Multi-Analytical Characterization of Minerals of the Bowieite–Kashinite Series From the Svetly Bor Complex, Urals, Russia, and Comparison With Worldwide Occurrences

Abstract

Grains of the bowieite-kashinite solid-solution series were characterized by electron microprobe analysis, single-crystal Xray diffraction, and Raman spectroscopy. The grains were recovered from dunitic rocks located in the Svetly Bor Ural-Alaskan type massif, Urals, Russia. Bowieite and kashinite occur as small inclusions (up to 100 lm in size) in isoferroplatinum grains up to 1 mm in diameter. Single-crystal X-ray diffraction data for two selected grains, with compositions (Rh 1.16 Ir 0.82 Cu 0.02 ) R2.00 S 3.00 and (Ir 1.06 Rh 0.87 Cu 0.04 ) R1.97 S 3.03 , confirm that the minerals are orthorhombic with similar cell dimensions: a 8.46(1), b 6.00(1), c 6.14(1)Å for bowieite, and a 8.46(1), b 5.99(1), c 6.14(1)Å for kashinite. The Raman spectra of the same two single grains show similar characteristic bands. One grain with composition (Ir 0.26 Rh 0.13 Pt 0.12 Ni 0.18 Cu 0.18 Fe 0.11 ) R0.98 S was found associated with the kashinite. It shows a distinctive Raman spectrum and may represent a new platinum-group mineral, although the small size (less than 20 lm) prevented us from obtaining X-ray diffraction data. Our data for the bowieite-kashinite series are compared with selected worldwide occurrences.

Platinum-Group Minerals of Pt-Placer Deposits Associated with the Svetloborsky Ural-Alaskan Type Massif, Middle Urals, Russia

“…The comparison of the peculiarities of the remaining PGM in this case is inexpedient due to their relative rarity in the studied objects, although the bowieite was established of dunite-type mineralization [27], whereas it was not found in the placers. The absence of a wide variety of rarer minerals in the studied assemblages emphasizes once again the difference of the PGM from the placers and dunite-type mineralization, where the Rh analogue of tolovkite, hollingworthite, irarsite, sperrylite, hexaferrum, etc.…”

“…20), in Table 2 for tetraferroplatinum-tulameenite (No. [27][28][29][30][31] and in Table 3 for osmium (No. 19,20).…”

“…Isf-isoferroplatinum, Os-osmium, and Chr-chromite.Osmium composition varies considerably (Table 3). Like most Os-Ir-Ru inclusions in Pt-Fe alloy grains from placers associated with the Ural-Alaskan type massifs and their lode sources[6][7][8][9][10][11][12][13][14][18][19][20][21][22][23][24][26][27][28][29][30][31][32][33], Ru is low in the Os-Ir-Ru solid solutions(Figure 9), and its concentration does not exceed 15 at. %.…”

Zaykovite, Rh3Se4, a new mineral from the Kazan placer, South Urals, Russia

“…Based on the euhedral form of the inclusions of bowieite–kashinite and cuprorhodsite in early-formed Pt–Fe alloy grains, their crystallisation from melt during the early magmatic stages has been suggested (Zaccarini et al , 2016; Stepanov et al , 2020). The thermodynamic advantage of crystallisation of Rh 3 S 4 in terms of the Gibbs energy minimisation in comparison with phases with other Rh:S ratios has been proven experimentally (Jacob and Gupta, 2014).…”

Trace-Element Geochemistry of Sulfides in Upper Mantle Lherzolite Xenoliths from East Antarctica

“…Anomalously high concentrations of Ir (69-86 ppm) accompanied by low concentrations of Os (1.5-5.3 ppm) suggests a state of disequilibrium and rapid solidification of the Cu-Ni mss. High Ir concentrations that are inconsistent with low Os concentrations may also suggest that sulfide liquid of such composition could be parental to the Ir-bearing sulfides of the Bowieite-Kashinite series known as orogenic peridotite massives [54]. Enrichment in Pd relative to Pt is consistent with overall metasomatic/melt origin of the Cu-Ni mss.…”