Abstract

This study is aimed at identifying highly altered zones by applying concentration area (C-A) fractal model technique on Landsat ETM+ image of area around Bakwani-Bagwa, Northwestern Nigeria. Multifractal analysis was used to quantify degree of alteration on satellite images processed using crosta technique. A log–log plot was used to display the multifractal characteristics for clay and iron altered images and identify threshold values. Maximum and minimum threshold values obtained from fractal analysis are 1.74 and 4.01 for clay altered images and 0.607 and 3.04 for iron altered images. High clay and iron alteration zones accounts for 5.89% and 7.84%, covering an area of 22.28km2 and 29.65km2 respectively. Delineating highly altered zones from these images reveals higher alteration largely within silicified sheared rocks and areas around faults. The current study proved the multifractal processing techniques to be valuable mapping tools for geological reconnaissance which can be extended to a large area of the Nigerian basement and provide preliminary hydrothermal alteration maps that are accurate as well as cost and time effective.

Key words: clay and iron alterations, mineral exploration, multifractal analysis, threshold measurement