Elemental mass balance during alteration of eudialyte ore

The strongly layered kakortokites of the Ilímaussaq intrusion.

The giant rare-earth element (REE) and zirconium, a.o. deposits in the Ilímaussaq intrusion in South-West Greenland include the 'Kringlerne' eudialyte deposit. Eudialyte is a complex zirconium silicate that is concentrated in minable layers. Eudialyte is commonly totally replaced by a lower-temperature paragenesis with a whole set of new minerals.

What was lost and what was gained as eudialyte is replaced? Eudialyte was replaced by phases with higher zirconium contents and the replacing phases did not fill the volume of the former eudialyte crystal. Voids were filled with natrolite and only little REE was lost from the pseudomorphed eudialyte. The alteration of eudialyte does not affect the bulk concentration of REE to any great extent but does affect the mineral paragenesis with possible consequences for exploitation and extraction of elements of economic interest.


Eudialyte altered to a complex mineral paragenesis with zirconium in catapleiite containing most of the zirconium and monazite containing most of the rare-earth elements (REE).

These findings are the result of a three year PhD-research activity, and contributes to the overall understanding of the mineralization model for the Ilimaussaq Intrusion, which in turn is vital for the economic assessment of the rare earth element resource potential of Kringlerne, It exemplifies how GEUS’ petrological research should be considered as applied science.

Troels F D Nielsen
Mapping and Mineral Resources