Integrated Geology and Geochemical analysis of Eruku Basement Complex, Southwestern Nigeria

Abstract

Eruku, located within Osi which is part of the southwestern  Nigerian Basement Complex plays host to principal exposures of Precambrian – Paleozoic crystalline rocks in the region. Detailed geological mapping revealed the area to comprise essentially of migmatite – banded gneiss complex and diorites and minor rock types that include pegmatite and quartz veins with associated superficial stream deposits occurring proximally along channels in the vicinity. While efforts have been committed to regional  mapping, petrography and geochemistry of rocks in the region, little attention was paid to detail delineations and integrating the observed associated stream sediments. This study employs  detailed geological mapping, granulometric analysis and the use of XRF and ICP – MS to establish the geology and geochemical properties of the rocks and surrounding deposits in the area. Migmatitic rocks predominates the southwestern and part of the northwest, while the granite gneisses with some occurrence of diorite are mainly confined to the northeastern part of the study area. Granulometry of the sediments revealed a predominantly medium – coarse grained, poorly sorted leptokurtic sands,  indicating products of in-situ weathering of host rocks.  Geochemical analysis supports a strong correlation between the rocks and the sediments. The study is useful as guide to regional mapping and is applicable in geochemical prospecting of  minerals.

Keywords: Basement complex, migmatite – gneiss complex,  stream sediments, granulometric analysis, elemental abundance, southwestern Nigeria