Application of Raman spectroscopy for identification of rinneite (K₃NaFeCl₆) in inclusions in minerals

Abstract

Solid daughter phases in fluid and salt melt inclusions in minerals provide important clues to characterization of mineral-forming processes. The analysis of the fluid inclusions often requires the exposure of the daughter minerals. Rinneite (K 3 NaFeCl 6), which is a hygroscopic mineral, decomposes in air and cannot thus be identified by conventional methods. A combined approach has been applied for investigation of synthetic and natural rinneite to acquire its diagnostic Raman spectrum for a nondestructive identification. We used natural rinneite inclusions in halite, suitable for applying a complex of methods, to clear up the reference spectrum. Improved high-resolution X-ray diffraction (XRD) data obtained from natural rinneite inclusion are comparable with that of previously published, with similar unit cell dimensions. Polarized Raman spectra of natural inclusions were obtained using different geometries and polarization of the incident and scattered light. Interpretation of experimental Raman spectra was performed within the framework of lattice dynamics simulations and group analysis. Individual spectral bands are interpreted in terms of Raman-active vibrational modes of K 3 NaFeCl 6 structural units. Raman spectrum of synthetic rinneite with main peaks at 75, 91, 103, 143, 167, 171, 187, and 239 cm −1 agrees well with the spectra of rinneite inclusions in halite from the Nepa potash deposit and rinneite daughter minerals in salt melt inclusions hosted by quartz veinlets from the porphyry gold systems in the Central Slovakia Volcanic Field. This provides a firm basis for any future identification of this mineral worldwide, using nondestructive Raman spectroscopy.

Micro‐Raman study of cesanite (Ca2Na3 (OH)(SO4)3) in chloride segregations from Udachnaya‐East kimberlites

“…[14] A number of unusual minerals in kimberlites of Udachnaya-East pipe have been described and characterized. [15][16][17] Current work continues a series of Raman characterizations of minerals [18,19] within chloride segregations as opposed to descriptions of alkali compounds in kimberlite groundmass and secondary inclusions in olivin.…”

Halogen Enrichment of Siberian Traps Magmas During Interaction With Evaporites

“…Interactions between magmas and evaporites, including the incorporation of sedimentary pore fluids (e.g., brines), can significantly increase the volatile contents of magmas (Heimdal et al, 2019), as has been suggested to explain some high chlorine contents of melt inclusions in Siberian Traps Large Igneous Province rocks (Sobolev et al, 2009;Black et al, 2012). Previous studies have described the textures and skarn mineralogy produced at the contact between dolerites and evaporites in the Nepa River region (Grishina et al, 1991;Grishina et al, 1992;Istomin et al, 2000;Mazurov et al, 2007;Polozov et al, 2016;Grishina et al, 2018;Grishina et al, 2020). Evidence for interactions with magmas may be retained in the basalts and the contact aureole in the salts.…”

Supplemental Material: Melt inclusion evidence for limestone assimilation, calc-silicate melts, and “magmatic skarn”

“…This type of inclusion occurs together with vapor-rich inclusions as primary assemblages and secondary trails. The translucent crystals in these inclusions are halite (NaCl), sylvite (KCl), Rinneite (K3NaFeCl6; Grishina et al, 2020), Javorieite (KFeCl3; Koděra et al, 2017), and anhydrite (Fig. DR5A).…”