Geophysical Exploration of a Potential Geothermal Energy Source in Eastern Mexico
Geothermal energy and volcanism are often associated phenomena. There are large regions in the planet in which recent volcanism is present. Efforts at elucidating the conditions under which ascending magmas create reservoirs or induce eruptions are underway at several locations throughout the world. In central-eastern Mexico a basin called the Oriental-Serdán basin is being explored to evaluate its potential resources for geothermal energy. In this area the surface manifestations of underground energy transport appear as extrusive rhyolitic domes, explosion craters (maars), cinder cones, and volcanic cones with extensive lava flows. They appear in two apparent clusters: one to the north of the basin and the other to the south. We use gravity and magnetic fields to create 2-D and 3-D geologic models consistent with such fields. In this work we focus on the north cluster of the field. A positive, residual Bouguer anomaly of ~20 km wavelength and 28 mGal amplitude is located over the north cluster; the positive portion of an aeromagnetic anomaly of 400 nT partially overlaps it. 2-D models of both fields are consistent with the presence of an intrusive of dimensions similar to those of the corresponding anomalies. The upper surface of this intrusive is located at an average depth of 1 km below the terrain surface but in some locations it reaches considerably closer. We infer that some of these irregularities of the surface of the intrusive may constitute diatrem-like bodies that sometimes heat up surficial aquifers inducing explosion crater formation and others give rise to monogenetic cones. Additionally we present 3-D inversions of the gravity and magnetic fields that independently yield regional density and magnetic susceptibility distributions. They confirm the 2-D results to −3300 mbsl regarding the presence of an intrusive of density within 2.74 to 3.04 g/cm3 and a range of magnetic susceptibilities from 0.0030 to 0.0052 SI. At depths between −3500 to −6500 m a NW susceptibilty trend of ~0.006 SI, south of the intrusive body, coincides with the surface location of the extrusive rhyolitic domes, suggesting that their roots reach to those depths. Geophysical modeling of these anomalies will allow for evaluating, and eventually tapping, this resource for geothermal energy.
AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015