The La Laja spring system in the Argentine Precordillera: A conceptual model based on geochemical and isotopic data

ASTINI, RICARDO; VENERDINI, AGOSTINA; ORTIZ, GUSTAVO; OROZCO, PAOLA; ALVARADO PATRICIA; PEREZ LUJAN SOFIA; SAEZ MAURO; PRESA, JIMENA; RIVAS, CAROLINA; PERALTA, YESICA

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021 vol. 109

0895-9811

The La Laja Spring System (LLSS) (31.34°S; 68.48°W) in the Argentine Precordillera iswell-known for its low enthalpy thermal baths since pre-Columbian times and itssurroundings full of travertine fields. This work focuses on geochemical and isotopicanalysis of the thermal waters and their hydrological implications. We found a system withpartially equilibrated waters with dominant and subordinated and compositions, whichseem affected to the basin fill composed of thick Cenozoic synorogenic deposits overlyingearly Paleozoic carbonate successions. Several geothermometers suggest a reservoir withaverage temperatures reaching 91°C. The average temperature of the springs is 25.5°C andthe low-geothermal gradients (~27°C/km) in the region indicate a relatively deep (~2500m) reservoir. The source of heat is related to orogenic belt because this region is on top ofthe flat-slab subduction of the South-Central Andes, with absence of active volcanism.Hence, this spring system is mainly affected by the relatively low-geothermal gradientwithin the Eastern Precordillera. The geochemical and isotopic characteristics as well asratios of waters indicate their meteoric origin associated with evaporation and Villicumrange origin. Our conceptual model for the LLSS indicates the N-S trending Villicum-Zonda regional thrust and the minor accommodation faults within the Eastern Precordilleradomain seem to behave as the preferential zone for recharging and a latter thermal waterrising.