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Title: Asthenospheric low-velocity zone consistent with globally prevalent partial melting
The asthenosphere plays a fundamental role in present-day plate tectonics as its low viscosity controls how convection in the mantle below it is expressed at the Earth’s surface above. The origin of the asthenosphere, including the role of partial melting in reducing its viscosity and facilitating deformation, remains unclear. Here we analysed receiver-function data from globally distributed seismic stations to image the lower reaches of the asthenospheric low-seismic-velocity zone. We present globally widespread evidence for a positive seismic-velocity gradient at depths of ~150 km, which represents the base of a particularly low-velocity zone within the asthenosphere. This boundary is most commonly detected in regions with elevated upper-mantle temperatures and is best modelled as the base of a partially molten layer. The presence of the boundary showed no correlation with radial seismic anisotropy, which represents accumulated mantle strain, indicating that the inferred partial melt has no substantial effect on the large-scale viscosity of the asthenosphere. These results imply the presence of a globally extensive, partially molten zone embedded within the asthenosphere, but that low asthenospheric viscosity is controlled primarily by gradual pressure and temperature variations with depth.  more » « less
Award ID(s):
1925939 1853856 2045292 1927216
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Date Published:
Journal Name:
Nature Geoscience
Page Range / eLocation ID:
175 to 181
Medium: X
Sponsoring Org:
National Science Foundation
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