Seismic Evidence for Plume‐Slab Interaction by High‐Resolution Imaging of the 410‐km Discontinuity Under Tonga
Journal
Geophysical Research Letters
Journal Volume
46
Journal Issue
23
Start Page
13687
End Page
13694
ISSN
0094-8276
1944-8007
Date Issued
2019-12-03
Author(s)
Abstract
The Tonga-Samoa system provides a unique tectonic context to study how a cold subducting slab interacts with a hot rising mantle plume. Here we present a 3-D high-resolution image of the 410-km mantle discontinuity (the 410) using seismic signals excited by deep-focus earthquakes. The 410 is found to be ~30 km shallower inside the Tonga slab relative to the ambient mantle and ~20 km deeper further to the northwest under Fiji Islands. The downward deflection of the 410 under Fiji supports the hypothesis of a plume migration around the northern edge of the Tonga slab from Samoan hot spot to under Fiji due to fast trench rollback. The 50-km topography difference in the 410 between the plume and the slab corresponds to a temperature difference of ~500 ± 100 K. The Samoan plume is inferred to be 200 ± 50 K hotter than the ambient mantle and supports a thermal origin for the plume.
Subjects
discontinuity
mantle plume
plume-slab interaction
Samoa
Tonga
SDGs
Publisher
American Geophysical Union (AGU)
Type
journal article