Abstract
Electrical Resistivity Methods involving Schlumberger Vertical Electrical Sounding (VES) and Wenner Electrical Profiling (EP) were carried out to map the Geological features of the earth subsurface in Zainawa Area of Kano State, Nigeria. Five profiles were established; consist of six (6) VES points at each profile. GEOPULSE resistivity meter (SAS 300) was used for the data acquisition. The field data obtained have been analyzed using computer software (IPI2win) which gives an automatic interpretation of the apparent resistivity. A maximum of three geoelectric subsurface layers were delineated from the VES master curves. The geoelectric section beneath the study area was composed of top soil (clayey-sandy and sandy-lateritic), weathered layer, partly weathered (fractured basement) and fresh basement. The resistivity value for the topsoil layer varies from 20 Ωm to 600 Ωm with thickness ranging from 0.5 to 7.2 m. The weathered basement has resistivity values ranging from 15 Ωm to 593 Ωm and thickness of between 2.75 to 33.04 m. The fractured basement has resistivity values ranging from 201 Ωm to 835 Ωm and thickness of between 11 to 20.4 m. The fresh basement (bedrock) has resistivity values ranging from 1161 Ωm to 3115 Ωm with infinite depth. The depth to basement map was produced to give a good picture of the basement topography within the study area. The depth to basement ranges from 11 m around VES 01 to 85 m around VES 25 m. The map also reveals linear structures (VES 05, 21, 22 and VES 23) which trends in the NE-SW direction. These structures suggest a basement depression at these points. However, the depth from the topsoil to the bedrock surface varies between 2.5 to 37.75 m.
Highlights
The purpose of electrical survey is to determine the subsurface resistivity distribution by making measurements on the ground surface
In this research IP12Win is used in Vertical electrical sounding interpretation while Surfer V.12 is used for the electrical profiling interpretation
The geoelectric sections were carefully examined to see the regions where extensive weathering occurs along fractures
Summary
The purpose of electrical survey is to determine the subsurface resistivity distribution by making measurements on the ground surface. From these measurements, the true resistivity of the subsurface can be estimated. The ground resistivity is related to various geological parameters such as mineral and fluid contents, porosity and degree of water saturation in the rock [1]. Electrical resistivity surveys have been used for many decades in hydrogeological, mining and geotechnical investigations. It has been used for environmental surveys. The resistivity measurements are normally made by injecting current into the ground through two current electrodes
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