Archean high-Mg magmas: Their significance for continental growth at Archean cratonic margins

The growth of Archean cratons has been linked to either stagnant or mobile lid processes in models that ultimately depend on the accurate interpretation of high-Mg volcanism. Recognition of the diversity of such greenstone belt magmas highlights a need for accurate classification of the sub-types, which is potentially offered by the boninite discrimination scheme of Pearce and Reagan (2019). The utility of the scheme is assessed at two localities in the western Superior Craton where komatiites have been reported but not extensively studied: the Lake of the Woods greenstone belt of the Western Wabigoon terrane and the Shebandowan greenstone belt of the western Wawa-Abitibi terrane. It is then applied to the southern Abitibi belt where evidence for both mantle plume and subduction-style magmatism presents complex geodynamic challenges. In combination with previously recognized boninites or boninitic rocks in the Kidd-Munro Assemblage and Opatica Terrane, the new results support models of short-lived subduction events in the Archean and underlines their role in craton growth prior to the development of a global network of tectonic plates.