5:15 PM - 6:30 PM
[SIT06-P12] Stability field of phase Egg under high temperature and high pressure:
Possibility of phase Egg as a water reservoir in mantle transition zone
Keywords:water cycle in the earth’s interior, phase Egg, multi-anvil apparatus, high pressure and high temperature, mantle transition zone, superdeep diamond
Here, we conducted high-pressure experiments using Kawai-type 3000 ton multi-anvil apparatus and 1000 ton multi-anvil apparatus at Tohoku University in order to determine the stability field of phase Egg. Experiments were performed in the pressure range of approximately 17-21GPa and in the temperature range of 1000–1200℃. Starting material was a mixture of Al2O3, Al(OH)3, and SiO2 compounded similarly to ideal phase Egg composition, which was different from those of two previous studies (Sano et al., 2004; Pamato et al., 2014).
In this study, we found that phase Egg decomposed under the pressure corresponding to the mantle transition zone at 1000℃. This indicates that phase Egg is unstable in the top of lower mantle and can be a water reservoir in the mantle transition zone. In addition, this implies that the superdeep diamond, which Wirth et al. (2007) reported, does not originate from the lower mantle but from the wet mantle transition zone.