The Kigom igneous complex of northern Nigeria is a small intrusive complex made up of peralkaline arfvedsonite granite, riebeckite-biotite granite and riebeckite-aegirine granite. The granites show coherent major-element chemistry typical of that of the Nigerian Younger Granites, and are enriched in Rb, Li, Zr, Nb, Th, Y, F and REE, and depleted in Ba and Sr compared to the world average for rocks of similar composition. The riebeckite-aegirine granite exhibits a two- to three-fold increase in the concentration of Zr, Nb, Li, F, Th, Zn and REE over comagmatic granites. Concentrations of the highly charged cations in these granites are believed to be the result of halogen—alkali-rich fluid activity during the fractionation of the magma. Corresponding trace-element increases in the granites in areas of alkali metasomatism (albitization) support this argument, and reflect the partial confinement of this alkali volatile phase within the high-level magma chambers. It is important to recognize that the chemical signatures of this liquid-state fractionation process may be explanatory mechanisms in the formation of some kinds of lithophile ore deposits. The degree of peralkalinity maintained miscibility in the residual fluid between silicate and aqueous phase to low temperatures so that mineralizing components continuously accumulated together. The interaction between this phase and early-formed minerals led to Mo mineralization. The well-known classification of granites into sedimentary protolith (S-type); igneous protolith (I-type) and A-type indicates that the granites studied here have typical A-type features. An origin by partial melting of lower-crustal material (probably granulite facies) under a high flux of mantle-derived volatiles is suggested for these rocks. As a result of mixing of crustal and mantle-derived fluids a syenitic magma was produced which then experienced selective contamination as a result of further reaction melting during fractionation and ultimately produced a peralkaline differentiate.