NATURE OF THE MAGMATIC ACTIVITY RELATED T O A PRE-PAN-AFRICAN EXTENSION - DOLERITES OF THE EARLY NEOPROTEROZOIC COMBA AND SEMBE-OUESSO BASINS (CONGO)

In the early Neoproterozoic, a continental rift system developed in We st-Gondwana, between the Congo, Sao Francisco and West-Africa cratons, on the site of the future Pan-African belts. In Congo, a branch of th is system extended from the West-Congolian belt to the NNE. The fillin g up sediments are dated around 1 Ga and 900 Ma. Subcontemporaneous in trusions of dolerites are related to the lithospheric extensional proc ess. They belong to tholeiitic mildly alkaline intra-plate series whic h are characteristic of continental rifts generated by an asthenospher ic mantle plume.