Petrology and Geochemical Constraints on the Origin of Banded Iron Formation-Hosted Iron Mineralization from the Paleoproterozoic Nyong Serie (Congo Craton, South Cameroon), Pout Njouma Area (Edea North): Evidence for Iron Ore Deposits

The Pout Njouma area is located in the Nyong unit, which is the northwestern extension of the Congo Craton in southern Cameroon. The assessment of iron mineralization in this area is carried out through rock sampling survey. Representative rock samples were analysed by inductively coupled plasma mass spectrometry (ICP-MS) combined with instrumental neutron activation analysis (INAA) technologies to completely characterize the iron- rich rock samples. The Pout Njouma area is made up of magnetite- gneiss, magnetite- quartzite and banded iron formations; these rocks display microband textures and granoblastic microstructures. The mineral assemblages indicate that magnetite- gneiss and magnetite- quartzite have been metamorphosed under greenschist facies conditions, while banded iron formations display the paragenesis of greenschist to amphibolite facies. This iron deposit belongs to the oxide facies, with magnetite and quartz being the common predominant minerals while sericite and limonite occur as accessory minerals. The Pout Njouma iron occurrence exhibits significant concentration of Fe2O3 + SiO2 (95%), relative elevated values of Al2O3 and TiO2 contents, lower high field strength elements (Y, Hf, Sc, Zr) and variation in enrichment in transition metals. Post Archaean Australian Shale- normalized rare earth elements patterns show slight enrichment in light rare earth elements relative to heavy rare earth elements. The Pout Njouma iron deposits have the composition of Fe-sand, and their geochemical signature indicates that low input of detrital materials contributed to the chemical precipitation of their formation. The absence of a large positive Eu anomaly (Eu/Eu* = 1.01-1.54) indicates that an important role of low-temperature hydrothermal solutions contributed to the deposition of the Pout Njouma ion deposits. Pout Njouma area is of low grade siliceous ore (43.19 to 48.49% Fe2O3) corresponding to depleted iron ore (30 to 50% Fe). The Pout Njouma iron deposits derived from Precambrian rocks which were deposited in an oceanic island-arc margin (ARC) setting where conditions were anoxic and fast sedimentation. The average chemical composition of Pout Njouma iron formations is compared with the known BIFs and the result show SiO2 and Fe2O3 enrichment except in Mballam and Mayo Binka where Fe shows significant elevated values compared with SiO2. Also, data show low concentration of Al2O3, TiO2, CaO and MnO, which infers the non-volcanogenic origin.