Some metallogenetic features of the Nigerian basement

Abstract

The Nigerian basement consists of Eburnean granitic and metamorphic rocks into which are folded Upper Proterozoic supra-crustal low grade metasedimentary and metavolcanic rocks forming N-S elongate belts. Pan-African granitoids mark the last major event and they have intrusive and/or tectonic relationships with the earlier units. Structural features are often complex. The Basement can be divided into the Eastern and Western Provinces, where the latter is marked by the occurrence of a variety of metallogenetic types and greater development of the supracrustal N-S belts, while the Eastern province is dominated by Pan-African granitoid rocks and a paucity of metallic mineral occurrences.

The principle metallogenetic types that are (or have been) exploited are iron deposits, gold vein mineralization and SnTaNb-bearing pegmatites. Small occurrences are known of chromite, asbestos, CuNi sulphides, manganese and a variety of industrial minerals including talc, kyanite and magnesite. Metallogenetic types found in other Pan-African terrains that are markedly absent in Nigeria include basemetal deposits of plate accretion type (e.g. Saudi Arabia) and uranium (e.g. of Rossing type). It is suggested that Nigeria's relatively low metal production from basement deposits is attributable to a regional low metallogenetic inheritance which in turn has discouraged intensive prospecting but there is good potential especially for industrial mineral deposits.