Statistical Analysis Of Reconnaissance Geochemical Data From Orle District, Southwestern Nigeria

Abstract

The results of concentrations of 22 trace elements, namely, Au, Ag, As, Pb, Zn, Cu, Co, Mo, Hg, Sb, Tl, Sc, Cr, Ni, La, W, V, U, Th, Bi, Sr and Ga in 56 stream sediment samples collected from Orle drainage system were subjected to univariate and multivariate statistical analyses. The univariate methods used include frequency distribution and cumulative probability plots, while the multivariate methods used are correlation and factor analyses.
Frequency distribution plots showed that the elements are either log-normally or near log-normally distributed at 95 % confidence level. Cumulative probability plots of the elements show that the concentrations of Cu, Pb, Zn, Co, Sc, Ni, Cr and Ga consisted of one population, whereas those of Au, Hg, Mo, As, La, W, U, Th, Bi, Sr, Tl and V were made up of two populations. Pearson correlation coefficients show that strong correlations exist among Cu-Pb-Zn-Mo-As-Sc-Ni-Bi-V, Au-Hg-Ni-Co-Cu-V, Co-Ni-Cr-Sr-Au, W-As-Mo-Bi, La-Cu-Pb-Zn-Sc-Bi-Ga-Tl, U-Th-La, Co-Tl-V-Ga-Cu-Zn-As-Sc-Ni-Cr, Mo-Ga-V and Hg-Cu-ZnNi-V-Mo-Co. Five factors, whose structures were similar to the subjective groupings derived from the correlation matrix, were derived from R-mode factor analysis and have been interpreted in terms of underlying rock lithology, potential mineralization, and physico-chemical conditions in the environment.
A high possibility of occurrence of mineralization of different metals exists in some of the Precambrian basement complex rocks that underlie the study area. The possible mineral potential of the area include base metals (Pb, Zn, Cu, Mo, etc.), Au-Sb-Hg and U-Th-La mineralization. Some elemental associations reflect basement geology and the likelihood of occurrence of the possible mineralization with specific rocks types. Gold and base metal mineralization is likely to occur within the mafic-ultramafic rocks, most probably amphibolite, and U-Th-La mineralization is likely to occur within the felsic rocks, most probably pegmatite in this area.


Keywords: Reconnaissance, stream sediment, trace elements, statistical analysis, mineralization.

Global Journal of Geological Sciences Vol. 6 (1) 2008: pp. 63-74