A New Geophysical Framework for Evaluating Mineral System Fertility in the Nigerian Basement Complex Using Terrane-Scale Structural Analysis

The concept of mineral system fertility describes the set of crustal-scale geodynamic and structural conditions that predispose a terrane to the formation of ore deposits, and its rigorous geophysical evaluation in the Nigerian Basement Complex has not been pursued, resulting in an empirical and under-theorised approach to mineral exploration that misses district-scale and camp-scale controls on mineralisation. This research develops a new geophysical framework for evaluating mineral system fertility at the terrane scale in the Nigerian Basement Complex, using the Benin-Borgu-Ibadan terrain junction in Kwara and Oyo states as the primary study area. The framework integrates aeromagnetic structural geology, crustal-scale gravity modelling, airborne radiometric lithogeochemistry, and mantle xenolith thermobarometry from the sparse available kimberlite-hosted data to characterise the deep architecture of the basement at four fertility dimensions: heat flux, crustal thickness, structural focusing, and metasomatic enrichment. Aeromagnetic data reprocessed at 50-metre flight-line spacing reveal a network of transpressional shear zones that are modelled as crustal-scale structures penetrating to 20 to 30 kilometres depth based on magnetic source depth estimates. Gravity inversion indicates a zone of anomalously low crustal density beneath the Ife-Ilesha gold district, interpreted as a fertile felsic to highly evolved magmatic system at 15 to 25 kilometres depth. The fertility framework generates a quantitative prospectivity map that ranks 15 sub-areas across the study terrain by their predicted fertility for orogenic gold, skarn iron-copper, and pegmatite-hosted rare metal systems. Keywords: mineral system, fertility, basement complex, terrane analysis, aeromagnetic