Geochemical Characterization and Petrogenesis of Granitoids and Migmatites in the Rimin Zayam Area, North-Eastern Nigeria: Implications for Tectonic Setting and Mineralization Potential

Abstract

This study presents a comprehensive geochemical investigation of granitoids and associated migmatitic rocks from the Rimin Zayam area, Bauchi State, north-eastern Nigeria, situated within the Pan-African basement terrane. Whole-rock geochemical analyses of forty (40) representative samples encompassing Biotite Granites (Younger Granites), metatexites, diatexites, quartz diorites, pegmatites, and dolerite dykes were conducted using X-ray fluorescence spectrometry to determine major, minor, and trace element compositions. The metatexites and diatexites exhibit average SiO₂ contents of 64 wt% and 62 wt%, respectively, with strongly peraluminous character (A/CNK > 1.1) and high-K calc-alkaline to shoshonitic affinities. The Jurassic Biotite Granites display higher SiO₂, averaging 73.3 wt%, are ferroan, alkalic, and peraluminous, plotting predominantly in the within-plate granite field on tectonic discrimination diagrams. Trace element patterns reveal characteristic negative Nb-Ta, Ti, Sr, and P anomalies, positive Pb anomalies, and moderate to strong negative Eu anomalies (Eu/Eu* = 0.3-0.8), indicating significant plagioclase fractionation and crustal contamination. Rare Earth Element (REE) chondrite-normalized patterns show strong light REE enrichment with (La/Yb)ₙ ratios ranging from 8.5 to 45.2, consistent with partial melting of metasedimentary protoliths. Tectonic discrimination diagrams (Nb-Y, Rb-Y+Nb, Ta-Yb) demonstrate that the migmatitic suites plot in volcanic arc and syn collisional granite fields, reflecting their origin during the Pan-African orogeny, while the Biotite Granites exhibit within-plate signatures characteristic of anorogenic Jurassic magmatism. Of significant economic importance, the geochemical data reveal extreme enrichments in critical metals, including Tin (Sn) concentrations up to 2,100 ppm, Tantalum (Ta) up to 120.8 ppm, and Niobium (Nb) up to 900 ppm—values orders of magnitude above average crustal abundances. These anomalous concentrations, coupled with elevated Tungsten (W: up to 30 ppm), Zirconium (Zr: up to 3,270 ppm), and Rare Earth Elements (Ce: up to 570 ppm), establish the Rimin Zayam area as a highly prospective Sn-Ta-Nb mineral province, directly analogous to the world-class Jos Plateau Tin Fields. Fractional crystallization modeling using Harker variation diagrams demonstrates that magmatic differentiation was the dominant process in generating these highly evolved, metal-enriched compositions. The study concludes that the geochemical signatures reflectderivation from metasedimentary crustal sources (S-type affinity) under post-collisional to within plate tectonic regimes, with extensive fractional crystallization concentrating incompatible elements to economically significant levels.