Sharpness of the paired 660-km discontinuity beneath the Izu-Bonin area

Wang, Liming; He, Xiaobo

doi:10.26464/epp2020067

Cited by 2 publications

(1 citation statement)

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“…However, previous similar seismic observations of LVZs at ∼700–750 km depth have been interpreted as the transition of garnet to bridgmanite (e.g., Deuss et al., 2006; Simmons & Gurrola, 2000). A sharp interface at these depths has been suggested to be evidence of high basalt content due to subducting material (Maguire et al., 2018; Wang & He, 2020). We indicate examples of positive RF values below the 660‐km discontinuity in Figure 3c and Figures S3, S4 & S5 in the Supporting Information .…”

Section: Discussionmentioning

confidence: 96%

Seismic Evidence of Mid‐Mantle Water Transport Beneath the Yellowstone Region

Frazer

Park

2021

Geophysical Research Letters

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The hydration potential of Earth's mantle transition zone (MTZ) may be responsible for long-term (∼100 Ma) ocean-mass regulation, driven by plate tectonics and mantle convection (Bercovici & Karato, 2003;Karato et al., 2020). Constraining the solid-Earth water cycle over geologic time is key in understanding the volatile-compound budget and planetary habitability (Langmuir & Broecker, 2012). Minerals within the MTZ, primarily wadsleyite and ringwoodite, are able to store 1-3 wt% of water (Kohlstedt et al., 1996), far greater than minerals in the upper or lower mantle. Typical upper-mantle rock is estimated to have a maximum water content of ∼0.1 wt% from mid-ocean ridge basalts and a water storage capacity of ∼0.1 wt% (Hirschmann, 2006;Saal et al., 2002). The lower-mantle is estimated to have similarly low water capacity (Bolfan-Casanova, 2005). High water capacity does not necessarily imply high water content, but some deep xenoliths provide evidence for a hydrous MTZ. Water-rich diamond inclusions have been found with water content of 1.4 wt% (Pearson et al., 2014) and ice VII inclusions (Tschauner et al., 2018). Electrical conductivity measurements have also supported high water content in the MTZ, with large regional variations (Karato, 2011). The combination of high-water storage capacity and geologic evidence suggest the MTZ is a key component of the solid-Earth water cycle.When water-rich material from the transition zone penetrates the upper or lower mantle, partial melting occurs due to the decrease in water capacity after phase transition, generating a seismic low-velocity zone (LVZ). In order for melt to generate low-velocity anomalies, grain-boundaries must wet significantly (Yoshino et al., 2007). Such LVZs have been detected above and below the MTZ, and have been interpreted as

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