Chemical composition and origin of platinum-group minerals from placers of the Aunik River, Buryatia, Russia

Airiyants, E. V.; Belyanin, Dmitriy; Жмодик, С. М.; Agafonov, L. V.; Romashkin, P. A.

doi:10.1016/j.oregeorev.2020.103453

Cited by 3 publications

(4 citation statements)

References 29 publications

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“…Barkov et al [23] noted the predominance of stoichiometry of the AB 2 type for such compounds, with the formation of structures most optimal for the placement of Se under the given crystallization conditions. Earlier, we also described IPGE selenides with laurite-like structures in alluvial deposits of the r. Aunik (Western Transbaikalia) and in chromitites of the Dunzhugur ophiolite massif (Eastern Sayan) [46,57]. In the River Kitoy placer, we see a wide variety of similar compounds with a ratio of 1:2.…”

Section: Pge Selenides Arsenoselenides Telluridessupporting

confidence: 55%

“…Sufficiently high platinum contents in the initial melt led to the appearance of idiomorphic Pt-Fe alloy inclusions in the matrix during cooling of the system, corresponding in stoichiometric composition to isoferroplatinum (Figure 4). It appears that Pt behaved somewhat incompatibly during the crystallization of the Os-Ir-Ru alloy [16,[43][44][45][46]. For comparison, we plotted on the ternary diagram the compositions of the Os-Ir-Ru alloys studied by us from the chromitites of the ophiolite complexes of SEPES [28,29,39,41,42].…”

Section: Grains Of Os-ir-ru Alloysmentioning

confidence: 99%

“…We also identified magnesian olivine (Fo-90), biotite, and chlorite in the inclusions (Figure 6a-c). We present data on the chemical composition of silicate inclusions in Table 2 and for comparison give the compositions of silicate inclusions in chromian spinel and PGMs from various ultrabasic-basic complexes [46,48,49]. Note: the data used (1)- [48], (2)- [49], (3)- [46].…”

Section: Inclusions In Grains Of Os-ir-ru Alloysmentioning

confidence: 99%

“…Compounds of selenides and tellurides of the iridium subgroup of PGE (IPGE: Ir, Os, and Ru), as well as Se-rich phases of PGE, are exotic for ophiolite complexes. However, recently in the literature, there have been more and more references to findings of Se-enriched PGE compounds in ophiolite complexes and primitive ultrabasic rocks [22,23,46,56,57]. Barkov et al [23] noted the predominance of stoichiometry of the AB 2 type for such compounds, with the formation of structures most optimal for the placement of Se under the given crystallization conditions.…”

Section: Pge Selenides Arsenoselenides Telluridesmentioning

confidence: 99%

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Platinum-Group Minerals in the Placer of the Kitoy River, East Sayan, Russia

et al. 2021

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The platinum-group minerals (PGM) in placer deposits provide important information on the types of their primary source rocks and ores and formation and alteration conditions. The article shows for the first time the results of a study of placer platinum mineralization found in the upper reaches of the Kitoy River (the southeastern part of the Eastern Sayan (SEPES)). Using modern methods of analysis (scanning electron microscopy), the authors studied the microtextural features of platinum-group minerals (PGM), their composition, texture, morphology and composition of microinclusions, rims, and other types of changes. The PGM are Os‑Ir‑Ru alloys with a pronounced ruthenium trend. Many of the Os‑Ir‑Ru grains have porous, fractured, or altered rims that contain secondary PGE sulfides, arsenides, sulfarsenides, Ir-Ni-Fe alloys, and rarer selenides, arsenoselenides, and tellurides of the PGE. The data obtained made it possible to identify the root sources of PGM in the placer and to make assumptions about the stages of transformation of primary igneous Os-Ir-Ru alloys from bedrock to placer. We assume that there are several stages of alteration of high-temperature Os-Ir-Ru alloys. The late magmatic stage is associated with the effect of fluid-saturated residual melt enriched with S, As. The post-magmatic hydrothermal stage (under conditions of changing reducing conditions to oxidative ones) is associated with the formation of telluro-selenides and oxide phases of PGE. The preservation of poorly rounded and unrounded PGM grains in the placer suggests a short transport from their primary source. The source of the platinum-group minerals from the Kitoy River placer is the rocks of the Southern ophiolite branch of SEPES and, in particular, the southern plate of the Ospa-Kitoy ophiolite complex, and primarily chromitites.

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Section: Pge Selenides Arsenoselenides Telluridessupporting

confidence: 55%

Section: Grains Of Os-ir-ru Alloysmentioning

confidence: 99%

Section: Inclusions In Grains Of Os-ir-ru Alloysmentioning

confidence: 99%

Section: Pge Selenides Arsenoselenides Telluridesmentioning

confidence: 99%

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Platinum-Group Minerals in the Placer of the Kitoy River, East Sayan, Russia

et al. 2021

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Sulfide and Selenide PGE Mineralization in Chromitites of the Dunzhugur Ophiolite Massif (East Sayan, Russia)

Kiseleva,

Ayriyants,

Zhmodik

et al. 2024

Geol. Ore Deposits

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Sulfide and selenide PGE mineralization in chromitites of the Dunzhugur ophiolite massif (East Sayan, Russia)

Kiseleva,

Ayriyants,

Zhmodik

et al. 2024

Geologiâ rudnyh mestoroždenij

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The paper presents the first data on PGE sulfide and selenide mineralization formed in podiform chromitites at different stages of evolution of the Dunzhugur ophiolite massif. The chromite bodies are local-ized in listvenitized aposerpentinites, which are part of the Dunzhugur ophiolite complex. The forms of occurrence, microstructural features and compositions of platinum-group minerals in chromitites were stud-ied by scanning electron microscopy. The enrichment of chromitites with a refractory platinum group-ele-ment (PGE) sulfides and alloys in the Os-Ir-Ru system (IPGE) testify that the for-mation of magmatic platinum-group minerals (PGMs) occurred under mantle conditions. Primary PGMs were replaced by iridium sulfoarsenides and sulfoantimonides due to the interaction of mantle peridotites and chromitites with As–Sb-bearing fluid generated during dehydration and melting of the subducting slab. Native osmium was formed as a result of desulfurization of magmatic PGE-bearing sulfides with the partic-ipation of reduced fluids at the serpentinization stage. The replacement of Ru–Os sulfides by selenides of these metals in chromitites could occur at the stages of subduction or obduction at high oxygen fugacity under the influence of acid hydrothermal/metamorphogenic fluids. A qualitative assessment of physicochemical parameters of the formation of ruthenium selenides was carried out. Oxygen fugacity values estimated from the mag-netite–hematite association are log fO2 (–30.5) at 300օC and log fO2 (–40.5) at 200օC. The minimum sulfur fugacity value was determined by the stability line of laurite at 300օC, log fS2 = –20; the maximum sulfur fugacity values—by the stability line of iron and nickel sulfides: log fS2 –4.5 at 300օC and log fS2 –10.5 at 200օC. The selenium fugacity at T = 300օC is log fSe2 (–8…–13); at T = 200օC, log fSe2 (–12…–17). Au–Ag selenides were formed at T = 200օC, log fS2 (–9…–10.5); log fSe2 is from –13.5 to –20.5, log fO2 (–40). An important factor for the possibility of replacement of Ru–Os sulfides by selenides is Se occurrence in the ore-forming system. The source of Se may be the substance of the subducting slab—volcanogenic–sedimentary rocks containing fragments of Se-rich hydrothermal–sedimentary sulfide ores. They were involved in the processes of magma genesis and accompanying hydrothermal circulation.

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Chemical composition and origin of platinum-group minerals from placers of the Aunik River, Buryatia, Russia

Cited by 3 publications

References 29 publications

Platinum-Group Minerals in the Placer of the Kitoy River, East Sayan, Russia

Platinum-Group Minerals in the Placer of the Kitoy River, East Sayan, Russia

Sulfide and Selenide PGE Mineralization in Chromitites of the Dunzhugur Ophiolite Massif (East Sayan, Russia)

Sulfide and selenide PGE mineralization in chromitites of the Dunzhugur ophiolite massif (East Sayan, Russia)

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