Structures and petrography of the neoproterozoic Rey Bouba Greenstone Belt in the Northern Cameroon: Implications for deformational characterization

The mylonitic band of Rey Bouba Greenstone Belt (RBGB), oriented NE-SW that straddles between the Neoproterozoic batholite of the northern domain to the NW and the Adamawa-Yadé Paleoproterozoic domain to the SE, is a Neoproterozoic back-arc basin made of deformed volcanosedimentary rocks. A tectonic and microtectonic study of this basin was carried out under a petrographic and structural approach both in the field and in the laboratory. Structural analysis carried out in the study area allowed the identification of a complex four-phase D 1 –D 4 polyphase deformation. The first three phases are ductile and the fourth essentially brittle. The D 1 deformation phase, which is not very visible in the field, is characterized by a general flattening induced by a shortening oriented N-S in a pure shear regime leading to the development of S 1 foliation and L 1 mineral stretching line oriented E-W. The deformations D 2 and D 3 , characteristics of sub-basins, are very intense and complex and implemented in two stages. The D 2 deformation phase, essentially ubiquitous, is first a tangential tectonics associated with the formation of the composite S 0 /S 2a /C 2a surface and a single shear C 2b of major direction NE-SW parallel to the Tcholliré-Banyo Shear Zone (TBSZ), C 2b shear affecting the S 2b foliation axial plane of the right P 2b folds, synforms, and antiforms. NNE-SSW is the overall direction. D 3 deformation also begins with the placement of the S 0 /S 3a /C 3a surface and the open folds P 3a , then a simple shear, a translation in extensive speed materialized by the stretching lineation L 3b , and ends with the ductilo-fragile deformation. The D 4 deformation phase is represented by the syntectonic basic and acid veins oriented NE-SW and N-S to NNE-SSW, respectively, faults and breakages.