Dedova

The Dedova alkaline massif, which forms a small mountain, cuts plagioclase porphyries of Lower Cambrian age. It is composed of leucocratic trachytic textured gabbro, theralite and nepheline syenite. The last forms two bodies the larger of which forms an elongate lens-like intrusion situated along the western boundary of the gabbro while the smaller is a dyke. Theralite lies between the nepheline syenite and gabbro. The nepheline syenite is a foyaite consisting of alkali feldspar, nepheline, titanaugite and accessory titanite, apatite and Ti-Fe oxides. The nepheline syenite of the dyke is an albitized ferrohastingsite-nepheline syenite in which a varied suite of accessory minerals has been found including yttrium-bearing garnet, lavenite, zircon, eudialyte, orthite, Fe-Ti oxide minerals and sulphides.