Rare earth element (REE)-enriched granitic pegmatite pockets of Lagoa Real Uranium Province, Brazil

Abstract

Rare-earth-element (REE) bearing minerals have been recognized for the first time within rare-element granitic pegmatite pockets from Lagoa Real Uranium Province (LRUP), Bahia state, NE Brazil. The Province is one of the chief U deposits in the world and the largest in South America. Notwithstanding its economic and strategic importance, there are gaps in the geological knowledge about other mineral resources which could occur in the area. One of them, is the lack of petrographic and chemical data sets on its REE content, especially in pegmatite pockets which occur in the contact between Juazeirinho (1755 ± 6 Ma) and São Timóteo (1741 ± 4 Ma) granites. In this paper, it is reported a petrographic description and geochemical characterization of allanite, bastnäsite, monazite, xenotime, cheralite, and parisite recognized in three spongy mineral assemblages within unzoned granitic pegmatite pockets from Lagoa Real Uranium Province. The REE-bearing minerals present moderate-to-high REE content with significant amounts of Ce, La, Y, and critical REE such as Nd, Er, and Yb, totalling to up to 49 wt%. Petrographical and geochemical evidence arguably indicate that the REE-enrichment in granitic pegmatite pockets of Lagoa Real Uranium Province is a result of late-magmatic and hydrothermal events involving F−, OH−, CO32− and PO43− REE-bearing fluids. The report and characterization of these recently recognized minerals indicate that the Lagoa Real Uranium Province, might hold important REE mineralization as U by-product.