Malaysian Journal of Geosciences (MJG)

This research investigates and report zircon U-pb age of a migmatite-gneiss in Idanre, southwestern Nigeria and the petrological implications of this U-Pb age. Field geology reveals Idanre migmatite isa diatexite withnebulitic structures and the gneiss,a metatexite with perverse deformation. The migmatite-gneiss which forms the country rockis a low-lying geomorphologic unitintruded by granite plutons and batholiths. Zircon grains recovered from the migmatite-gneiss have variable sizes and morphology. Geochemicalinvestigation of the zircon revealed Uranium contents range between 80.838 to 116.736 ppm, Th contents between 25.647 ppm and 38.227 ppm while Th/U ratio falls between 0.299 and 0.365. 206Pb/207Pb age of the migmatite-gneiss ranges from 1051 to 1082 Ma with weighted average 1065.1 ± 7.1 Ma (MSWD = 0.28).The age of migmatite-gneiss fallsoutside the Archean-Early Proterozoic (3200-1600 Ma) age bracket reported for migmatite-gneissin other parts of Nigeria.Even though, the 1.065 Ga age of the migmatite-gneissis comparableto granite-gneiss from central Zambezi which crystallized around 1005–1018 million years ago and Phyllite from the Maru schist belt of north central Nigeria which yielded 1110 Ma.However,the migmatite-gneiss age is uncommonin neighbouring Pan-African belt, it is older than the Bayudian event (~0.92 Ga) of the Bayuda Desert of Sudan. This suggests the Idanre migmatite-gneiss probably represents anatectic product of yet another ancient Archean protolith.