THE TURIY MASSIF, KOLA PENINSULA, RUSSIA: ISOTOPIC AND GEOCHEMICAL EVIDENCE FOR MULTI-SOURCE EVOLUTION

Abstract

The Turiy Massif, lying within the Kandalaksha Graben, and on the southern coast of the Kola Peninsula, contains carbonatites, phoscorites, melilitolites, ijolites and pyroxenites within one central and four surrounding satellite complexes. Sr–Nd isotopic data from the central complex phoscorites and carbonatites, and the nearby Terskii Coast kimberlites, combined with other recently published data on the Devonian Kola Alkaline Province, allow us to redefine the position of the Kola Carbonatite Line (KCL) of Kramm ( European Journal of Mineralogy 5 , 985–989, 1993). We propose that the revised-KCL mantle sources include a lower-mantle plume, and a second enriched source, which also contributed to the Terskii Coast and Archangelsk kimberlites. The Turiy Massif silicate rocks and northern complex carbonatites have more enriched isotopic signatures than the distinct, and depleted signatures of the central complex phoscorites and carbonatites, particularly with respect to εSr. This is probably due to the contamination of parental magmas, originally derived from the KCL end-members, by crustal material. The phoscorites and carbonatites show unusually enriched stable isotope δ13 C PDB values with respect to their conjugate δ18 O SMOW values. The trace element signatures of the silicate rocks are generally consistent with derivation from the magma sources proposed above.