GEOLOGICAL INTERPRETATION OF LANDSAT IMAGERY OF NIGERIA’S HAWAL PRECAMBRIAN BASEMENT COMPLEX TERRAIN

The Hawal Basement Complex is located in Nigeria’s NE region. Satellite imagery used in this study covers longitude 12º 00’ to 13º 30’E, and latitudes 9º 30’ to 11º 00’N. The aim of the study is to decipher the regional geologic structures based on analysis and to determine the mineralization implications from the landsat lineament data. The total land surface area covered is about 23,674.88 km2 and includes part of the north sector of Yola sedimentary Rift Basin. The data consists of LANDSAT TM and SPOT XS scenes collated as mosaics. The imagery was monoscopically studied. Classical aerial imagery interpretation techniques of mapping lineaments and tracing regional geological boundaries were used. A total of 368 lineaments were mapped and analyzed using multi-graphical analytical techniques. The results are presented as isolinear contour maps (isodensity and lineaments intersection maps). The isodensity lineament maps show two main areas of lineament concentrations, namely Shani area lying westward and Michika-Mubi area to the east. Reasons advanced for the preponderance of lineaments in parts of the study area are the combined effects of isostatic basement uplift and lithospheric stretching during the formation of Yola Rift and Chad Basin respectively, which caused large scale crustal deformations. Also, Precambrian and Cenozoic magmatic activities that caused emplacements of older granites and basaltic bodies respectively in the area contributed to fracturation of the crust. Fewer lineaments are observed over the sedimentary Rift zone and this is attributed to masking effect of the sediments on basement fractures. The lineament intersection map shows a prominent NE-SW zone of highest intersection which is parallel to the general flow direction of the Hawal River. Prominent lineament directions are N-S (0-20º), and NE-SW (40º- 60º), which are Pan African Orogenic directions. Aerogeological studies of this type are important in national economic development.