The Euler deconvolution solution map highlights more clustered solutions from south to north of the study area. Generally, the Euler solutions for different structural indices show a depth range of 0.39 km to 11.44 km (Fig. 4a and Fig. 4b). The greatest depth of geological features is found in the central part of the study area and is relatively scattered around the southwestern edge. The basement rocks in the northwest and southeast regions are relatively shallow. These clustered solutions highlighted several main E‒W, NE‒SW and NW‒SE trends, which fit the regional trends. With regard to the major directions, spatial distributions, and roof depths of the investigated structures obtained by the application of Euler’s deconvolution method, these geological formations would indeed be deep-seated. The structural trends highlighted suggest that the main NE geological feature is the tectonic imprint of the Katanguian orogeny, which controls the tectonic arrangement of the Pan-African domain and was confirmed by the Massenya-Ounianga heavy gravity anomaly line (Poudjom-Djomani et al., 1995, Abate Essi et al., 2017). In addition, according to some authors (Poudjom-Djomani et al., 1995; Loule et al., 2009; Ganno et al., 2010), this dominant structural trend could also be due to the opening of the South Atlantic Ocean, for which the direct insight was the collapse of the unstable corridor of northern Cameroon and southern Chad, with a main NNE‒SSW structural trend (Cornachia & Dars, 1983). Thus, this configuration suggests the earlier hypothesis for global NE‒SW geological and tectonic features.
The geological models obtained through 2.75D modelling highlight a mainly faulted geological environment. These geological models revealed sedimentary, metamorphic, and igneous formations overlying a syntectonic granitic basement. The presence of strongly foliated metamorphic rocks such as schists and gneisses in this area suggests that this region could either have been affected by regional metamorphism or originated from deformation under differential stress conditions resulting from tectonic forces, as witnessed by the several metamorphosed rocks occurring in the eroded mountain chain (e.g., as seen in Mindif surroundings) (Stephen, 2018). The hypothesis of regional metamorphism seems to be confirmed by the presence of a thick schist layer in the four subsurface 2.75D models. In addition, according to previous geophysical works and geological information (Poudjom et al., 1993 & 1995; Kamguia et al., 2005; Nguimbous et al., 2010), with regard to the geometry, thickness, and spatial disposition of layers, the dominant metamorphic facies in the area under study result from high-temperature and high-pressure geothermal gradients.
These geological models also highlighted faulting and a southwards progressive thickening of the crust. This occurs because the crust in that area sinks farther either to compensate for the added weight or to react to compressional stresses in the rocks due to tectonic forces. The upwelling or crustal thinning zones, considering the hypothesis of an isostatic phenomenon, could be due to a shallow or deep prominent magmatic source. Several authors (Kamguia et al., 2005; Nguimbous et al., 2010) have linked this configuration to the tectonic accidents affecting this region. For example, those affecting Central Cameroon with the establishment of horsts represented by the Adamawa granites or an E‒W extension phase prevailed on the Cameroon Volcanic Line (Popoff et al., 1983, Reusch et al., 2010). Therefore, the several probable subbasins observed in these modelled transects could result from the manifestations of regional isostatic compensation following the elevation of the Adamawa horst, which is in isostatic equilibrium at altitudes below 1000 m (Poudjom et al., 1993). In addition, since the Pan-African belt, in which the study area is located, underwent various tectonic events marked by several rifting phases characterized by prerift deformation followed by crustal thinning. Accordingly, with Poudjom et al. (1995), the idea of crustal thinning on a regional scale seems more plausible.
Furthermore, the modelled sections revealed several high magnetic signatures interpreted as intrusions with different susceptibility values. These intrusions vary from one profile to another and suggest potential mineralization zones in this region. Their presence could result from the upwelling of igneous material in the area, probably through diapiric activity, which is a sliding regime leading to the segregation of granodioritic magma (Pons et al., 1995). In fact, the green schist facies encountered in the field results from thermal changes leading to the transformation of clays (shale) and limestone into schists and marble, respectively, reaching the green schist facies. This modified the original stratification of the layers observed in the field, giving them a subvertical dip. This hypothesis could explain the presence of high magnetic susceptibility (k = 0.051 SI) granodiorites observed in profile P1 near Mindiff and another high susceptibility intrusion (k = 0.062 SI) in profile P3. In addition to syntectonic plutonism resulting in occasional erosion of orthogneisses, this area records Pan-African late- and postorogenic intrusive rocks such as Mindiff syenite or granodioritic rocks. The evidence of these various intrusive bodies is facilitated by a densely fractured basement, which allows upwelling of mantle materials leading to several batholiths or dikes, swarms all emanating from a large intrusive body at depth. These faults likely weaken the crust in various areas; if they are not filled by crustal material, they are filled by sedimentary or volcano-sedimentary formations.