Vestnik MGTU (Apr 2020)
Structures of sulfide melt crystallization as an indication of metamorphism of the ores in the Oleninskoe gold deposit
Abstract
Multiphase fine aggregates of galena, pyrrhotite, freibergite, pyrargyrite, diaphorite, fizelyite, uchucchacuaite, ullmanite, and some other minerals are found in the ores of the Oleninskoe gold deposit in the Kolmozero-Voronya greenstone belt (Kola Peninsula, Russia). The aggregates are considered to be the product of crystallization of sulfide melt formed of the minerals of low-melting-point chalcophile elements (Zn, Ag, Cd, Tl, Pb, As, Sb, Bi, Se, Te, etc.) during heating to the temperature above 500 °C. This origin of the aggregates is affirmed by: 1) multiphase composition (up to 6 minerals) of the aggregates; 2) absence of signs of replacing early minerals by the late ones; 3) essential presence in the aggregates of the minerals of chalcophile elements Ag, Pb, Sb, i. e. elements with a low melting point of their compounds; 4) roundish droplet form of inclusions of minor minerals in the main sulfide, and 5) aggregates' position at the boundary sulfide – quartz or in fractures in vein minerals. Partial melting and crystallization of sulfide melts took place during Paleoproterozoic metamorphic event, when the Neoarchean sulfide-bearing rocks were mid-amphibolite metamorphosed under the temperature > 500 °C. Signs of the Paleoproterozoic metamorphism are found in the ores of the neighboring Cu-Mo porphyry Pellapahk deposit as well.
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