Geological Mapping, Petrography and Ground Magnetic Survey in Gidan Doya, Lokoja, North Central, Nigeria

Abstract

The geological mapping, petrographic and ground magnetic Survey in Gidan-Doya, Lokoja, North Central, Nigeria was carried out. The geomagnetic data were acquired along 8 traverses using 3 axes MCL6 Proton Precession Magnetometer and Magnetic Susceptibility Meter. The data were processed using Surfer 11 software, corrected for variations in geomagnetic fields as well as upward continuation and residual magnetic field. The anomaly patterns identified in the upward continued map revealed distinct structural zones. The North Eastern and South Western zones have the maximum magnetic intensity values ranging from 700 nT to 1100 nT suggesting shallow basement while the North Western zone is characterized by relatively low magnetic intensity values ranging from -300 nT to 700 nT suggesting a deeper basement. The direct measurement of magnetic susceptibility varies between 0.36 x 10^-3 SI to 39.00 x 10^-3 SI. The contour map shows the relative thickness of the overburden to be between 15 to 40 m. The study concludes that magnetic potential of the survey area is controlled principally by the subsurface structures, thickness of the overburden and mineral composition. The faults, fractures, and lithological contacts provide channels for mineralization fluids and flow of underground water. Petrographic study shows that the area is dominated by Migmatite and granite. The major minerals include feldspar, quartz and biotite, while magnetite, ilmenite and hematite occur as accessory minerals.

Keywords: Magnetic Susceptibility, Petrography, Paramagnetic, Structures, Residual magnetic map and shallow Basins