The Role of the Seismically Slow Central‐East Atlantic Anomaly in the Genesis of the Canary and Madeira Volcanic Provinces.

The Canary and Madeira provinces in the Central‐East Atlantic Ocean are characterized by an irregular spatio‐temporal distribution of volcanism along the hotspot tracks, and several alternative scenarios have been suggested to explain it. Here, we combine results from seismic tomography, shear‐wave splitting and gravity along with plate reconstruction constraints to investigate the mantle structure and dynamics beneath those provinces. We find that the Central‐East Atlantic Anomaly (CEAA), which rises from the core‐mantle boundary and stalls in the topmost lower mantle, is the deep source of distinct upper‐mantle upwellings beneath the region. The upwellings detach intermittently from the top of the CEAA and appear to be at different evolutionary stages. We argue that the accumulation of plume material in the topmost lower mantle can play a key role in governing the first‐order spatio‐temporal irregularities in the distribution of hotspot volcanism. Plain Language Summary: The Canary and Madeira provinces, located in the Central‐East Atlantic Ocean, show lineaments of volcanic islands and seamounts, known as hotspot tracks, which differ from most other tracks for their irregular distribution. These lineaments cannot be easily explained by the African plate movement over a fixed, narrow plume of hot mantle material rising from the deep Earth and alternative mechanisms may be required. Here, we integrate observations from seismology and gravity to demonstrate that some first‐order spatio‐temporal irregularities of volcanism in both provinces are due to small‐scale upper‐mantle plumes ("plumelets"), which sporadically rise from the top of a wide lower‐mantle low‐velocity structure, here named "Central‐East Atlantic Anomaly" (CEAA). The CEAA extends vertically from the base of the African large low‐shear‐velocity province (LLSVP), a structure in the lowermost mantle situated under Africa and adjacent oceans and characterized by low‐shear seismic velocities. According to the interpretation of global and regional tomography models, the CEAA material stalls in the topmost lower mantle, between ∼700 and 1,200 km depth, intermittently generating plumelets under the Central‐East Atlantic. Plate reconstructions from Cenozoic to present confirm that the CEAA is underlying these and other volcanic provinces (e.g., Western Iberia and NW Morocco) since at least 90 Ma. Key Points: The Canary and Madeira hotspots are underlain by distinct upwellings sourced from the lower‐mantle Central‐East Atlantic Anomaly (CEAA)A "vote" analysis of 34 tomography models shows that the CEAA extends vertically from the African LLSVP up to the topmost lower mantleThe plumelets seem at different stages of evolution and rise sporadically from mantle material accumulated below the 660‐km discontinuity [ABSTRACT FROM AUTHOR]