RARE-EARTH CHEMISTRY OF PEROVSKITE GROUP MINERALS FROM THE GARDINER COMPLEX, EAST GREENLAND

Perovskite group minerals, general formula ABX(3), from the intrusive ultramafic alkaline Gardiner Complex, East Greenland, range from almos t pure CaTiO3 (perovskite, sensu stricto), to the rare earth element ( REE) variety, loparite-(Ce). Chemical zonation in the perovskites (sen su lato), is described by the substitutions 2Ca(2+) (Na+ + REE3+) on t he A-site and 2Ti(4+) = (Fe3+ + Nb5+) on the B-site. Other trace eleme nts detected include Th, Sr, Al, Si, Zr, Ta and Sn. Excellent agreemen t was found between the determinations of the REE by electron micropro be and neutron activation analysis. Chondrite-normalized REE patterns display enrichment in the light rare earths for perovskite, loparite, apatite, melilite and diopside. Mean perovskite/apatite partition coef ficients from four of the Gardiner rocks were calculated as La = 10.4, Ce = 13.8, Nd = 13.9, Sm = 9.9, Eu = 7.7, Gd = 5.2, Tb = 5.6, Tm = 5. 5, Yb = 2.7 and Lu = 1.6, indicating that perovskite concentrates all REE to a much greater extent than apatite. Light-REE enrichment occurs in both perovskite and apatite.