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Thermal equation of state of lower‐mantle ferropericlase across the spin crossover
Author(s) -
Mao Zhu,
Lin JungFu,
Liu Jin,
Prakapenka Vitali B.
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl049915
Subject(s) - spin crossover , thermoelastic damping , condensed matter physics , diamond anvil cell , equation of state , geodynamics , materials science , spin transition , silicate perovskite , thermal , mantle (geology) , bulk modulus , thermal expansion , geology , diffraction , thermodynamics , physics , geophysics , optics , paleontology , tectonics , metallurgy
The thermal equation of state of ferropericlase [(Mg 0.75 Fe 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 ∼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 ∼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.