The Nlonako anorogenic complex (NAC) is located in the south western part of the Cameroon Line and is superposed on the N50E section of the central Cameroon shear zone. It is suggested to be a ring complex of 10 km diameter which was emplaced as sill intrusive body during the Tertiary. In order to do characterize the Nlonako complex shape and characterize the tectonic history in the study area and surrounding, spatial technology (Landsat 8 ETM+ and SRTM images) were used for geological mapping and structural reconstruction based on lineament analysis. Data extracted from Landsat 8 ETM and SRTM images show a sub-circular shape for the NAC and the superposition of field and petrographic data from our previous research works confirm the fact that the NAC is a ring or annular complex slightly elongated NNE-SSW, thus it is known as the Nlonako ring complex (NRC). Map of lineament synthesis and the SRTM image of the study area display NE-SW, NW-SE and N-S trend structures. (1) The dominant NE-SW trend mostly displayed by the NRC and its basement rock is parallel to (i) the main metamorphic foliation trend and (ii) to the central Cameroon shear zone regional fault, corresponds to the trending of the regional foliation, structures and the Ngondo pluton elongated shape. (2) The secondary N-S direction may correspond to the late deformational phase in the area because, the N-S-related structures transposing NE-SW structures towards a meridional direction in the NRC basement rock. (3) The NW-SE trend corresponds to the direction of NW-SE fault cross cutting the NRC. Field data and synthetic lineament map enable to identify: (1) a Compressive deformational phase D1 whose main markers are NNW-SSE to NW-SE S1 foliation; (2) an early left-lateral deformational phase D2 characterized by anticlockwise rotation of clasts and NE-SW sinistral transposition of early structures; (3) a NE-SW right-lateral deformational phase D3 marked by clockwise rotation and dextral transposition of preexisting structures as well as the NE-SW S3 foliation and (4) a late left-lateral deformational phase D4 marked by the N-S transposition of NE-SW dextral D3-related structures by late sinistral shear movement. This suggests a more complex tectonic history for the Pan-African Belt in Cameroon showing at least three shear phases, that is a right-lateral phase, sandwich by two left-lateral phases.

The Fotouni volcanic rocks outcrop within mylonitic corridor, in the southern domain of the continental part of Cameroon Line (CL). The NE-SW shape display by these volcanic rocks within the mylonitic corridor is an uncommon case along the CL. Field and petrographic data and spaces image analysis were performed in order to understand the NE-SW shape display by these rocks. Geochemical data display two distinct volcanic compositional groups: alkaline lavas and transitional lavas. Alkaline series ranges in composition from basanite, basalt to hawaiite and transitional series range from basalt, trachy-basalt to basaltic trachy-andesite. Field investigations show that the Fotouni, Fangam, Song and Mbeng basalts outcrops as NE-SW trending prismatic dykes which displaying well differentiated vertical tetragonal, pentagonal and hexagonal prisms within the Fotouni-Kékem shear zone (FFSZ). The overall NE-SW orientation of hills, where these prisms outcrop suggests the tectonic control on the emplacement of these rocks. Indeed, the activation of the FFSZ developed various fracture networks that facilitate magma uplift and the emplacement of the Fomopéa and Bandja plutons during the Pan-African orogeny. These Pan-African activations of the Fotouni fault weaken the crust during the Paleozoic. These weaken zones constitute path way for emplacement of volcanic dykes during the Tertiary within the NE-SW faults, probably facilitated by the general extension at the end of Cretaceous.