Terra Nova, 25, 30–37, 2013
The late Mesoproterozoic Sveconorwegian orogen in southwest Baltica is traditionally interpreted as the eastward continuation of the Grenville orogen in Canada, resulting from collision with Amazonia, forming a central part in the assembly of the Rodinia supercontinent. We challenge this conventional view based on results from recent work in southwest Norway demonstrating voluminous subduction-related magmatism in the period 1050–1020 Ma, followed by geographically restricted high-T/medium-P metamorphism between 1035 and 970 Ma, succeeded by ferroan magmatism over large parts of south Norway in the period 990–920 Ma. This magmatic and metamorphic evolution may be better understood as reflecting a long-lived accretionary margin, undergoing periodic compression and extension, than continent–continent collision. This study has implications for Grenville–Sveconorwegian correlations, comparisons with modern continental margins, Rodinia reconstructions and how we recognize geodynamic settings in ancient orogens.