GEOCHEMICAL EVALUATION ON ANTHILL SOILS IN OWO AREA, SOUTHWEST NIGERIA
Abstract
ABSTRACT
This study presents a detailed geochemical investigation of anthill soils from the Owo area in Southwestern Nigeria, aimed at assessing their provenance and paleoweathering implications. Ten anthill soil samples were systematically collected and analyzed using Energy Dispersive X-ray Fluorescence (EDXRF) to determine major and trace element compositions. The anthill soils, formed through termite bioturbation, incorporate materials from various depths of the soil profile, including fragments of the underlying bedrock. This characteristic makes them valuable proxies for geochemical exploration and paleoenvironmental reconstruction. The results reveal moderate silicon dioxide (SiO₂: 49.86–54.92 wt.%) and high aluminum oxide (Al₂O₃: 21.00–25.02 wt.%) contents, suggesting derivation from felsic to intermediate source rocks such as granite, gneiss, and mica schist. Trace element concentrations, including elevated levels of thorium (Th), uranium (U), rubidium (Rb), niobium (Nb), and barium (Ba), further support the felsic provenance, aligning with the lithological characteristics of the Nigerian Basement Complex. Weathering indices indicate intense chemical weathering in the region: Chemical Index of Alteration (CIA: 90.22–96.84), Chemical Index of Weathering (CIW: 93.06–98.56), Plagioclase Index of Alteration (PIA: 92.91–98.53), and Mineralogical Index of Alteration (MIA: 91.52–98.09). These values are indicative of advanced feldspar alteration under humid tropical conditions, resulting in the formation of clay minerals such as kaolinite and gibbsite. Low K₂O and Na₂O concentrations, along with low Index of Compositional Variability (ICV < 1), further confirm the maturity and high leaching status of the sediments. Correlation analysis among major oxides shows distinct geochemical trends, including inverse relationships between MgO and SiO₂, and Al₂O₃ and SiO₂, reflecting mineral sorting, redox conditions, and intense chemical transformation. Elevated Fe₂O₃ and TiO₂ levels point to the presence of weathering-resistant heavy minerals and possible oxidizing depositional environments. Ternary plots (A–CN–K and A–CNK–FM) highlight significant clustering towards the aluminum apex,
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