Integrated Landsat 9 OLI, SRTM-DEM and Field-based Mapping of Regolith Regimes for Gold Exploration in Dabakala, Côte d’Ivoire
Konan Roger Assie *
Université Jean Lorougnon Guédé, UFR Environnement, Département des Sciences de la Terre, Laboratoire des Sciences et Technologies de l’Environnement, BP 150 Daloa, Côte d’Ivoire.
Koffi Kossonou Jean-Marie Pria
Université Jean Lorougnon Guédé, UFR Environnement, Département des Sciences de la Terre, Laboratoire des Sciences et Technologies de l’Environnement, BP 150 Daloa, Côte d’Ivoire.
Kouadio Florentin Tani
Université Jean Lorougnon Guédé, UFR Environnement, Département des Sciences de la Terre, Laboratoire des Sciences et Technologies de l’Environnement, BP 150 Daloa, Côte d’Ivoire.
Doua Ivan Morel Dan
Université Jean Lorougnon Guédé, UFR Environnement, Département des Sciences de la Terre, Laboratoire des Sciences et Technologies de l’Environnement, BP 150 Daloa, Côte d’Ivoire.
Kouamelan Serge Kouamelan
Université Felix Houphouët-Boigny, UFR des Sciences de la Terre et des Ressources Minières, Laboratoire de Géologie, Ressources Minérales et Energétiques, 22 BP 582 Abidjan 22, Côte d’Ivoire.
*Author to whom correspondence should be addressed.
Abstract
Extensive regolith cover and supergene weathering complicate the interpretation of gold anomalies in Birimian terrains of West Africa. This study integrates Landsat 9 Operational Land Imager (OLI) imagery, a 30 m Shuttle Radar Topography Mission digital elevation model (SRTM-DEM), field observations and soil geochemistry to map regolith regimes across a 564 km² area of Dabakala, Côte d’Ivoire. The B4/B2 and B6/B7 band ratios were used to examine iron-oxide- and clay-related spectral responses, while selective principal component analysis, Sobel directional filtering and geomorphological interpretation supported structural and regolith mapping. The B4/B2 index ranged from approximately 1.83 to 2.53, and B6/B7 ranged from 1.19 to 1.90. Three regolith regimes were distinguished: residual (approximately 65%), depositional (20%) and erosional (15%). Analysis of 498 extracted lineaments identified 121 structures in the 0°–30° orientation class and 106 in the 30°–60° class. The residual regime is widespread across northern and eastern sectors and shows a spatial association with structurally influenced gold anomalies. Erosional environments can redistribute weathered material, whereas depositional lowlands may contain transported geochemical signals displaced from their bedrock sources. The combined spectral, morphological, structural and geochemical interpretation provides a practical basis for distinguishing potentially local from redistributed anomalies and selecting areas for follow-up exploration. The findings support considering regolith regimes alongside geological structure when evaluating surface anomalies, rather than regarding individual spectral responses as direct evidence of mineralised bedrock.
Keywords: Landsat 9 OLI, SRTM-DEM, regolith mapping, Dabakala, Birimian terrains, gold exploration, principal component analysis, spectral band ratios, structural lineaments, geochemical anomalies