Long-term convergence along SW fennoscandia: 330Â m.y. of proterozoic crustal growth

This near-continuous, oceanward-stepping growth of Fennoscandia over this 330 m.y. period represents a remarkably persistent convergent-margin system that permits evaluation of Proterozoic processes of continental growth and pre-Rodinian plate reconstructions. Several stages of arc magmatism were followed by intracratonic episodes of “A-type” magmatism up to 1500 km inboard of the evolving margin. These typically bimodal magmatic episodes also swept westward with time such that the oldest episode in the Idefjorden terrane (1502 Ma) provides a minimum age for this crustal segment to occupy an intracratonic position, inboard of an inferred “proto-SW Norway”. The origin and final fate of such a pre-Sveconorwegian segment are speculative, but juxtaposition alongside the Idefjorden terrane during the 1.50-1.20 Ga interval is supported by independent evidence in SW Fennoscandia.