The Hajar prospect is located in the Guemassa Paleozoic massif, about 30 km southwest of Marrakesh, Morocco. Visean volcano‐sedimentary formations are present in this massif and in the Jebilets massif north of Marrakesh. In these formations, syngenetic massive sulfides occur, and one of these bodies, Kettara in the Jebilets, has been partially mined. Using the Kettara magnetic anomaly to establish the magnetization parameters, we performed a preliminary interpretation of the Hajar anomaly. Our 2.5-D model determined the depth of the structure to be about 150 to 200 m below the surface. This relatively shallow depth was a decisive factor in siting a reconnaissance drillhole, which encountered massive sulfides between 158 and 276 m. After completing a systematic gravity and magnetic survey, 3-D magnetic modeling was attempted, constrained by the results of four drillholes. Now that more than 20 holes have been drilled, this magnetic model still conforms to the newly revealed geology. Unfortunately, it was not possible to extract useful information concerning the orebody from modeling and interpreting the gravity data. The gravity response is masked by disturbances such as faults and variations in depth and nature of the Visean basement. The discovery of the Hajar deposit shows that magnetic investigations, improved by pertinent modeling techniques, can be used at various stages of exploration to help recognize and define massive sulfide bodies.
Three-dimensional gravity and magnetic modeling of crustal indentation and wedging in the western Pyrenees-Cantabrian Mountains
