Systems Using MT: an Example of the Villarrica Area

Abstract

The mostly untapped geothermal potential in Chile has been estimated to about up to 16 GWel (Lahsen et at., 2010). Besides this potential for electric power, in particular, in southern Chile applications for heat supply from low to medium temperature resources may be beneficial to the development of the rural areas. In this respect, the thermal spring areas around the Villarrica volcano have been investigated geochemically (Held et al., 2018) and geophysically (Held et al., 2016) with the aim to visualize and improve the understanding of such types of reservoirs. In this study, we combine findings from 3D inversion of magnetotelluric (MT) data. The MT inversion was carried out with the data collected from 31 MT stations that were measured along two profiles, one in an E-W orientation and perpendicular to the branches of the Liquiñe-Ofqui Fault System (LOFS) and a second one in the N-S orientation along the LOFS and sub-perpendicular to an Andean Transverse Fault (ATF) and the Villarrica-Quetrupillán-Lanín volcanic chain. 3D inversion results can be interpreted as two anomalies of maximum electrical conductivity at shallow depth; one of these is located on the eastern branch of LOFS and links to a number of thermal springs and the second maximum is located below the volcanic chain. Additionally, intermediate resistivity minima along the LOFS coincide with the thermal sources and the monogenetic volcanic activity in the northern and the active rise of magma near the volcano in the southern part of the profile