Telyashkin Ulus

This is a small stock having a diameter of up to 100 m and composed predominantly of teschenite. The stock is confined to a dome formed by volcanogenic strata of Devonian age and is intruded into lower Devonian rocks. The teschenites contain needle-like barkevikite crystals and segregations of labradorite laths with the interstices occupied by aggregates of zeolite and analcime. Clinopyroxenes, which may be zoned from fassaite in the centre to aegirine-augite at the margins, occur together with small quantities of alkali feldspar and nepheline; a little apatite and Fe-Ti oxide minerals are also present. The teschenite is characterized by the presence of occasional fine veinlets of urtite comprising nepheline, aegirine-augite, hornblende, apatite and analcime. Chemical analyses of the rocks are given by Luchitsky (1960).