Performing a pseudo-panchromatic SAR image of Radarsat-1 for lithostructural mapping of the Precambrian basement in Korhogo region (North of Côte d'Ivoire)

This study shows the potential for discrimination of lithological units of the Precambrian basement with a monoband RADARSAT-1 low spatial resolution (50 m) image. The methodological approach was to produce and exploit a pseudo-panchromatic (15 m) SAR image. SAR image was first denoised then georeferenced using the panchromatic band of Landsat ETM+. The wavelet fusion and multi-resolution analysis technique has been used to produce a pseudo-panchromatic SAR image (15 m) marked "PR". The "Wallis" adaptive filter, synthetic colors transformation and texture parameters calculation were applied to "PR" to enhance the lithological units contours. Primary analysis associated with the interpretation of images deriving from the directional weighted 7x7 Sobel filters, revealed image discontinuities similar to geological fractures. The use of images derived treatments applied to "PR" has allowed bringing out lithostructural various information. According to tone and texture variations, four major geological ensembles consist of mafic and intrapaléozoïques Birimian formations were distinguished from six images facies that characterize the region's geology. These are Baoulé type granite of craton forming the Korhogo massif, Baoulé type granite of geosynclines forming the Ferké massif, sedimentary facies Birimian series forming the Dioula and Haut-Bandama series. The lineaments and major fractures study gave the main structural directions with SW-NE as the dominant orientation. Similarly, extensions of some fractures, not apparent on existing maps, have been revealed. Synthesis of this information gave a new lithostructural map. Comparing it with previous works showing that the geological contours mapped are the same with those references. However, the Niellé massif and Dioula volcano-sedimentary series could not be differentiated. Similarly, simulated image was ineffective at detailed mapping.