Mineralogy and geochemical features of Foumban clay deposits (west Cameroon): genesis and potential applications

Five clay deposits in Foumban, west Cameroon, were studied for their morphological, mineralogical and geochemical properties to determine their suitability for ceramics. The clays were examined with X-ray diffraction, X-ray fluorescence, thermal gravimetric analysis and Fourier-transform infrared spectroscopy. Field studies showed that a homogeneous clayey layer occurs at the upper part of the laterite cover of the interfluves, while the valleys are occupied by a clayey heterogeneous hydromorphic material. The clays are composed of kaolinite, illite, smectite and chlorite, associated with quartz, K-feldspars, plagioclase, goethite, traces of rutile and hematite. Geochemical analyses of these samples showa relatively large amount of SiO2 (45-71%), Al2O3 (14-31%) and relatively little Fe2O3 (up to 11%), suggesting weathering of mainly granitic and rhyolitic parent rocks. The majority of these clays may be used in the production of structural ceramics such as bricks (refractory or not) and tiles. The relatively high proportion of the alkalis (K2O + Na2O; 6-8%) in some samples from Marom and Njindare areas might be responsible for the low firing temperatures. The abundance of smectite limits the application of some Koutaba and Marom clays for structural ceramics, while the high Fe2O3 contents (>8%) in some Bangourain clays indicate that some pre-treatment might be necessary prior to use.