Pavel Borisovich SHIRYAEV, Nadezhda Vladimirovna VAKHRUSHEVA


УДК 549.514.81+550.93(470.5) https://doi.org/10.21440/2307-2091-2018-4-33-40 


P. B. Shiryaev, N. V. Vakhrusheva / News of the Ural State Mining University. 2018. Issue 4(52), pp. 33-40

The relevance of the work is due to insufficient knowledge of the redox state of chromitites of the Voikar-Syninsky massif. The aim of the work is to establish how did redox conditions change during the formation of Al-rich chemical type chromitites within the Yambotyvissky area.
Research methodology: study of the composition of ore-forming chrome-spinels and olivines from chromitites of the Yambotyvissky area; evaluation of the temperature of olivine-spinel equilibrium and oxygen fugacity in chromitite samples; study of variation in the composition of minerals and T – fO2 parameters within the whole area and within individual ore bodies.
Results of the work. The composition features of ore-forming chrome-spinels and redox state of the chromitites of the Voikar-Syninsky massif of the Yambotyvissky area are studied. It was shown that ore-forming spinels of ore bodies occurring in dunites have lower Cr-number compared to chrome spinels of ores localised in harzburgites. It was found that Fe/(Fe+Mg) of olivines and spinels, which compose the chromitite of the area, were directly proportional. It indicates the rock – ore equilibrium existence in the system. The change in the chemical composition of ore-forming chrome spinels, the temperature of olivine-spinel equilibrium and oxygen fugacity within individual ore bodies were studied. The oxygen fugacity increases from the inner parts of chromitite bodies towards their endocontacts. It was shown that in Al-rich chromitites an increase in oxygen fugacity is followed by an enrichment of chrome spinel quantity in the ore. Chromitites occurring both in the dunite bodies and harzburgites, have been formed under close redox conditions. The data obtained were compared with the results of mineral composition and redox state of the chrome ores of the Ray-Is massif
from previous studies.

Keywords: redox state, chromitites, ultramafites, Voikar-Syninsky massif, metamorphism, ore formation.




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