Abstract:The structural order of Cretaceous-Tertiary kaolins of the Douala Sub-Basin in Cameroon was determined in this study. This was achieved using Fourier Transform Infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) on the Bomkoul, Dibamba, Ediki, Logbaba, Missole and Yatchika kaolins. Transmittance spectra of 20 samples were recorded in the mid-infrared regions (MIR). Results show that most of the kaolins had the four distinguishable bands in the hydroxyl (OH) stretching region, though the second transmittance band (3670 cm −1 ) had low intensities. The hydroxyl stretching of water bands (3457 and 3442 cm −1 for KGa-1b and KGa-2, respectively) were mainly observed in all Logbaba samples at 3443 cm −1 and 3445 cm −1 . The two bands reflecting OH deformation of inner-surface hydroxyl and inner hydroxyl groups (937 and 915 cm −1 ) were quite visible in the Bomkoul, Dibamba, Logbaba and Missole II samples; slightly visible in all Yatchika and two of the Ediki; and not visible in Missole I and one of the Ediki samples. Therefore, based on the empirical classification of the degree of order of kaolinite, 10 of the studied samples had ordered structures. Three displayed partially ordered structures; four had poorly ordered structures, and three exhibited disordered structures. This study revealed that kaolins from Dibamba, Logbaba and Missole II in the Douala SubBasin had the best crystallinity, which is one of the important characteristics needed for industrial applications.

Large quantities of earth materials are consumed daily in Mashau Village; nonetheless, this practice had not been studied. Furthermore, the motivations for this geophagic behaviour in the study area were unclear. Thus, questionnaires were distributed to 200 participants in the study area with the aim of generating data on the motivations of and potential medical conditions associated to this practice. About 91% of the participants were geophagists, of which 98.5% were female. Craving was found to be the main reason (73.9%) why people of the Mashau communities consume soil. The majority of the geophagists in Mashau craved for the soil upon seeing it (31.2%), during pregnancy (22.5%) and when experiencing sleeplessness (21%). About 60% of the geophagists had chronic illnesses, and they were diagnosed with headaches (31.6%), low haemoglobin level (29.9%), constipation (18.8%), iron deficiency (12.0%) and high blood pressure (7.7%). There is a concern that the soil from the study area may be adversely affecting individuals ingesting these soils. Since females mostly reported practicing geophagia, counselling and education of women and girls would be a useful public health measure. Soil characterisation and beneficiation for healthy geophagic practices should also be carried out at Mashau Village.

This study assessed the mineralogical and geochemical characteristics of geophagic clays sold in some markets in Cameroon to ascertain their provenance, contamination status and human health risk. To achieve this, 40 samples from 13 markets in Cameroon were purchased and analysed using X-ray diffractometry, X-ray fluorescence and laser ablation inductively coupled plasma mass spectrometry for their mineralogy and geochemistry, respectively. The geophagic clays were dominantly made up of kaolinite and quartz. Their chemistry was dominated by SiO2, Al2O3 and LOI with means of 48.76 wt%, 32.12 wt% and 13.93 wt%, respectively. The major, trace and rare earth elements data showed that these geophagic clays were predominantly derived from felsic rocks. The contamination assessment indicated no enrichment of metals from anthropogenic sources, except for Zn in samples from Acacia, Madagascar and Mfoudi markets. The index of geo-accumulation indicated no contamination to moderate contamination of the clays. The non-carcinogenic index values for Fe, Co, Cr, Cu, Ni, Pb and Zn were generally less than 1, suggesting no non-carcinogenic risk exposure to children and adults consuming the geophagic clays from these metals. The carcinogenic risk index (TCR) for Ni and Cr were above 10−6, which implies that children and adults are vulnerable to minimal carcinogenic health risk. The TCR values from Ni posed the highest risk, especially to children consuming clays from some markets.

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: SiO 2 (56.96)>Al 2 O 3 (24.09)>Fe 2 O 3 (3.78)>TiO 2 (1.53)> K 2 O (1.26)> MgO (0.27)>CaO (0.20)>Na 2 O (0.17)>P 2 O 5 (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, Na 2 O, K 2 O and TiO 2 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.

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The aim of the present study was the paleoenvironmental reconstruction of the prevailing environment under which the Lwamondo and Zebediela kaolin deposits were formed. Hence, this study reports deuterium and oxygen stable isotope values and trace and rare earth element concentrations for two samples of kaolin. Upper continental crust-normalised trace-element patterns reveal that large ion lithophile elements and high-field-strength elements are generally depleted in Lwamondo and Zebediela kaolins, whereas transition trace elements are generally enriched in these kaolins. Upper continental crust-normalised rare earth element (REE) patterns show that there is a slight enrichment of heavy REEs (HREEs) compared to light REEs (LREEs) in these kaolins. The δ18O and δD stable isotope values for kaolinite from Lwamondo ranged from 17.4‰ to 19.1‰ and from −54‰ to 84‰, respectively, whereas those values for kaolinite from Zebediela varied from 15.6‰ to 17.7‰ and from −61‰ to –68‰ for δ18O and δD, respectively. The REE patterns and the content of other trace elements indicate ongoing kaolinitisation in the Lwamondo and Zebediela kaolins with minimum mineral sorting. The sources of the kaolins varied from basic to acidic and these were derived from an active margin tectonic setting. Lwamondo kaolin was deposited in an oxic environment whereas Zebediela kaolin was deposited under suboxic/anoxic conditions. Based on the δ18O and δD values of the kaolinite, they formed in a supergene environment at temperatures generally below 40 °C.

The study area, located on the southwestern flank of Mt. Cameroon, is underlain by basalts. The occurrence of groundwater in these rocks has been evaluated in order to determine their potentials as a source of water for a water bottling and soft drink plant. To achieve this, the constant separation traversing (CST) was used and the data qualitatively analyzed to determine the occurrence of fractures as most probable borehole sites. From this analysis, three sites were selected, sites at which a vertical electrical sounding (VES) was done and interpreted. Results obtained show a four layered earth profile model type KHKH, corresponding to a typical weathered/fractured confined aquifer type curve. This profile was later confirmed from borehole information after drilling at three of the selected sites. The comparison of VES data with geological sections is corroborative. A constant rate pumping test was done at rates as well as the investigation of other hydraulic properties. The results obtained for hydraulic properties investigated for all three boreholes reveal that productivity is very good and these results also reveal that at maximum exploitation rates, lowest tolerable drawdown for all three boreholes may not be reached after ten years. Chemical analysis done in-situ and on samples at the laboratory reveal that this water has a better mineralisation compared to other bottled water brands sold on the Cameroon market.