Characterization of REE(+/-Ba)-bearing minerals from granitic rocks (Central Portugal) and metasomatic rocks (Bayan Obo, China)

Abstract

Detailed characterization of REE-bearing minerals in granitoid rocks from the Idanha-a-Nova and Castelo Branco plutons (Central Portugal) and in a few metasomatic rocks associated to the Bayan Obo Fe-REE-Nb mineralization (Inner Mongolia, China) provided an interesting basis for the interpretation of the bulk-rock REE patterns. Of the REE-bearing minerals analysed in the granitoid rocks, monazite exhibits the highest total REE contents and a LREE-enriched pattern which explains the bulk-rock LREE enrichment, and is quite distinct from the REE patterns obtained for zircon and xenotime, which probably occur in lower modal concentrations. In the Bayan Obo rocks, monazite and fluorcarbonates (bastnäsite and/or Nd-cebaite) are the main REE-bearing minerals, both exhibiting very high REE contents and pronounced LREE-enrichment quite matching that of the bulk-rocks, while REE contents in pyrochlore and in minerals of the hejtmanite-bafertisite group are much lower.