Meliphanite and Leucophanite from the Sakharjok Alkaline Massif, Kola Peninsula

Abstract—Meliphanite is an abundant mineral within a large nepheline syenite pegmatite and surrounding metasomatite of the Sakharjok alkaline massif, Kola Peninsula. In the pegmatite, it occurs as euhedral crystals enriched in Al, whereas in metasomatite, it forms poikilitic crystals substantially depleted in Al with a higher OH– content. Compared to meliphanite from deposits in Norway, the Sakharjok mineral is richer in Na and contains OH groups. Leucophanite is rare in the Sakharjok massif. It is closely intergrown with meliphanite in metasomatic rocks. Its chemical composition is constant in most components (except fluorine) and its formula is close to ideal. The unique paragenesis of meliphanite and leucophanite, which was previously considered as impossible, resulted from the metasomatic origin of the minerals.