stripes
A number of bodies of nepheline syenite comprise this occurrence and extend over a total area of about 3.7 km2 within coarse-grained biotite syenites. They have sinuous contacts and vary widely in size, the largest body being about 1,000 x 250 m. The nepheline syenites have massive, foliated or heterogeneous structures and the nepheline tends to form phenocrysts 3-5 cm in diameter within a background of fine-, medium- and sometimes coarse-grained rock. The modal composition of these rocks is alkali feldspar (55-70%), nepheline (20-30%), biotite (2-3%), riebeckite (2-5%), andesine (0-5%), garnet (1-2%), titanite, fluorite, apatite and some secondary minerals, including liebenerite, cancrinite, epidote and zoisite. Albitization of the nepheline syenites is widespread and accompanied by the formation of mariupolites. In the mariupolites the nepheline content varies between 15 and 30% and aegirine or biotite and hastingsite are also present. The bodies of mariuploite contain nests and vein-like areas of nepheline syenite pegmatite up to 1 x 0.2 m.
ANDRE’E V, G.V., SHARAKSHINOV, A.I. and LITVINOVSKY, B.A. 1969. Intrusions of nepheline syenite of Western Transbaikalia. Nauka, Moscow. 188 pp.
KUZNETSOVA, F.V. 1975. Nepheline syenites of the margin of the Borgoi depression. Nauka, Siberian Branch of the USSR Academy of Sciences, Novosibirsk. 92 pp.
