Kamafugite Magma Pathways and Lava-Flow Paleotopography From Three-Dimensional Audiomagnetotelluric Imaging Constrained by Borehole Data

Abstract

An audiomagnetotelluric (AMT) survey was conducted within the Alto Paranaíba Igneous Province, southeastern Brazil, to delineate shallow occurrences of kamafugite, a rare ultrapotassic volcanic rock worldwide. A dense grid of AMT stations was deployed, allowing the construction of a high-resolution 3D electrical resistivity model. Dimensionality analyses revealed a structurally complex subsurface dominated by pronounced three-dimensional behavior. The interpretation of the resistivity model enabled the characterization of a complex and extinct volcanic system, including the reconstruction of paleo-volcanic conduits at depth. The model delineated probable zones of hydrothermal fluid percolation related to volatile exsolution during magma ascent, which are intensely deformed and suggest the past occurrence of hydraulic fracturing and seismic swarm activity. To validate these interpretations, the AMT results were integrated with seismic reflection data, well-log resistivity, magnetic data, and lithological information from shallow boreholes, acquired in a noisy agricultural environment. The results demonstrate that audiomagnetotellurics is an effective tool for investigating the volcanic evolution of igneous provinces and for imaging subsurface volcanic architectures in mineral exploration settings. Moreover, the identification and characterization of kamafugite bodies highlight the potential for producing kamafugite-based soil remineralizers, which could contribute to Brazil's future self-sufficiency in fertilizer production.