Title

M. N. Goloburdina, L. I. Lukyanova, E. N. Lepekhina

Alkali-ultramafic rocks of the Blagodat Mountain region (western slope of the Middle Urals)

Composition and age of potassic alkaline ultramafic rocks of the Blagodat mountain in the western slope of the Middle Urals are considered. Thin alkaline ultramafic rock bodies in the form of diatremes, dikes, and veins. It is shown that by material composition (petrographic, mineralogical, geochemical) breccias and porphyritic alkaline-ultramafic rocks are significantly different from typical kimberlites, but close to the specific types kimberlites of gr. II. According to the geological data and results of local U-Pb dating of zircons by ion microprobe SHRIMP II, Middle Paleozoic (D₃–C₁) age of kimberlites was determined. It is proposed to distinguish magmatic alkaline ultramafic rocks into an independent Chikmansky kimberlite complex. To date, studied magmatism has been considered Precambrian, however new data enable to attribute it to the Middle Paleozoic stage of the East European Platform activation, productive for diamondiferous kimberlites, and to predict diamondiferous kimberlites or lamproites within the Western Urals.
Key words: Western Ural, Mt. Blagodat, kimberlites, zircon, U-Pb dating, Middle Paleozoic age, complex.