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Unveiling the distinct structure of the upper mantle beneath the Canary and Madeira hotspots, as depicted by the 660, 410 and X discontinuities
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  • Luciana Bonatto,
  • David Schlaphorst,
  • Graça Silveira,
  • João Mata,
  • chiara cciviero,
  • Claudia Piromallo,
  • Martin Schimmel
Luciana Bonatto
Universidad de La Serena

Corresponding Author:[email protected]

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David Schlaphorst
Faculdade de Ciências, Instituto Dom Luiz (IDL)
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Graça Silveira
Faculdade de Ciências, Instituto Dom Luiz (IDL)
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João Mata
Faculdade de Ciências, Instituto Dom Luiz (IDL)
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chiara cciviero
Instituto de Ciencias del Mar
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Claudia Piromallo
Istituto Nazionale di Geofisica e Vulcanologia
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Martin Schimmel
Geosciences Barcelona
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Abstract

The Canary and Madeira Islands are two distinct hotspots in the Central-East Atlantic that are close to each other. Their volcanism is generally attributed to underlying mantle plumes, but the detailed structure of these plumes is still not well understood. The thermal and compositional structure of the plume introduces complexities in the phase transitions of the mantle, which impact the depth and magnitude of seismic discontinuities. We use 1268 high-quality receiver functions from stations located at the two hotspots to detect P-to-s converted phases through a common-conversion point stacking approach and conduct a detailed analysis of mantle seismic discontinuities. The results show that both hotspots are characterized by a thin mantle transition zone (MTZ), with sharp 410 and 660 discontinuities at depths of 429-420 km and 647-664 km, beneath the Canaries and Madeira respectively. The results indicate that the Canary plume crosses the MTZ, whereas the Madeira plume mainly influences the upper portion of the MTZ. Furthermore, we find reliable detections of a sharp X discontinuity beneath the Canaries at 289 km. Its presence suggests the accumulation of silica-rich recycled eclogite at these depths. We also use the amplitudes of P410s and PXs to derive velocity jumps at corresponding discontinuities. Based on these measurements, we estimate that the basalt proportion is 60-80\%, with accumulation being more significant in the Canaries than in Madeira. The MTZ thickness, the presence of the X discontinuity, and the high basalt proportion provide compelling evidence for a deep-rooted thermochemical plume beneath the study area.
06 Nov 2023Submitted to ESS Open Archive
08 Nov 2023Published in ESS Open Archive