Crystal Chemistry of Pyroaurite from the Kovdor Pluton, Kola Peninsula, Russia, and the Långban Fe–Mn deposit, Värmland, Sweden

• Published in: Geology of ore deposits 2017-12, Vol.59 (7), p.652-661
• Main Authors: Zhitova, E. S., Ivanyuk, G. Yu, Krivovichev, S. V., Yakovenchuk, V. N., Pakhomovsky, Ya. A., Mikhailova, Yu. A.
• Format: Article
• Language: English
• Subjects: Absorption; Absorption spectra; Analytical methods; Carbonates; Cations; Diffraction; Earth and Environmental Science; Earth Sciences; Electron microprobe; Hydroxyl groups; Manganese; Mineral Resources; Mineralogical Crystallography; Plutons; Polytypes; Raman spectroscopy; Single crystals; Spectroscopy; Water chemistry; X ray powder diffraction; X-ray diffraction
• ISSN: 1075-7015; 1555-6476
• DOI: 10.1134/S1075701517070121

Pyroaurite [Mg 6 Fe 2 3+ (OH) 16 ][(CO 3 )(H 2 O)] from the Kovdor Pluton on the Kola Peninsula, Russia, and the Långban deposit in Filipstad, Värmland, Sweden were studied with single crystal and powder X-ray diffraction, an electron microprobe, and Raman spectroscopy. Both samples are rhombohedral, space group R 3̅ m , a = 3.126(3), c = 23.52(2) Å (Kovdor), and a = 3.1007(9), c = 23.34(1) (Långban). The powder XRD revealed only the 3 R polytype. The ratio of di- and trivalent cations M 2+ : M 3+ was determined as ~3.1–3.2 (Kovdor) and ~3.0 (Långban). The Raman spectroscopy of the Kovdor sample verified hydroxyl groups and/or water molecules in the mineral (absorption bands in the region of 3600–3500 cm –1 ) and carbonate groups (absorption bands in the region of 1346–1058 cm –1 ). Based on the data obtained, the studied samples should be identified as pyroaurite-3 R (hydrotalcite group).