Application of electrical resistivity and electromagnetic methods to explore mineralized veins (copper and barite) in Tinejdad area (south-eastern Morocco)

Abstract

The electromagnetic method by the measure of the angle of inclination of wide axis and the ellipticity of the ellipse of polarization can be used to prospect the maximum field and to validate the electric data. this technique is known for its speed and ease of implementation. The VLF electromagnetic results show two types of Karous-Hjelt anomalies: i) positive anomalies with an apparent current density ranging between 30 and 40%, indicating that the explored areas are affected by a network of faults. In the Paleozoic sandstone formations, the faults are generally oriented in NE- SW direction, while in the Neoproterozoic pyroclastic formations, are oriented in NW-SE direction. ii) negative anomalies with an apparent current density varying between -30 and -40% corresponding to resistant zones probably associated with mineralized veins oriented in the same direction of the fractured zones. The VLF measurements confirm the anomalies obtained by the electrical resistivity. Thus, the resistant zones correspond to the passage of mineralized veins and the conductive zones are correlated with the fractured areas. The coupling of electromagnetic and electrical resistivity methods suggest that the mineralization is controlled by three parameters (i) Structural: the mineralization is examined by two fault systems, the NW-SE family in the Precambrian basement (Banigounssa site) and the NE -SW family in the Paleozoic blanket (Gardmıyt area), (ii) Lithological: the mineralization is hosted by the Paleozoic detrital and the Neoproterozoic pyroclastic formations and (iii) Hydrothermal: the explored mineralization is related to two major hydrothermal events; a Pan-African event linked to the late Neoproterozoic extensive phase responsible for the establishment of mineralization within the Precambrian basement, and then a Hercynian event manifested by the remobilization of metals in the structures oriented in NE-SW direction.