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- Title
Tracking the origin of ultralow velocity zones at the base of Earth's mantle.
- Authors
Chen, Jiuhua
- Abstract
Besides melt-related causes of the ULVZs [3], several hypotheses of solid phases, such as the iron-rich post-perovskite phase [4], pyrite-type FeO 2 H x (0 <x <1)[5],ironoxidesor iron-enriched magnesium oxides [6,7], havebeenreportedtobeabletoproduce the velocity reductions corresponding to what is observed at the ULVZs. If Fe-C melt behaves in a similar way to Fe-S melt, its dihedral angle is likely below 10 o at the core-mantle boundary (CMB)[9],and,therefore,R >2.3isexpected for any melt-related ULVZs. Fe-richoxide (Fe 0.84 Mg 0.16)O Pyrite-type FeO 2 H x Meltsfrom C +Fe Meltsfrom (Mg,Fe)SiO 3 +Fe Post-perovskite (Fe 0.4 Mg 0.6)SiO 3 R 1.2-1.5 1.6-2.0 2.3-2.8 a 2.7-3.3 3.5-4.5 Maximum lnV S, lnV P -69%, -57% -42%, -20% -100%, -40% b -100%, -40% b -44%, -13% Maximum ln +40% +24% +78% +78% b +7% c References [7][5][8][3][4] Note:R = lnV S / lnV P;V S:shear-wavevelocity;V P:compressional-wavevelocity; :density. a Fordihedralanglesof10 o. b Calculatedassuming100%outercoremelt. c Combined withthethermalexpansionfromRef.[10].
- Subjects
EARTH'S mantle; VELOCITY; SEISMIC wave velocity; SEISMIC anisotropy; FRICTION velocity
- Publication
National Science Review, 2021, Vol 8, Issue 4, p1
- ISSN
2095-5138
- Publication type
Article
- DOI
10.1093/nsr/nwaa308