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.

Highlights

  • The Mgbanji granites and their host gneisses present several deformation features testifying multiple deformation phases underwent by the area and the complex rock emplacement mechanism

  • We present structural and petrographic data derived from systematic geological mapping, detailed petrographic descriptions, and structural characterization carried out in outcrops and rock thin sections coupled with kinematic studies in order to determine the petrography, the deformation phases, the origin, and the emplacement condition of the rocks

  • Even though it has been proved that high stresses may cause cataclasis at greater depths or higher temperatures, the mechanism we suggest for the Mgbanji magma emplacement operates on three different crustal levels, namely lower, middle, and upper crustal levels (Figure 8)

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Summary

Introduction

Metamorphic, and sedimentary rocks generally host structures or features characterizing their condition or their emplacement environment. For igneous and metamorphic rocks, the deformation features provide information on the condition of the emplacement, the tectonic environment, and or the protolith nature. The Central African Fold belt to which belongs the Mgbanji area is situated. The Mgbanji granites and their host gneisses present several deformation features testifying multiple deformation phases underwent by the area and the complex rock emplacement mechanism. We present structural and petrographic data derived from systematic geological mapping, detailed petrographic descriptions, and structural characterization carried out in outcrops and rock thin sections coupled with kinematic studies in order to determine the petrography, the deformation phases, the origin, and the emplacement condition of the rocks

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