Thorium deposit, consisting of magnetite stockworks in highly weathered alkaline rocks. The deposit was studied as a natural analogue for nuclear waste disposal. Once the world's largest baddeleyite deposit, but now depleted.

The Morro do Ferro deposit is hosted within the Poços de Caldas alkaline complex (Fig. 2) and developed on strongly hydrothermally altered alkaline rocks, with mineralogical and mass balance evidence indicating a non-outcropping carbonatitic protolith enriched in Th and REEs relative to surrounding silicate rocks. The ore body forms shallow NW–SE elongated argillaceous lenses extending from the hilltop down its southeastern slope, largely confined to the upper tens of meters and is structurally controlled and preserved by a stockwork of magnetite veins. The weathering profile exceeds 100 m in depth and reflects intense lateritization under tropical conditions, with complete destruction of the primary carbonatitic-dominated protolith, forming a thick clay-rich regolith.
The mineralogical evolution of the system reflects an early hydrothermal stage followed by supergene overprint. Hydrothermal alteration transformed primary REE-bearing minerals into assemblages dominated by K-feldspar, clay minerals (illite, kaolinite), pyrite, and Ti-oxide phases, while REEs were partly incorporated into early-formed minerals such as monazite within breccia-related mineralization. Supergene processes led to extensive alteration and redistribution, generating a mineral assemblage dominated by clay minerals (kaolinite, illite), gibbsite, and Fe–Mn oxyhydroxides, together with secondary REE- and Th-bearing phases including bastnäsite, cerianite, florencite, and other secondary phosphate minerals, with REEs additionally retained by Fe–Al oxyhydroxides through adsorption and coprecipitation.

Originally known as "Morro Alto e Consulta".

Other Regions, Features and Areas containing this locality

References