The Upper Riphean of the Yenisei Range: Sr Chemostratigraphy and Pb–Pb Age of Limestones of the Tungusik and Shirokaya Groups

Аннотация

The Pb–Pb isotope age and the Sr isotope signature of the Upper Riphean sedimentary limestones from the south of the Yenisei Range on the western margin of the Siberian Craton were obtained. The Pb–Pb age of carbonate deposits of the Dadykta Formation of the Tungusik Group in the Kamenka facial zone in the east of the Yenisei Range is 1020 ± 20 Ma. The Pb–Pb age of limestone of the Gorevka Formation of the Shirokaya Group in the Glushikha facies zone in the western part of the region is estimated at 1020 ± 70 Ma. The ⁸⁷Sr/⁸⁶Sr ratio in limestones of the Dadykta Formation lies within 0.70536–0.70590 and that of the Gorevka Formation lies within 0.70552–0.70578. This coincides with a decrease in the ⁸⁷Sr/⁸⁶Sr ratio in a paleo-ocean immediately after the culmination of the Grenville orogeny. The correlation of the Shirokaya Group with the Oslyanka Group of the Kamenka Zone in combination with other data has shown that the accumulation of the Tungusik, Shirokaya, and Oslyanka groups occurred within an interval of 1030–950 Ma. The isotope age of the Middle and Upper Riphean boundary at the base of the Tungusik Group of the Yenisei Range is estimated at 1030 Ma, which is consistent with the age of this boundary in the sections of the Turukhansk Uplift and the Uchur-Maya Region of Siberia. It was revealed that the greater part of the Upper Riphean (Neoproterozoic) in the sedimentary record of the Yenisei Range is missing. The observed facial zoning of the Riphean deposits of the Yenisei Range represents the configuration of the ancient sedimentary basin that existed at the western margin of the Siberian Craton long before the collisional events accompanied by granite intrusions and superimposed metamorphism in the Neoproterozoic.