Geology and Economic Potential of Manawaji and Environs, Gulani Area, Upper Benue Trough, Nigeria

Abstract

Understanding the geology of an area is vital for assessing its economic potential. This study evaluates the lithology and economic significance of rocks around Manawaji, Upper Benue Trough, northeastern Nigeria. Field mapping and petrographic examination of representative samples identified Bima Formation sandstones, fossiliferous Pindiga limestones, crystalline limestone, mylonite, and columnar basalts in the area. The sandstones are medium- to coarse-grained, quartz-dominated, and cemented by hematite with minor microcline feldspar. The Pindiga limestones contain ammonite assemblages, whereas the crystalline limestone shows a microcrystalline calcite with fine-grained texture and absence of twinning, suggesting formation under low-stress, non-metamorphic, hydrothermal conditions. The mylonite occurs as boulder-like outcrops showing grain-size reduction, oriented quartz and biotite, and depletion of feldspar and muscovite in thin section, consistent with a quartz–biotite mylonite type. Columnar basalts consist mainly of olivine, pyroxene, and opaque minerals that are possibly titanomagnetite or ilmenite. Collectively, these lithologies record a tectonomagmatic evolution involving Pan-African crustal reworking, Mesozoic rifting and sedimentation, Tertiary volcanism, and post-magmatic hydrothermal alteration. The rocks exhibit economic potential as sources of construction aggregate, basalt fiber, dimension stone, gemstones, and groundwater reservoirs, with possible metal enrichment in sedimentary units. Future studies should incorporate geochemical mapping, geophysical surveys, and advanced analytical techniques (XRF, XRD, SEM, LA-ICP-MS) to confirm the rocks classification, delineate enrichment zones and evaluate the extractive viability of the identified resources.