摘要：Abstract
The Tiksheozero carbonatite in northern Russian Karelia is a transitional type between alkaline ultramafic — carbonatitic and alkaline gabbroic suites. The complex is dominated by pyroxenite with a variety of subordinate mafic and ultramafic phases and nepheline syenite. Carbonatite occurs in a main central body and in veins. In this study we have obtained a reliable age for the complex by single grain ID-TIMS U-Pb analyses of zircon and baddeleyite. The age of 1999 ± 5 Ma is important because it places the emplacement of the alkaline complexes in the context of craton-wide extension and break-up events which preceded the initiation of a major Paleoproterozoic orogenic cycle. The Paleoproterozoic age also emphasizes the fact that not all members of the Kola alkaline province are of Paleozoic age.
