Geophysical model of the hydrothermal system of the Amado Nervo Volcano (Nayarit, Mexico) and preliminary evaluation of its geothermal potential

Abstract

This study presents a conceptual model of the hydrothermal system associated with the Amado Nervo Volcano in western Mexico, integrating geological, gravity, magnetic, and geothermal data. The objectives were to characterize the subsurface structure of volcanic system, identify geophysical signatures potentially associated with hydrothermal alteration, and provide a prelimi-ry estimate of the region's exploitable geothermal potential. Aeromagnetic data were processed using reduction to the pole. analytical signal, and upward continuation, and spectral analysis techniques, whereas gravity data were derived from the Global Gravity Model (GGM+) and transformed into simple and residual Bouguer anomalies. The radially averaged power spectrum method was applied to estimate magnetic source depths, the Curie point depth, the geothermal gradient, and conductive heat flow. The geophysical results reveal a special association among magnetic attenuation zones, analytical signal minima, and negative gravity anomalies, delineating structurally complex domains characterized by reduced density and magnetization.Spectral analysis yielded a Curie point depth of approximately 7.5 km, from which a geothermal gradient of 70.8 °C-km' and a conductive heat flow of 176 mW-m 2 were estimated. These values are consistent with those reported for geothermal regions of the Trans Mexican Volcanic Belt. Integration of geophysical and geological information enabled the development of a conceptual hydrothermal model of a structurally controlled volcanic hydrothermal system potentially sustained by a residual intrusive heat source. A preliminary geothermal resource assessment was conducted using the volumetric Heat in Place method coupled with 9.999 Monte Carlo simulations. The results vielded a mean geothermal potential of 19.75 MW. with simulated values ranging from approximately 5 to 34 MW. Although subject to uncertainties in reservoir geometry and thermophysical parameters, the estimated resource ranks the Amado Nervo volcanic system among medium-scale geothermal prospects in Mexico. The proposed hydrothermal architecture shows similarities to that of the nearby San Pedro Domes geothermal field and supports continued exploration through detailed geophysical, geochemical, and drilling investigations. Overall, this study demonstrates the value of integrating indirect geophysical methods for early-stage geothermal assessment in volcanic regions of the Trans-Mexican Volcanic Belt.