A comparative study of ree geochemistry in precambrian pegmatites and associated host rocks from western Oban Massif, Se – Nigeria

Abstract

The area of study (Igbofia-Akwa Ibami-Iwuru) is located between Latitudes 5o20'N and 5o27'N, and Longitudes 8o09'E and 8o18'E, south-eastern Nigeria. The pegmatites of this area have been studied by several authors for several decades till now. The present study evaluates the use of trace and rare-earth elements (REE) as finger prints in comparing the geochemistry of pegmatites and their associated host rocks, and to deduce if there is any co-genetic relationship between them. Sixteen representative samples of pegmatites and their host rocks (schist and
granodiorites) were collected and analysed using the ICP-MS analytical method. The pegmatites were found to be richer than their host rocks in SiO2, Al2O3 Na2O+K2O (alkali), Rb, Li, Cs, Be, Na, Zn, Nb, and Ga while they are poorer in Fe2O3, CaO, Sr, Ba, Zr, U, Cr, Th, and all the REEs. Only in the MgO contents are the rocks similar. Compared trace elements and REE data of schist and granodiorite (host rocks) against associated pegmatite samples in this work, show that the pegmatites are not necessarily products of their host rocks.