A three-dimensional temperature model of the Acoculco caldera complex, Puebla, Mexico, from the Curie isotherm as a boundary condition

Abstract

Three-dimensional temperature simulations of the Acoculco caldera complex are undertaken to improve our understanding of its thermal regime. This volcanic caldera has been considered a Conduction-Dominated Crystalline-Rock geothermal play based on evidences of low permeability of the formations hosting the heat source. An estimated Curie isotherm at depth is obtained from the de-fractal method to establish the background heat flow in the area. Additionally, local thermal anomalies and radiogenic heat generation are considered. The description of the structures controlling the heat flow is based on limited borehole data along with field observations, it includes stratigraphic columns and fracture zones. The heat transfer equation is solved in steady state with a Finite Volume numerical method and a Conjugate Gradient algorithm. The resulting computational model constitutes a workable instrument to test assumptions on the thermal regime in the Acoculco caldera that can be gradually constrained, as more data become available. Numerical results show that shallow and localized thermal anomalies (750 °C) lead to geothermal gradients as high as those measured in the field. The thermal anomalies turn out between 3300 and 3800 m below ground surface as the mean depth, shallower than those assumed in previous 1D thermal models in this caldera complex.