Petrographic and Geochemical Characterization of Alabata Pegmatites, Sheet 260 SE Abeokuta, Nigeria: Petrogenetic Insights and Framework for Sustainable Rare-Metal Exploitation
Abstract
We present an integrated petrographic and geochemical study of eleven pegmatite bodies from the Alabata area (Sheet 260 SE Abeokuta, Nigeria) to unravel their petrogenesis and assess their potential as critical-raw-material resources. Discrimination diagrams—K?O–TiO?–P?O? (pearce et al., 1975, —K?O–TiO?–P?O? (Tarney, 1997), and K?O/Al?O?–Na?O/Al?O? (garrels & Mackenzie, 1971) — demonstrated that Alabata pegmatites occupy a transitional field between metasedimentary and igneous granitoids. AFM plots (Irvine & Baragar, 1971) and WPG classification (Pearce et al, 1984) place them in an “extensional within-plate setting”, whereas trace-element spidergrams (Sun & McDonough, 1989) record both crustal enrichment and subduction signatures. Harker variation trends and SiO?–K/Rb ratios highlight “highly evolved, silica-rich melt” undergoing fractional crystallization (Belevin, 2004), while alumina saturation indices (Shand, 1943) confirm a peraluminous, S-type affinity typical of collisional metasedimentary sources. Petrographically, the suite comprises seven monzogranites, with subordinate granodiorite, monzonite-granite, syenogranite, and quartz-monzonite facies, all displaying graphic quartz- feldspar intergrowths and late-stage tourmaline and columbite-group minerals. Lithium (up to 1.2 wt % Li?O) and light rare earth element (?LREE ? 800 ppm) enrichments position these pegmatites alongside economically viable depositions in Nigeria (Dada, 200; Okunlola & Oyedokun, 2010), Brazil (?erný et al., 2005), and Canada (Linnen et al., 2012). Given the predominance of artisanal mining-with minimal dust control, water recycling, site rehabilitation-we outline a sustainable exploitation framework: closed-circuit processing to reduce tailings (Linnen et al., 2012), community-led environmental monitoring, and local value addition through beneficiation. Our findings shed light on S-type pegmatite evolution in continental crust settings and p
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