Can hydrous sediments supply water to the deep mantle?

  • Project title: Can hydrous sediments supply water to the deep mantle?
  • Supervisors (*corresponding): Takashi Yoshino*, Akira Yoneda, Daisuke Yamazaki
  • Number of students: up to 2

Water plays an important role in most processes within the Earth’s mantle. Many works on stability of some hydrous minerals have suggested that Al and Fe-bearing hydrous minerals are stable at temperatures higher than normal mantle geotherm under the lower mantle condition. In particular, hydrous minerals such as pyrite-type FeOOH and δ-AlOOH forming subducted sediment can extend the stability field to higher temperatures compared to dense hydrous Mg silicates (DHMS) forming hydrous peridotitic rocks. However, stability of these hydrous minerals at lower pressures is not well defined. Dehydration temperature of ε-FeOOH is determined to be around 400˚C at 5 GPa (Gleason et al., 2008). This temperature is very close to the predicted temperature from geotherm of the normal cold slab. Thus, it is necessary to determine the dehydration temperature of these phases to verify the water supply model. In this study, the dehydration temperatures of FeOOH and AlOOH will be experimentally explored up to 20 GPa using a Kawai-type multianvil press.