Zr-Rich Eudialyte from the Lovozero Peralkaline Massif, Kola Peninsula, Russia

• Published in: Minerals
• Main Authors: Taras L. Panikorovskii, Julia A. Mikhailova, Yakov A. Pakhomovsky, Ayya V. Bazai, Sergey M. Aksenov, Andrey O. Kalashnikov, Sergey V. Krivovichev
• Format: Text
• Language: English
• Published: Multidisciplinary Digital Publishing Institute 2021
• Subjects: eudialyte; eudialyte-group minerals; Lovozero alkaline massif; zirconium; Arctic; mineralogy; Kola Peninsula; Lovozero; Alluaiv; kola peninsula
• Online Access: https://doi.org/10.3390/min11090982

The Lovozero peralkaline massif (Kola Peninsula, Russia) has several deposits of Zr, Nb, Ta and rare earth elements (REE) associated with eudialyte-group minerals (EGM). Eudialyte from the Alluaiv Mt. often forms zonal grains with central parts enriched in Zr (more than 3 apfu) and marginal zones enriched in REEs. The detailed study of the chemical composition (294 microprobe analyses) of EGMs from the drill cores of the Mt. Alluaiv-Mt. Kedykvyrpakhk deposits reveal more than 70% Zr-enriched samples. Single-crystal X-ray diffraction (XRD) was performed separately for the Zr-rich (4.17 Zr apfu) core and the REE-rich (0.54 REE apfu) marginal zone. It was found that extra Zr incorporates into the octahedral M1A site, where it replaces Ca, leading to the symmetry lowering from R3¯m to R32. We demonstrated that the incorporation of extra Zr into EGMs makes the calculation of the eudialyte formula on the basis of Si + Al + Zr + Ti + Hf + Nb + Ta + W = 29 apfu inappropriate.