Evolution of the Mayo Kebbi region as revealed by zircon dating: An early (ca. 740 Ma) Pan-African magmatic arc in southwestern Chad

Abstract

The Mayo Kebbi region in SW Chad is part of the NNE-SSW trending Neoproterozoic Central African Fold Belt (CAFB) and is made up of three calc-alkaline granitoid suites emplaced into a metavolcanic–metasedimentary sequence. The first suite is represented by mafic to intermediate rocks (gabbro-diorite and metadiorite) emplaced between 737 and 723 Ma during early Pan-African convergence. The second consists of the Mayo Kebbi batholith and includes tonalites, trondhjemites and granodiorites, emplaced during several magmatic pulses between 665 and 640 Ma. The third suite includes porphyritic granodiorite and hypersthene monzodiorite dated at ca. 570 Ma. The Mayo Kebbi domain extends southward into Cameroon and is interpreted as a middle Neoproterozoic arc stabilized at ca. 650 Ma. This study also revealed a diachronous evolution between Mayo Kebbi and western Cameroon (e.g., the Poli region). The overall evolution of this part of the CAFB is interpreted as the result of successive development of magmatic arcs, since ca. 740 Ma, and tectonic collage of three different domains (Adamawa-Yade, Mayo Kebbi, and West Cameroon) which, after suturing, were intruded by post-collisional granitoids (<600 Ma).