Characterization of Southern Peru Hydrothermal Systems: New Perspectives for Geothermal Exploration Along the Andean Forearc

This study provides a comprehensive characterization of various hydrothermal systems in Southern Peru ranging from the faulted Precordillera's steep topography up to the volcanic High Cordillera (>4,000 m asl). The objective is to investigate thermal anomalies that may potentially serve as new geothermal resources. Our integrated approach combines: (a) geochemistry from 14 hot springs sampled throughout the Tacna region, and (b) 3D numerical modeling of coupled groundwater and heat transfer considering topography and faults embedded in homogeneous permeability. Water and gas analysis indicates that the springs located near volcanoes discharge Na-K-Cl waters with high temperatures (>87 degrees C), high Total Dissolved Solid concentrations (TDS >3,452 mg/L), and free gases dominated by CO2 (>90 vol%). Springs located along the regional faults in the Precordillera discharge Ca-SO4 and Na-K-Cl waters with moderate temperatures (27-53 degrees C), intermediate TDS concentrations (464-2,458 mg/L), radiocarbon ages between 1.4 and 7.9 kyr, and free gases dominated by N-2 (>95 vol%). The Aruma springs, which are located at the transition between the High and the Precordillera, display intermediate characteristics. Numerical models accurately replicate the locations and temperatures of the fault-related springs only for permeable faults (>10-14 m(2)), revealing the creation of 100-km long thermal plumes along faults, locally rising up the 150 degrees C-isotherm to about similar to 1,000 m below the surface. This approach clearly distinguishes the spring origins, which are volcanic in High Cordillera and tectonic in Precordillera. Moreover, we highlight that steep topographic gradient and permeable reverse faults in the Andean forearc may generate considerable thermal anomalies, opening perspectives for the geothermal exploration.