AND

Zoned hibonites from a kalsilite, leucite, spinel, corundum, perovskite gneiss from the southern Indian granulite terrain near Punalur, Kerala, have rims that are the most Ti-rich yet recorded (0.83-0.87 Ti atoms per 19 O) and are essentially free of REE elements (ZREE < 0.01 atoms per 19 O) while the cores are the most REE-rich compositions yet recorded (YREE = 0.55-0.65 atoms per 19 O). Within the limits of analytical uncertainty, the compositions of the hibonite can be related to the theoretical end-member CaA112019 by the substitutions REE R 2+ ~ CaA1 and R2+R 4+ ~ AI2 with the REE-rich cores containing in excess of 50 % of the REE R2+A111019 end member. Minor substitution of Na for Ca occurs in the rims, while non-stoichiometry in both the cores and rims is indicated by partial 12-fold site occupancy. Ion-microprobe analysis of the REE-rich hibonites reveals trong enrichment in LREE with La/Lu c. 250 000