Eudialyte and eudialyte-group minerals (EGM) are unique tracers of peralkaline silica-undersaturated melts. They receive global interest as potential resources for high-field-strength elements (HFSE) (e. g. Zr, Nb, Ta, and rare-earth elements; REE), i. e. critical materials for modern technologies. The main condition for magmatic crystallization of eudialyte and EGM is that the concentration of Zr in parental melt should reach the saturation level. Thus, the solubility of eudialyte was studied in the system at temperatures between 750 and 1000 °C and pressures of 100 and 200 MPa. Liquid phases in run products are eudialyte, parakeldyshite and albite. Eudialyte is stable between 750 and 900 °C, and decomposes to parakeldyshite between 900 and 1000°C. Eudialyte crystallization in dry peralkaline silica-undersaturated melt at 750 and -850 °C requires minimum 0.2-0.22 wt.% ZrO2 in the melt. In melts with high amounts of dissolved H2O the saturation level in within the same temperature interval is much higher, at 1.1-2.85 wt.% ZrO2. Thus, peralkaline melts should be dry to crystallize EGM at ZrO2 concentrations between 0.2 and 0.3 wt.%.
LA-ICP-MS results show that REEs and HFSEs are strongly compatible with eudialyte as the eudialyte-melt distribution coefficients (D) vary from 2 to 90. Light REEs and especially La tend to have lower D values than heavy REEs. The data reflect that the concentrations of REEs and HFSEs in the eudialyte solid solution are mainly determined by the Zr concentrations in the melt: the lowest partition coefficients are observed in experiments with the highest eudialyte solubility, i.e., in experiments at high temperature and with H2O content
This data report is the supplement to the publication (Nikolenko et al., 2024, in prep.). This study presents a combined experimental research, EPMA and LA ICP-MS studies. This document describes the LA-ICP-MS analytical methods, sample preparation and the in-situ LA-ICP-MS element composition of eudialyte and peralkaline silica-undersaturated melts.
Eudialyte, which was used in experiments is a natural mineral, that had been collected from a pegmatite body on mount Eveslogchorr in the Khibina Massif, Kola Peninsula, Russia. Eudialyte crystals were crushed in a mortar and clear, inclusion-free fragments were hand-picked under a binocular.
Three synthetic glasses with variable Na-Al molar ratios were prepared from finely ground mixtures of silica (p.a., Merck®), aluminium oxide (γ-phase, 99.97%, 3 μm powder, Alfa Aesar®), and sodiumcarbonate (anhydrous, p.a., Merck®). The glasses were synthesized by sintering starting mixtures in a platinum crucible first at 900 °C for 1 hour, then crushing of the sintered material and remelting it two or three times at 1100-1200 °C for about 2 hours, with intermediate quenching in cold water and grinding the crushed glass fragments to the grain size of less than 1 mm.
Mixtures of the Khibina eudialyte and one of the synthetic glasses were ground in agate mortar to fine powders under acetone, dried at 100 °C for 2 hours, loaded into platinum capsules (outer and inner diameters 4.4 and 4.0 mm respectively) and welded shut. In some runs, distilled water (Merck, Suprapur®) was added to the starting charges before welding.