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Products of weathering usually clay minerals, are commonly characterized through mineralogical, chemical and geochemical analysis, emphasizing their implications in industrial applications, initiation of landslides and their impact on surface water geochemistry. In this study the vertical variations in textural characteristics and clay mineral type within weathered profiles in the Sabga area were investigated. Two exposed weathered profiles were logged from bed rock to topsoil and each horizon was sampled separately. Granulometric analysis on the samples indicated mixtures of clay, silt and sand size particles in all horizons. Smectite and kaolinite were identified by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The two logs show that the lower horizons display whitish colors with fine laminations, middle horizons are brownish and the upper horizons display dark brown colors. Graphic mean values for both sections gave values that range between 2.02 - 3.7f with an average standard deviation value of 1.9f, indicating that the grains are poorly sorted sand, silt and clay. SEM micrographs show laths of smectite in the lower horizons, flakes of kaolinite and laths of smectites in the middle horizons while the upper horizons show flakes of kaolinite with microlites of quartz + feldspars. XRD patterns show broad basal reflections for kaolinite at 2θ 36.8° (3.15 ?), smectite at 2θ 33.5° (3.34 ?), both contaminated with quartz at 2θ 36.5° (3.32 ?) typical for these minerals.

The Kamo Volcanic Field (KVF), a partly preserved Quaternary volcanic sequence of three small-volume basaltic volcanoes located about 10 km northwest of the Aira caldera in the Kagoshima graben in southwestern Kyushu, Japan. It forms part of the volcanic arc of Japan and consists of the Late Pleistocene Aojiki volcano and two Holocene maars: Sumiyoshiike and Yonemaru. Here, we report the first results of a combined lithostratigraphic and petrogenetic study of these three volcanoes. Eruptive products of Aojiki volcano comprise an initial scoriaceous tephra, a lava flow and scoria fall from the cone. Sumiyoshiike and Yonemaru maar products are mainly scoria fall and pyroclastic surge deposits, which are closely related in time and were principally emplaced by phreatomagmatic explosive eruptions. Major and trace element data of the eruptive products suggest four groups of magmas. Aojiki scoria (G1: SiO2= 50.3-51.4) are the most evolved, followed by Aojiki tephra/lava (G2: SiO2 = 48.1-50.7), while Sumiyoshiike (G3: SiO2 = 47.0-48.5) and Yonemaru (G4: SiO2= 46.3-48.5) are relatively less evolved. These magmas are derived from the same spinel bearing (lithospheric) mantle source previously metasomatized by subducting fluids and might have evolved in independent magma chambers mainly by fractional crystallization and crustal contamination except for G1 magma which may have suffered some associated mixing.

The present study is the first appraisal of regional hydrogeochemical programme for environmental assessment of the mineralized Lom Basin in East Cameroon. Fifty-two streamwater samples were collected and analysed for major cations (Ca2+, Mg2+, Na+, K+) and major anions (HCO3–, F–, Cl–, NO2–, NO3–, Br–, PO43–, SO42–). Calcium and HCO3– were the dominant ions. The chemical facies for the surface water were CaHCO3 and NaHCO3 types indicating a fresh water source. Major ion geochemistry demonstrated the potential to discriminate between natural and anthropogenic origins. Calcium ion, Mg2+, Na+, K+and HCO3– had similar distribution trends reflecting weathering from the parent rocks. Sulphate distribution correlated with the occurrence of sulphide minerals associated with hydrothermal gold mineralization in the area while the distribution patterns of NO3–and Cl– reflected pollution from domestic activities within the municipality. Overall, the chemistry of stream water in the Lom Basin is mainly controlled by silicate weathering with only minor anthropogenic influence. This study forms an analogue for hydrogeochemical mapping in other mineralized terrains in Cameroon.