Abstract

In the last decade, broad, vertically oriented low velocity conduits, originating at the core-mantle boundary, have been imaged seismically beneath major hotspots and interpreted as deep mantle plumes. Likewise in the upper mantle, horizontally elongated low-velocity channels aligned with the absolute plate motion with a spacing of ~1800-2000 km have been documented beneath the young parts of the Pacific Ocean. We present the results of a targeted higher resolution full waveform tomography study of the whole mantle beneath the central and southern Atlantic ocean, that brings these features into increased focus, and suggests interaction of deep mantle flow with meso-scale flow in the upper mantle that is at least partially driven from below. We discuss the possible source(s) of isotope geochemical signatures found in the lavas of several major hotspots on the eastern side of the Atlantic and the nature of the large low shear velocity provinces (LLSVPs) at the base of the mantle, that are more likely bundles of plumes rooted in patches of distinct composition, rather than unbroken piles extending high into the mantle.