Geochemistry of Muro Banded Iron-Formation, Central Nigeria

Muro Banded Iron-Formation occurs in the Proterozoic Toto Schist Belt, central Nigeria. It consists preponderantly of oxide facies and minor carbonate facies. The oxide facies is made up of alternating bands of quartz (metachert) with those of hematite + magnetite + martite plus or minus goethite, chlorite, pyrrhotite and garnet. The carbonate facies consists of quartz (metachert) + siderite plus or minus goethite. In the oxide facies the total iron content (Fe sub( 2)O sub( 3)t) ranges from 33.95% to 48.08% and the SiO sub( 2) content from 50.33% to 64.50%. In the case of the carbonate facies, the Fe sub( 2)O sub( 3)t content varies from 15.42% to 20.66% and SiO sub( 2) content from 66.84 to 72.86%. The Al sub( 2)O sub( 3) content is generally low ranging from 0.1% to 0.54% in the oxide facies, and 0.24% to 0.31% in the carbonate facies. Chemically, the Muro Iron-Formation is similar to the Lake Superior-type iron-formations in terms of the distribution of the major and trace elements. This taken to-gether with similarities in lithological associations indicates its deposition in similar environments i.e. shallow in-tra-continental or restricted/barred marine basin. The very low Al sub( 2)O sub( 3) contents indicate minor clastic dilution of the original chemical precipitates.