The bauxitic region of Sumbi and its surroundings in Central Kongo (DR
Congo) is located in an area corresponding to “bands” of basic rocks made up of
microdolerites, basalts and andesites. The problem of this study is linked to
the similarity of the phenomena that generated the depositional process of
these ferruginous and aluminous formations. The aim of this article is to carry
out a chemical and petrographic study of samples of bauxitic materials from the
Mayedo and Kinzoki regions, with a view to their possible recovery. To this
end, the chemical and petrographic analysis of the weathering formations
outcropping in the study area was carried out using X-ray fluorescence and thin section methods. The latter revealed that
two lithologies were detected in the
healthy rocks: basalts with a mineralogical assemblage of plagioclase crystals, pyroxene microcrystals and oxide
opaques; and dolerites represented by plagioclase crystals, pyroxenes
and a few quartz crystals. X-ray fluorescence
revealed high levels of Al2O3 (32.69%) in the Mayedo zone (MHb1). This visibly gibbsite-rich level corresponds to the zone of friable, homogeneous bauxite with a massive, blood-red
texture, with an estimated gibbsite
percentage of 55.50. The percentage of Fe2O3 is high in
these zones at 42.77%, hence the dark red colour, reflecting a strong zone of
ferruginasation. This horizon contains a high concentration of hematite and
goethite minerals. Highly variable SiO2 contents ranging from 13.48%
to 40.82%. These variations are essentially due to the dissolution of silica by
leaching and resilification.
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