Textures in mylonitised granite from Banefo area in the central part of the Cameroon Central Shear Zone (central Africa) — Kinematics and gradian deformation indicators

Abstract

The North Equatorial Panafrican belt is constituted by orthogneissified metamorphic and magmatic sets linked to tectonometamorphic events of the neoproterozoic orogeny. This belt whose formations are situated in the North of the congo craton is divided into three distinct geodynamic domains: a southern domain, a northern domain and a central domain. The deformation and metamorphism relationships are a function of the different geodynamic domains of the belt. The central domains, to which belongs the Banefo region, is affected by large strike-slip faults among which is the central cameroonian shear zone. This domain is marked out by numerous syntectonic granitoids. At Banefo (NE Bafoussam, West Cameroon), those massifs are mainly constituted by mylotinised orthogneisses and granites of various degrees. The country rock is made up of gneiss and amphibolite. In the Banefo massifs, the orthogneiss is the least deformed petrographic unit. It shows a heterogranular granoblastic texture with a mineral assemblage formed by quartz, K-feldspars, biotite, etc., within the orthogneiss, remains of magmatic fluidality can still be observed marked by feldspar megacrystal. Field observations reveal a net progression of the intensity of deformation of orthogeisses to ultramylotinised granites having an identical chemical composition as the orthogneisses...