The World’s Largest Fouta Djallon–Mandingo Bauxite Province (West Africa): Part 2. The Effect of Parent Rock Composition on the Abundance and Quality of Bauxites

— The general trends and specific features of the effect of the parent rock lithology on the geographic distribution and quality of bauxites in the Fouta Djallon–Mandingo bauxite province are discussed. The parent rock lithology affects bauxite abundance and quality both at the regional (areal) and local scale. More than 99% bauxite deposits and occurrences are confined to structural–stratigraphic complexes of the platform cover. The spatial distribution of poor- and medium-quality bauxites is predominantly controlled by clayey parent rocks (mudstones, siltstones, and silty mudstones), as well as dolerites, Konga diabases, and sometimes gabbro–dolerites, which occur regionally. Local lithological control is provided by local reworked accumulations of bauxite-bearing lateritic mantle destruction products. The main factors of favorability degree of the aluminosilicate parent substratum are its iron index (Al 2 O 3 /Fe 2 O 3 ) and the quantity and size of quartz grains. Other regional lithological factors are Middle Miocene freshwater sediments of the Sangaredi Group, their epigenetic alteration together with the underlying rocks, and subsequent laterization, producing high- and premium-quality sedimentary–lateritic and infiltration–metasomatic bauxites.