THE EVOLUTION OF LOPARITE COMPOSITIONS IN THE LOVOZERO MASSIF

The evolution of loparite compositions of the Lovozero Massif during t he differentiation of a peralkaline magma is discussed. Up the sequenc e of the massif, the loparites are demonstrated to become progressivel y enriched in SrO (from 0.84 to 7.68%), Nb2O5 (from 7.40 to 13.35%), T a2O5 (from 0.54 to 0.77%), ThO2 (from 0.50 to 1%), Sm (from 0.84 to 1. 19%), and Na2O (from 8.60 to 10%), and depleted in CaO (from 4.35 to 3 .08%), FeO (from 0.56 to 0.09%), TiO2 (from 40.04 to 36.62%), Ce2O3 (f rom 20.38 to 14.76%), La2O3 (from 10.05 to 7.8%), Nd2O3 (from 4.6 to 3 .3%), and total rare earths (from 36.6 to 27.6%). Our study revealed t he presence of a cryptic layering in terms of loparite composition on the scale of the entire intrusive complex; this indicates the main pro cess that governed the loparite chemical evolution was a closed-system crystal differentiation in an enormous magma chamber.