Water distribution across the mantle transition zone and its implications for global material circulation

Continental flood basalts derived from the hydrous mantle transition zone

“…The mantle transition zone (MTZ) has been considered to act as a gigantic water tank in deep-Earth fluid cycling [10][11][12][13][14][15][16][17] due to water-enriched wadsleyite and ringwoodite at depths between 410 and 660 km (refs 11,13,16,17), which can host enough water to comprise up to 2.5% of the weight of these minerals 13,14 . This implies that the MTZ may play a key role in terrestrial magmatism and plate tectonics 12,18 .…”

“…Hydrous phases in the MTZ would eventually decompose into anhydrous phases by releasing fluids to produce wet upwellings that pool within the MTZ 11,19 . However, direct observations for the water content of the MTZ are spare and mainly inferred from geophysics 16,17 . With the exception of a single B10 mm ringwoodite grain from one location 13 , there is no geochemical evidence that the MTZ is water rich.…”

Mantle roots of the Emeishan plume: an evaluation based on teleseismic P-wave tomography

“…7). tential water reservoir in the Earth's interior (Karato, 2011;Kuritani et al, 2011). The accumulation of delaminated crust and/or mantle lithosphere in the MTZ are speculated to give rise to "second continents" at the bottom of the upper mantle (Kawai et al, 2013;Lustrino, 2005).…”

Optimal Timing of Transfer Out of the Intensive Care Unit

“…These boundaries originate in the pressure-driven phase transformations of mantle rock minerals-in particular, the transformations of olivine to wadsleyite at 410 km and from ringwoodite to bridgmanite and periclase at 660 km depth. The UM contains only modest amounts of water on average (7), whereas the average water content in the TZ has been estimated at~0.1 weight percent (8), or more than 10 times that of the UM. The abundance of water in the LM is unknown, but its constituent minerals appear to have much lower solubility of water than the minerals of the TZ (9,10).…”

“…The question of water abundance in the deeper mantle can therefore only be decided on the basis of actual samples from these regions whose mineralogical or petrographic record is placed in context with geochemical and geophysical observations, such as seismic wave attenuation and electrical conductivity (1,4,8), and by using experimentally obtained thermodynamic properties. Diamond is the main source of minerals from the deeper mantle: A mineralogical record from depths as great as 660 km or even beyond has been identified as inclusions in natural diamonds (12,13).…”