Mesoproterozoic Age of Phonolites from the Mara Volcanic Field, Biryusinskoe Prisayan’e: Pb–Pb Stepwise Leaching Method

The Pb‒Pb age of phonolites from the Mara volcanic field located within the Uvat Uplift of the Biryusa protrusion of the Siberian craton has been determined for the first time. A direct estimate of the age of the volcanic rocks is obtained using the stepwise leaching method for the whole rock. The obtained age of the phonolites, equal to 1513 ± 11 Ma, determines the timing of alkaline volcanism associated with the extension of the continental crust within the Biryusa protrusion. The Mesoproterozoic age of alkaline volcanism on the southwestern margin of the Siberian craton coincides with the stage of the formation of the Kuonamka igneous province on the Anabar Shield on the northeastern margin of the Siberian craton.