Geophysical Evaluation of Gold Occurrence in Part of Bishini Sheet 165 SW Kafin-Koro Northwestern Nigeria

Abstract

The distribution of gold mineralization in the Nigeria Basement Complex is favored by different geologic orogenic episodes that deposit gold in a structurally control quartz veins. The principal physical properties that have been the focus of geophysical exploration methods are: density, magnetization (induced and remnant), conductivity, chargeability, radioactivity and seismic velocity. Sometimes the desire mineralized target has physical properties that permits direct discovery, while others by virtue of the physical properties of association with other minerals that permit indirect method. The geology of the study area is a typical geology of Kusheriki – Minna region, comprising of crystalline rocks that have been divided into three groups like that of the Nigeria basement complex, namely; gneisses and migmatite, schist belts composed of medium-to low grade supracrustal cover, and intrusive granitic rocks. Magnetic methods was used in the survey as an indirect approach to map the linear structural features like veins, fractures and contacts which act as conduits and host gold mineralization, also electrical imagining geophysical survey involving Induced polarization (IP) and resistivity methods was carried in a potential gold mineralized zone within the area to complement the other methods. Magnetic survey measurements were taken with GSM-19v7.0 Over Hauser Instrument manufactured by GEM SYSTEMS. Also, IP and resistivity imaging survey was carried out simultaneously with Geomative GD-10 Supreme 2D Geoelectrical system. The residual magnetic field intensity map generally shows major NE/SW and N/S trending. IP survey revealed that most of the magnetic anomalies investigated are chargeable and that their chargeability increases with depth