Volcanism and long-term seismicity controlled by plume-induced plate thinning

Mantle plumes, the hot upwellings from the Earth's core-mantle boundary, are thought to trigger surface uplift and the emplacement of large igneous provinces (LIPs). Magmatic centres of many LIPs are scattered over thousands of kilometres. This has been attributed to lateral flow of plume material into thin-lithosphere areas, but evidence for such flow is scarce. Here, we use new seismic data and new methods of seismic thermography to map previously unknown plate-thickness variations in the Britain-Ireland part of the North Atlantic Igneous Province, linked to the Iceland Plume. The locations of the ~60 Myr old uplift and magmatism are systematically where the lithosphere is anomalously thin at present. The dramatic correlation indicates that the hot Iceland Plume material reached this region and eroded its lithosphere, with the thin lithosphere, hot asthenosphere and its decompression melting causing the uplift and magmatism. We demonstrate, further, that the unevenly distributed current intraplate seismicity in Britain and Ireland is also localised in the thin-lithosphere areas and along lithosphere-thickness contrasts. The deep-mantle plume has created not only a pattern of thin-lithosphere areas and scattered magmatic centres but, also, lasting mechanical heterogeneity of the lithosphere that controls long-term distributions of deformation, earthquakes and seismic hazard.