Encyclopedia of Solid Earth Geophysics

Living Edition
| Editors: Harsh K. Gupta

Seismic Discontinuities in the Transition Zone

  • Lev P. VinnikEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-030-10475-7_41-1

Definition

The transition zone (TZ) is the mantle layer bounded by the 410- and 660-km seismic boundaries. The high P-wave and S-wave velocity gradients within the TZ are caused by a series of polymorphic phase transitions, the depths (pressures) of which are controlled by temperature and composition. Structure of the TZ plays an important role in the heat/mass transfer between the upper and the lower mantle.

Mineral Physics Data on the Phase Transitions in the TZ

The most frequently used model of mantle composition is pyrolite which contains ∼60% of olivine (Mg,Fe)2SiO4. At a depth of ∼410 km olivine (α) transforms to wadsleyite (β, modified spinel). The Clapeyron slope of this transition is positive (4.0 MPa/K, Katsura et al. 2004); the increase of the S-wave velocity is ~12%. At a depth of ∼550 km wadsleyite transforms to ringwoodite (γ, silicate spinel). At a depth of ∼660 km ringwoodite transforms to a mixture of perovskite (Mg,Fe)SiO3and magnesiowüstite (Mg,Fe)O. The S velocity...

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Bibliography

  1. Du Z, Vinnik LP, Foulger GR (2006) Evidence from P-to-S mantle converted waves for a flat “660-km” discontinuity beneath Iceland. Earth Planet Sci Lett 241:271–280CrossRefGoogle Scholar
  2. Flanagan MP, Shearer PM (1998) Global mapping of topography of transition zone velocity discontinuities by stacking SS precursors. J Geophys Res 103:2673–2692CrossRefGoogle Scholar
  3. Hirose K (2002) Phase transitions in pyrolitic mantle around 670-km depth: implications for upwelling of plumes from the lower mantle. J Geophys Res 107(B4):2078.  https://doi.org/10.1029/2001JB000597CrossRefGoogle Scholar
  4. Jenkins J, Cottaar S, White RS, Deuss A (2016) Depressed mantle discontinuities beneath Iceland: evidence of a garnet controlled 660 km discontinuity? Earth Planet Sci Lett 433:159–168CrossRefGoogle Scholar
  5. Karato SI (2011) Water distribution across the mantle transition zone and its implications for global material circulation. Earth Planet Sci Lett 301(3–4):413–423CrossRefGoogle Scholar
  6. Katsura T, Yamada H, Nishikawa O, Song M, Kubo A, Shinmei T, Yokoshi S, Aizawa Y, Yoshino T, Walter MJ, Ito E, Funakoshi K (2004) Olivine-wadsleyite transformation in the system (Mg,Fe)2SiO4. J Geophys Res 109:B02209.  https://doi.org/10.1029/2003JB002439CrossRefGoogle Scholar
  7. Litasov KD, Ohtani E, Sano A, Suzuki A, Funakoshi K (2005) Wet subduction versus cold subduction. Geophys Res Lett 32(13).  https://doi.org/10.1029/2005GL022921
  8. Ohtani E, Sakai T (2008) Recent advances in the study of mantle phase transitions. Phys Earth Planet Inter 170:240–247CrossRefGoogle Scholar
  9. Suetsugu D, Shiobara H, Sigioka H, Fukao Y, Kanazawa T (2007) Topography of the mantle discontinuities beneath the South Pacific superswell as inferred from broadband waveforms on seafloor. Phys Earth Planet Inter 160(3–4):310–318CrossRefGoogle Scholar
  10. Vinnik L, Silveira G, Kiselev S, Farra V, Weber M, Stutzmann E (2012) Cape Verde hotspot from the upper crust to the top of the lower mantle. Earth Planet Sci Lett 319:259–268CrossRefGoogle Scholar

Copyright information

© Springer Nature Switzerland AG 2020

Authors and Affiliations

  1. 1.Institute of Physics of the EarthMoscowRussia