Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 106, Issue 21, Pages 8447-8452Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0812150106
Keywords
Earth's lower mantle; viscosity; thermodynamics; thermal expansivity
Categories
Funding
- National Science Foundation (NSF)/Division of Earth Sciences [0635990]
- NSF/Division of Atmospheric Sciences [0428774]
- NSF/Division of Materials Research [0325218]
- NSF/Division of Ocean Sciences
- University of Minnesota-Materials Research Science and Engineering Center
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [0325218] Funding Source: National Science Foundation
- Directorate For Geosciences
- Div Atmospheric & Geospace Sciences [0428774] Funding Source: National Science Foundation
- Division Of Earth Sciences
- Directorate For Geosciences [0810272, 0635990] Funding Source: National Science Foundation
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The thermoelastic properties of ferropericlase Mg1-xFexO (x = 0.1875) throughout the iron high-to-low spin cross-over have been investigated by first principles at Earth's lower mantle conditions. This cross-over has important consequences for elasticity such as an anomalous bulk modulus (K-S) reduction. At room temperature the anomaly is somewhat sharp in pressure but broadens with increasing temperature. Along a typical geotherm it occurs across most of the lower mantle with a more significant K-S reduction at approximate to 1,400-1,600 km depth. This anomaly might also cause a reduction in the effective activation energy for diffusion creep and lead to a viscosity minimum in the mid-lower mantle, in apparent agreement with results from inversion of data related with mantle convection and postglacial rebound.
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