Geologic correlation between the Neoproterozoic Sergipano belt (NE Brazil) and the Yaounde belt (Cameroon, Africa)

Abstract

The Yaounde belt (Cameroon) and the Sergipano belt (NE Brazil) belonged to a major and continuous Neoproterozoic orogen at the northern margin of the ancient Congo-So Francisco craton. The Yaounde belt comprises schists, quartzites, gneisses and migmatitic gneisses grouped into three domains; the low-grade Mbalmayo Group in south and the medium- to high-grade Yaounde and Bafia Group in north. The Sergipano belt is divided into six domains, the three southernmost of which are mostly made up of clastic and chemical metasedimentary rocks whereas the others are more diverse with a migmatite-gneiss complex, and two metavolcanicplutonic complexes. In general, the two belts show structural vergence and decrease of metamorphic grade towards the craton; three main deformation phases are recognized in the Sergipano belt in contrast with two described in the Yaounde belt. The minimum age of Pan-African-Brasiliano collision in the Sergipano belt is constrained at 628 12 Ma on syn-collision granites, whereas in the Yaounde belt collision took place between 620 and 610 Ma, i.e. the age of granulite facies metamorphism. Sm-Nd isotope geochemistry and U-Pb age dating indicate that most clastic metasedimentary rocks in both belts were derived from sources to the north and, to a lesser degree, from the cratons to the south.