Structural control on geothermal circulation in the Tocomar geothermal volcanic area (Puna plateau, Argentina)

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

Congreso; EGU General Assembly; 2016

The reconstruction of the stratigraphical?structural framework and the hydrogeology of geothermal areas isfundamental for understanding the relationships between cap rocks, reservoir and circulation of geothermalfluids and for planning the exploitation of the field. 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-Andeantectonic lineament known as the Calama?Olacapato?Toro (COT) fault system, which favours a high secondarypermeability testified by the presence of numerous thermal springs.This study presents new stratigraphic, structural, volcanological, geochemical and hydrogeological data on thegeothermal field.Our data suggest that the main geothermal reservoir is located within or below the Pre-Palaeozoic?Ordovicianbasement units, characterised by unevenly distributed secondary permeability. The reservoir is recharged byinfiltration in the ridges above 4500 m a.s.l., where basement rocks are in outcrop. Below 4500 m a.s.l., thereservoir is covered by the low permeable Miocene?Quaternary units that allow a poor circulation of shallowgroundwater. Geothermal fluids upwell in areas with more intense fracturing, especially where main regionalstructures, particularly NW?SE COT-parallel lineaments, intersect with secondary structures, such as at theTocomar field.