COMPOSITION OF SPINEL GROUP MINERALS FROM LATE PROTEROZOIC ULTRAMAFIC LAMPROPHYRES OF THE BOLSHETAGNINSKII ALKALINE ULTRAMAFIC CARBONATITE COMPLEX LOCATED AT THE URIK-IYA GRABEN, EASTERN SAYAN REGION

This paper provides the results on spinel sampled from ailikites of Bolshetagninskii massif East Sayan region. The study aimed to determine history formation ultramafic lamprophyres Ziminsky complex. Spinel three dikes with different mineral compositions groundmass but similar textural and structural features (BTG 2/21, TGK 3, BTG 6/21) was analyzed. content main elements microcomponents in determined using electron microscope microprobe. All crystals are zonal, following types have been identified regard composition: chromites (Chr), aluminum-chromites (Al-Chr), chromium magnetites (Cr-Mgt), titanomagnetites (Ti-Mgt) (Mgt). composition sample 2/21 shows trend: chromite→ aluminum-chromite→ magnetite→ titanomagnetite→ magnetite. Sample 3 contains compositional change Chromite cores 6/21 overgrown magnetite, as well titanomagnetite. We assume primary melt, which chromite crystallized, be same for all samples studied. After formed melt possibly chamber, each portion experiences its own evidenced by study.