The rare earth elements (REE) La, Ce, Nd, Sm, Eu, Th, Dy, Yb, Lu and the elements Se, Hf, Th were determined by instrumental neutron aetivation analysis in 18 Ordovician greenstones of the Norwegian Caledonian geosyncline south of Trondheim. The greenstones are enriehed in REE by a factor of 10 to 30
eompared to the average chondrites. Post-crystallization redistribution of the REE has taken place in individual pillows. REE are not insensitive to secondary alterations. The REE contents of the least altered unpillowed massive greenstones give evidenee to support the opinion that the Støren greenstones
were formed in an Ordovician istand are.