The Ebaka Para Derivative Migmatite (Central African Fold Belt): Typology, Petrology, U–Th–Pb Age and Hinterland Evolution

Abstract

ABSTRACT The Yaoundé Group is one of numerous Pan‐African basins located north of the Congo Craton in central Africa. One of the main characteristics of this basin is the presence of high‐grade gneisses and granulites which have been considered the root of the collision between the Central Africa Fold Belt and the Congo Craton. Interpretation of these high‐grade rocks is mainly based on studies (petrology metamorphism, geochronology) carried out in the southern part of the WSW–ENE trending Yaoundé basin. The northeastern part of the basin (Belabo area) was filled by detritus of magmatic rocks (Sm/Nd = 0.182) of Rhyacian (2263 Ma) to Statherian (1677–1757 Ma) eras, of the southern Adamawa domain, and which have been later transformed by in situ partial melting into metatexitic to diatexitic migmatites (with a melt fraction less than 85%). Whole‐rock chemical analyses show that the melanosome portion (sample EB1) is enriched in refractory elements with respect to the leucosome (sample EB3). This high‐grade paroxysmal episode of metamorphism is characterised by a Sil–Kfsp–Pl–Bt–Grt assemblage and took place between 724 and 620 Ma ( 206 Pb/ 238 U zircon apparent ages). Few metamorphic transformations took place, especially Bt + Sil + Qtz = Grt + Kfsp + melt and Bt + Grt = Pl + Opq + melt. The evolution of the Yaoundé sedimentary basin was diachronic, starting earlier in the northeastern part (Ebaka region) with respect to the southwestern part (Yaoundé region).