Geochemistry of Major Elemental Oxides on a Lithosequence in Kaduna State Nigeria

Geochemistry of major elemental oxides of soils developed on basement complex rocks namely: older granite (OG), migmatite gneiss (MG), mica schist (MS) and quartzites (QZ) was studied in Kaduna State. The contents of major elemental oxides were similar in the soils, except for K2O and TiO2 that varied significantly between the soils. Relative weathering intensity showed significant variation in all the major elemental oxides’ relative retention in the soils. Thus elemental concentrations and retention were attributed to inheritance from parent rocks and differential weathering (pedogenic age). Two main behavioural groups exist for the major elemental oxides in the soils due to relative accumulation and loss of concentration of elemental oxides. Calcium group (Ca, Si, K and Mn) exhibited loss through leaching and desilication, whereas, Fe group (Fe, Al and Ti) accumulated through illuviation and recrystallization. Relative retention of CaO compared to other elemental oxides was found to be an indicator of pedogenic order in comparing soils developed on different basement complex rocks as parent materials. Several features of the soils such as Si/C ratio, mineral constituents, relative weathering intensity (loss/ gain) and CaO relative retention all indicated order of weather intensity (pedogenic age) as MG > QZ ≥ OG > MS. Sequential order of dominantly retained elemental oxides reflected key constituent of dominant minerals in the different soils.