New insights into El Chichón (Chiapas, Mexico) hydrothermal system from an aeromagnetic survey

Abstract

El Chichón is the northernmost and youngest volcano of the modern Chiapanecan volcanic arc and is responsible for the deadliest volcanic disaster in Mexico's modern history. Forty years after the eruption, there are still uncertainties in the subsurface architecture of the volcano and its basement. Based on this, we performed aeromagnetic data analyses using reduction–transformation techniques, spectral analysis, and forward modeling to delineate the magnetic rock–strata and to image the boundaries of the magmatic reservoir or regions of molten rock. Results show that the magnetic alignments identified correlate well with the local geological features. Our preferred interpretation of the estimated Curie point depth is as a region of mush composed of crystals and molten rock below the volcano (4.77 km), depicting the transitional sector to a deeper magma reservoir. We compute values of 101.57 °C km−1 and 253 mW⋅m−2 for the geothermal gradient and conductive heat flux, respectively. In addition, we identify two complementary aquifer formations representing the shallow−local and deeper−regional aquifer units using geomorphology, topographic, and stratigraphic characteristics. The magnetic anomalies analyzed and the identification of aquifer units in this study provide new detailed information about the geological, geophysical, and hydrogeological conceptual models of the El Chichón geothermal system.