Petrography and Geochemistry of Manganese Protores from Laniokaha (Korhogo, Northern Côte d’Ivoire)

Abstract

The manganese protores of Laniokaha (Korhogo, Northern Côte d’Ivoire) are metamorphic rocks. Petrographic studies have identified three rock types: garnet amphibolite, garnet tephroitite, and gondite. These formations occur in succession within the same drilling profile. The minerals constituting garnet bearing amphibolite include amphibole, garnet, plagioclase, kaolinite, and opaque minerals. Garnet tephroitite is comprised of tephroite, garnet, calcite, plagioclase, and opaque minerals. Gondite is characterized by garnet, quartz, and opaque minerals. The manganese-bearing silicates identified are garnet and tephroite. Supergene alteration and enrichment of gondite led to the formation of hollandite and manganite. Manganese oxyhydroxides, manganite and hollandite were observed using metallographic microscopy. Scanning electron microscopy (SEM) revealed the presence of manganese carbonate kutnohorite in garnet tephroitite. The metals associated with manganese mineralization include pyrite, hematite, sphalerite, magnetite, goethite, gahnite, and rutile. These protores have high manganese contents ranging from 27% to over 38% Mn metal. Petrographic and geochemical characteristics indicate that these protores consist of silicate, oxyhydroxide, and carbonate minerals containing significant primary and secondary manganese mineralizations.