Etude petro-structurale des formations geologiques de Yemassi (Centre -Cameroun)

Abstract

The Yémassi area is located in the Centre Region, Lékié Division, Lobo Sub-Division. This work was undertaken with a view to characterise the tectono-metamorphic evolution of the said area and to situate it in relation to the dynamism of the central Africa orogenic fold belt. The petrographic study of the study area has made it possible to inventory a metamorphic assemble made up of garnet micaschists, garnet and kyanite micaschists, two-mica gneiss and kyanite gneiss. On the structural level, a relative chronology of the structural elements reccorded by the different lithological types has made it possible to distinguish four stages of deformation. The first stage is characterized by foliation S, B boudins and P folds. It is a stage of compressive tectonics with a mean NE-SW axial direction. The second stage, essentially marked by C shear zone, B boudins, folds, f stringers and L mineral lineations (with a mean N135E orientation with 05° deeps to the NW or SE). The D3 deformation stage is transpressive in tendency and marked by structural elements such as : B3 flanges, F3 veinlet. The D stage is essentially brittle marked by NW-SE oriented fractures. The composition of these metamorphic rocks with the presence of alumina silicates (kyanite and andalusite) on the one hand and the abundant presence of aluminous minerals on the other suggest the existence of a sedimentary protolith. Thus, the Yémassi sector presents a monocyclic and multistage tectonic evolution that is similar to that of the Pan-African formations of the southern domain.