Ultramafic–Alkaline–Carbonatite Complexes as a Result of Two-Stage Melting of a Mantle Plume: Evidence from the Mid-Paleoproterozoic Tiksheozero Intrusion, Northern Karelia, Russia

The Tiksheozero ultramafic–alkaline–carbonatite intrusive complex, like numerous carbonatite-bearing complexes of similar composition, is a part of a large igneous province related to the ascent of a thermochemical mantle plume. The geochemical and isotopic data indicate that the formation of the ultramafic and alkaline rocks was related to crystallization differentiation of a primary alkali picritic melt, whereas carbonatite magmas were derived...