Geologic and Petrographic studies of the Rocks in Dumne area, Northeastern Nigeria

Abstract

Lithological mapping of the Dumne area revealed that the area is underlain by rocks that constitute members of the Basement Complex represented by migmatite-gneiss, porphyritic granite, coarse-grained granite, dolerite and pegmatite. The Cretaceous sedimentary rock is examplified by sandstone of Bima Formation and the Tertiary/Quaternary extrusives is typified by basalt. Structurally controlled, epigenetic fracture-filling, vein-type baryte-fluorite mineralization occurs in three locations of the Dumne area. The baryte-fluorite veins are hosted within fractures and fault zones in the migmatite-gneiss and porphyrytic granite. Thin-section investigation indicates that the migmatite-gneiss, porphyritic and coarse-grained granite are mineralogically similar having essential minerals consisting of quartz, orthoclase, biotite, plagioclase, hornblende and microcline with variable accessory minerals such as zircon, apatite, sericite, sphene and iron oxide. Dolerite and basalt have identical mineralogical composition characterized by presence of pyroxene, olivine, plagioclase, biotite and iron oxide while pegmatite has quartz, orthoclase, plagioclase and muscovite as its mineralogical composition. Bima sandstone is typified by presence of quartz, orthoclase, zircon and limonite. This study has succeeded in revealing the mineralogical and composition of the rocks in Dumne area and has outline baryte-fluorite mineralization as the main mineral of interest which is economically viable.