Hydrogeochemical Characterization of Thermal Springs, Los Lagos, Chile

Abstract

Los Lagos District is considered to be an area of interest for geothermal development because of the presence of numerous volcanic complexes and thermal springs as well as two major tectonic features: the NNE-SSW dextral-reverse Liquiñe-Ofqui Fault System (LOFS) and the WNW-ESE sinistral Arc-Oblique Long-lived Faults System (ALFS). Two identified groups of hot springs are believed to have formed based primarily on geographic location. The first group formed along the ALFS (Porcelana Chico, El Comau and Porcelana Grande), and is characterized as having a direct volcanic influence related to horizontal transport of fluid (expressed by higher B/Cl ratios), a geothermal source of chlorides and a minor cation exchange. These thermal waters record the highest temperatures. The second group is comprised of thermal waters along the LOFS and is subdivided into two subsets: (i) hot springs localized in the intertidal zone (Rollizos, Cochamó, Sotomó y El Yate) that have a slight interaction with saline water and a chloride mix origin; and (ii) those located in the continental zone, (Puyehue, Aguas Calientes, Rupanco, El Callao, Cayetué, Ralún, Puelo, Pichicolo, Llancahué, Cahuelmó y El Amarillo hot springs) which are especially far from estuaries and fjords and show an important cation exchange, this behavior is believed to reflect vertical transport of fluids that has ultimately led to an interaction with North Patagonian Batholith (NPB) rocks.