Petrographic and geochemical characterization of weathered materials developed on BIF from the Mamelles iron ore deposit in the Nyong unit, South-West Cameroon

Abstract

Iron ore deposits hosted by Precambrian banded iron formation (BIF) are the most important source of mineable iron. In Cameroon, they are located in the southern part of the country. This study reports the petrological and geochemical data of iron ores collected from a weathering profile in the Mamelles BIF deposit, SW Cameroon. The profile is composed of three levels which are from the bottom to the top: the saprock, the ferruginous horizon, and the loose horizon. Eight representative iron ore samples (rock fragments and loose clayey material) were collected along the profile and were subjected to petrographic and geochemical analyses. Their mineralogy consists of martite, goethite, quartz, and lesser amounts of hematite, magnetite, kaolinite, and halloysite. The presence of minerals such as kaolinite and goethite in the Mamelles iron ores suggests their supergene origin. Geochemically, the saprock is characterized by high iron content (70.25 wt% Fe2O3t), and low silica (26.38 wt% SiO2) and alumina (1.14 wt% Al2O3). The rock fragments collected from the ferruginous horizon display higher Fe2O3t (72–76.40 wt%), Al2O3 (2.80–5.43 wt%), and lower SiO2 (16.70–18.35 wt%) contents, suggesting the leaching of silica during the enrichment process. The loose clayey samples collected from both the ferruginous horizon and the upper loose horizon show lower iron and higher silica contents. When normalized to the underlying BIF saprock, both rock fragments and loose clayey ores display LREE enrichment, suggesting that they formed through supergene processes. Economically, most of the Mamelles iron ores are classified as medium-grade ores and a few display acceptable contents in contaminants. Overall, this petrological and geochemical study of the Mamelles iron ores revealed encouraging results. Given its strategic location near the deep seaport, the deposit should be investigated in more detail for its mining potential.