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Ubiquitous lower-mantle anisotropy beneath subduction zones

Ferreira, A; Faccenda, M; Sturgeon, W; Chang, S-J; Schardong, L; (2019) Ubiquitous lower-mantle anisotropy beneath subduction zones. Nature Geoscience , 12 pp. 301-306. 10.1038/s41561-019-0325-7. Green open access

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Abstract

Seismic anisotropy provides key information to map the trajectories of mantle flow and understand the evolution of our planet. While the presence of anisotropy in the uppermost mantle is well established, the existence and nature of anisotropy in the transition zone and uppermost lower mantle are still debated. Here we use three-dimensional global seismic tomography images based on a large dataset that is sensitive to this region to show the ubiquitous presence of anisotropy in the lower mantle beneath subduction zones. Whereas above the 660 km seismic discontinuity slabs are associated with fast SV anomalies up to about 3%, in the lower mantle fast SH anomalies of about 2% persist near slabs down to about 1,000–1,200 km. These observations are consistent with 3D numerical models of deformation from subducting slabs and the associated lattice-preferred orientation of bridgmanite produced in the dislocation creep regime in areas subjected to high stresses. This study provides evidence that dislocation creep may be active in the Earth’s lower mantle, providing new constraints on the debated nature of deformation in this key, but inaccessible, component of the deep Earth.

Type: Article
Title: Ubiquitous lower-mantle anisotropy beneath subduction zones
Open access status: An open access version is available from UCL Discovery
DOI: 10.1038/s41561-019-0325-7
Publisher version: https://doi.org/10.1038/s41561-019-0325-7
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Geodynamics, Seismology, Solid Earth sciences
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10071886
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