Steeve Greaux, Norimasa Nishiyama, Yoshio Kono, Tetsuo Irifune, Laurent Gautron
PHYSICS AND CHEMISTRY OF MINERALS 38 8 581 - 590 2011年09月
[査読有り] 研究論文(学術雑誌)
The thermoelastic parameters of the CAS phase (CaAl4Si2O11) were examined by in situ high-pressure (up to 23.7 GPa) and high-temperature (up to 2,100 K) synchrotron X-ray diffraction, using a Kawai-type multi-anvil press. P-V data at room temperature fitted to a third-order Birch-Murnaghan equation of state (BM EOS) yielded: V (0,300) = 324.2 +/- A 0.2 (3) and K (0,300) = 164 +/- A 6 GPa for K' (0,300) = 6.2 +/- A 0.8. With K' (0,300) fixed to 4.0, we obtained: V (0,300) = 324.0 +/- A 0.1 (3) and K (0,300) = 180 +/- A 1 GPa. Fitting our P-V-T data with a modified high-temperature BM EOS, we obtained: V (0,300) = 324.2 +/- A 0.1 (3), K (0,300) = 171 +/- A 5 GPa, K' (0,300) = 5.1 +/- A 0.6 (a,K (0,T) /a,T) (P) = -0.023 +/- A 0.006 GPa K-1, and alpha(0,T) = 3.09 +/- A 0.25 x 10(-5) K-1. Using the equation of state parameters of the CAS phase determined in the present study, we calculated a density profile of a hypothetical continental crust that would contain similar to 10 vol% of CaAl4Si2O11. Because of the higher density compared with the coexisting minerals, the CAS phase is expected to be a plunging agent for continental crust subducted in the transition zone. On the other hand, because of the lower density compared with lower mantle minerals, the CAS phase is expected to remain buoyant in the lowermost part of the transition zone.