Mapping mafic dyke swarms, structural features, and hydrothermal alteration zones in Atar, Ahmeyim and Chami areas (Reguibat Shield, Northern Mauritania) using high-resolution aeromagnetic and gamma-ray spectrometry data

Abstract : Analysis of an airborne geophysical data covering the Tasiast-Tijirit Terrane in the western part of the ReguibatShield (including the 1:200,000 geological sheets of Chami, Ahmeyim and Atar), provided an improved mappingof mafic dyke swarms, structural features, and hydrothermal alteration zones. It also extended the mapping intoextensive areas covered by sand. A low-altitude (100 m) airborne survey collected high-resolution magnetic andgamma-ray spectrometry data. The magnetic data were enhanced using techniques such as reduction to the pole,analytic signal andfirst vertical derivative, and revealed dyke swarms with trends of NNE-SSW to NE-SW, NW-SEto WNW-ESE and E-W. The use of the Euler deconvolution method provided constraints on the continuity andthe depth of magnetic sources.Gamma-ray spectrometry which maps the three main radioactive elements, i.e. potassium, uranium andthorium helped discriminate lithological units of the Archean basement, notably felsic intrusions. The radio-metric data also helped delineate potassic alteration zones, which could testify to hydrothermal activities ofrelevance to sulfide mineralisation.