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Title: Metastable olivine within oceanic lithosphere in the uppermost lower mantle beneath the eastern United States
Approximately two-thirds of Earth’s outermost shell is composed of oceanic plates that form at spreading ridges and recycle back to Earth’s interior in subduction zones. A series of physical and chemical changes occur in the subducting lithospheric slab as the temperature and pressure increase with depth. In particular, olivine, the most abundant mineral in the upper mantle, progressively transforms to its high-pressure polymorphs near the mantle transition zone, which is bounded by the 410 km and 660 km discontinuities. However, whether olivine still exists in the core of slabs once they penetrate the 660 km discontinuity remains debated. Based on SKS and SKKS shear-wave differential splitting times, we report new evidence that reveals the presence of metastable olivine in the uppermost lower mantle within the ancient Farallon plate beneath the eastern United States. We estimate that the low-density olivine layer in the subducted Farallon slab may compensate the high density of the rest of the slab associated with the low temperature, leading to neutral buoyancy and preventing further sinking of the slab into the deeper part of the lower mantle.  more » « less
Award ID(s):
2149587 1830644
NSF-PAR ID:
10383481
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
Geology
ISSN:
0091-7613
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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