Magnetite in Sokli carbonatite massif and in Tulppio olivinite

Occurrence, ilmenite exsolutions and composition of magnetite in the carbonatite massif of Sokli and in the olivinite of Tulppio have been studied. In the carbonatite massif, magnetite of magmatic carbonatites is hypidio-idiomorphic, contains only very fine-grained ilmenite exsolutions (ulvöspinel), and the minor components TiO-2, MgO, MnO and AI2O3 of magnetite show a decreasing tendency in the successive I II -*• IV magmatic stages. Magnetite of metacarbonatite is xenomorphic, containing a great number of ilmenite exsolutions indicating a complicated thermal history of these rocks. The magnetite of the magmatic carbonatites has lower TiOa and higher MnO, AI2O3, MgO and ZnO contents than that of the metacarbonatites, on the average. Magnetite of the Tulppio olivinite is fine-grained, and the minor element contents, excepting Cr and Si, are lower than those in the carbonatite massif.