A link between seamount volcanism and structures of the deep Earth
Abstract
One of the most remarkable discoveries in Earth science in the last decade has been the realization that most hotspots, Large Igneous Provinces and kimberlites—when reconstructed to the location of their original eruption/emplacement—seem to lie over the edges of the Large Low Shear Velocity Provinces (LLSVPs) of the lowermost mantle. This coincidence suggests that the edges of the LLSVPs may act as the nucleation site for mantle plumes or are otherwise related to sites of mantle upwelling that manifest at Earth's surface as intraplate volcanism. Here we present evidence of a link between the LLSVPs and another example of intraplate magmatism: seamounts. We first mapped the spatially-dependent density of seamounts in the world's oceans (as determined via satellite altimetry) to a geographic grid by defining the effective volcanic layer thickness. For each seafloor location, this layer thickness defines a volume equal to that of the seamounts within 500 km of that location. This grid was then compared against a variety of 'LLSVP residence time' grids, which record the length of time (arbitrarily in Ma) that each node of the grid has spent directly above the LLSVPs or their edges, as determined using two alternative plate reconstructions and LLSVP delineations. Globally, we observe a statistically-significant positive correlation between effective volcanic layer thickness and LLSVP residency time, meaning that seamount volumes are greater for those parts of the seafloor that have passed over the LLSVPs (notably their edges), and that seamount volumes increase with increasing time spent above the LLSVPs. Although this finding holds globally, the correlation is notably stronger for the Pacific basin than for the Atlantic and Indian basins. These results suggest that intraplate seamounts, which have long remained enigmatic despite their abundance on Earth's surface, are related to heat transport via mantle upwelling associated with the LLSVPs at depth.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T43H0517D
- Keywords:
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- 1219 Gravity anomalies and Earth structure;
- GEODESY AND GRAVITYDE: 7270 Tomography;
- SEISMOLOGYDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8124 Earth's interior: composition and state;
- TECTONOPHYSICS