The first discovery of the paleoproterozoic aillikite dykes in Sarmatia: geochemistry and petrogenesis

The aillikite dykes of carbonate-biotite composition, intersecting the Paleoproterozoic banded iron formations, were discovered in the Kursk block of Sarmatia for the first time. Their age is 2.10–2.07 Ga. The aillikite dykes have undergone epidote-amphibolite facies metamorphism (550 °С, 2–3 kbar), they are deformed and fouled; primary magmatic olivine and pyroxene did not survive. Geochemically, the ultramafic lamprophyres of the Kursk block are close to the petrotypical aillikites. They have low SiO2 and Al2O3 concentrations, high MgO, TiO2, K2O, Cr, Ni, Nb and strongly fractionated LREE and HREE. According to available data, the aillikites and the Dubravinsky complex carbonatites could have been formed at different stages of melting of the uniform deep lithospheric source, which was enriched by lithophile elements shortly before the melting episode, possibly at the suprasubduction environment at ca. 2.1 Ga.