Pyrrhotite-nisbite-breithauptite-sulphoantimonide micromineral assemblage from Yuzhnoe (Sikhote-Alin, Russia)

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Marco E. Ciriotti
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Pyrrhotite-nisbite-breithauptite-sulphoantimonide micromineral assemblage from Yuzhnoe (Sikhote-Alin, Russia)

Messaggio da Marco E. Ciriotti » sab 10 apr, 2021 18:13

▪ Ratkin, V.V., Simanenko, L.F., Eliseeva, O.A., Gonevchuk, V.G. (2020): Pyrrhotite-nisbite-breithauptite-sulphoantimonide micromineral assemblage:a product of high-temperature recrystallization of ores in the vein-type tin-silver-polymetallic deposit Yuzhnoe (Sikhote-Alin, Russia). Zapiski RMO (Proceedings of the Russian Mineralogical Society), 149(3), 54-77.

The paper presents the results of mineralogical studies of tin-silver-polymetallic ores localized in the deep horizons (500–700 m from the present surface) of the Yuzhnoe deposit of Cenomanian age. At the deep southwestern flank of vein No. 4, signs of ore recrystallization have been revealed. In recrystallized ores at the boundaries of grains of nickel-containing pyrrhotite and galena impregnated with abundant silver-antimony minerals, very fine mineral segregations (inclusions) with sharp external boundaries and an interior made up of myrmekite-like thin intergrowth of pyrrhotite and nisbite NiSb2 or pyrrhotite and breithauptite NiSb have been found. Less often, myrmekite-like segregations are represented by pyrrhotite graphically intergrown with gudmundite or with non-stoichiometric sulphoantimonide Ag (phase X). The tiny grains of Ag-containing chalcopyrite and stannite are often present in pyrrhotite-sulphoantimonide myrmekites. The formation of the myrmecite-like segregations is supposedly associated with transformation of ore in the fluid-thermal field of the post-ore Maastrichtian leucogranite intrusion. In the process of recrystallization of ores, at temperature of about 600 °C, as a result of redistribution and migration of trace elements to contacts of mineral grains, local mobilizate was appeared in the form of a metalliferous sulphoantimonide melt. Inhomogeneities of distribution and variations of mineral composition of micrographic segregations reflect the participation of the mechanism of immiscibility and differentiation of the formed metal-bearing sulphoantimonide melt in the course of its liquidus evolution. The final avalanche-like crystallization of molten droplets in the form of quenching occurred at a temperature below 300 °C.
Marco E. Ciriotti

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