ORIGINAL PAPER Structural characterization of the Pan-African Ndieki area in the Foumban-Bankim Shear Zone (West Cameroon): constraints from field observations and microstructures Efon Awoum Julios 1 & Fozing Eric Martial 1 & Kwékam Maurice 1 & Tcheumenak Kouémo Jules 2 & Choumele Kana Styve Cliff 1 & Achu Megnemo Ludovic 1 Received: 7 November 2019 /Accepted: 29 July 2020 # Saudi Society for Geosciences 2020 Abstract The Ndieki area displays elongated NE-SW hill which crop out along the Foumban-Bankim Shear Zone. In petrographic point of view, it is made up of amphibolites, biotite-hornblende gneisses, and two-mica granites, all of which are wrapped by mylonites. Structural data indicate (1) NE-SW (N30°E) to ENE-WSW (N70°E) trending foliation, dipping moderately (50°–60°) towards NW; (2) stretching lineation striking NNE-SSW (N12E-N25E) and moderately (25°–35°) plunging towards SSW in mylonite and biotite-hornblende gneisses. It strikes NE-SW (N40E) and plunges strongly (66°–81°) towards SW in the two-mica granites; and (3) asymmetric folds (NE-SW) and σ-type displaying dextral kinematics evolution in mylonites and biotite-hornblende gneisses, and N-S sinistral shear planes in mylonites and biotite-hornblende gneisses respectively correlated to the dextral transpressive and sinistral transcurrent deformation. All these rocks show that microstructures were acquired from the sub- magmatic to the solid-state deformation. The structural features show that the mylonitization was initiated in the early NE-SW dextral deformation event which has favored the evolution of fractures in pull-apart structures that induce the upwelling of magma and the emplacement of the Ndieki pluton, followed by the N-S trend sinistral shearing. Structural, kinematic features of the Ndieki pluton characterized deep crustal deformation, probably at the ductile-brittle boundary structural level during a major dextral shear deformation. Keywords Structuresandmicrostructures . Ndieki area . Foumban-Bankim Shear Zone . Syn-tectonicemplacement . Pan-African Belt Introduction The tectonic evolution of the Pan-African Belt of Central Africa (PBCA) in Cameroon is characterized by large shear zones and thrusts that have intensely transposed early struc- tures (Njonfang et al. 2006, 2008; Ngako et al. 2008; Ngako and Njonfang 2011; Fozing et al. 2013; Tcheumenak Kouémo et al. 2014; Ntieche et al. 2017; Nomo Negue et al. 2017). These shear zones trend either N-S (Mayo Nolti Shear Zone, Rocher du Loup Shear Zone, and Godé-Gormaya Shear Zone, Ngako et al. 2008), NE-SW (Central Cameroon Shear Zone (CCSZ), Sanaga Shear Zone, and Foumban-Bankim Shear Zone (FSZ), Toteu et al. 2001; Ngako et al. 2008; Njonfang et al. 2008), or E-W (Demza Shear Zone) and display dextral or sinistral sense of shear motion. In these shear zones, syn- to post-tectonic granites crop out within remobilized meta- sedimentary and meta-igneous medium- to high-grade Pan- African basement rocks (Tchameni et al. 2006). Complex structural features identified in the PBCA result in controver- sial formation mechanism models. The most recent model proposed by Ngako and Njonfang (2011) considers the PBCA in Cameroun as the result of convergence between the West African craton, the Congo-Sao Francisco craton with the enigmatic east Saharan metacraton (Abdelsalam et al. 2002) during the assembly of the super Gondwana continent. The model proposed that the major events of transpression Responsible Editor: François Roure * Kwékam Maurice mkwekam@yahoo.fr 1 Department of Geology, University of Dschang, P.O. Box 67, Dschang, Cameroon 2 Department of Earth Science, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon Arabian Journal of Geosciences (2020) 13:831 https://doi.org/10.1007/s12517-020-05775-z