CONTRIBUTION TO THE GEOCHRONOLOGY OF THE BASEMENT OF THE CENTRAL-AFRICAN-REPUBLIC

The age and isotope geology of the most striking geological elements of the basement in the south-central CAR have been investigated. The granite-greenstone belts of Bandas and Dekoa, as well as the amphibolitic complexes and associated gneisses of the Ouham and the Mbomou rivers, belong to the Archaean period. Granitic bodies intruding the post-Archaean Quartzito-schistose or "intermediate" series are of Lower Proterozoic Eburnean age. All former units have suffered on a limited scale from the Panafrican reactivation, as they belong to autochtonous areas constituting either a foreland or lateral ramps relatively to thrust belts developing during the latter period. The granulitic areas of central CAR are of Panafrican age. They have, together with the associated gneisses, been tectonized during the same period of orogeny. The granulites resulted from the remobilization of a crustal segment of Lower Proterozoic or older age. As a result of this tectonic complexity, it is no longer licit to put all the granulitic and gneissic series of the CAR in a single stratigraphic unit.