Alteration, Chemical Processes, and Parent Rocks of Haléo-Danielle Plateau Bauxite, Adamawa–Cameroon

Abstract

The Haleo-Danielle Plateau bauxite deposit forms the largest part of the 15 km long Minim-Martap Bauxite ore district in the Adamawa Region of Cameroon. The plateau is covered with thin Upper Pleistocene to Holocene alluvial layer. It covers by laterites and bauxites formed on Tertiary-Quaternary basalts. Gibbsite and boehmite are the aluminum oxide found in the bauxite, while goethite is the main oxyhydroxide iron mineral. Bauxite rock samples from the plateau were collected and investigated with the XRF technique for their chemical composition and parent rocks. Chemical investigation reveals average concentration of the major ore components as: Al2O3 (43.73%), Fe2O3 (24.53%), SiO2 (2.12%), and TiO2 (3.54%). Abundant trace and rare elements include Zr (667.25 ppm), V (446.4 ppm), Ce (107.93 ppm), Sr (98.46 ppm), Nb (92.1 ppm), La (58.05 ppm), Ga (55.3 ppm), Ba (53.53 ppm), Nd (37.96 ppm), and ΣREE (245.8%). Calculations of the degree of chemical weathering (Ruxton Ratio) and geochemical coefficient (CIA) indicate that plateau rocks were subjected to intensive weathering, which led to the formation of industrial bauxite deposits. According to the results of processing the chemical composition of bauxites using three independent classification systems, plateau deposits can be classified as ferruginous bauxites. Parent rocks investigation indicates that bauxite was formed due to the decomposition of magnesium-ferrous andesite-basalts under conditions with a near neutral redox potential.