Regional Magnetic Field Trend and Depth to Magnetic Source Determination from Aeromagnetic Data of Maijuju Area, North Central, Nigeria

Abstract

The aim of this study is to estimate regional magnetic field trend and depth to magnetic rocks within Maijuju area, North-Central, Nigeria. The Total Magnetic Intensity (TMI) map was gridded, contoured and interpreted for trends, closures and dislocations. The TMI map was reduced to the equator; Upward continuation to depth 1, 2, 3, km was carried out; the magnetic residual field map was divided into 4 blocks of area each 27 m ´ 27 m for 2-D spectral analysis of the magnetic anomalies over the area. All resultant maps were interpreted. The TMI map revealed anomalies observed in the study area to trend largely in the NE-SW and E-W directions. Low magnetic intensities values were observed at Jos-Bukuru, Jarawa, Shere, and Kofai and Rop Complexes. Intermediate negative magnetic values (-54.5 to -5.3 nT/m) were observed at the Sara-Fier Complex. Positive magnetic intensity range of 72.9 to 270.7nT/m was seen to dominate the Older Granite region, the Basement Complex and part of Sara-Fier Complex, Magnetic Discontinuities which could represent geologic fractures were also observed. The TMI reduced to equator map was used to centre the peaks of magnetic anomalies over their sources. The upward continuation maps revealed that TMI continued upward to elevations of 1 km, 2 km and 3 km permits a clearer view of the deeper anomaly sources and showed the regional magnetic field trend to be in the NE-SW direction. The spectral depth analysis result showed that the deeper magnetic sources have an average depth of 1.47 km while the shallow magnetic sources have an average depth of 360 m (0.36 km). The regional magnetic field trend as observed from the upward continuation process is NE-SW trend while the spectral depth analysis result revealed that the deeper sources have an average depth of 1.47 km while the shallow sources have an average depth of 360 m (0.36 km).