Application of GIS technique to the interpretation of the aeromagnetic map and landsat imagery of Buji Younger Granite Complex, northern Nigeria

Abstract

Analysis of digitized total intensity magnetic field map of the Buji Younger Granite Complex and environs revealed three major trends of magnetic lineaments, in the northeast-southwest, northwest-southeast, and north-south directions. Application of gradient filters in the X(east) and Y(north) directions showed these lineaments clearly. The lineaments may represent structural trends in the underlying rocks. Some digitized lineaments on the landsat imagery of the area coincide with sections of the drainage system, which suggests that the drainage system may be structurally controlled. The lineaments from the landsat imagery and some fractures observed during fieldwork show four major directions namely, north-south, east-west, northeast-southwest and northwest-southeast. The north-south trend may be due to an imprint of the Pan African Orogeny, while the northeast-southwest and northwest-southeast may be conjugate fractures superimposed on the north-south structures. The length-azimuth graphs show that the longest lineaments trend N57o W for landsat lineaments, and N20o E for fractures observed in the field. Histograms of these data show a tri-modal distribution for the landsat lineaments and a northward clustering for the fractures observed in the field. Rocks of the Buji Complex have lower magnetic intensity than rocks of the surrounding Basement Complex.