Saybar

The alkaline rocks of this occurrence, which are predominantly peralkaline syenites, form intrusive sheets. The country rocks are siliceous shales and volcanics of variable composition; there are limestones which are presumed to be of Cambrian age. Theperalkaline syenites are mainly represented by two varieties: coarse-grained trachytic syenite and fine-grained, massive granosyenite. The latter forms dyke-like bodies among the coarse-grained syenite. Within the coarse-grained peralkaline syenite intrusive sheets of nepheline syenite are also found; their size varies from 10x10 to 200x500m. The nepheline syenites contain nepheline, aegirine, alkali feldspar, albite-oligoclase, alkali amphibole and such accessory minerals as apatite, fluorite, titanite and Fe-Ti oxide minerals. The texture is usually trachytic with idiomorphic nepheline and aegirine, the former usually being replaced by natrolite and hydromica. The nepheline syenites have a banded structure reflecting quantitative variations of the aegirine content. Chemical analyses of the rocks are given by Luchitsky (1960).