The influence of Al on the stability region of DHMS and water transports into the Earth's interior

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(1) We investigated the stability of the Al-rich dense hydrous magnesium silicate Phase D (PhD) in a MgO-Al2O3-SiO2-H2O system between 14 and 25 GPa at 900℃-1,500 ℃. Al-rich PhD decomposes to Phase Egg at pressure of the mantle transition zone, whereas it decomposes to δ-AlOOH phase with a temperature increase at pressure of the uppermost lower mantle.The wide stability region of Al-bearing PhD would contribute an important storage site for water in the mantle transition zone.(2)We investigated the phase relation of a water-undersaturated (2 wt%) analog of Martian mantle in simplified MgO-Al2O3-FeO-SiO2-H2O (MAFSH) system between 15 and 21 GPa at 900℃-1500 °C . Results showed that phase E coexisting with wadsleyite or ringwoodite was at least stable at 15-16.5 GPa and below 1050 °C. Phase D coexisted with ringwoodite at pressures higher than 16.5 GPa and temperatures below 1100 °C.(3) In this study, we ascertain the phase relations in the AlOOH-FeOOH binary system at 15-25 GPa and 700℃-1200 °C. X-ray diffraction measurements of quenched samples show that δ-AlOOH and ε-FeOOH partly form solid solutions over wide pressure and temperature ranges. Our results demonstrate that a binary eutectic diagram is formed without dehydration or melting below 1200 °C at 20 GPa. Our results suggest that the CaCl2-type hydroxides subducted into the deep mantle form a solid solution over a wide composition range.Until now, I have published three papers. We will punlish three more papers a few months later.