Abstract
Upper-mantle upwellings are often invoked as the cause of Cenozoic volcanism in the Ibero-western Maghreb region. However, their nature, geometry and origin are unclear. This study takes advantage of dense seismic networks, which cover an area extending from the Pyrenees in the north to the Canaries in the south, to provide a new high-resolution P-wave velocity model of the upper-mantle and topmost lower-mantle structure. Our images show three subvertical upper-mantle upwellings below the Canaries, the Atlas Ranges and the Gibraltar Arc, which appear to be rooted beneath the upper-mantle transition zone (MTZ). Two other mantle upwellings beneath the eastern Rif and eastern Betics surround the Gibraltar subduction zone. We propose a new geodynamic model in which narrow upper-mantle upwellings below the Canaries, the Atlas Ranges and the Gibraltar Arc rise from a laterally-propagating layer of material below the MTZ, which in turn is fed by a common deep source below the Canaries. In the Gibraltar region, the deeply rooted upwelling interacts with the Gibraltar slab. Quasi-toroidal flow driven by slab rollback induces the hot mantle material to flow around the slab, creating the two low-velocity anomalies below the eastern Betics and eastern Rif. Our results suggest that the Central Atlantic plume is a likely source of hot mantle material for upper-mantle upwellings in the Ibero-western Maghreb region.
| Original language | English |
|---|---|
| Pages (from-to) | 157-172 |
| Number of pages | 16 |
| Journal | Earth and Planetary Science Letters |
| Volume | 499 |
| Early online date | 31 Jul 2018 |
| DOIs | |
| Publication status | Published - 1 Oct 2018 |
Funding
We thank two anonymous reviewers for their thoughtful reviews. The present research is supported by the Fundação para a Ciência e a Tecnologia under the Project SPIDER ( PTDC/GEO-FIQ/2590/2014 ). We would like to thank the many scientists involved in the collection of data used in this study. Most of the data provided for this study is archived at the ORFEUS data center ( https://www.orfeus-eu.org ). The digital object identifier (DOI) for each network is provided in the Supplemental Information. Some instruments deployed in Portugal belong to the Portuguese national seismic network operated by IPMA ( https://www.ipma.pt/ ). Thanks to Ingo Grevemeyer for access to data from the TOPOMED OBS deployment as well as Luis Matias for NEAREST OBS data. We thank the Instituto Geografico National (Spain) for providing us with seismic data recorded from stations deployed in Canary Islands. We thank Mitchell Liddell for his precious help with the Adaptive Stacking and FMTOMO codes. We also thank João Duarte and João Mata for their constructive comments, which helped us improve our manuscript. SAC ( Helffrich et al., 2013 ) and GMT ( Wessel and Smith, 1995 ) software were used to process seismic data. Appendix A
Keywords
- Canary mantle plume
- Ibero-western Maghreb region
- mantle transition zone
- mantle upwellings
- P-wave tomography
- subduction-induced mantle flow
