Lithogeochemistry and petrogenesis of A-type granites and associated rocks from the Tongolo area of northeastern Nigeria and implications for lead-zinc-copper mineralisation

Abstract

The Nigerian Younger Granite (NYG) province hosts numerous anorogenic ring complexes that are prospective for base metal mineralisation, yet detailed lithogeochemical investigations linking petrogenesis to mineralisation controls remain sparse for many complexes in the northeastern sector. This study presents a whole-rock geochemical investigation of the Tongolo area, Bauchi State, northeastern Nigeria, to characterise the lithogeochemical composition of the granitic suite, establish its petrogenetic affinity, and evaluate the structural and geochemical controls on the documented Pb–Zn–Cu mineralisation. Seventeen representative samples were analysed by Microwave Plasma-Atomic Emission Spectroscopy (MP-AES). Major-element compositions indicate A-type granitoid affinity, characterised by high SiO₂ (mean 72.66 wt%, excluding the dolerite), elevated iron numbers (Fe* mean 0.74), and low Mg# (mean 37.8). Trace-element signatures show enrichment in U, Pb, Zn, and Cu relative to the Upper Continental Crust (UCC), consistent with significant crustal input and advanced fractional crystallisation. Spatial analysis of Pb, Zn, and Cu distributions reveals that Cu anomalies are proximal to intrusive contacts, reflecting magmatic–hydrothermal fluid inputs, whereas Pb–Zn anomalies are more widespread and structurally controlled by NW–SE and NE–SW lineaments in the southern sector. These results identify the Tongolo area as a high-potential target for base-metal exploration and contribute new geochemical constraints on A-type magmatism and base metal metallogenesis within the NYG province.