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 71

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Integrated Geochemical and Geophysical
Approach to Mineral Prospecting -
A Case Study on the Basement
Complex of Ilesa Area, Nigeria
Emmanuel Abiodun Ariyibi
Earth and Space Physics Research Laboratory,
Department of Physics,
Obafemi Awolowo University (OAU), le - Ife,
Nigeria
1. Introduction
The crust of the earth is composed of solid rocks. When the rocks are closely examined, they
are found to be composed of discrete grains of different sizes, shapes, and colours. These
grains are minerals, which are the building blocks of all rocks (Mazzullo, 1996).
The formation of soils from rocks generally involves the combination of mechanical and
chemical weathering resulting from surface processes. Climatic conditions under which the
weathering is affected determine which of the two forms of weathering becomes more
pronounced than the other. In arid climates where there is little or no water and where there
are appreciable diurnal variations in temperature, chemical weathering is considerably
subordinated to mechanical weathering and the rocks simply become broken into increasingly
small grains and pieces in which the individual minerals that constitute the rock are easily
recognized. If, on the other hand, the climate is warm and humid with appreciable rainfall,
chemical weathering becomes markedly pronounced and the individual minerals that form
the rock are each subjected to rather intense chemical and comparatively modest mechanical
weathering with the formation of different products which are all constituents of soils
(Adewunmi,1984). In most Basement Complex rocks, weathered products, reflect certain
characteristics (geochemical and mineralogical) of the parent rock.
Previous studies by Ako et al. (1979), Ako (1980), Ajayi (1988) and Elueze (1977) on the Ilesa
area have been suggestive ofsulphide mineralization but the scope of coverage have been
limited to the Amphibolite and the area around the Iwara fault. The present work is regional
in scope and seeks to uniquely use an integrated geochemical and geophysical approach
around the Ilesa area which is within the Schist belt of southwestern Nigeria and consists of
Schist Undifferentiated, Gneiss and Migmatite Undifferentiated, Pegmatite, Schist Epidiorite
Complex, Quartzite and Quartz Schist, Granite Gneiss, Ampibolite, Schist Pegmatised and
Granulite and Gneiss aimed at delineating the area for mineral exploration. The geochemical
data from 61 sampling locations were subjected to multivariate analysis and interpreted to
delineate geochemical anomalous zone. The geophysical investigation of the anomalous