The structural architecture of the Los Humeros volcanic complex and geothermal field

Abstract The Los Humeros Volcanic Complex (LHVC) is a large silicic caldera complex in the Trans-Mexican Volcanic Belt (TMVB), hosting a geothermal field currently in exploitation by the Comision Federal de Electricidad (CFE) of Mexico, with an installed capacity of ca. 95 MW of electric power. Understanding the structural architecture of LHVC is important to get insights into the interplay between the volcano-tectonic setting and the characteristics of the geothermal resources in the area. The analysis of volcanotectonic interplay in LHVC benefits from the availability of subsurface data obtained during the exploration of the geothermal reservoir that allows the achievement of a 3D structural view of the volcano system. The LHVC thus represents an important natural laboratory for the development of general models of volcano-tectonic interaction in calderas. In this study, we discuss a structural model of LHVC based on morphostructural and field analysis, integrated with well logs, focal mechanism solutions and magnetotelluric imaging. The structural analysis suggests that inherited regional tectonic structures recognized in the basement played an important role in the evolution of the magma feeding system, caldera collapses and post-caldera deformations. These inherited weak planes have been reactivated by resurgence faults and post-caldera magma-driven hydrofractures under a local radial stress field generated by the shallow LHVC magmatic/hydrothermal system. The local stress field induced caldera resurgence and volcanotectonic faulting. The results of this study are important to better constrain the structural architecture of large caldera complexes. Also, our study is useful to understand the structure of the Los Humeros geothermal field and support the exploration of deeper Super-Hot Geothermal Systems (SHGSs) and engineering of Enhanced Geothermal Systems (EGSs) for electric power production in the LHVC and other active resurgent calderas.