Lateritization and enrichment of ferruginous protore during the peneplanation between uplifts – the case of Mekaneselam iron deposit, NW Ethiopian plateau

Abstract

Mekaneselam iron deposit is located in the NW Ethiopian Plateau. The area is constituted by limestone at the bottom followed by mudstone, sandstone and basalt at the top. Geological mapping, geochemical, mineralogical and stratigraphic investigations were conducted to explain the genesis of the deposit. The orebody is hosted by the quartz arenitic Upper Sandstone. At places where the sandstone is removed by erosion the orebody is unconformably overlain by basalt. It occurs as stratified bed and massive (the primary ore orebodies), and lateritic residual to reworked clastic varieties (the secondary/residual ore bodies). The dominant ore minerals are hematite and goethite with gangue minerals quartz and kaolinite. Geochemical composition is dominated by Fe2O3 and SiO2 with subordinate amount of Al2O3. The alkalis and alkaline earth elements were not detected in almost all samples. The stratigraphy, orebody morphology, mineralogy and geochemistry suggest that mineralization was a two-stage process. A primary ore deposition took place during sedimentation of the host sandstone and formed a ferruginous protore. This was later upgraded through deep tropical weathering and lateritization. The supergene process is believed to be facilitated by the relatively long-term peneplanation happened in Ethiopia after the Cretaceous and before the plume-induced Oligocene uplifts of East/Northeast Africa.

Keywords

• Peneplanation
• lateritization
• uplift
• Ethiopia
• iron ore
• protore