Gold Potential of the Pan African Trans-Sahara Belt and Prospect for Further Exploration

Abstract The Trans-Sahara belt is one of the mobile belts formed during the Pan African orogeny that spans between ∼870 to∼550 Ma. The Trans-Sahara belt was formed as result of the collision between the converging West African craton, Congo craton, and the Sahara metacraton continental blocks. The belt, with major exposure in the Tuareg and Dahomeyan, consists of pre-Neoproterozoic basement which were thoroughly reworked during the Pan African orogeny, Neoproterozoic metasedimentary and metavolcanics, and syn-tectonic Pan African granitoids which intrude Archean and Paleoproterozoic rocks. The Trans-Sahara belt, though less endowed when compared to older Archean orogenic greenstone belts in terms of gold mineralization, displays reasonable gold mineralization in both the Tuareg shield and Dahomeyan shield with about 160 tons of gold reported so far across the belt. Mineralization is associated with varying lithologies across the belt and appears to have been regionally controlled by N-S trending Pan African shear zones. In the Tuareg shield, mineralized quartz veins are associated with syntectonic granitoids, mylonitic and meta-volcanosedimentary rocks. Conversely, gold mineralization is only associated with metasediments and migmatite gneisses in the Dahomeyan shield, with occurrences largely confined to metasedimentary sequence in Benin and Nigeria. The prevailing tropical climate in the Dahomeyan shield has also facilitated secondary concentration of gold in alluvial bed of river draining supracrustal rocks hosting primary gold mineralizations. The occurrence of primary mineralization in variety of rocks across the Tuareg and Dahomeyan shield and widespread occurrence of placer gold deposits in the Dahomeyan shield justifies the need for further exploration and evaluation of mineralization potential. The emplacement of gold, which occur between 535-500 Ma is controlled by N-S trending Pan African mega-shear zones. However, at the district scale, it is evident that the Pan African mega-shear zones are not the only important structures. Lower order faults and shear zones are important structures to consider in exploration targeting. Exploration particularly at district-scale might benefit from GIS-based prospectivity mapping, considering the mineralizations are generally structural controlled. GIS-based prospectivity mapping which integrates multifaceted digital data sets can provide a foundation for vectoring towards explorations targets in many mineralized districts within the Trans-Sahara belt.