GEOCHRONOLOGY OF ALKALINE ROCKS FROM THE BURPALA MASSIF (NORTHERN PRIBAIKALYE): NEW U-Pb DATA

Geochronological studies have been made on the main types of rocks from the Burpala alkaline massif and two gabbro and gabbro-diorite dikes located nearby. U-Pb LA-SF-ICP-MS zircon geochronology for the Burpala massif yielded a date of 294±2 Ma for gabbro crystallization, 607±4 Ma for diorite crystallization, 298±2 and 296±2 Ma for melanocratic alkaline and nepheline syenite crustallization, 291±2 and 293±3 for quartz and quartz-containing syenite crystallization, and 293±3 Ma for alkaline granite crystallization. The stage of formation of the massif rocks (298–291 Ma) coincides with the formation period of alkaline rocks from the Synnyr pluton and some alkaline complexes of the Vitim segment of Transbaikalia and confirms a widespread occurrence of post-collisional alkaline magmatism in Western Transbaikalia.