RARE-EARTH ELEMENTS IN THE PLUTONIC AND D YKE ALKALINE ROCK SERIES OFTHE NIZHNESAYANSKY CARBONATITE COMPLEX

REE content and La/Yb ratio are found to decrease along with the alkal inity increase and basicity decrease of rocks in the plutonic and dyke alkaline series of the Nizhnesayansky complex. The specific character of the REE distribution pattern in ijolites as well as some geologica l and pertological evidences indicate that the ijolites could not be c onsidered as the derivates of a primary alkaline-ultrabasic magma. It is assumed that the ijolites as well as early carbonatites were formed as a result of interaction of mantle alkaline CO2-rich fluid wiht the ultrabasic plutonic rocks (jacupirangites, melilitolites). The carbon atites are found to be enriched in light REE in relation to coexisting ijolites.