Scientific publications

The Jatulian-Ludicovian period is an essential stage in the Palaeoproterozoic evolution of the earth crust on the Fennoscandian Shield (FSS). A global anomaly of Lomagundy-Jatulian heavy-isotope carbonate carbon and the enormous accumulation of free carbon that has a lighter isotopic composition are associated with the period. An oxidative carbon cycle is transformed to a reducing cycle with changes in the magmatic regime of basic volcanism and sedimentation conditions in basins. The Lomagundy-Jatulian anomaly suggests the supply of heavy-isotope СО₂, to the atmosphere and basins. Manifestations of partially oxidized phases of Jatulian volcanism are assumed to be a source of CO₂. Analysis of cross-sections suggests that a biogenicoxidative cycle resulted in the accumulation of Jatulian heavyisotope carbon not compensated by biogenic fractionation. As the basin increased in depth in Ludicovian time, a carbon cycle was transformed to a biogenic-reducing cycle. As a result of biogenic fractionation, the isotope composition of buried carbon progressively becomes lighter. The authors discuss a relationship between the evolution of magmatism and carbon cycle transformation on the FSS in Early Proterozoic time.