Rare earth chemistry of perovskite group minerals from the Gardiner Complex, East Greenland

Perovskite group minerals, general formula ABX3, from the intrusive ultramafic alkaline Gardiner Complex, East Greenland, range from almost pure CaTiO3 (perovskite, sensu stricto), to the rare earth element (REE) variety, loparite-(Ce). Chemical zonation in the perovskites (sensu lato), is described by the substitutions 2Ca2+ = (Na+ + REE3+) on the A-site and 2Ti4+ = (Fe3+ + Nb5+) on the B-site. Other trace elements detected include Th, Sr, Al, Si, Zr, Ta and Sn. Excellent agreement was found between the determinations of the REE by electron microprobe 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 coefficients 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.