Age and composition of perovskite in ultramafic lamprophyres from the Zima alkaline-ultramafic carbonatite complex, the southern margin of the Siberian craton: Petrogenetic implications

Abstract

This paper presents data on the age and trace element composition of perovskites from dykes of ultramafic lamprophyres (aillikites) of the Zima alkaline-ultramafic carbonatite complex (Bolshaya Tagna and Bushkanay) located within the Urik-Iya graben, Eastern Sayan region, southern margin of the Siberian craton. The studied samples exhibit similar textural and structural features but differ slightly in the mineral composition of the groundmass. They have a porphyritic structure, a massive texture, and consist of olivine macrocrystals embedded in a fully crystallized groundmass composed of perovskite, apatite, spinel, phlogopite, garnet, carbonates, clinopyroxene and other minerals. The macrocrystals quantity varies between 40 and 50 vol%. With the exception of a single sample from the Bushkanay dyke, olivine is entirely replaced by serpentine and/or talc.