Srednevorogovskii

This occurrence comprises one body of 2.2x0.8 km and about 70 smaller ones each occupying only hundreds of square metres and concentrated in an area of 10-12 km2. The alkaline intrusions, which appear to represent the upper parts of eroded intrusive cupolas, are small stocks, dykes and veins. The larger body consists mainly of leucocratic quartz syenite (nordmarkite), which gradually grades into peralkaline syenite, granosyenite and peralkaline granite, the last situated close to the contact zone. Small bodies (from 1 to 100 m across) and dykes of granite porphyry and syenite porphyry belong to the final stage of the magmatic history. Nordmarkite is the most widespread rock type and consists of microcline perthite (70-80%), antiperthite (10-15%), quartz (5-10%), biotite (5-8%) and some riebeckite and arfvedsonite. Accessories are zircon, apatite, titanite, monazite, fluorite, rutile, Fe-Ti oxides and sulphides, including pyrite, pyrrhotite, molybdenite and chalcopyrite. Peralkaline syenites are compositionally similar to the nordmarkite except for less quartz (up to 3%) and some additional accessories including tourmaline and orthite. Peralkaline granite consists of microcline perthite (30-40%), quartz (30-35%), albite (20-25%), biotite (1-3%) and sometimes riebeckite. Accessories are apatite, garnet, rutile, titanite, zircon, ilmenorutile, pyrochlore, euxenite, tourmaline, Fe oxides, cassiterite and sulphides. Postmagmatic alteration has enriched some rocks in albite and microcline. There are quartz-fluorite-feldspar-carbonate and quartz veins enriched in rare minerals.