Petrological evidences of syndeformation segregation of chromites during dunite formation: example of Kraka ophiolites, South Urals

D.E. Saveliev, E.V. Belogub , I.A. Blinov, D.A. Kozhevnikov, V.A.Kotlyarov

UDК 552.321.6+553.46

Results of structural and mineralogical studies of chromitite-bearing zone localized in spinel peridotites of the Middle kraka ophiolite massif are presented. The rocks of the studied area are characterized by deformation structures, which are cuased by plastic fow under high-PT conditions. Olivine in dunites was mostly deformed along the slide system of {0kl} [100]. The plastic fow of the peridotites led to the formation of the dunite veins and zones. Plastic deformation of olivine was accompanied by the formation of fne thread-like chromites, which have further been coalesced. X-ray-tomographic studies showed that the increase in the Cr-spinel value and redistribution of ore minerals occurred even in thin dunite veinlets. Some arguments are provided in favor of rheomor-phic diferentiation of matter in the mantle, which caused the formation of chromite bodies.

Figures 12. Tables 4. References 72.

Key words: mantle ultramafc rocks, Cr deposits, plastic deformation, olivine, chromite, segregation, coalescense, kraka, South Urals.

МINERALOGY № 4 2016