DISTRIBUTION OF CERIUM, LANTHANUM AND YTTRIUM IN ALLANITES AND ASSOCIATED EPIDOTES OF METAVOLCANIC ROCKS IN HORNSUND AREA, VESTSPITSBERGEN

Zoned allanites, REE-bearing epidotes1 and REE-free epidotes from gnei sses, amphibolites and schists of amphibolite and greenschist facies r ocks were analysed with the electron probe. In zoned grains, the dark brown allanite with the highest content of REE forms the cores corresp onding to protolith stage. Outside of this is a zone of olive-grey all anite corresponding to an early stage of metamorphism, and the epidote rims are the result of later stages of metamorphism. Crystallochemica l aspects related to chemical variations of allanites and epidotes are found to be complex. The compositional thresholds in zoned grains ref lect different conditions of origin rather than miscibility gaps.