NORWEGIAN JOURNAL OF GEOLOGY Vol 98 Nr. 3 https://dx.doi.org/10.17850/njg98-3-07 A common mid-Neoproterozoic chemostratigraphic depositional age of marbles and associated iron formations (Fe ± Mn ± P) in the Scandinavian Caledonides Victor A. Melezhik1, Peter M. Ihlen1, Terje Bjerkgård1, Jan Sverre Sandstad1, Agnes Raaness1, Anton B. Kuznetsov2, Arne Solli1, Igor M. Gorokhov2, Boris G. Pokrovsky3 & Anthony E. Fallick4 1Geological Survey of Norway, P.O. Box 6315 Torgard, 7491 Trondheim, Norway. 2Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, Makarova 2, 199034 St. Petersburg, Russia. 3Geological Institute, Russian Academy of Sciences, Pyzhevsky drive 7, 109017 Moscow, Russia. 4Scottish Universities Environmental Research Centre, Rankine Avenue, G75 0QF East Kilbride, Scotland. E-mail corresponding author (Peter M. Ihlen):
[email protected] 13 18 87 86 Carbon and strontium isotope chemostratigraphy (178 δ Ccarb and δ O, and 81 Sr/ Sr analyses of carbonate components in whole-rock samples) was applied to constrain apparent depositional ages of the carbonate protoliths of amphibolite-grade, calcite marbles occurring in siliciclastic sedimentary sequences within the Upper and Uppermost Allochthons in the North–Central Norwegian Caledonides. The Sr-rich marbles hosting banded iron formations occur only in the Uppermost Allochthon. The marbles show, over a distance of 350 km, rather similar least-altered 87Sr/86Sr (0.70645–0.70665) and δ13C (+6 to +8‰) values which are all consistent with a late Tonian (800–735 Ma) age. This sets up a maximum depositional age for the overlying iron formations and somewhat younger diamictites. The apparent maximum ages of the Scandinavian iron formations suggest their contemporaneous deposition with the oldest known Neoproterozoic iron formations reported from China (Shilu Formation) and Namibia (Chuos Formation).