Geophysical signature of felsic intrusions in the Toumodi-Fêtêkro belt (evidence from Akakro, Côte d’Ivoire): Insights into the Birimian basement evolution

The Toumodi-Fêtêkro Belt in central Côte d’Ivoire is a Paleoproterozoic volcano-sedimentary basin intruded by granitoids and granodiorites. Despite its recognized geological importance, subsurface characterization of felsic intrusions has remained limited. This study applies to integrated magnetic and electrical geophysical methods to investigate the geophysical signatures of felsic rocks in the Akakro sector. Magnetic surveys revealed strong positive anomalies, with vertical gradients delineating shallow intrusive bodies and contact zones. Electrical resistivity measurements conducted using Schlumberger and dipole–dipole configurations, distinguished fresh felsic formations from altered and fractured domains. Fresh granitoid and granodiorite bodies were identified as high-resistivity zones (>1000 Ω·m), while altered felsic formations showed reduced resistivity values (<300 Ω·m) and an average alteration thickness of 15 m. Sounding analyses highlighted fracture-controlled conductive corridors-oriented NE–SW and NNE–SSW, consistent with regional tectonic lineaments. Synthesis maps quantified reserves, showing 54.09 ha of fresh felsic rocks and 31.47 ha of altered domains, with mafic units limited in extent. These results confirm that felsic intrusions dominate the Akakro sector, producing distinctive geophysical signatures characterized by elevated magnetic susceptibility and high resistivity. The findings extend earlier geological observations by providing subsurface quantification and highlight the role of felsic magmatism and tectonic fracturing in the evolution of the Birimian basement.