Determination of thermal expansivity of the mantle minerals

Temperature is the most fundamental parameter to discuss the dynamics of the Earth's interior. Nevertheless, the temperature distribution in the deep mantle is not well constrained. The mantle geotherm is considered nearly adiabatic, because heat is mainly transferred by convection in the majority of the mantle. The adiabatic temperature gradient is given by:

 (dT/dz)_S = αgT/C_P

where α is the thermal expansivity, g is the gravity acceleration, C_P is the isobaric heat capacity. Since the gravity acceleration and isobaric heat capacity in the mantle do not vary largely, the thermal expansion coefficient is a key parameter to estimate the temperature distribution in the deep mantle. we determined thermal expansion coefficient of mantle minerals under conditions realistic for deep mantle.

Contents

New apparatus

P-V-T measurement

Re-evaluation of temperature at the 410-km discontinuity

Adiabatic temperature distribution

Appendix: Table of the geotherm

High-pressure apparatus

Katsura, T., K. Funakoshi, A. Kubo, N. Nishiyama, Y. Tange, Y. Sueda, T. Kubo, and W. Utsumi (2004), A large-volume high-pressure and high-temperature apparatus for in situ X-ray observation, 'SPEED-Mk.II', Phys. Earth Planet. Inter., 143, 497-506.

EOS of olivine

Katsura, T., et al. (2009), Thermal expansion of forsterite at high pressures determined by in situ X-ray diffraction: The adiabatic geotherm in the upper mantle, Phys. Earth Planet. Inter., 174(1-4), 86-92.

EOS of wadsleyite

Katsura, T., et al. (2009), P-V-T relations of wadsleyite determined by in situ X-ray diffraction in a large-volume high-pressure apparatus, Geophys. Res. Lett., 36, doi: L11307
10.1029/2009gl038107.

EOS of ringwoodite

Katsura, T., et al. (2004), Thermal expansion of Mg2SiO4 ringwoodite at high pressures, Journal of Geophysical Research-Solid Earth, 109(B12).

EOS of bridgmanite

Katsura, T., et al. (2009), P-V-T relations of MgSiO3 perovskite determined by in situ X-ray diffraction using a large-volume high-pressure apparatus, Geophys. Res. Lett., 36.
Errata: Correction to “P-V-T relations of the MgSiO₃ perovskite determined by in situ X-ray diffraction using a large-volume high-pressure apparatus”

Adiabatic temperature profile

Katsura, T., A. Yoneda, D. Yamazaki, T. Yoshino, and E. Ito (2010), Adiabatic temperature profile in the mantle, Phys. Earth Planet. Inter., 183(1-2), 212-218.