Figure 6

Iron and REE contents across an ankerite grain from the ore body of the Bayan Obo deposit.
Iron and REE contents are lower in the centre. Consistently, REE patterns also change systematically from the rim to the centre. These can plausibly be interpreted as the result of hydrothermal metasomatism of a calcite/dolomite grain by Fe-, Mg- and REE-enriched fluids.