Petrogenesis and Mineralization Potential of a Highly Evolved Post-Collisional Granitic Suite: Insights from the Pan-African Igbeti Granitoids, Southwestern Nigeria

Abstract

The Pan-African granitoids of the Nigerian Basement Complex are known for their metallogenic potential, yet many suites remain poorly characterized. This study presents an integrated geochemical investigation of the granitic rocks from the Igbeti area. The suite comprises porphyritic quartz monzonite, granite, and silica-rich pegmatite. Whole-rock geochemistry reveals a strong fractional crystallization trend marked by increasing SiO₂ (65.38 to 96.10 wt. %) and initial K₂O enrichment followed by drastic depletion in the pegmatite. The rocks are chemically ferroan (Fe# > 0.9), alkalic to alkali-calcic (MALI = +3.71 to +11.54), and predominantly peralkaline (A/CNK < 1.0), classifying them as postcollisional intra-plate granites. Trace element patterns show significant absolute enrichment in LILE (Rb, Ba), HFSE (Nb, Ti, P) and LREE, depletion in HREE as well as depletion of HFSE relative to LILE, and a pronounced negative Eu anomaly. Tectonic discrimination plots (Nb-Y; Rb-(Y+Nb)) indicate a within-plate setting. The geochemical signature—notably high concentrations of Zr (up to 1060 ppm), Nb (up to 52.5 ppm), ∑LREE (up to 826 ppm), and hydrothermal indicators (S, Cl)—suggests high prospectivity for rare metal (Nb-Ta-Zr) and rare earth element (REE) mineralization hosted within the highly fractionated granitic suite. This study identifies the Igbeti suite as a promising target for critical raw material exploration in West Africa.