Ancient slabs beneath Arctic and surroundings: Izanagi, Farallon, and in-betweens

Abstract

A detailed 3-D tomographic model of the whole mantle beneath the northern hemisphere (north of ~ 30°N latitude) is obtained by inverting a large amount of P-wave arrival time data (P, pP, and PP) to investigate transition of subducted slabs beneath Eurasia–Arctic–North America. We apply an updated global tomographic method that can investigate the whole mantle 3-D structure beneath a target area with high resolution comparable to that of regional tomography. The final tomographic model is obtained by performing independent calculations for 12 different target areas and stitching together the results. Our model clearly shows the subducted Izanagi and Farallon slabs penetrating into the lower mantle beneath Eurasia and North America, respectively. In the region from Canada to Greenland, a stagnant slab lying below the 660-km discontinuity is revealed. Because this slab has a texture that seems to be due to subducted oceanic ridges, the slab might be composed of the Farallon and Kula slabs that had subducted during ~60–50 Ma. During that period, a complex rift system represented by division between Canada and Greenland was developed. The oceanic ridge subduction and hot upwelling in the big mantle wedge above the stagnant slab caused a tensional stress field, which might have induced these complex tectonic events.