Origin, mineralogical distribution, and industrial suitability of clay-rich soils in the semi-arid zone of Cameroon

• Clayey materials are composed of kaolinite, illite and smectite. • Mineral contents show spatial variation but not significantly with depth. • Grain size distribution is dominated by sand and silt fractions. • Clay minerals originate from inheritance, neoformation and transformation processes. • Textural composition of clay materials is suitable for building products. This study discusses the distribution of clay minerals and their origins. Fieldwork was conducted in the semi-arid zone of Cameroon. Fifty-six (56) soil samples were collected and were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), simultaneous thermal analysis (STA), laser granulometry, Atterberg limits and organic matter. Statistical interpretations were used to evaluate the spatial and vertical variation and factors affecting the distribution of minerals. The studied clayey materials present moderate organic matter content (2.64 ± 0.97%), and are yellowish brown to brownish yellow dominated by a loamy texture. The soil structure is polyhedral but becomes massive at the base of soil profiles with mean proportions of clay, silt and sand fractions respectively of 8 ± 3%, 62 ± 15% and 29 ± 17%. Non-clay minerals as quartz (57 ± 19%), potassium feldspar (13 ± 10%) and plagioclase (10 ± 11%) dominate the mineralogical content. Kaolinite (13 ± 8%), illite (3 ± 2%) and smectite (3 ± 4%) are clay minerals identified. Kaolinite might be formed from the weathering of feldspars in a warm and humid climate toward the lower latitude. In the higher latitudes, higher temperatures favour the leaching of silica and the transformation of 2/1 clay minerals into kaolinite. The abundance of primary minerals, reflects a low degree of weathering specific to the climatic conditions of the study area, characterized by low precipitation and high temperatures. Regarding clay mineral contents, significant differences are noted between sites. The high spatial variability observed in the mineral contents is consistent with the variable weathering conditions. No significant difference with depth regarding the mineral content was observed, testifying a homogeneous weathering factor and pedogenetic mechanisms. Clay mineral content and particle size