Strel'Ninskii And Purnachskii

It is very probable that Strel'ninskii and Purnachskii represent a single body of peralkaline granite. With an area of about 60 km2 the intrusion lies in metabasites of Archaean age. It has a concentric, zonal structure, the outermost ring being composed of arfvedsonite-aegirine granites with a clearly defined orientation of the mafic minerals. The middle ring is composed of aegirine-arfvedsonite granites containing aenigmatite and astrophyllite; the mafic minerals are not orientated in this ring. The contacts between the granites of different petrographic facies are sharp, from which it is inferred that they represent separate intrusive phases. The granites sometimes assume a very coarse-grained pegmatitic texture.