Regional and local structural controls on gold mineralization in the Ngoura-Colomines shear zone, Eastern Cameroon: Implications for gold exploration in shear systems

Abstract

Several gold occurences have been identified in eastern Cameroon, within the Pan-African-North Equatorial Fold Belt. However, unraveling the complex interplay between deformation history, tectonic setting, and gold mineralization demands further investigation. Collaborative research efforts focused on these aspects are key to unlocking the full potential of this region's gold resources at least from relatively shallow levels (a few kilometers) to deep crustal levels (tens of kilometers). This paper presents a structural analysis of the Ngoura-Colomines ductile-to-brittle shear zone, located within the Boden District. The zone comprises mineralized S-C granitoid plutons and their associated veins emplaced into gneisses. New U-Pb zircon dating constrain the intrusive event to ∼630 Ma. Satellite, field, and petrographic studies reveal evidence of four main deformation events: (1) D₁ records NNW-SSE ductile shortening with compressional structures in the metamorphic country rocks; (2) D₂ records an extended period of dominantly ductile shear deformation divided into pre-, syn- and post-gold mineralization sub-events; (3) D₃ records a ductile-to-brittle transition that is superposed on the ductile D₂ structures; and (4) D₄ is a brittle event mainly marked by fractures, aplitic dykes and mineralized quartz veins mostly trending NNE–SSW to ENE–WSW. The tectonic history of the Ngoura-Colomines area is consistent with a protracted history of mostly shear-related Pan-African deformation continuing from mid-crustal to upper crustal levels. Gold genesis is linked to two particular stages of deformation: disseminated gold was formed during ductile shear deformation in the middle of the D₂ stage and lode gold developed during the final D₄ brittle event.