A numerical model for the magmatic heat reservoir of the Las Tres Virgenes volcanic complex, Baja California Sur, Mexico

Abstract

Numerical models of geothermal systems have achieved considerable progress when dealing with fundamental transport processes. Site-specific geothermal models however, often face the lack of sufficient field data, which leads to under constrained models. Recent field studies in the Las Tres Virgenes volcanic complex (TVVC) provide us with a sound framework to build a numerical model for the magmatic heat reservoir of the geothermal area. Here we present a conceptual model of the system from 30 ka to present based on updated structural and geochronological studies. The heat reservoir is described from Enhanced Seismic Tomography of the TVVC. New field data also allow an estimate of the radiogenic heat generation in the batholith of the study area. Latent heat of crystallization is also considered in the cooling of magmatic intrusions. The transient heat transfer equation is solved with a finite volume numerical method and a conjugate gradient algorithm. The model is calibrated using the estimated heat flow in the area from the literature. The simulation results predict slow cooling of the heat reservoir, with the maximum temperature decreasing about 9 °C in 30 ky. The temperature field within the magmatic heat reservoir overall remains between about 790 °C (8 km bsl) and 300 °C (3 km bsl), in the order of the temperatures at which magmatic processes, such as magma mixing and replenishments, have been inferred from the eruptive history. Whereas the phase ratio (solid/melt) ranges from 1, at the top, to below 0.1 at the bottom of the heat reservoir. Convective transport and explicit thermal-chemical coupling in the heat reservoir is proposed as a future expansion of this work.