Abstract
Magnetic and resistivity geophysical methods were used to investigate the location and depth of mineral rocks at Olode village, Oyo State, Nigeria. 80 magnetic data points were acquired in 10 profiles using G-816 proton precession magnetometer with 10 m spacing in between each profiles and 10 m stations interval. After correcting diurnal variations, the raw magnetic data obtained were plotted as 2D and 3D magnetic contour maps. The residual anomalies obtained were plotted against distance using Microsoft Excel, and Peter’s half-slope method was used to find the depth to the magnetic sources. The magnetic signature obtained show considerable varying amplitude from a minimum value of 155.3 nT at a depth of 6.37 m to a maximum value of 670.3 nT at a depth of 6.25 m. Resistivity data were obtained using Campus Tiger resistivity meter and 9 VESs were acquired using Schlumberger configuration. All VESs were 150 m long, 75 m on each side of the referenced points which were 10 m apart. VESs 1–4 and 7–9 are underlined with rocks of high conductivity and susceptibility values. VESs 5 and 6 show rocks with low conductivity and susceptibility values. The results of these geophysical methods show that there are rocks with high magnetic susceptibility and conductivity values from the centre towards the eastern region of the study area and low magnetic susceptibility and conductivity values at the western region. On the average, the depths of these rocks from the surface fall in the interval of 5.80 m to 6.72 m.
Highlights
Geophysics plays a large part in a multitude of disciplines
The origin of the earth’s magnetism is commonly believed to be the liquid core, which cools at the outside as a result of which material becomes denser and sinks towards the inside of the outer core and new warm liquid matter rises to the outside; convection currents are generated by liquid metallic matter which move through a weak cosmic magnetic field which subsequently generates induction currents [25]
This study focused on the subsurface geological structures based on the qualitative interpretations of both resistivity and magnetic data collected from surveys carried out
Summary
Geophysics plays a large part in a multitude of disciplines. Geophysics is a technique which has recently begun to be used by a number of disciplines to give information about the underlying ground without having to engage in invasive digging of the area. It has been used to help solve practical environmental, geotechnical, and exploration problems. The typical scenario is first to identify the physical property, that is, diagnostic of the sought geologic structure or buried object. The appropriate geophysical survey is designed and field data are acquired and plotted. The information needed to solve the problem may be obtained directly from these plots, but in most cases more information about the subsurface is required [1, 2]
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