Metamorphic Evolution and Mineralization of the Pan-african Orogen in the Nigerian Basement Complex: A Tectonometamorphic Synthesis

Abstract

The Nigerian Pan-African Orogen represents a medium pressure–temperature (Barrovian-type) collisional terrane formed during Neoproterozoic continent–continent convergence associated with the assembly of Gondwana. This study presents an integrated petrological, structural, thermobarometric, and metallogenic synthesis of the orogen, based on compiled data from 47 independent peak metamorphic estimates across multiple study areas. Five deformational phases (D₁–D₅) are recognized, including early nappe stacking and prograde metamorphism (D₁), peak collision and Barrovian metamorphism (D₂), transpressional exhumation (D₃–D₄), and post-collisional stabilization (D₅). The Nigerian Basement Complex exhibits a dual lithotectonic character involving reworked Archean–Paleoproterozoic crust and Neoproterozoic supracrustal Schist Belts, reflecting polycyclic evolution. Rare-metal pegmatites and orogenic gold are interpreted as late- to post-collisional mineral systems associated with structural conduits developed during exhumation. Reconstruction of pressure–temperature–time–deformation (P–T–t–d) paths suggests a coherent relationship between deformation, metamorphism, and mineralization. Comparative analysis with global collisional belts, including the Scottish Highlands, Himalayas, Arabian–Nubian Shield, and East African Orogen, supports classification of the Nigerian belt as a Barrovian-type collisional system, offering a process-based model for exploration and tectonic interpretation. However, interpretations are based on compiled secondary datasets and therefore depend on the spatial coverage and analytical consistency of existing studies.