Characterization of Pegmatites in Ogodo-Odobola Area of Idah Sheet 267NW, Central Nigeria

Abstract

The pegmatites of Ogodo-Odobola area around Ajaokuta, Central Nigeria belong to the pegmatite belt of Central Nigeria. A detailed geological mapping of the pegmatites and host rocks was conducted with the aim of understanding their mode of occurrence and field relationship and to assess their mineralization potentials. Twelve (12) representative samples of rocks were selected for petrographic analysis. The results show that the area is underlain by migmatite-gneiss, schist, with intrusions of granite and pegmatite. The pegmatites occur in tabular form with varying widths (2 centimetres – 6 metres) and lengths (12 – 200 metres). Principal joint direction is NNE-SSW which is believed to have influenced the pegmatite emplacement. Petrography of the representative rock samples revealed an average mineralogical composition of biotite (23.90%), microcline (22.15%), hornblende (15.05%), quartz (10.65%), plagioclase (10.35%), muscovite (8.00%), myrmekite (0.20%), and opaque and accessory minerals (9.70%). The pegmatites were found to be dominated by microcline and plagioclase feldspars, and then muscovite, biotite, and accessory and opaque minerals. The pegmatite of the Ogodo-Odobola area is worth probing as the results have shown prospect for possible economic minerals. Keywords: Mineralization, Basement Complex, Structural Features, Petrography, Ajaokuta