Applied geophysics to morphostructurally characterize a hydrothermal system: La Laja, San Juan (Argentina)

Abstract

The La Laja Hydrothermal System is located in a tectonically and seismically active area in the southern Central Andes, in the San Juan Province of Argentina. Here we present a geomorphological and geophysical characterization of this system, aimed at constructing geological-structural models to explain its origin, configuration, and main manifestations. The geomorphological analysis allowed the identification of travertine cones and terraces, mudflats, springs, and channels, geoforms that were studied using gravimetry, magnetometry, electrical tomography and audio-magnetotelluric methods. The combination of these techniques, which provide information at different depths and resolutions, together with surface geological data, made it possible to refine the interpretation and generate robust models at the sites of interest. Results suggest that the geothermal manifestations are distributed along a ~NE-SW structural zone, subparallel to the mountain front, and that their origin is tectonic. Two systems controlling the flow of thermal waters were identified: to the north, the El Museo Fault, where the structure acts as a conduit for hydrothermal fluid circulation; and another to the south, which involves a more complex tectonic deformation, including the development of faults, folds, and zones of weakness.