A QUALITATIVE INTERPRETATION OF AEROMAGNETIC MAP OF TAKUM (SHEET 273) THROUGH IMAGE – BASED DISPLAY AND DEPTH CALCULATIONS.

Abstract

A qualitative interpretation of aeromagnetic map of Takum (sheet 273) of the lower Benue, Nigeria through image-based display and depth calculation was carried out at a scale of 1:100,000. The study area is located within longitudes 9 30′E-10 00′E and latitudes 7 00′N-7 30′. The principal purpose of this work is to recognize and delineate anomaly that may be related to structure and their relationship to metallurgy as well as visualizing the structural features within the study area. The technique of image processing was employed. A 1’ by 1’ cell size was used to display the magnetic field values as colour rasters. A total of 900 grid cells which represents the 900 digital numbers of aeromagnetic data were geographically registered on a base map and contoured to produce the required total field aeromagnetic map of the study area. Depth calculations made use of peter’s maximum slope method. The range of anomaly depths is about 90m to 2850m. The susceptibility values range from (0.5 - 4.8) * 10-4 c.g.s.  The prominent strike direction is the NE-SW trend. Ten possible major faults were identified and mapped out. The anomaly trends conform to the susceptibility trend. Visualization and quantification of subsurface geology were enhanced. The basement is of non-uniform magnetization. It is characterized by short wavelength anomalies which are probably caused either by susceptibility changes within the basement or near surface intrusive. Differing colours in visual display show areas of varying ruggedness which are useful tools in demarcation of lithologic structures and boundaries.