Tracking lateral δ 13 C carb variation in the Paleoproterozoic Pechenga Greenstone Belt, the north eastern Fennoscandian Shield

The Kuetsjarvi Sedimentary Formation (KSF) records the global Paleoproterozoic (ca. 2200-2100 Ma) positive delta C-13 excursion of sedimentary carbonates. This event is here called as the Lomagundi-Jatuli isotopic excursion. In this study, lateral delta C-13(carb) variation in the KSF and local basinal factors amplifying global delta C-13(carb) value were investigated and a secular delta C-13 curve for the KSF was constructed. Sedimentary carbonate samples from a new drillcore (Drillcore 5A) from the KSF were analysed for delta C-13, delta O-18 and selected major and trace elements. The delta C-13 values of the samples vary from 5 to 8%. (VPDB) and the delta O-18 values from -18 to 10 parts per thousand (VPDB). Most of the samples have retained their primary C isotopic composition, as they do not show correlation between the Mn/Sr ratios and the delta C-13 and delta O-18 values. The new results were compared to those previously obtained from another drillcore (Drillcore X) from the KSF (ca. 25 km along strike from Drillcore 5A). Both cores show a similar kind of generally upward decreasing trend in delta C-13, excluding some negative and positive spikes in Drillcore X and samples close to a contact with a Fe-picrite dyke in Drillcore 5A. A secular delta C-13 curve of the KSF was constructed based on the least altered delta C-13 data from the cores 5A and X. The secular delta C-13 curve of the KSF may represent the latest part of the Lomagundi-Jatuli isotopic excursion. (C) 2013 Elsevier B.V. All rights reserved.