Evidence of Middle Neoproterozoic extensional tectonic settings along the western margin of the Siberian craton: Implications for the breakup of Rodinia

The new results of U–Pb and 40Ar/39Ar dating and petrological and geochemical studies of rocks from the Yenisey regional shear zone (YRSZ) in the Transangarian part of the Yenisey Ridge were used to identify a dike belt at the western margin of the Siberian craton and constrain the timing of formation of rift-related structures accompanied by within-plate magmatism. The magmatism of this epoch produced felsic and mafic intrusive rocks. The extension processes are recorded by the 797–787 Ma dike swarms. The rift origin of the rocks studied here is confirmed by their occurrence as dikes and sills confined to the YRSZ, bimodal composition of magmatic rock associations, and petrochemical characteristics of rocks typical of within-plate settings. The formation of the 800 Ma dike belt within the study area could be associated with the Neoproterozoic extensional tectonic events along the western margin of the Siberian craton which coincided with the onset of the breakup of the Rodinia supercontinent. These events provide the upper age limit for the collisional metamorphism that took place at the final stage of orogeny. The evolutionary phases identified in the region agree well with the sequence and style of tectonothermal events within the Valhalla Orogen at the Arctic margin of Rodinia and provide further support for the spatial proximity between Siberia and North Atlantic cratons during this epoch, as indicated by recent paleomagnetic data.