Combining ammonium mapping and short-wave infrared (SWIR) reflectance spectroscopy to constrain a model of hydrothermal alteration for the Acoculco geothermal zone, Eastern Mexico

A deep circulating, active hydrothermal system cannot be ruled out in Acoculco although it may be confined to the deep caldera structure by an impermeable cap-rock of silicic and argillic alteration. In this scenario, hydrothermal fluids would reach the surface periodically, when explosive hydrothermal fracturing allowed it. The occurrence of hydrothermal explosion features and of acid-sulfate alteration supports this scenario. Therefore, further exploration by drilling would be advisable in Acoculco.