The petrology and geochemistry of Koriga iron-formation, N .W. Nigeria

Abstract

The Koriga iron-formation is located in the Kushaka Schist belt of north-western Nigeria. It occurs as thin intercalations in the phyllites and pelitic schists which also contain concordant bands of amphibolite. A Kibaran (ca 1100Ma) age has been suggested for the rocks of the Kushaka Schist belt which have been intruded by granitic rocks dated ca 600Ma. The iron-formation consists dominantly of silicate minerals: grunerite, spessartine-rich almandine garnet, quartz and some martite, but occassional thin, more oxide-rich bands with martite, magnetite and silicate minerals also occur. Fe2O3, (total iron content varies from 26.20 to 34.05% and SiO2 content from 46.61 to 62.51% in the silicate-rich rocks. The oxide-rich bands are richer in total iron with Fe2O3, contents of about 59% . High values of Al2O3 (3.87-9.69%) and MnO (1.30 to 7.62% characterise the Koriga iron-formation.