Sakhariokskii

Sakhariokskii is situated in the central part of the Kola Peninsula along the upper reaches of the Uzkaya River, which is a tributary of the Sakharnaya River. The intrusion is some 6 km in length and 2 km wide and emplaced in Archaean granite and peralkaline granite of Western Keiv (Fig. 13 and locality 13). The southern contact is tectonic and poorly exposed. The rocks of the occurrence are syenites and nepheline syenites, which cover about 4 km2, of which the nepheline syenites extend over 1.7 km2. It has the form of a steeply dipping dyke-like body the hanging wall of which is composed of nepheline syenite and the footwall of syenite. The contact between the two types of syenite is sharp. According to Batieva and Bel'kov (1984) the two rock types were not intruded simultaneously but the nepheline syenites were only emplaced after crystallization of the syenites, which they nephelinised. The syenites comprise albite, microcline, biotite and ferrohastingsite with accessory orthite, apatite, fluorite, calcite and zircon. The nepheline syenites vary from leucocratic to melanocratic varieties the former being composed dominantly of albite, microcline and nepheline and the latter enriched in aegirine, aegirine-augite, amphibole and biotite. Within the nepheline syenites are bands or layers up to 10s of metres wide with concentrations of pyroxene, amphibole and biotite. Accessories in the nepheline syenites include pyrochlore, britholite, fluorite, galena and orthite.