New K–Ar data in the northeastern edge of the Adamawa-Yadé domain, Central African Pan-African Fold Belt: shedding light on the transition age between convergent and divergent tectonic regimes

Abstract

The tectonic evolution of the Central African Pan-African Fold Belt in Cameroon has been intensively studied during the last two decades. However, the timing of the last stages of the Pan-African orogenic cycle is still not well constrained, thus leading to controversial interpretations. The present work provides new insights into the late Pan-African tectonic evolution of the Adamawa-Yadé domain. It includes a complex crustal assemblage of the Central African Pan-African Fold Belt, which has undergone a polycyclic evolution since the Palaeoproterozoic. We infer the late Pan-African events of this domain from in-situ dating of biotite in five thin sections of plutonic rocks. The dated rocks are calc-alkaline metaluminous to weakly peraluminous I-type granitoids, consisting of Qz-monzonites and granites, medium- to high-potassic, with shoshonitic affinities, all displaying adakitic signature. The ages obtained were correlated with the available geochronological data for rocks from post-collision events of the Adamawa-Yadé domain and the Central African and Brazilian orogenic belts. The new biotite age range spans 67 Myr geological history of the studied area, from Ediacaran (549 ± 19 Ma) to Early Ordovician (482 ± 6 Ma), which marks the transition between convergent and extensional tectonics regimes in the Central African Pan-African Fold Belt.