Bericul'

This stock-like body, which has an area of about 6 km2, is mainly composed of gabbro, pyroxenite and rocks intermediate between gabbro and syenite. These rocks are cut by peralkaline syenite and dykes of nepheline syenite. The nepheline syenite dykes are 3-12 m thick and vary in structure and composition with foyaite, nepheline syenite aplite, miaskitic nepheline syenite, nepheline monzonite and pulaskite represented. Some dykes have complex structures, for example, foyaite with central aegirine zones and marginal miaskitic aplite, or central foyaite zones with marginal melanocratic nepheline monzonite. The foyaites are composed of nepheline (20-45%), microcline (up to 40%), aegirine-augite, aegirine, hastingsite and biotite. Secondary minerals are cancrinite, liebenerite, zeolite and accessories include Fe-Ti-oxide minerals, titanite, apatite and fluorite. The miaskitic nepheline syenites have modal compositions of albite (32%), nepheline (23%), other feldspar (25%), hastingsite, biotite and muscovite. The secondary and accessory minerals are the same as in the foyaites. Nepheline monzonites comprise hastingsite (28%), nepheline (25%), plagioclase (20%), K-feldspar (12%) and andradite (13%) and sometimes contain biotite and clinopyroxene. Peralkaline syenites, which include pulaskites and nordmarkites, have porphyritic textures; they are mainly composed of microcline-perthite and aegirine-augite and sometimes Fe-Ti oxide minerals; accessories are apatite, titanite and zircon.