The nature and origin of the ~1880 Ma Circum-Superior Large Igneous Province

The Circum-Superior Large Igneous Province (LIP) consists predominantly of ultramafic-mafic lavas and sills with minor felsic components distributed as various segments along the margins of the Superior Province craton. Ultramafic-mafic dykes and carbonatite complexes of the LIP also intrude the more central parts of the craton. Most of this magmatism occurred at ∼1880 Ma. New major and trace element and Sr-Nd-Pb-Hf-Os isotopic data reveal that the segments of the Circum-Superior LIP can be treated as a single entity formed in the same tectonomagmatic environment. In contrast to most previous studies, the Circum-Superior LIP is interpreted to have formed from a single mantle plume and this is consistent with the high MgO and Ni contents of magmas, oceanic-plateau-like incompatible trace element profiles, ocean-island-like positive Nb-Ta anomalies, Icelandic plume-like Nb/Y and Zr/Y ratios, oceanic-plateau-like Zr/Nb and Nb/Th ratios and Nd-Hf isotopic compositions which differ from that of the estimated depleted upper mantle at ∼1880 Ma. Further support for a mantle plume origin comes from calculated high degrees of partial melting, high mantle potential temperatures and the presence of a radiating dyke swarm. The location of most of the magmatic rocks along the Superior Province margins probably represents the deflection of plume material by the thick cratonic keel toward regions of thinner lithosphere at the craton margins. There is no obvious geochemical distinction between segments of the Circum-Superior LIP which host ore deposits and those which do not. The geochemistry of the Circum-Superior LIP differs markedly from that of other ∼1880 Ma igneous provinces on other cratons which questions the validity of the formation of a very large LIP and the occurrence of a superplume event at ∼1880 Ma.EThOS - Electronic Theses Online ServiceGBUnited Kingdo