Abstract

The tectonic structures of the Mako area in the Kédougou-Kéniéba inlier (KKI) were mapped with tele-analytical investigation which is validated by field data. This study is based on different images processing in particular: 1) the colored combinations (1 to 5) and panchromatic (8) thematic mapping bands of the Landsat-8 (ETM+) satellite; 2) Digital Elevation Model (DEM) image of Space Shuttle Radar Topography Mission (SRTM); 3) airborne geophysics (aeromagnetic and radiometric) images. In these images, four major directions of lineaments NS, NNE-SSW, NW-SE and EW would be related to the tectonic structures, have been identified and mapped. Field data confirm these four structural directions and show that most of these lineaments are related to faults, shear and/or thrust zones, or even basic rock dykes. N-S to NE-SW oriented lineaments are more frequent followed by those NW-SE oriented. These two directions of lineaments are generally in correlation with trajectories of major sinistral shear zones in the Mako area. They would be associated with the S2a and S2b schistosities relative to the D2 Eburnean major deformation. They often intersect the E-W oriented lineaments which are less frequent and sometimes folded and crenulated. This E-W oriented lineament would be prior and are associated with the S1 schistosity of the D1 Eburnean thrust phase of deformation. At the scale of the studied area, these major linear structures (shear zones) are conjugated and create a partitioning of deformation through an anastomosed network of mylonitic shear zones which surround weakly deformed rock bodies. All these structures would be related to the Eburnean or post-Eburnean orogenic events in this Mako area.

Highlights

  • In the Kédougou-Kéniéba Inlier (KKI), the major tectonic structures that affect the Paleoproterozoic (Birimian) formations are essentially related to the Eburnean orogeny ([1] [2] [3] [4])

  • This study presents the results of the lineaments analysis in the Mako area, extracted by image processing methods and compared to field data in a Geographic Information System (GIS)

  • The lineaments extracted on the filtered image in the different filtering directions (NS, EW, NW-SE and NE-SW) are systematically compared to the lineaments obtained on the multispectral images (4.3.2 bands combination of Landsat-8, ETM+) and on geophysical images before being confirmed and digitized

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Summary

Introduction

In the Kédougou-Kéniéba Inlier (KKI), the major tectonic structures that affect the Paleoproterozoic (Birimian) formations are essentially related to the Eburnean orogeny ([1] [2] [3] [4]) They are characterized by major shear zones, faults, folds, fractures related to Eburnean and even post-Eburnean tectono-magmatic events. Because of the problems associated with the sometimes sporadic distribution of rock outcrops, vegetation cover and surface weathering of outcrops, the lineaments of satellite images will be combined with those resulting from the processing of aeromagnetic geophysical images. These lineaments of aeromagnetic geophysical images are characteristic of sub-surface structures

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