Gravity and magnetic investigations in the Haour Basin, Morocco. Interpretation and mining implications
Résumé
The Marrakech region is known for its significant mining potential concealed by the Hercynian basement. In order to extend the exploration of this basement beyond its outcrops in the Jebilets and Guemassa massifs, we used magnetic and gravity data from a sub-area in the Haouz basin. Our methodology in this study consists of processing the data, so as to highlight the buried geological contacts and to reveal their dips. The study of the geological contacts is ensured by the upward continuation processing of the residual gravity map at various altitudes, followed by the determination of the horizontal gradient maxima for each level. The progressive migration of these maxima while increasing the upward continuation altitude indicates the dip direction. The structures deduced from gravity are superimposed on the magnetic map in order to emphasize their possible association with magnetic sources. Comparison between gravity anomalies and local geology shows that these anomalies are mainly caused by basement topography undulations. Moreover, lows coincide with granite and thick sedimentary depressions while highs coincide with basement outcrops. The local maxima of the horizontal gradient of the residual gravity data and its upward continuation at various altitudes define a field of features, organized into groups oriented both NESW and NWSE, which correspond to the regional Hercynian structures. Moreover, the main highlighted lineaments coincide perfectly with known fractures such as the North-Atlas and the Guemassa faults whose dip and direction are well documented. These detected features allow us to complete and enrich the structural map of the Haouz basin. A joint detailed analysis of the mapped gravity contacts and the magnetic data was carried out, through the use of Magnetic and Gravity Euler Trends in terms of depth and rooting, taking into account the local geology, to identify potential structures for mining exploration.