Jurnal Internasional A mantle plume origin for the Scandinavian Dyke Complex: a “piercing point” for 615 Ma plate reconstruction of Baltica? – Tegner – – Geochemistry, Geophysics, Geosystems
The origin of the Large Igneous Provinces (LIPs) is associated with continental breakup and the reconstruction of continents older than c. 320 million years (pre-Pangea) are contentious research problems. Here we study the petrology of 615-590 Myr dolerite dyke complex that intruded rift ‐ basins of the magma-rich margins of Baltica and now is exposed in the Scandinavian Caledonides. These are dykes are part of the Central Iapetus Magmatic Province (CIMP), a LIP emplaced in Baltica and Laurentia during the opening of the Caledonian Wilson Cycle. The> 1000 km long dyke lateral geochemical zonation complex displays from enriched basaltic compositions from south to north. Geochemical modeling of major and trace elements shows these compositions are best explained by melting hot mantle 75‐250 ° C above ambient mantle. Although the trace element modeling solutions are unique, the best involves melting a laterally zoned plume with enriched and depleted peridotite lithologies, similar to present-day Iceland and the North Atlantic Igneous Province. The origin of CIMP appears to have involved several mantle plumes. This is best explained if rifting and breakup magmatism coincided with volume generation zones at the margins of a Large Low Shear Wave Velocity Province (LLSVP) at the core mantle boundary. If the LLSVPs are quasi-stationary back in time as suggested for recent geodynamic models, the CIMP provides a guide for reconstructing the paleogeography of Baltica and Laurentia 615 million years ago to the LLSVP now positioned under the Pacific Ocean.