Geochemistry of Selected Kaolins from Cameroon and Nigeria

Abstract

The geochemical characteristics of selected kaolins from Cameroon and Nigeria are presented, with an attempt to elucidate on their possible industrial applications by comparing them to world-known kaolin deposits. Major oxides concentrations were subjected to factor analyses in interpreting their relationships. Geochemical indices, including chemical index of alteration (CIA), chemical index of weathering (CIW) and the index of compositional variability (ICV) were computed and plotted on binary and ternary diagrams to determine the intensity of weathering of the kaolins and discriminate their different source rock types. Kaolinite was the major phase, followed by quartz, illite and goethite as minor phases. Minerals in trace phases included smectite, anatase, muscovite, gibbsite, microcline, palygorskite and calcite. Mean abundances of major oxides in wt% were: SiO2 (56.96)>Al2O3 (24.09)>Fe2O3 (3.78)>TiO2 (1.53)> K2O (1.26)> MgO (0.27)>CaO (0.20)>Na2O (0.17)>P2O5 (0.05)>MnO (0.04). The CIW versus CIA and ICV versus CIA plots showed that most of the kaolins clearly depicted extreme silicate weathering. The current applications of kaolins from Cameroon and Nigeria include ceramics and manufacturing of bricks and tiles. Low MgO, CaO, Na2O, K2O and TiO2 further position the kaolins for pharmaceutics, cosmetics, rubber and plastic applications. Thus, the studied kaolins have the potential to contribute to improved economic development of these countries.

Keywords

• chemical index of alteration
• chemical index of weathering
• kaolinite
• major oxides