Geological mapping, petrological study and structural analysis of precambrian basement complex rocks in part of Ago-Iwoye Southwestern Nigeria

Abstract

Geological map is a veritable planning tool for economic development of any nation. This map contains the distribution of various types of bedrock in the area. Geological map of Nigeria geographic landmass has been produced since 1964 with the recent update being in 2009. This map largely omits some local geology of interest, possibly owning to its large area coverage. Thus, local geologic mapping must be encouraged to bridge this lacuna; the focus of this study. Four different rocktypes were identified: porphyroblastic (augen) gneiss, hornblende-biotite gneiss, banded gneiss and quartz schist with mineralogical assemblages ranging from quartz, micas (biotite and muscovite), hornblende, feldspars (plagioclase and microcline) feldspars to accessory and opaque minerals (iron oxide). Deformational tectonic events that accompanied Pan African orogeny were mapped out in the area resulting to the development of structural elements such as mineral lineation, foliation, jointing and veins. Faulting and folding were absent which suggest possible low-intensity deformation. This was further corroborated in the development of sericite (porphyroblast) clast which is an intermediate clay mineral between micas and feldspar. Measured structural parameters were integrally statistically processed. The result reveals NW-SE trending of foliations and mineral lineation, which conforms with the direction of stream flow as an indication of the streams being structurally controlled.