EVIDENCE FOR LATE PRECAMBRIAN PLATE TECTONICS IN WEST-AFRICA

In the Gourma and Iforas regions (Mali) rifting occurred around 800-850 Myr ago along the eastern margin of the West African craton with a triple point in Mali, the Gourma being interpreted as an aulacogen. Oceanic closure around 600 Myr led to a collision between the passive continental margin of the West African craton and an active continental margin to the east displaying island arc and marginal trough volcano-clastic assemblages bordering a deformed continental mass intruded by a high-level batholith. The suture is marked by a string of positive gravity anomalies corresponding to the emplacement of ultrabasic and basic rocks including perhaps ophiolites. East-West shortening was accompanied by the translation onto the West African craton foreland of nappes including internal nappes displaying high pressure-low temperature metamorphism assemblages. © 1979 Nature Publishing Group.