Magmatismes tholéiitique et alcalin des demi-grabens crétacés de Mayo Oulo–Léré et de Babouri–Figuil (Nord du Cameroun–Sud du Tchad) en domaine d'extension continentale

Abstract

Two major dykes of basalts, microgabbros, olivine dolerites (continental tholeiites), and of camptonites and benmoreites (alkaline rocks) are respectively exposed in the Mayo Oulo–Léré and Babouri–Figuil Early Cretaceous half-grabens (Northern Cameroon–Southern Chad). The tholeiites were probably derived from an asthenospheric source in connection with a lithospheric thinning occurring between Santonian and Eocene times. In contrast, the alkaline rocks may be derived from a deeper metasomatized mantle source.