Soil Geochemical Survey of Eruku and Environs

Abstract

The study area, Eruku and its environs, is located approximately 124km east of Ilorin and lies within Osi migmatite gneiss complex to the west and Egbe schist belt in the east. The area falls within longitudes 5⁰23’E and 5⁰30’E and latitudes 8⁰05’N and 8⁰13’N represented in Osi sheet 224SE . Detailed mapping and sampling of rocks and soils were carried out in this area. The soil samples were collected from the B horizon at a depth of 20cm-25cm. Twenty-five selected soil samples were analyzed for trace and rare earth elemental concentration using ICP, INAA, MS and ICP-MS analytical methods. The result of the geochemical analysis was thereafter subjected to statistical analysis and isograde plotting.

The multivariate statistical analysis shows a total of eleven factor groups. Seven of the factor groups are of importance in the study area with five related to mineralization. The correlation coefficients of some selected elements show that Be is strongly correlated with Rb, Ga, Sn and Ta while Nb is strongly correlated with Ta. The area and bar charts show that the highest concentrations of Be, Nb, Sn and Ta are in the northeastern part of the study area. The isograde plots show that almost all the elements have their peaks in the northeastern part of the study area.

From the integration of geochemical and multivariate analyses, and isograde plotting, the study area has anomalous concentration of cassiterite-tantalite-columbite minerals. These mineralizations are hosted by pegmatites that intrude the country rocks in the study area. This establishes similarity in terms of host rocks and mineralization type of the Eruku area compared to Egbe.

Keywords: Mineralization, soils, geochemical data, cluster groups, isograde plotting, Eruku.