Morphology, Composition, and Ontogenesis of Platinum-Group Minerals in Chromitites of Zoned Clinopyroxenite–Dunite Massifs of the Middle Urals

Abstract

—We present results of analysis of the morphology and chemical composition of platinum-group minerals from chromite– platinum orebodies of zoned clinopyroxenite–dunite massifs in the Middle Urals (Nizhnii Tagil, Svetlyi Bor, Veresovyi Bor, and Kamenushenskii). Study of more than 500 grains has given an insight into the sequence of formation of platinum-group minerals in chromitites of the studied massifs. Three assemblages of platinum-group minerals have been revealed: magmatic (Os–Ir–Ru intermetallic compounds, isoferroplatinum, ferroplatinum, sulfides of the isomorphous series erlichmanite–laurite and kashinite–bowieite, and thiospinels of the series cuproiridsite–cuprorhodsite–malanite); postmagmatic (with a predominance of tulameenite, tetraferroplatinum, and ferronickelplatinum, resulted from serpentinization of dunites); and latest secondary (minerals with a predominance of PGE sulfides, arsenides, sulfoantimonides, sulfoarsenides, plumbides, and amalgams).

Kufahrite, PtPb, a new mineral from Ledyanoy Creek placer, Galmoenan ultramafic complex, Koryak Highlands, Russia

“…The main evidence for this conclusion are: (1) the occurrence of both tetraferroplatinum and tulameenite as rims over isoferroplatinum grains (Fig. 2; Nixon et al , 1990; Tolstykh et al , 2004, 2015; Stepanov et al , 2019, 2020); and (2) the presence of these minerals as separate phases in serpentine veinlets (Fig. 2e,f); and (3) experimental studies which proved the possibility of formation of Pt–Fe alloys under hydrothermal conditions (Evstigneeva and Tarkian, 1996).…”

“…Spiridonov et al , 2015). The only description of Pd–Pb minerals in Ural–Alaskan type complexes is those of zvyagentsevite in the altered parts of isoferroplatinum grains of the Veresovoborsky Complex, Urals (Stepanov et al , 2020). Here its textural position and assemblage irrefutably points towards post-magmatic origin.…”

Rare minerals of noble metals in the collection of the Mining Museum: new data

“…Various approaches have been proposed to study such objects [42]. A detailed study of complex ore aggregates using high-precision composite contrast and local microanalysis methods allows us to solve this problem and expand our knowledge of the mineral composition of both already known [43,44] and newly discovered noble metal deposits [45,46].…”

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

“…Rhodium and selenium are the rare elements with a different geochemical fate and, as a consequence, a low probability to be combined into rhodium selenide minerals. Platinum-group elements (PGE) are constituents of more than 20 selenides from the different localities worldwide (e.g., Johan et al, 1970;Davis et al, 1977;Jebwab et al 1992;Cook et al 1994; (Tolstykh et al, 2011(Tolstykh et al, , 2015Malich et al, 2015;Stepanov et al, 2019Stepanov et al, , 2020. Hollingworthite is known as secondary mineral developed after primary Pt-Fe alloys in the Nizhny Tagil and Kamenushensky massifs (Tolstykh et al, 2011(Tolstykh et al, , 2015.…”

“…The PGE mineralogy of ultramafic rocks and placers of the Uralian Platinum Belt located along the Main Uralian Fault, mainly in the Middle Urals, is well studied (e.g. Stepanov et al , 2019, 2020) (Fig. 1).…”