Abstract
Mbalam is a major emerging iron ore district in Cameroon. The regolith over the Mbalam itabirite, consists of relict, erosion and depositional units. Itabirite rock fabric is preserved in the relict regolith, the erosion unit is marked by erosion of the carapace cap regolith, with the depositional unit dominated by canga (loose fragments of hematite and/or itabirite cemented by goethite) or loose scree. Fe concentration increases from average of 46.18 wt% in the depositional soil material to as much as 79.08 wt% in the relict regolith regime with variation due to supergene weathering. Fe is the least mobile of the major elements, and the Fe oxides become significant phases and control the distributions of many elements. Absorption of P by iron oxides or oxyhydroxides appears to be the major mechanism of P retention in the different regolith environment. Au dispersion in the weathering profile occurs by two possible mechanisms (mechanical and hydromorphic) and it distribution is sporadic. Zr maintains a positive correlation with Al and Ti indicating extensive chemical weathering in the source area and resulting in a relative concentration of those residual elements. The weathered material show relatively high ΣREE; this is due to upward remobilisation from the lower primary itabirite, and the downward leaching of the upper mineralisation horizons by the descending epigenetic solutions.
Highlights
As the search for ore deposits continues worldwide, the use of regolith geochemistry will play an increasingly important role in mineral exploration [1]
Itabirite rock fabric is preserved in the relict regolith, the erosion unit is marked by erosion of the carapace cap regolith, with the depositional unit dominated by canga or loose scree
The weathered material show relatively high ΣREE; this is due to upward remobilisation from the lower primary itabirite, and the downward leaching of the upper mineralisation horizons by the descending epigenetic solutions
Summary
As the search for ore deposits continues worldwide, the use of regolith geochemistry will play an increasingly important role in mineral exploration [1]. Regolith or soil geochemistry finds global significance in geochemical mapping, development of geochemical databases and in the determination of the background composition of the soils in a region before mining activity starts. Such baseline data on regolith composition applicable to exploration, are vital to monitoring pollution when the ore extraction process starts. It is against this dual background that the present study was conducted. The main ore is hematite derived from itabirite (metamorphosed banded iron formation)
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