PETROGRAPHIC, STRUCTURAL FEATURES AND GEOCHEMICAL INVESTIGATIONS FOR RARE METAL (TA-NB) POTENTIALS OF PRECAMBRIAN PEGMATITES OF OLUGBO AREA, SOUTH WESTERN NIGERIA

Abstract

This study is on the petrographic and geochemical evaluation of low lying pegmatic veins intruding into the older assemblages of migmatite-gneisses around Olugbo area, south-western Nigeria. This was carried out with a view to understanding their petrographic, structural and geochemical features. Thin section Petrographic studies we're carried out. From the orientation of the veins and dykes measured in the field, it was observed that they do not have a uniform direction. The rocks in the study area can be said to date from
Pre-Pan-Africa. However, this age is tentative since the exact age of the rocks cannot be determined without carrying out radiometric dating. A total of twelve samples comprising whole rocks pegmatites and extracts of feldspar, mica (biotite) and suspected ore (opaque) mineral were analyzed for major, trace and rare earth elements using combination of inductively coupled plasma emission spectroscopy (ICPES) and inductively coupled plasma mass spectroscopy (ICMPS) analytical methods which showed the pegmatite samples to be generally highly siliceous with SiO2 values ranging from 67.32-69.38%. In general, the Olugbo pegmatites fields are relatively poorer when compared with highly mineralized Tanco (Canada), Homestead and Wodinga Australia pegmatites and low-medium Ta-Nb pegmatites of Buck, Oasis and Noumas pegmatites of South Africa.