Phosphate mineralization of Sapucaia (Pará, Brazil) and its genetic relationship with peraluminous pegmatites of the Gurupi Belt

Brazil is one of the world's largest food producers, but it remains dependent on the import of phosphate fertilizers. In this context, national phosphate deposits gain strategic importance, such as the Sapucaia Mine (Pará, Brazil), which hosts the first aluminous phosphate deposit in Brazil and the second in the world. Through lithological, petrographic, geochemical, and gamma spectrometric analyses, the Sapucaia Mine represents an important case study for understanding the genesis and evolution of phosphate mineralization. The profile was divided into three units from base to top: (1) a clay unit, with an aluminosilicate-rich facies dominated by kaolinite and zoned phosphates such as crandallite group minerals; (2) a phosphate-rich unit, characterized by a mineralogical association of amblygonite, wavellite, woodhouseite-svanbergite, and crandallite-goyazite series; and (3) an iron-phosphate crust, rich in iron oxides, ankerite, dufrenite, triphylite, and wavellite fillings. Strongly peraluminous signatures (A/CNK > 2), enrichment in rare earth elements (REEs), Sr, and Ba, as well as a negative Eu anomaly in REE patterns, are inferred as compatible with S-type magmatic sources. Botryoidal and colloform textures, pseudomorphic substitutions, and altered mineral features indicate a polygenetic regolithic system. The correlation between petrographic and geochemical data suggests at least three genetic processes: (i) a lithium-bearing igneous phase, associated with the intrusion of a granitic-pegmatitic body; (ii) a late-magmatic/hydrothermal phase, with significant mobilization of alkaline-earth metals; and (iii) a supergene phase, characterized by intense weathering in a tropical climate, with dissolution and reprecipitation of phosphates and clay minerals. The Sapucaia Mine constitutes a unique geological example of phosphate enrichment in peraluminous granitic terrains exposed to tropical weathering conditions, with potential applications for the exploration of analogous deposits in northern and northeastern Brazil.