Tectonic evolution of the Yaoundé segment of the Neoproterozoic Central African Orogenic Belt in southern Cameroon

TLDR: The deformation history of the Neoproterozoic Central African Orogenic Belt in southern Cameroon is well recorded in the low-to high-grade rocks outcropping in the area around Yaounde as mentioned in this paper.

Abstract: The deformation history of the Neoproterozoic Central African Orogenic Belt in southern Cameroon is well recorded in the low- to high-grade rocks outcropping in the area around Yaounde. The fabrics in these rocks are con- sistent with two main ductile deformation events D1 and D2 .D 1 predated emplacement of calc-alkaline dioritic bodies and caused the formation of nappes that resulted in high-pressure granulite metamorphism of soft sediments. A strong overprinting of these nappes during D2 symmetric extension, probably associated with large-scale foliation boudinage and (or) gneissic doming and intense magmatic underplating, gave rise to regional flat-lying fabrics. The latter were further buckled by D3 and D4 folding phases defining a vertical constriction occurring with a major east-west to NW- SE shortening direction. The corresponding F3 and F4 folds trend north-south to NE-SW and east-west to NW-SE, respectively, and represent the main regional strain patterns. Based on the east-west to NW-SE maximum shortening orientation indicated by F3 folds, it is proposed that the nappe-stacking phase D 1 occurred in the same direction. The deformation history in the area can thus be described as corresponding principally to alternating east-west to NW-SE contractions and north-south to NE-SW orogenic-parallel extensions. At the regional scale, this could be due to the Transaharan east-west collisional system.