Abstract:
Clay has found its use in every century and at this period in Nigeria a lot of demand for cement
and cement products warrants a search for alternatives of which clay fits in perfectly. Thus, there
is need to explore and evaluate clay deposits in order to establish the nation’s clay reserves with
the purpose of setting up and expanding clay products industries. Hence, a clay deposit in Ire-Ekiti
was chosen for geophysical investigation with the aim of characterizing and quantifying its
reserve. The survey covered a total area of 55,322m2 along five traverses while the target area of
25,224.78m2 was divided into six blocks. Magnetic, VLF-EM and combined Vertical Electrical
Sounding (VES) and Horizontal Profiling (HP) technique of electrical resistivity methods were
used for the preliminary study. The magnetic method gave depth estimates to structures and the
bedrock. While VLF-EM method is rarely used on clay deposits, it was employed in this work to
delineate enhanced conductive structures, if any, that may cause geotechnical problem at the period
of mining. The dipole-dipole survey was used to determine the areal distribution of clay and its
electrical properties. The study also involved VES technique using the Schlumberger electrode
configuration to delineate the geoelectric layers and determine their thicknesses. A maximum of
three to five layers were delineated, namely; top soil, sand, lateritic clay, clay, and partly
weathered/fractured/fresh bedrock. The resistivity and thickness values ranges of the clay layer are
54 - 99 Ωm and 5.3 - 67m respectively. Two methods were used to estimate the clay reserve and
the excavable volume. Method 1 involved the generation of thickness contour lines by krigging
method across the study area while the Method 2 utilized the thickness of clay as obtained at VES
data points. The results were 858.78 tonnes and 482,461.24m3; and 896.41 tonnes and
137,086.03m3 respectively. And statistically, Method 2 proved more representable.
