Mineralogical Characterization of REE-Y Occurrences in the A-Type Serra Da Mesa Granitic Massif, Goiás, Brazil

Rare earth elements (REEs) are not scarce in nature; however, they rarely occur in economically viable concentrations. Over recent decades, demand for REE has increased substantially due to advances in high-technology industries and the expansion of clean energy technologies. At present, global REE production is highly concentrated, leading to instability in the international market and reinforcing the need to identify new resources. This study presents a mineralogical characterization of REE+Y occurrences in the Serra da Mesa Granitic Massif (SMGM), the type granite of the Tocantins Subprovince, Goiás Tin Province, Brazil. The objective is to evaluate its potential for REE+Y enrichment in ion-adsorption–type (IA-type) weathering profiles. Petrography, electron probe microanalysis (EPMA), and scanning electron microscopy (SEM) were applied to samples of the parental granite and associated alluvial sediments. The main REE-bearing minerals identified are allanite, bastnäsite-(Y), fluocarbonates, xenotime-(Y), zircon, and fergusonite-(Y), showing wide compositional variability. Bastnäsite-(Y) and xenotime display the highest REE+Y contents, reaching up to 74.2 wt.% and 65.1 wt.%, respectively. Bastnäsite and other fluocarbonates occur as alteration products of allanite, indicating REE+Y mobilization associated with F- and CO₂-rich fluids under low-temperature hydrothermal conditions. Alteration textures and low EPMA analytical totals suggest hydration, metamictization, and fluid-mediated neoformation processes. The abundance of REE+Y-bearing minerals, their susceptibility to weathering, and the presence of secondary fluocarbonates indicate that the SMGM represents a promising target for IA-type REE+Y mineralization within the Goiás Tin Province.