Factor Analysis of Stream Sediment Geochemical Data from Onyami Drainage System, Southwestern Nigeria

摘要

An R-mode quartimax rotated factor matrix was applied to a statistical study of stream sediment geochemical data from Onyami drainage system within Igarra area in southwestern Nigeria. The area is underlain by the gneiss-migmatite complex, the low grade supracrustal schist belts and the Pan-African granitoids which intruded both the gneiss-migmatite complex and the supracrustal units. A four-factor model which accounts for 76.49% of the total variance of the stream sediment geochemical data was established. Factor 1 (Sc-Ga-V-La-Ni-Co-Ag-Bi-Sr-Pb-Hf-Nb-Cu-Cr) probably defines an underlying complex granitic lithology with contributions from mafic and ultramafic rocks. Factor 2 (Th-U) is attributable to a granitic lithology which reflects the parent rock as the influencing factor. Factor 3 (Mo-Nb-Zn) appears to define a minor sulphide mineralization associated with granitic rocks that intruded the schists and granite gneiss in the area. Factor 4 indicates the occurrence of gold and its pathfinder element, As, in the study area. This inference is consistent with the reported occurrence and mining of gold during the colonial era in Dagbala, which lies within the Onyami river catchment area.