Mineral and elemental distribution in soils formed on the River Niger floodplain, eastern Nigeria

Studies of mineral distribution in soils provide vital information for understanding the genesis of the soil. We studied the soils formed on the floodplain of the River Niger to determine the occurrence, distribution, and weathering transformations of minerals in a soil chronosequence in eastern Nigeria. Five soil profiles representing 5 depositional stages were studied. The soils have aquic moisture regimes and an isohyperthermic temperature regime by Soil Taxonomy. Gleysation due to poor drainage is very dominant. The soils are low in pH, organic matter, and exchangeable cations. Plinthisation and ferralitisation resulting in high values of [Fe.sub.2][O.sub.3] and [Al.sub.2][O.sub.3] were observed in the coarse sand, while in the fine sand fractions, quartz and feldspar grains have accumulated with mica being next in abundance. The occurrence of expansible minerals and kaolinite in the clay fractions is as a result of transformation of mica and feldspars giving rise to these minerals. We postulate that the origin and abundance of [K.sub.2]O and MgO in the clay fractions were from the breakdown of the structural units of the expansible minerals, micas and feldspars. Illite undergoes a transformation process to expansible minerals, while kaolinitisation is the major process in the clay fractions. Principal component analysis shows that 23 mineral variables which relate with kaolinite and other silicate clays can be reduced to 5 principal components. Additional keywords: feldspars, mineral transformation, principal component, expansible clay minerals, Fe-precipitation.
Introduction Studies on the mineral and elemental distribution within soils provide vital information for the assessment of their genesis and behaviour. Teveldal et al. (1990) reported that, in some soils, [...]