Azores–Canaries mantle plume interactions revealed by seismic imaging

Katrina Harris , Ana Ferreira, Michael Witek, Sung-Joon Chang, Maxim Ballmer, Miguel Miranda

Mantle plumes transport heat and material from the deep Earth towards the surface, yet how neighbouring plumes interact and influence mantle flow remains poorly understood. The Azores--Madeira--Canaries region, which hosts several closely spaced mantle upwellings, provides a unique opportunity to investigate these processes. Here we use data from the UPFLOW experiment, an unprecedented ocean-bottom seismometer deployment across the region, to image two mantle upwellings across the upper mantle and transition zone using multimode waveform tomography. We find widespread lateral spreading of low-velocity anomalies between ~230 and 400 km depth, accompanied by pronounced radial anisotropy variations. These observations are consistent with large-scale ponding and lateral flow of eclogitic material predicted by geodynamic models of thermochemical plumes. Where the lateral spreading associated with the two upwellings converges, fast-SV radial anisotropy indicates localised downwelling. Our observations provide evidence that neighbouring mantle plumes can interact dynamically, with their lateral spreading possibly driving localised downwelling that returns material to greater depths. This provides a rare observational window into the three-dimensional flow and interaction of thermochemical plumes in the upper mantle.