ALLUAIVITE AND GENETIC ASPECT OF THE FORMING OF ENRICHED IN TI EUDIALYTES IN KHIBINY MASSIF

摘要

Alluaivite - the rare Ti-bearing analog of eudialytes - has been found in Khibiny; previously it was only known in the neighboring Lovozero massif. The Khibiny alluaivite occurs as accessory mineral in the 《soda》 horizon of massive coarse-grained urtites underlying the ore-bearing rocks of ijolite-urtite series at the Rasvumchorr Mt. On the contrary to Lovozero alluaivite, which epitaxially overgrow faces of eudialyte crystals, her it forms freely growing homogenous greenish-yellow crystals as large as 0.5-3.0 mm. It didn't show fluorescence in UV-lights. Chemical composition of the mineral is very similar in both cases, but alluaivite in Khibiny, differing from the Lovozero one, bears smaller amounts of Mn, Nb, K, Sr and Cl, and the greater quantities of Ca and Ti; it contain Fe and S also. Alluaivite is associated with eudialytes enriched in Ti in various degree. The same varieties of eudialyte were detected in rocks of the poikilitic nepheline syenites (pyroxene rischorrites) complex developed at the same area (Rasvumchorr Mt.), but in the overlapping - upper part of the ore-bearing formation. There is a continuous isomorphic row between compositions of alluaivite and eduialyte. Both, alluaivite and Ti-rich eudialytes occur in Khibiny massif in similar but specific conditions. They associate with the hyper-alkaline minerals (zirsinalite, koashvite, villiaumite, nakafite, etc.) and are forming from the Ti-enriched extremely rich in alkali sodium solutions effecting the massive urtites either in zone of their contact with poikilitic syenites, or in linear zones known under name of 《soda》 horizons.