Interprétation des données magnétiques du chapeau de fer de Laachach (Jebilets centrales, Maroc): Implications minières

In the hercynian massif of Central Jebilets (Morocco), outcrop a large number of gossans which sometimes top economical orebodies (Kettara, Draa Sfar, etc.). The present study is devoted to the interpretation of magnetic data covering one of these iron hats, located near of the Laachach village, at about thirty kilometres north-westward of Marrakech. The magnetic map of Laachach highlights several anomalies which coincide with the outcrop of the gossan. Detailed analysis of reduced to the pole data allows us to conclude that these anomalies may be due to submeridian magnetic structures cut by a set of dextral transverse faults. These structures are generally dipping westward but they can be locally sub vertical. The Euler deconvolution of the magnetic data gives moderately deeping solutions (22 to 254 m). The quantitative interpretation of the two principal magnetic anomalies highlighted in the study area lead to better characterising of the deep structure of the Laachach magnetic bodies, that may correspond to massive sulphide occurrences, according to the geological and mining context of the study area. The two modelled bodies constitute priority recognition targets for any mining exploration program to be car ried out on the Laachach site.