Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 111, Issue 29, Pages 10468-10472Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1322427111
Keywords
seismic tomography; lateral heterogeneity; elastic modulus; density functional theory; mantle plume
Categories
Funding
- National Natural Science Foundation of China [41274087]
- State Key Development Program of Basic Research of China [2014CB845905]
- Chinese Academy of Sciences International Partnership Program for Creative Research Teams
- National Science Foundation [EAR-1341862, EAR-1047629]
- Directorate For Geosciences
- Division Of Earth Sciences [1319361, 1348066, 1341862] Funding Source: National Science Foundation
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Deciphering the origin of seismic velocity heterogeneities in the mantle is crucial to understanding internal structures and processes at work in the Earth. The spin crossover in iron in ferropericlase (Fp), the second most abundant phase in the lower mantle, introduces unfamiliar effects on seismic velocities. First-principles calculations indicate that anticorrelation between shear velocity (V-S) and bulk sound velocity (V-phi) in the mantle, usually interpreted as compositional heterogeneity, can also be produced in homogeneous aggregates containing Fp. The spin crossover also suppresses thermally induced heterogeneity in longitudinal velocity (V-P) at certain depths but not in VS. This effect is observed in tomography models at conditions where the spin crossover in Fp is expected in the lower mantle. In addition, the one-of-a-kind signature of this spin crossover in the R-S/P (partial derivative ln V-S= partial derivative ln V-P) heterogeneity ratio might be a useful fingerprint to detect the presence of Fp in the lower mantle.
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