Silas Dada¹, Onema Adojoh^2,, Adisa Rahaman³, Ibrahim Garba⁴

Whole rock and mineral extracts from Nigerian goldfields of late Proterozoic age are significantly more radiogenic than those from the much younger Mesozoic lead-zinc mineralization in the Benue Trough, their common formation by hydrothermal processes notwithstanding. Their marked contrasts in lead isotope compositions can be attributed to differences in source reservoirs, structural settings and geological history rather than their age of mineralization. The Mesozoic sulphides have a remarkable uniformly unradiogenic composition for their age, placing the deposits in the lower crustal geotectonic environment that indicate a source of much lower µ. In contrast, mineral extracts from the southwestern and northwestern Nigeria gold deposits show increasingly radiogenic composition and plot in the mixed and upper crustal geotectonic fields respectively, typical of sources enriched in U/Pb and Th/Pb ratios, with clear indication of larger upper crustal reservoir of much higher µ. Therefore, exploration efforts may need to emphasize near-source mineralization prospects of low radiogenic Pb composition for economic deposits.

lead reservoirs, metallization, U/Pb and Th/Pb ratios, Benue trough, economic deposits