How can we have a fixed T?

• A simple way : T at the seismic discontinuity
• • by comparing the discontinuity depth with the transition pressure
  • • This is a quite old idea, but…
• However, is the discontinuity depth a simple function of T?
• • Effect of water and iron content  on the phase relations

Phase diagram of Ol-Wd transition

• Phase diagram of the Ol-Wd transition by Katsura et al. [2004a]
• • Calculate P using the MgO scale proposed by Matsui et al. [2000]
  • • Recently new pressure scales were proposed
    • P calculation by Katsura et al. [2004a] using Matsui scale had insufficient precision

• Recalc. of the trans. P by
• • Two new P scales prop. by Tange et al. [2009].
  • • Reproduce recent exp. data
    • 2 EoS’s
    • • 3rd-order B-M EoS
      • Vinet EoS
    • More precise program for the Matsui scale
  • The recalc. trans. P are 0.35~0.65 GPa lower than Katsura et al. [2004]
  • Matsui (rev) > Tange-V > Tange-3BM
  • • Difference of each:  0.15 GPa

Temperature at D410

• Assuming
• • Mg# = 89  & No effect of water
  • Reflect. plane : Ol : Wd ratio is 1:2 [Stixrude, 1997]
• The depth of D410 at 1900 and 1600 K :
• • • 421 & 389 km (Matsui)
    • 416 & 385 km (Tange-V)
    • 412 & 382 km (Tange-3BM)
  • D410 shift with T at a rate of 0.1 km/K.
• Average depth of D410
• • 409 km [Chambers et al., 2005], 410 km [Houser et al., 2008]
• Temperature at D410 : 1830+-40 K
• • 70 K higher than that proposed by Katsura et al. [2004]