Abstract:
This study investigates the geolectrical and structural architecture of a volcano-sedimentary system associated with a kamafugite occurrence in the Alto Paranaíba Igneous Province, southeastern Brazil. Kamafugites are ultrapotassic alkaline volcanic rocks with significant economic potential for the agricultural sector and for rare-earth element exploration. However, characterizing these bodies in the subsurface remains challenging, particularly in ancient and stabilized volcanic systems, where their physical properties are not controlled by active thermal processes. To address this issue, audiomagnetotelluric data were integrated with complementary geophysical methods, including seismic reflection and magnetometry, as well as geological and petrographic descriptions and geochemical data. The analysis of electromagnetic data was carried out using established methodologies, including dimensionality analysis, sensitivity tests, three-dimensional inversion, and forward modeling for conductor testing. The resulting resistivity models were interpreted alongside structural and lithological data, thereby constraining the geometry and physical properties of subsurface units. The results reveal a complex geolectrical framework, primarily controlled by mineralogical alteration processes and fluid circulation along structural discontinuities. Conductive zones are interpreted as regions of intense hydrothermal alteration and fluid accumulation, whereas resistive domains are associated with more preserved volcanic units and sedimentary sequences. The proposed model indicates that fluid percolation along faults and fractures plays a fundamental role in modifying the physical properties of the studied volcano-sedimentary succession. The results contribute to understanding ancient volcanic systems, demonstrate the applicability of the audiomagnetotelluric method for characterizing volcanic rocks in the subsurface, and provide support for evaluating alternative agricultural inputs in Brazil.
