Geochemical features and age of baddeleyite from carbonatites of the Proterozoic Tiksheozero alkaline–ultramafic pluton, North Karelia

On the basis of the local composition, baddeleyite grains that were less altered due to interaction with an alkaline melt and corresponded to the primary stage of crystallization of the intrusion were selected from the carbonatite intrusion of the Proterozoic polyphase Tiksheozero alkaline–ultramafic complex. The single age of carbonatite crystallization characterized of the bulk volume of the intrusion was estimated for the first time on the basis of 40 local U–Th–Pb (SHRIMP II) analyses of these grains. The overall concordant age of baddeleyite is 1994.8 ± 9.4 Ma, and the lower age limit of the polyphase complex formation is less than 1998.4 ± 3.5 Ma.