Magnetic and Radiometric Signatures of Carbonatite Complexes from the Western Reguibat Alkaline Province (West African Craton, Moroccan Sahara): Tectonic and Weathering Implications

The Western Reguibat Alkaline Province comprises rare earth elements (REE) and niobium (Nb)-bearing carbonatites complexes of different ages hosted by the peri-cratonic Ouled Dlim Massif located in the southernmost regions of the Moroccan Sahara, adjacent to the West African Craton. This alkaline province includes the Cretaceous Twihinat-Lamlaga-Lahjeyra carbonatite complexes (TC-LmC-LhC) that have intruded the Massif during the Middle Cretaceous Peri-Atlantic Alkaline Pulse. Their emplacement is argued to be controlled by tectonics, though no structural evidences were presented due to recent sediments covering them. In this study, we aim to explain their emplacement control and assess the weathering processes they underwent based on the interpretation of airborne magnetic and radiometric data. Magnetic data reveal that the TC-LmC-LhC aligns with NNE-trending magnetic lineaments, which are interpreted as dikes related to the Central Atlantic Magmatic Province. This alignment is explained by tectonic reactivation of these NNE-trending dikes by a N-trending shortening during the Lower-Middle Cretaceous, leading to opening of pull-apart structures via a strike-slip motion, creating areas of emplacement for the studied carbonatite complexes. Radiometric data indicate a widespread weathering across the entire western margin of the Ouled Dlim Massif and its associated carbonatite complexes, primarily controlled by the hydrographic network. Our findings suggest that major streams might be promising targets for REE-Nb exploration, given their potential to contain substantial amounts of placer-type REE-Nb deposits.