Prospect of metallic mineralization in Gbongan area of southwestern, Nigeria

Abstract

Thirty-six stream sediment samples were collected from an area of approximately two hundred and seventy three square kilometers, around Gbongan, delineated by longitude 40°20² and 4°30² and latitude 7°22² and 7°30². The objective was to determine the distribution pattern of some heavy metals in the area, with a view to discovering any indication of metallic mineralization. The samples were air-dried and the minus 80 mesh fraction analysed for Au, Ta, Co, Sn, Fe, Ni, Mn, Cr, Hg, Pb, and Cu, after hot HCIO₄/HNO₃ (7:3) acids digestion, using the Atomic Absorption Spectrophotometer. Both simple and R-mode factor statistical techniques were employed in data interpretation. The distribution maps of the elements were also plotted. The results of the simple statistical analysis showed that all the elements except Cr and Pb were log- normally distributed and revealed both background and anomalous populations, in varying proportions of between 10% and 90%. The Pearson correlation study shows positive correlation between Fe/ Au, Pb/ Au, Ni/Co, Mn/Co, Ni/Fe, Fe/Cu, Mn/Ni, Pb/Zn, Hg/Cu, and Pb/Hg for example, with 'r' values ranging between 0.33 and 0.92. All these positive correlations are significant at 95% and above confidence level. The R - mode factor analysis, of the elements, identified three factors, which accounted for 75% of data variability. The factors are Fe-Ni-Mn-PbCu-Co-Zn-Cr-Au, Hg Vs Ta, and Sn. From the result of the statistical analysis and the distribution maps, it is deduced that the dominant factor controlling metal dispersion in the surfacial environment of the study area is lithology. There are also subtle but notable contributions from environmental and mineralization factors.