Abstract

A microtomographic study of the internal structure of sulfide minerals from ore varieties of rocks of two industrial deposits of the Arctic zone of the Russian Federation – disseminated ore of the Pilgujarvi Cu–Ni deposit of Pechenga and ore gabbronorites of the platinum-bearing Fedorovo-Pansky complex (Kola Peninsula) was carried out. It is shown that all studied sulfide samples have a homogeneous structure without obvious defects or silicate inclusions larger than 1 µm. The absence of silicate microinclusions larger than one micron in sulfides suggests an isomorphic form of REE occurrence in sulfides and, to some extent, eliminates the debatable problem of the influence of microinclusions on the results of Sm–Nd isotope-geochronological studies of sulfides. The presence of smaller (10–500 nm) silicate microinclusions is highly likely to be unable to control the total REE budget in a sulfide mineral. The conclusion about the absence of a significant effect of microinclusions on the obtained ages is confirmed by the results of Sm–Nd dating using sulfides from the same mineral samples: the Sm–Nd ages of the ores of the Pilgujarvi Cu–Ni deposit were 1965 ± 87 Ma; ore gabbronorites of the Fedorovo-Pansky complex – 2482 ± 61 Ma, which is in good agreement with the dates obtained earlier using other isotopic systems (U–Pb, Re–Os).

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