REE-rich minerals of the Passo Feio Metacarbonatite, Dom Feliciano Belt, Brazil: microscopy and electron probe microanalysis

This study presents a comprehensive petrographic analysis of REE-rich minerals in the Passo Feio Metacarbonatite, located within the São Gabriel Terrane of the Dom Feliciano Belt, Brazil. The investigation employs microscopy and electron probe microanalysis to examine the mineralogical characteristics in detail. The metacarbonatite exhibits complex field relationships, marked by post-magmatic and tectonic features. It is primarily composed of calcite with subordinate dolomite, displaying granoblastic textures. Apatite and accessory minerals, including pyrochlore and monazite, serve as hosts for rare earth elements (REEs), with their compositions indicating a combination of magmatic and hydrothermal processes. Electron probe microanalysis reveals consistent compositional trends in apatite, monazite, and pyrochlore, demonstrating an enrichment in light REEs. These findings underscore the potential of the Passo Feio Metacarbonatite for REE exploration, particularly in monazite- and pyrochlore-bearing phases.