Northward drift of the Azores plume in the Earth’s mantle

Abstract

Mantle plume fixity has long been a cornerstone assumption to reconstruct past tectonic plate motions. However, precise geochronological and paleomagnetic data along Pacific continuous hotspot tracks have revealed substantial drift of the Hawaiian plume. The question remains for evidence of drift for other mantle plumes. Here, we use plume-derived basalts from the Mid-Atlantic ridge to confirm that the upper-mantle thermal anomaly associated with the Azores plume is asymmetric, spreading over ~2,000 km southwards and ~600 km northwards. Using for the first time a 3D-spherical mantle convection where plumes, ridges and plates interact in a fully dynamic way, we suggest that the extent, shape and asymmetry of this anomaly is a consequence of the Azores plume moving northwards by 1–2 cm/yr during the past 85 Ma, independently from other Atlantic plumes. Our findings suggest redefining the Azores hotspot track and open the way for identifying how plumes drift within the mantle.

Plate tectonics and mantle controls on plume dynamics

“…Finlayson et al, 2018;Konrad et al, 2018) to explain the bent Hawaii-Emperor hotspot track. Petrological data also suggest that the Azores plume has drifted northwards by 1-2 cm yr −1 along the Mid-Atlantic ridge over the last 85 Myr (Arnould et al, 2019).…”

“…S9). The possible slow motion of the Azores plume could fall in that category (Arnould et al, 2019). Finally, mantle plumes interacting with fast-migrating ridges, usually neighbouring small plates affected by fast reorganisations, tend to move laterally faster and more eratically (Fig.…”

“…2 and Movies S1 and S2), 2/ the nature of the impacted lithosphere (thickness, type, plate boundary proximity) and 3/ the relative motion between the plume and the lithosphere, which can shear the conduit and result in an asymmetric shape of the plume trail (Fig. S2, Movies S1 and S2; see also Arnould et al, 2019).…”

Mantle plumes and their role in Earth processes

“…are not unexpected in a convecting mantle, as computer models show that rising mantle plumes will be advected in Earth's overall mantle circulation regime 62,163,276,277 and cause the locations of hotspots on the Earth's surface to wander over geological time.…”

“…An exciting and growing field of mantle geodynamics involves the generation of 3D spherical shell numerical models of the Earth that solve the governing equations for appropriate physical parameters and can include increasingly complex rheologies. These models can evolve through geological time, allowing us to study the interactions between tectonic processes, large-scale mantle flow and plumes 140,165,277,304,305 . The simulation output can then be used to improve the interpretation of complex seismic tomographic features.…”