Comparative field results for electrical resistivity, magnetic, gravity and LVF methods over a marble lens

Abstract

Electrical resistivity, magnetic, gravity and VLF data obtained along five W-E traverses in a basement complex area of southwestern Nigeria were used to delineate the areal extent of a marble lens situated in a geologic setting consisting of calc gneiss and schist. The methods show diagnostic anomalies over the deposit. The marble deposit is characterised by a local low-amplitude resistivity high, a modest reduction in magnetic field intensity and a local low-amplitude gravity high. When the overburden thickness is significant, the magnetic method displays the best resolution of the target. Any of the methods can be used in delineating the marble, most especially when the overburden is thin. The VLF method is sensitive to vertical discontinuities within the marble deposit and could therefore be relevant in lithological contact delineation.