Application of Raman spectroscopy for identification of rinneite (K3NaFeCl6) in inclusions in minerals. (6th October 2020)

• Record Type: Journal Article
• Authors: Grishina, Svetlana; Koděra, Peter; Goryainov, Sergey; Oreshonkov, Aleksandr; Seryotkin, Yurii; Šimko, František; Polozov, Alexander G.
• Is Part Of: Journal of Raman spectroscopy. Volume 51:Number 12(2020)
• Page Start: 2505
• Page End: 2516
• Publication Date: 2020-10-06
• Subjects: daughter mineral -- Fe‐oxyhydroxides -- fluid inclusion -- rinneite -- weathering; Raman spectroscopy -- Periodicals; 535.846
• DOI: 10.1002/jrs.6005
• Languages: English
• ISSNs: 0377-0486

Abstract

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 (K3 NaFeCl6 ), 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 K3 NaFeCl6 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. Abstract : A combined approach has been applied to provide a new reliable reference Raman spectrum of rinneite, an important daughter mineral in fluid inclusions of ore‐forming paleofluids. We showed that even a short exposure of rinneite to atmosphere is enough for the decomposition of this elusive mineral.