Crustal Deformation Effects on the Chemical Evolution of Geothermal Systems: Case Studies from Southern Andes

Abstract

The nature of the interplay between active tectonics and fluid flow is a key feature to better understand the chemical evolution of fluids in geothermal systems and to improve efficacy of exploration. The Southern Andes volcanic zone is one of the best natural laboratories to address this issue because of the occurrence of numerous geothermal areas, recent seismic activity generated by regional fault systems, and intense volcanic activity. Geothermal systems have been understudied in this area, and limited scientific information exists about the role of local kinematic conditions on fluid flow and mineralization during the development and evolution of geothermal reservoirs. In this study, we combined the structural analysis of fault systems with chemical analyses of fluid in both regional (1:200,000) and reservoir scale. Our regional scale results reveal two magmatic-tectonic-geothermal domains based on fault systems, volcanic activity, and lithologies. The Liquiñe–Ofqui fault system (LOFS) domain encompasses geothermal areas located either along the master or subsidiary faults in the crystalline basement. In marked contrast, the arc-oblique long-lived fault systems (ALFS) domain includes geothermal occurrences located on the flanks of volcanoes forming WNW-trending alignments; these systems are built over faults that promote the development of crustal magma reservoirs. Although more studies are needed to constrain the complex interplay between tectonics and fluid flow, results from this study provide new insights towards efficient exploration strategies of geothermal resources in Southern Andes.