GEOLOGIC INVESTIGATION OF PEGMATITE VEINS IN PARTS OF THE OBUDU BASEMENT COMPLEX, SE NIGERIA

¹Igonor, Emmanuel E., ² Oden, Micheal I. and Horsley Robert J. (late)

¹Petra Prospectors Limited, (Nigeria)

²Department of Geology, University of Calabar, Cross River State, Nigeria.

ABSTRACT

Pegmatites the world over have been known to generate lots of interest because they sometimes play host to abundance of economically valuable mineral deposits like gemstones and rare-metal ores of tantalum, niobium, wolfram, lithum and tungsten, which drive the present day economic revolution. But the pegmatite veins of Obudu massif have received little or no research or commercial attention. A detailed geologic mapping exercise spanning over 30days  was undertaken to study the various lithological units of the area (Nigerian Topo-sheet Obudu 291SE), with special interest in the pegmatite veins as they occur in the area. From the field observation and analyses, the major lithological unit’s in Obudu SE area are: gneisses, schist, amphibolites, charnockites, dolerite dykes, quartz veins, and pegmatite veins. Traceable pegmatite vein length ranges from less than 1m to over 80m; though the most frequently occurring vein length is between 6m – 8m. Pegmatite vein widths range from <1cm to over 7m. The pegmatite veins of Obudu SE favour high angle fractures i.e fractures which dip at angles >50^o. Over 200 strike measurements of the pegmatite veins show that  more than 25% fall between 161^o – 180^o from north, which is the most preferred orientation. The pegmatites are mainly made up of quartz, feldspar and muscovite flakes but sometimes also contain gem mineralisation like amethyst, tourmaline, or aquamarine. Prospects for rare-earth mineralisation in the pegmatites of Obudu SE area look unpromising as they lack any visible occurrence of tantalite, niobium, lepidolite or any other rare-earth metal even though further geochemical analysis would be needed to ascertain this claim.

Keywords: pegmatites; Obudu massif; geologic investigation; strike and dip; orientation; southeast Nigeria;