Multidisciplinary approach for the exploration of remote geothermal fields: The Tocomar Geothermal System case study (Puna plateau, Argentina)

GIORDANO GUIDO; AHUMADA MA. FLORENCIA; ALDEGA LUCAS; BAEZ WALTER; BECCHIO RAÚL; BIGI SABINA; CHIARA CARICCHI; AGOSTINA CHIODI; SVEVA CORRADO; ARALDO DE BENNEDETTI; FAVETTO ALICIA; RUBEN FILIPOVICH; FUSARI ALESSANDRO; GIANLUCA GROPPELLI; INVERINIZZI; MAFFUCCI ROBERTA; GIANLUCA NORINI; ANNAMARIA PINTON; POMPOSIELLO C.; FRANCO TASSI; SARA TAVIANI; JOSÉ VIRAMONTE

Congreso; European Geothermal Congress; 2016

The reconstruction of the stratigraphical?structural framework and the hydrogeology and hydrogeochemistry of geothermal areas is fundamental for understanding the relationships between cap rocks, reservoir and circulation of geothermal fluids and for planning the exploitation of geothermal fields. The Tocomar geothermal volcanic area (Puna plateau, Central Andes, NW Argentina) has a high geothermal potential. It is crossed by the active NW?SE trans-Andean tectonic lineament known as the Calama?Olacapato?Toro (COT) fault system, which favours a high secondary permeability testified by the presence of numerous springs. This study presents new stratigraphic, structural and hydrogeological data on the geothermal field, together with preliminary geochemical and magnetotelluric data. Our data suggest that the main geothermal reservoir is located within the Pre-Palaeozoic?Ordovician basement units, characterised by unevenly distributed secondary permeability. The reservoir is recharged by meteoric waters via infiltration in the ridges above 4500 m a.s.l. The reservoir is covered by Miocene?Quaternary units that allow a local circulation of shallow groundwater. Geothermal fluids upwell in areas with more intense fracturing, especially where main regional structures, particularly NW?SE COT-parallel lineaments, intersect with secondary structures associated with the development of the Tocomar basin. Preliminary data indicate a reservoir temperature of ~ 200 °C and a local geothermal gradient of ~ 130°C/km associated with the Quaternary volcanic activity in the Tocomar area. The integration of field-based and geophysical analyses proved to be effective in approaching the exploration of remote geothermal fields, and in deepening the conceptual model for geothermal circulation.