Unusual IOA deposit associated with carbonatite in South Morocco: Mineralogy, geochemistry and REE-Nb-Ta mineralization

Iron oxide-apatite (IOA) deposits are known to be closely associated with silicate igneous rocks. However, a recent study in the Oulad Dlim massif (South Morocco) revealed the first occurrence of massive IOA deposits hosted by Paleoproterozoic dolomite carbonatite in the Gleibat Lafhouda area. In addition, significant REE-Nb-Ta enrichments seem to be unique to this IOA occurrence. Preliminary results have indicated an exploration tonnage target of ~49 million tons with mean compositions at 0.4% Nb2O5, 265 ppm Ta2O5, 508 ppm U3O8, 0.2% REE, and 35% Fe2O3. Columbite-(Fe) is the main Nb-mineral and occurs closely associated with Fe-phases, whereas microlite and Ta-rich pyrochlore are mainly associated with coarse-grained apatites hosted by Fe-oxides and silica breccia. Significant REE contents are hosted by monazite-(Ce), which is usually associated with large apatite crystals. The processes leading to this mineralization with direct links to carbonatite are still poorly understood. However, geochemical characteristics and textural relationship suggest that they are genetically linked to the carbonatite and intensively remobilized by late hydrothermal fluids at multiple stages. This study aims to provide new mineralogical and geochemical insights on the petrogenesis of the IOAs and their associated ore mineralization. Understanding new occurrence types of the IOAs will significantly advance our understanding of their formation and will provide important information on the magmatic/hydrothermal evolution of this unusual IOA occurrence and its significant REE, Nb, and Ta mineralization.