The unusual form of pyrrhotite inclusions in scapolite of magmatic rocks of the South Urals

Korinevsky V. G.,Korinevsky' E. V.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2015. V. 144. N 6. P. 74-83

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Language: Russian

Abstract

The description of the unique magmatic rock (scapolite-diopside gabbro) from the Ilimeny Mountains in the South Urals is provided. Gabbro is a part of the dike of 1.3 m wide, that cut calcite-dolomite carbonatites. Medium grain pyroxenites with scapolite observed in selvages change gradually into scapolite-bearing gabbro in the central part of the dike. Crystals of scapolite show surfaces of concurrent growth that are taken as evidence of their magmatic genesis. Scapolite (Me 63—70 %) contains numerous inclusions of pyrrhotite which appear as thin plates of 0.001 mm wide parallel to the cleavage plane {100}. Calculated formulae of pyrrhotite is consistent with its stoichiometry (Fe_1–xS). Morphology of plates (hexagonal sections) and their optical properties indicate hexagonal symmetry of pyrrhotite. Based on minor difference between scapolite grains containing and not containing pyrrhotite inclusions, scapolite and pyrrhotite are considered as a result of simultaneous crystallization in the magmatic melt.

Key words: scapolite, pyrrhotite, scapolite gabbro, Ilmeny Mountains, the South Urals.