Thermal equation of state of lower-mantle ferropericlase across the spin crossover

Journal Article · Tue Oct 23 04:00:00 EDT 2012 · Geophys. Res. Lett.

DOI:https://doi.org/10.1029/2011GL049915· OSTI ID:1049570

Mao, Zhu; Lin, Jung-Fu; Liu, Jin; Prakapenka, Vitali B ^[1]

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1. UC

The thermal equation of state of ferropericlase [(Mg{sub 0.75}Fe{sub 0.25})O] has been investigated by synchrotron X-ray diffraction up to 140 GPa and 2000 K in a laser-heated diamond anvil cell. Based on results at high pressure-temperature conditions, the derived phase diagram shows that the spin crossover widens at elevated temperatures. Along the lower-mantle geotherm, the spin crossover occurs between 1700 km and 2700 km depth. Compared to the high-spin state, thermoelastic modeling of the data shows a {approx}1.2% increase in density, a factor of two increase in thermal expansion coefficient over a range of 1000 km, and a maximum decrease of 37% and 13% in bulk modulus and bulk sound velocity, respectively, at {approx}2180 km depth across the spin crossover. These anomalous behaviors in the thermoelastic properties of ferropericlase across the spin crossover must be taken into account in order to understand the seismic signatures and geodynamics of the lower mantle.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSFDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1049570
• Journal Information: Geophys. Res. Lett., Journal Name: Geophys. Res. Lett. Journal Issue: 12, 2011 Vol. 38; ISSN GPRLAJ; ISSN 0094-8276
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

58 GEOSCIENCES
DIAMONDS
HIGH SPIN STATES
PHASE DIAGRAMS
SIMULATION
SPIN
SYNCHROTRONS
THERMAL EXPANSION
VELOCITY
X-RAY DIFFRACTION