Cretaceous Arctic magmatism: Slab vs. plume? Or slab and plume?

Tectonic models for the Cretaceous paleogeographic evolution of the Arctic Ocean and its adjacent landmasses propose that rifting in the Amerasia Basin (AB) began in Jura-Cretaceous time, accompanied by the development of the High Arctic Large Igneous Province (HALIP). During the same timespan, deformation and slab-related magmatism, followed by intra-arc rifting, took place along the Pacific side of what was to become the Arctic Ocean. A compilation and comparison of the ages, characteristics and space-time variation of circum-Arctic magmatism allows for a better understanding of the role of Pacific margin versus Arctic-Atlantic plate tectonics and the role of plume-related magmatism in the origin of the Arctic Ocean. In Jura-Cretaceous time, an arc built upon older terranes overthrust the Arctic continental margins of North America and Eurasia, shedding debris into foreland basins in the Brooks Range, Alaska, across Chukotka, Russia, to the Lena Delta and New Siberian Islands region of the Russian Arctic. These syn-tectonic sediments have some common sources (e.g., ~250-300 Ma magmatic rocks) as determined by U-Pb detrital zircon geochronology. They are as young as Valanginian-Berriasian (~136 Ma, Gradstein et al., 2004) and place a lower limit on the age of formation of the AB. Subsequent intrusions of granitoid plutons, inferred to be ultimately slab-retreat related, form a belt along the far eastern Russian Arctic continental margin onto Seward Peninsula and have yielded a continuous succession of zircon U-Pb ages from ~137-95 Ma (n=28) and a younger suite ~91-82 Ma (n=16). All plutons dated were intruded in an extensional tectonic setting based on their relations to wall-rock deformation. Regional distribution of ages shows a southward migration of the locus of magmatism during Cretaceous time. Basaltic lavas as old as 130 Ma and as young as 80 Ma (40Ar/39Ar)) erupted across the Canadian Arctic Islands, Svalbard and Franz Josef Land and are associated with radial dikes that emanate from the proposed locus of the HALIP on the Alpha Ridge (Buchan and Ernst, 2006). 112, 100, and 83 Ma (40Ar/39Ar) basaltic lavas dredged in 2008 from the northwestern edge of the Canada Basin bear geochemical similarity to HALIP magmatism on Ellesmere Island and Franz Josef Land. Geochemical data on terrestrial HALIP and dredged basalts is indicative of an evolving plume-related origin for basaltic magmatism by 112 Ma. No matter how the AB is reconstructed, its pre-mid-Cretaceous configuration requires that terrestrial exposures of the HALIP were much closer to the actively subducting and extending Russian-Alaskan margin. Likewise, the temporal overlap of the onset of extension along the Russian-Alaskan segment of the Arctic margin (~135-120 Ma) with eruption of Barremian-Aptian HALIP lavas needs to be considered in models for the opening of the AB. This geochronologic compilation and summary highlights the facts that before the opening of the AB, the HALIP originated in a back arc position with respect to slab-related magmatism along the Pacific margin of the Arctic and that the two types of magmatism overlap in age and were once closer in space.