Integrated Geochemical and Geophysical Approach to Mineral Prospecting – A Case Study on the Basement Complex of Ilesa Area, Nigeria - Advances in Data, Methods, Models and Their Applications in Geoscience - page 72

zone that follows employed the Very - Low Frequency Electromagnetic (VLF - EM),
Electrical resistivityand magnetic methods.
2. Geologic setting
The Ilesa area, lies within the Southwest Nigerian Basement Complex (Schist Belt) which is
of Precambrian age (De Swardt, 1953). De Swardt (1947) and Russ (1957) suggested that the
Nigerian Basement Complex is Polycyclic. This was confirmed by Hurley (1966, 1970) who
used radiometric method to determine the age of the rocks. The Nigerian basement is
believed to have had structural complexity as a result of folding, igneous and metamorphic
activities with five major rock units recognized within the Basement Complex by Rahaman
(1976). These are:
The migmatite-gneiss-quartzite complex
i. Slightly migmatized to unmigmatized paraschists and meta-igneous rocks which
consists of pellitic schists, quartzites, amphibolites, talcose rocks, metaconglomerate,
marble and calc-silicate rocks.
ii. Charnockitic rocks
iii. Older Granites and
iv. Unmetamorphosed acid-basic intrusives and hypabyssal rocks
Geochronological data on all these rock groups were summarized by Rahaman (1988). The
geological map of Ilesa area is as shown in Figure 1.
Fig. 1. Geological map of the study area (After Adebayo, 2008 and Adelusil, 2005)