Geochemistry of plastic deformed olivine from ophiolite peridotites and dunites of Kraka massifs (the Southern Urals)
Saveliev D. E., Artemyev D. A.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2021. V. 150. N 1. P. 101-126
Rock-forming olivines from mantle ultramafic rocks of Kraka massifs have been studied by several methods, including microstructural analysis, scanning electron microscopy and LA-ICP-MS. In all studied samples of peridotites and dunites, olivine demonstrates a strong preferential crystallographic orientation, which testifies for rock formation under high-temperature plastic flow conditions. Olivine from circum-ore dunites at deposits of podiform chromitites is substantially depleted in Al, as compared to olivine from peridotites and thin dunite veinlets in the dunite-peridotite complexe. In olivine aggregates from the primary dunites, there were found numerous newly-formed high-Al chromspinel segregations in form of thin needles and rods, turning into morphologically more complicated forms as they grew larger. Their appearance displays consequence of processes including segregation of trace elements, coalescence and spheroidization of newly-formed chromspinel grains induced by plastic deformation of olivine.
Keywords: olivine, Cr-rich spinel, ophiolite, ultramafic rocks, plastic flow, deformation-induced processes, segregation of impurities, the South Urals, Kraka