Alkaline igneous complexes host deposits of rare earth elements (REE), which represent
one of the most economically important resources of heavy REE and Yttrium (Y). The hosts
are differentiated rocks ranging from nepheline syenites and trachytes to peralkaline granites.
These complexes usually occur in continental within-plate tectonic settings associated with rifts, faults,
or hotspot magmatism. The REE mineralization is found in layered alkaline complexes, granitic
stocks, and late-stages dikes and rarely trachytic volcanic and volcaniclastic deposits. The bulk
of REE is present in accessory minerals, which can reach percentage levels in mineralized zones.
The mineralization contains various REE-bearing minerals that can display complex replacement
textures. Main REE minerals present in these deposits are bastnäsite, eudialyte, loparite, gittinsite,
xenotime, monazite, zircon, and fergusonite (Dostal, 2017).
Well-known REE-deposits from the world
REE-Y deposits from (Barakos, G. et. al. 2016)