Enhancement and modeling of aeromagnetic data of Akonolinga-Nguinda area, Centre-East Cameroon

Abstract

Previous works in southern Cameroon have highlighted prominent geological structures, including faults sub parallel to the Central Cameroon Shear Zone and the Sanaga Shear zone, exposed within the Central African Fold Belt along the northern margin of the Congo Craton. However, the relationships between these structures and the regional lithology require updating. Aeromagnetic data from the Akonolinga-Nguinda study area were processed using Oasis Montaj (v.8.4) software. Interpretation of the Reduced-To-Equator (RTE) magnetic anomaly field revealed multiple magnetic targets characterized by both positive and negative intensities. The RTE map provides a robust lithostructural framework, allowing for the correlation of structural faults with regional rock units. Derivative filter grids (horizontal gradient, vertical gradient, analytic signal, and tilt derivative) display an undulatory pattern, suggesting that the study area has undergone complex tectonic deformation, as corroborated by the mapped lineaments and intrusions. Consequently, the resulting structural map reveals a complex network of linear features predominantly oriented NE–SW, N–S, E–W and ENE–WSW. The 2.75D modeling along two NW–SE profiles drawn on the RTE grid indicates a crystalline basement composed of schists, quartzites, micaschists, gneisses and granulites intruded by pegmatite and quartz veins. Combined, these geophysical and structural results demonstrate that the study area has experienced intense, polyphase tectonic activity. The derivative filters highlighted the geologic contours/contacts and the general trend of structures. The maxima and multiscale maps helped to draw the structural map which showed lineaments whose main directions are NE-SW, ENE-WSW with variable dip. The 2.75D model inferred a subsurface down to 4 km depth with a lithology including sediment, schist, micaschists, gneiss and granulites; some intruded by pegmatite and quartz veins during tectonic movements. Beside intrusions, several tectonic discontinuities such as contacts/faults, factures and folds. The derivative filters highlighted the geologic contours/contacts and the general trend of structures. The maxima and multiscale maps helped to draw the structural map which showed lineaments whose main directions are NE-SW, ENE-WSW with variable dip. The 2.75D model inferred a subsurface down to 4 km depth with a lithology including sediment, schist, micaschists, gneiss and granulites; some intruded by pegmatite and quartz veins during tectonic movements. Beside intrusions, several tectonic discontinuities such as contacts/faults, factures and folds.