New conceptual model for the Tocomar Geothermal System (Central Puna, NW Argentina): insights from geological, structural and geochemical data

FILIPOVICH, R.; C. INVERNIZZI; AHUMADA MA. FLORENCIA; AGOSTINA CHIODI; BAEZ WALTER; ALDEGA LUCAS; BIGI SABINA; BECCHIO RAÚL; S. CORRADO; CHIARA CARICCHI; DE ASTIS, GIANFILIPPO; ARALDO DE BENNEDETTI; G. GROPPELLI; G. NORINI; SARA TAVIANI; TASSI FRANCO; J. G. VIRAMONTE; G. GIORDANO

Congreso; CONGRESSO SGI-SIMP 2018; 2018

The outlining of conceptual models, even in the earliest stages, represents a paramount aspect for geothermal􀁈􀁛􀁓􀁏􀁒􀁕􀁄􀁗􀁌􀁒􀁑􀀃 􀁖􀁌􀁑􀁆􀁈􀀃 􀁗􀁋􀁈􀁖􀁈􀀃 􀁖􀁆􀁋􀁈􀁐􀁈􀁖􀀃 􀁄􀁕􀁈􀀃 􀁅􀁜􀀃 􀁉􀁄􀁕􀀃 􀁗􀁋􀁈􀀃 􀁐􀁒􀁖􀁗􀀃 􀁈􀁉􀁉􀁈􀁆􀁗􀁌􀁙􀁈􀀃 􀁆􀁒􀁖􀁗􀀐􀁅􀁈􀁑􀁈􀂿􀁗􀀃 􀁗􀁒􀁒􀁏􀀑􀀃􀀺􀁋􀁌􀁏􀁈􀀃 􀁄􀁑􀁄􀁏􀁒􀁊􀁘􀁈􀀃 􀁐􀁒􀁇􀁈􀁏􀁖􀀃 􀁒􀁉􀀃􀁊􀁈􀁒􀁗􀁋􀁈􀁕􀁐􀁄􀁏􀀃􀂿􀁈􀁏􀁇􀁖􀀃􀁓􀁕􀁒􀁙􀁌􀁇􀁈􀀃􀁄􀁑􀀃􀁒􀁙􀁈􀁕􀁄􀁏􀁏􀀃􀁓􀁌􀁆􀁗􀁘􀁕􀁈􀀃􀁒􀁉􀀃􀁕􀁈􀁖􀁈􀁕􀁙􀁒􀁌􀁕􀁖􀀏􀀃􀁗􀁋􀁈􀁜􀀃􀁇􀁒􀀃􀁑􀁒􀁗􀀃􀁋􀁈􀁏􀁓􀀃􀁓􀁏􀁄􀁑􀁑􀁌􀁑􀁊􀀃􀁈􀁛􀁓􀁏􀁒􀁕􀁄􀁗􀁌􀁒􀁑􀀃􀁓􀁕􀁒􀁊􀁕􀁄􀁐􀁖􀀃􀁄􀁖􀀃􀁈􀁄􀁆􀁋􀀃􀁄􀁕􀁈􀁄􀀃􀁒􀁉􀀃􀁊􀁈􀁒􀁗􀁋􀁈􀁕􀁐􀁄􀁏􀀃􀁌􀁑􀁗􀁈􀁕􀁈􀁖􀁗􀀃􀁌􀁖􀀃􀁄􀀃􀁉􀁘􀁑􀁆􀁗􀁌􀁒􀁑􀀃􀁒􀁉􀀃􀁖􀁌􀁗􀁈􀀐􀁖􀁓􀁈􀁆􀁌􀂿􀁆􀀃􀁙􀁄􀁕􀁌􀁄􀁅􀁏􀁈􀁖􀀑􀀃􀀷􀁋􀁘􀁖􀀏􀀃􀁕􀁈􀁆􀁒􀁑􀁖􀁗􀁕􀁘􀁆􀁗􀁌􀁑􀁊􀀃􀁖􀁗􀁕􀁄􀁗􀁌􀁊􀁕􀁄􀁓􀁋􀁌􀁆􀀃and structural framework is fundamental for i) understanding the relationship among cap rocks, reservoirs􀁄􀁑􀁇􀀃 􀃀􀁘􀁌􀁇􀀃 􀁆􀁌􀁕􀁆􀁘􀁏􀁄􀁗􀁌􀁒􀁑􀀏􀀃 􀁌􀁌􀀌􀀃 􀁊􀁈􀁒􀁗􀁋􀁈􀁕􀁐􀁄􀁏􀀃 􀁓􀁒􀁗􀁈􀁑􀁗􀁌􀁄􀁏􀀏􀀃 􀁄􀁑􀁇􀀃 􀁌􀁌􀁌􀀌􀀃 􀁓��􀁄􀁑􀁑􀁌􀁑􀁊􀀃 􀁕􀁈􀁖􀁒􀁘􀁕􀁆􀁈􀀃 􀁈􀁛􀁓􀁏􀁒􀁌􀁗􀁄􀁗􀁌􀁒􀁑􀀑􀀃 􀀯􀁌􀁐􀁌􀁗􀁈􀁇􀀃 􀁊􀁈􀁒􀁗􀁋􀁈􀁕􀁐􀁄􀁏􀀃resource assessment in Argentina is based on weak exploration approaches as anomaly hunting or anomalystacking, more than on realistic conceptual models generated from detailed geological information. In thissense, a new conceptual model for the Tocomar Geothermal System (TGS) based on geological, structural andgeochemical data along with the available geophysical data is presented. The TGS is located in the Central Puna(Central Andes, NW Argentina), related to the 0.57 Ma Tocomar volcanic center (TVC) emplaced in a smallextensional basin ?Tocomar basin (TB)? linked to the active NW-SE trans-Andean tectonic lineament knownas Calama-Olacapato-Toro (COT) fault system. The pre-basin succession is made of low-grade metamorphicand sedimentary lower Paleozoic rocks, Cretaceous continental rift-related deposits and ignimbrites from the􀀤􀁊􀁘􀁄􀁖􀀃􀀦􀁄􀁏􀁌􀁈􀁑􀁗􀁈􀁖􀀃􀀦􀁄􀁏􀁇􀁈􀁕􀁄􀀃􀀋􀀔􀀓􀀐􀀔􀀚􀀃􀀰􀁄􀀌􀀑􀀃􀀷􀁋􀁈􀀃􀁅􀁄􀁖􀁌􀁑􀀃􀁌􀁑􀂿􀁏􀁏􀀃􀁆􀁒􀁑􀁖􀁌􀁖􀁗􀁖􀀃􀁒􀁉􀀃􀁄􀀃􀁗􀁋􀁌􀁆􀁎􀀃􀁄􀁏􀁏􀁘􀁙􀁌􀁄􀁏􀀃􀁇􀁈􀁓􀁒􀁖􀁌􀁗􀀃􀁉􀁒􀁕􀁐􀁈􀁇􀀃􀁅􀁜􀀃􀁓􀁒􀁏􀁜􀁐􀁌􀁆􀁗􀁌􀁆􀀃conglomerates and sandstones that evolve upwards to several pyroclastic deposits.The updated conceptual model for the TGS consists of a heat source related to the 0.57 Ma rhyoliticmagmatic activity of the TVC. The geothermal reservoir has a NW-SE geometry elongated along the COTlikeChorrillos fault, with a minimum area of ca. 6 km2. The average depth of the top of the reservoir is1,000-1,400 mbgs, probably hosted in Cretaceous sedimentary rocks. The primary permeability is enhanced by􀁌􀁑􀁗􀁈􀁑􀁖􀁈􀀃􀁇􀁈􀁉􀁒􀁕􀁐􀁄􀁗􀁌􀁒􀁑􀀃􀁄􀁏􀁒􀁑􀁊􀀃􀁗􀁋􀁈􀀃􀀦􀀲􀀷􀀑􀀃􀀥􀁒􀁗􀁋􀀃􀁗􀁋􀁈􀀃􀁌􀁑􀁗􀁈􀁕􀁅􀁈􀁇􀁇􀁈􀁇􀀃􀂿􀁑􀁈􀀐􀁊􀁕􀁄􀁌􀁑􀁈􀁇􀀃􀀦􀁕􀁈􀁗􀁄􀁆􀁈􀁒􀁘􀁖􀀃􀁉􀁄􀁆􀁌􀁈􀁖􀀃􀁄􀁑􀁇􀀃􀁄􀀃􀁋􀁜􀁇􀁕􀁒􀁗􀁋􀁈􀁕􀁐􀁄􀁏􀀃clay cap (argillic alteration) act as seal rocks. Hot springs occur in association with deep N30-N60 fracturesrelated to the COT. They show a Na-Cl composition, with pH values of 5.84 to 6.87, and outlet temperaturesranging from 30.3°C to 70.2°C. Temperature estimation using the NA-K geothermometer indicates reservoirtemperatures of 184-230°C. Estimated local geothermal gradient for the TB is ~150 °C/km and the minimumstored heat in the geothermal reservoir is of about 3.21x1015 kJ.