Archean shear tectonics in the Congo craton: insights from Petro-structural characterization and U-Pb geochronology of the Memve’ele mylonite, Southern Cameroon

The Congo craton is an early Archaean through Paleoproterozoic basement block in Central Africa. It consists of a vast heterogenous granulitic complex extending over 1200 km between the Lomami River (24°E) and the Atlantic coast in Angola. The well-exposed domains of the Congo craton are the Kasaï block, Tanzania block, West-Nile complex, and Ntem-Chailu complex. The latter represents the northwestern edge of the craton in southern Cameroon. The Memve'ele area belongs to the Ntem Complex, where recent investigations have highlighted various lithologies, including TTG gneiss and intensely sheared and folded charnockitic and granitic gneiss, pervasively intruded by younger monzogranite. This region provides a critical window into the complex tectonic evolution of one of Earth's oldest continental blocks. Both TTG and granitic gneiss are riddled with folded or sheared leucogranitic veins, suggesting a local origin through melting and dynamic recrystallization. This study presents a comprehensive investigation of the highly sheared Memve’ele mylonitic corridor. Through detailed field mapping, systematic kinematic analysis, and meticulous petrographic and microstructural studies, we aim to unravel the multiple deformation events that have shaped this region. U-Pb zircon geochronology was employed to precisely constrain the timing of these processes and to correlate them with regional tectonic events. The ultimate goal of this research is to better understand the broader geodynamic implications of these findings for the evolution of the Congo Craton. Initial results reveal that the Memve’ele area has undergone a complex polyphase deformation history, involving at least four distinct events. The early ductile deformation (D1) resulted in the development of a pervasive foliation and associated structures. Subsequent ductile-brittle deformation (D2) overprinted the earlier structures, while later brittle deformation events (D3 and D4) further modified the rock fabric. The studied mylonites yield Mesoarchean ages of 2927 ± 52 Ma. The presence of a sinistral shear zone within the area suggests that the region was subjected to significant shear stresses, likely related to regional tectonic processes such as continental collision or crustal extension. These findings have important implications for understanding the tectonic evolution of the Congo Craton and may provide insights into the potential for mineral exploration in the region.