Silicates from Lherzolites in the South-Eastern Part of the Kempirsay Massif as the Source for Giant Chromitite Deposits (the Southern Urals, Kazakhstan)

We provide results of a comprehensive mineralogical and microstructural study relict lherzolites the main ore field fresh rocks from deep structural borehole drilled in south-eastern part Kempirsay massif. Olivine orthopyroxene contain numerous pieces evidence material redistribution at different scales caused mainly by solid-state processes, such as plastic flow mantle, syntectonic recrystallization, annealing. The deformation-induced processes submicron scale are recorded optical electronic microscopy. In olivine, deformation segregation impurities defects. As result, abundant tiny rods newly formed Cr-spinels occurred inside its grains. Moreover, enstatite, partial or complete chemical decomposition with exsolution diopside, pargasite spinel lamellae up to formation “fibrous” structure. other cases, it provided recrystallization form new phases enstatite-2, forsterite, pargasite, spinel. Petrographic observations validated geochemical data, i.e., regularly decreasing concentrations minor elements neoblasts compared large grains (porphyroclasts). Further chromitite bodies is witnessed their permanent association most mobile phase upper which only mineral that remains stable under intense flow. An increased concentration Cr-spinel during massive chromitites could appear conditions close pressure sintering, evidenced stressed textures ores an grain size disseminated chromitites. unique deposits associated integration disparate podiform into “ore bunches” due tectonic impact shear-compression regime. This was likely transition rifting (spreading) regime mantle fore-arc basin.