Electromagnetic survey to constraints ore mining exploration in the eastern Anti-Atlas belt (case of Imiter inlier, Morocco):Application of frequency electromagnetic helicopter-borne method

摘要

The present work is based on data of a geophysical survey of the Imiter inlier that was carried out by DIGHEM(v) multi-coil, multi-frequency helicopter-borne electromagnetic system. Its main goals are (i) to interpret the results of this survey in light of regional geological settings; (ii) to define how geological factors controlled mineralization in the world-class Imiter silver mine, which is located in the central western part of the survey area; (iii) to correlate the modalities of this control with the electromagnetic response observed in the Imiter mine district; and (iv) to extend the model thus obtained to the whole study area in view of locating other potentially mineralized ore bodies.The obtained results showed that the Imiter mine district is covered by two important electromagnetic anomalies and three conductor axes, which are interpreted as directly reflecting the presence of metallic deposits in the subsurface. The most intense of these anomalies (B2) is located in the northern bloc of the main Imiter Fault, in an area which is highly fractured by secondary faults, is covered by Ediacaran volcanic and has never been mined. All mineralized bodies exploited so far are localized in the southern block of this important fault and are all essentially hosted by the Cryogenian black shales. Since we have established that there is a direct relation between faulting and mineralization, and that the intensity of the electromagnetic anomaly is directly related to ore concentration in hosted rocks; we conclude that the area covered by the electromagnetic anomaly B2 would be even more interesting to explore that the southern bloc presently in exploitation. Extending these results to the rest of the survey area, it was found that two other areas to the south-east of the Imiter mine district are also two potentially mineralized zones meriting future exploration.