Fate of water transported into the deep mantle by slab subduction

Eiji Ohtani, Liang Yuan, Itaru Ohira, Anton Shatskiy, Konstantin Litasov

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

The roles of water in the mantle transition zone, lower mantle, and the core-mantle boundary are investigated. The evidence for a wet mantle transition zone has been suggested based on hydrous mineral inclusions in diamond. Seismic wave velocity and electrical conductivity profiles together with mineral physics data are consistent with existence of stagnant slabs in a wet mantle transition zone. The transition zone may contain continental crustal components in these stagnant slabs. Dense hydrous magmas may exist at the base of the upper mantle. Fluids or volatile-rich magmas may also exist at the top of the lower mantle due to the large contrast in water contents between the mineral assemblages in the mantle transition zone and the lower mantle, and the crossing of the convective descent of the cold hydrated materials. Dense magmas are not likely to be formed at the top of the lower mantle and hydrous magmas generated in this region move upwards and metasomatize the overlying mantle transition zone. Water can be transported deeper into the lower mantle by gravitational collapse of the stagnant slabs, which supply water into the lower mantle, including the core-mantle boundary. Hydrous δ-H solid solution may be the most important hydrous phase in lower mantle, and existence of this phase reduces the aluminum content in coexisting bridgmanite and post-perovskite, and thus modifies the physical properties of the lower mantle. Hydrous δ-H solid solution can accumulate at the base of the lower mantle. The iron-water reaction at the core-mantle boundary can also create pyrite-type FeOOH which can be a potential candidate material for the ultralow velocity zone (ULVZ).

Original languageEnglish
Pages (from-to)2-10
Number of pages9
JournalJournal of Asian Earth Sciences
Volume167
DOIs
Publication statusPublished - Nov 2018
Externally publishedYes

Keywords

  • Core-mantle boundary
  • Hydrous phase
  • Lower mantle
  • Mantle transition zone
  • Stagnant slab
  • Water
  • SEISMIC EVIDENCE
  • HIGH-PRESSURE
  • EARTHS MANTLE
  • STABILITY
  • ELECTRICAL-CONDUCTIVITY
  • TRANSITION ZONE BENEATH
  • X-RAY-OBSERVATION
  • PHASE DELTA-ALOOH
  • TEMPERATURE PROFILE
  • HYDROUS SILICATE MELT

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