US EPA

8159589 

Journal Article 

Supergene Fe-Mn environment in the Precambrian banded iron-formation, Birnin Gwari, northwestern Nigeria 

Adekoya, JA 

1995 

31 

1 

63-72 

English 

Mineralographic and geochemical studies of Sofon Birnin Gwari banded iron-formation in the Kushaka schist belt have revealed that the iron deposit has undergone considerable secondary iron and manganese enrichments. This is probably a consequence of supergene alteration due largely to weathering processes. The Fe enrichment is achieved essentially through the formation of goethite, the replacement of gangue by goethite and the conversion of goethite to a variety of secondary hematite. Manganese enrichment has resulted in the formation of secondary manganese-bearing oxides which include cryptomelane, lithiophorite and nsutite in the altered zone. These minerals are derived from the alteration of spessartine-almandine garnet and other Mn-bearing minerals.