A new metamorphic–hydrothermal genetic type of zvyagintsevite

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Marco E. Ciriotti
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A new metamorphic–hydrothermal genetic type of zvyagintsevite

Messaggio da Marco E. Ciriotti » lun 07 giu, 2021 11:01

Referenza:
▪ Spiridonov, E.M. (2021): A New Metamorphic–Hydrothermal Genetic Type of Zvyagintsevite Pd3Pb. Doklady Earth Sciences, 498, 409–411.

Abstract:
A palladium and lead intermetallide, namely, zvyagintsevite, is a relatively widespread mineral of magmatic sulfide ores in Norilsk deposits and ores in the Bushveld, Konder, and Yoko-Dovyren intrusions. It is a relatively high-temperature pneumatolytic mineral and a member of the continuous solid solution range: rustenburgite Pt3Sn–atokite Pd3Sn–zvyagintsevite Pd3Pb. In general, zvyagintsevite contains up to 13 wt % Pt, 11 wt % Sn, 5–8 wt % Au, and an appreciable amount of Bi, Hg, Te, Sb, and Ge. Its composition corresponds to (Pd,Pt,Au)3(Pb,Sn,Bi,Sb,Hg,Ge)1. А different zvyagintsevite type was investigated in metamorphosed magnetite–pentlandite–putoranite ores of deep horizons in the northern flank of the Oktyabrskoye deposit within the Norilsk ore field. Almost pure zvyagintsevite Pd3Pb developed in small nests and miniveins of low-temperature metamorphic–hydrothermal hibbingite (Fe2+,Mn2+)2Cl(OH)3 and siderite. Zvyagintsevite and hibbingite have induction boundaries of joint growth. Metamorphogenic–hydrothermal zvyagintsevite accretions reach up to 35 × 15 μm in size. Its composition is stable and close to stoichiometric, wt % (n = 7): 60.24 (59.14–61.13) Pd, 38.75 (38.04–39.37) Pb, and 0 Cd (more often, 0.43); its formula is Pd3.001(2.991–3.011)Pb0.993(0.977–1.009)Cd0.006(0–0.021). Metamorphic–hydrothermal zvyagintsevite differs from the pneumatolytic one in the mineral assemblages and composition, specifically, in the absence of Pt, Sn, Au, Bi, Te, Sb, Hg, and Ge impurities. Metamorphic–hydrothermal zvyagintsevite was likely formed in the Norilsk ores under zeolite facies conditions with an extremely low sulfide sulfur fugacity in the stability field of native lead (log f S2 < –25 at 250°C).
Marco E. Ciriotti

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