Geochemical characteristics and genesis of Na-rich rocks in the Bayan Obo REE-Nb-Fe deposit, inner Mongolia, China

The giant Bayan Obo REE deposit is hosted mainly by middle and late Proterozoic Na-rich rocks, dolomitic rock and K-rich slate. Ore-bearing dolomitite and K-rich slate occur together with Na-rich rocks. The Na-rich rocks include albitite,albitite dyke, arfvedsonite dyke and arfvedsonitized dolomitite. Albitite is the most common variety of sodic rock at Bayan Obo. REE in the original dolomitic rock has been enriched by hydrothermal processes, which has caused redistribution of REE, but did not introduce additional REE to the system.