Combined analysis of helicopter-borne magnetic and stream sediment geochemical data around an ancient Tiouit gold mine (Eastern Anti-Atlas, Morocco): Geological and mining interpretations

Abstract

This study focuses on the Tiouit mining area, which is reputed for its gold mineralization associated with sulfides and hematite hosted in quartz veins. The composition of granitoid hosts and their tectonic structuring, guided by tectonic accidents, NE-SW, and E-W directions related to the late Pan-African phase, are metallotects for gold exploration. Besides, the physical properties of its mineralogical associations and their setting in the mining area of Tiouit and other mining sites in the Jbel Saghro massif are characterized by a strong contrast of magnetization that can be mapped by the magnetic method. This latter is supplemented by a geochemical exploration of 632 samples of stream sediment to emphasize the geochemical anomalies associated with magnetic anomalies and lineaments within which sources may generally not outcrop on the surface.The processing and interpretation of the magnetic data covering the Tiouit area have highlighted several zones with promising prospects from a mining viewpoint. The residual magnetic map reduced to the pole reveals close connections between high amplitude anomalies and Precambrian age formations, represented by diorites, granites, rhyolites, and ignimbrites. Those of low amplitude is linked to Paleozoic coverage marked by conglomerates, sandstones, dolomites, and argillites. The vertical gradient allowed a better understanding of Triassic volcanism, manifested by magmatic injections in the form of microgabbroic dyke with a NE-SW direction.From a mining point of view, a detailed mapping of the main magnetic axes has been carried out, and which are correlated with faults of E-W, NNW-SSE, NNE- SSW, and ENE-WSW directions, corresponding to highly crushed and hematized areas. Moreover, the magnetic contacts obtained by Euler's deconvolution show a dominance of the NE-SW to E-W directions, reflecting the structural and geological context of Tiouit, which is dominated by Hercynian faults characterized by a rooting exceeding 1600 m. The examination of geochemical anomaly maps in Arsenic, Zinc, and Iron shows very high levels in the order of 136 ppm, 392 ppm, and 10.63 %, respectively.The compilation of the various results and their calibrations with geological data makes it possible to highlight 7 main potential mining areas, which could be considered promising. Two of these areas are located in the Northern and Southern peripheries of the Tiouit gold mine.