Secondary Riedel faults in the Batouri region and inferences to major shear zones kinematics and gold mineralization

Abstract

The Pan-African domain of Batouri shows many generations of post-collisional granitoids emplaced between 640 and 500 Ma. They are affected by secondary Riedel faults systems R⁓N084E, R′⁓N016E P⁓N140E and T⁓N060E arranged into en-echelon systems oblique to the prominent Y shear bands directed N091E or to the related C′ or Y⁓N091E. The description and analysis of these brittle-ductile faults are based on classic structural geological methods, including structural surveys, analysis and stereographic projection of mesostructures (planar and linear fabrics) and microscopic observation. The results show two Riedel fault systems with two major bands, C′ and Y, oriented E-W with dextral and sinistral polarities. There are two shortening directions (Z) oriented: NW–SE, which accounts for dextral shear bands, and NE-SW, which develops the sinistral shear bands. The high values of dihedral angles (⁓78°–80°) between the R and R′ faults indicate a compressive tectonic regime of the basement, confirmed by the presence of the B_n and B_n+1 boudins stretching NE-SW and NW–SE. These faults likely interact with the neighbouring and regional scale CCSZ, which control gold mineralization in the Batouri granitoids. The mineralization is hosted by Qz-Fk veins in the R, R′, P and C′ Riedel faults. These mark the late-D₃ phase of deformation, which correlates with the nappes stacking event on the WAC at 600 Ma. The relative chronology of deformation at the regional scale suggests that gold mineralization is controlled by Qz-Fk veins in the R, R′, P and C′ Riedel faults, which correlate with the post-collisional phase of the CAFB around 585–580 Ma.