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

G. GROPPELLI; RAÚL BECCHIO; AGOSTINA CHIODI; FLORENCIA AHUMADA; SABINA BIGI; WALTER BÁEZ; LUCA ALDEGA; CHIARA CARICCHI

Workshop; IA VCEI Commission on Volcano Geology, 3rd International Workshop; 2016

The reconstruction of the stratigraphical and structural framework 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. An accurate interpretation of geophysical data depends on the reliability of the geological conceptual model of the investigated geothermal system (Vignaroli et al., 2013). In particular, reconstruction of the geothermal setting is invariably connected with the geological history of the site, and evaluation of the main geological features in the area is a primary goal before planning the exploration (Vignaroli et al., 2013). The Tocomar Geothermal System (TGS) is located in the Puna plateau, (Central Andes, NW Argentina) along the active NW?SE trans-Andean tectonic lineament known as the Calama?Olacapato?Toro (COT) fault system (Norini et al., 2013). The origin of TGS is associated with the evolution of the Tocomar basin and the profuse volcanic activity in the zone. The Tocomar basin is a 30 km2 wide, roughly triangular depression that interrupts locally the COT, and hosts a volcano-sedimentary succession. Extensional, transcurrent and reverse faults affect therecent deposits suggesting for this basin a pull-apart origin (Petrinovic et al., 2006; Giordano et al., 2013). Previous works present only a general conceptual model for the TGS and its future development requires a deepening in the knowledge of the present conceptual model. The main aim of this work was make a new geological mapp of the Tocomar area in order to reconstruct the geological evolution of the TGS. This work represents the first step in an ongoing multidisciplinary project which objective is to assessment the geothermal resource of the TGS.The exceptional exposure and lack of vegetation in the high-altitude hyperarid Puna region allowed a precise field mapping at the 1:30,000 scale of the TGS. The resulting geological map covers an area of c. 130 km2 and displays the spatial distribution of all lithostratigraphic units and main structures described and defined in the field. The stratigraphic sequence in the study area was divided into Pre- Tocomar basin units and Tocomarbasin units.