The Archean to Paleoproterozoic transition as recovered in the FAR DEEP cores: LA-ICP-MS U-Pb geochronology of detrital zircons and accompanying provenance analysis of siliciclastic sedimentary rocks

During the Archaean-Palaeoproterozoic transition many global environmental changes occurred in the Earth’s system at the same time as tectonic reorganisations led to the break-up of the supercontinent Kenorland. Stratigraphic successions registering these events were successfully drilled in northern Russia (Fennoscandia) in the FAR-DEEP/ICDP project.- The first part of our study aimed at improving age constraints by Laser Ablation ICP-MS U-Pb geochronology on detrital zircons for three of these events recorded in the FAR DEEP cores. The events are the Huronian glaciation, the Lomagundi-Jatuli positive excursion of δ13C, and the Shunga event of enhanced deposition of Corg-rich sediments. Our data resulted in tighter temporal constraints for these events. In rocks marking the transition from the Lomagundi-Jatuli to the Shunga event we also found U-Pb ages, now confirmed by ID-TIMS, which are too young regarding their stratigraphic position, and which are difficult to explain in view of the allegedly undisturbed stratigraphic succession. These need to be verified by additional analyses.- Also, the provenance of the analysed zircons and the nature of the recycled, partly Palaeoarchaean crust will be established by LA ICP-MS Hf isotope analysis on dated zircons and by ion microprobe analysis of heavy minerals like tourmaline and rutile.