Matyr

A narrow strip of peralkaline and nepheline syenite occurs along the contact of a Devonian volcanogenic sequence and Cambrian limestone, with the peralkaline syenite the predominant rock type. It consists of microcline-perthite and albite (up to 93%), aegirine-augite (9%), lepidomelane (6%) and minor apatite and magnetite. Nepheline syenite (foyaite) forms two elongate bodies and consists of microcline-perthite and albite (56-69%), nepheline (23-27%), aegirine-augite, barkevikite and lepidomelane, as well as accessory apatite and magnetite. The alkaline massif is crossed by a large number of dykes, up to 1-1.5m thick, consisting of tinguaite, syenite porphyry, fine-grained foyaite and kersantite.