Article révisé par les pairs
Résumé : Dykes of monchiquites of Cainozoic age (37.5 ± 2.3 Ma) are intrusive in Cretaceous sandstones in the Tchircotché area, Upper Benue valley (northern Cameroon). The differentiation of the monchiquites is explained by crystal fractionation ofolivine, clinopyroxene, magnetite, ilmenite and apatite. A studied rock has low Sr-isotope ratio (0.703 69 ± 10), which issimilar to those of the alkali basalts of the Cameroon Line. Therefore the continental crust appears to have no significant role inthe genesis of the monchiquites. 2003 Académie des sciences. Publié par Éditions scientifiques et médicales Elsevier SAS. Tous droits réservés.