U-PB DETRITAL ZIRCON SIGNATURE OF NEOPROTEROZOIC ROCKS IN SIBERIA: IMPLICATION FOR TECTONIC EVOLUTION AND PALEOCONTINENTAL RESTORATIONS

Neoproterozoic rocks are widespread on the Siberian Craton margins, and their deposition was mainly controlled by tectonic events occurred outside the craton. U-Pb detrital zircon studies carried out in the last few years supplied with important information on tectonic evolution of the Siberian Craton margins in Neoproterozoic and constrain paleocontinental restorations that involve Siberia.

The youngest detrital zircons in most samples are close in age to the age of sedimentation. On the northern margin of the Siberian Craton Neoproterozoic sandstones contain numerous zircons with ages varying from 800 Ma to 950 Ma. Approximately 40% of grains are Paleoproterozoic and Archean. Within the Siberian Craton, sandstones from the uppermost part of Neoproterozoic succession contain zircon grains with age varying from 570 to 640 Ma, although their amount varies greatly in different areas. On the eastern margin of the Siberian Craton Paleoproterozoic and Archean zircons predominate in the Neoproterozoic sandstones with only a few grains of 600-640 Ma. On the southern margin detrital zircon signature of Neoproterozoic sandstones varies greatly showing only Paleoproterozoic and Archean zircons in some samples and high content of ca. 650-750 Ma zircons in other samples.

Age of Neoproterozoic zircons correlates well with age of granite intrusions that are widespread in the accretionary belt of the Taimyr fold belt and in the Enisey Ridge showing occurrence of active margins on the northern and southwestern margins of the Siberian Craton. Erosion of basement highs was also locally important. Most clastics have local sources showing predominance of local to regional-scale, not continental-wide, river systems. However, amount of clastic sediments is too high to be eroded from known sources and likely requires erosion of Neoproterozoic rocks now located outside the Siberia.