Deformation Features and Structures in Some Igneous and Metamorphic Rocks: A Case Study of Central African Fold Belt in Cameroon

Abstract

The first phase is marked by the S1 foliation. The second phase is marked by fold (F2), lineation (L2), and boudins (B2). The third phase is marked by subvertical foliation (S3), shear (C3), and lineation (L3). The fourth phase is essentially a brittle phase. Granites present mostly magmatic deformation features; meanwhile, granite mylonites and gneisses present submagmatic to nonmagmatic deformation features. Mylonitization occurred during a ductile-brittle transition phase. Coarse-grained granites emplaced in the lower crustal level, while protomylonites and mylonites occurred in the middle crust and ultramylonites in the upper crustal level. Fine-grained granite was filtered and channeled through the middle crust shear zone areas to be settled on an upper crustal level as irregular spot within the ultramylonites and gneisses. Granites and granites mylonites were syntectonically emplaced during the D3 sinistral shearing phase.