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...
This is a preview of subscription content, log in via an institution to check access.
Bibliography
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 241:271–280
Flanagan MP, Shearer PM (1998) Global mapping of topography of transition zone velocity discontinuities by stacking SS precursors. J Geophys Res 103:2673–2692
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/10.1029/2001JB000597
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 433:159–168
Karato SI (2011) Water distribution across the mantle transition zone and its implications for global material circulation. Earth Planet Sci Lett 301(3–4):413–423
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/10.1029/2003JB002439
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
Ohtani E, Sakai T (2008) Recent advances in the study of mantle phase transitions. Phys Earth Planet Inter 170:240–247
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):310–318
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 319:259–268
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2020 Springer Nature Switzerland AG
About this entry
Cite this entry
Vinnik, L.P. (2020). Seismic Discontinuities in the Transition Zone. In: Gupta, H. (eds) Encyclopedia of Solid Earth Geophysics. Encyclopedia of Earth Sciences Series. Springer, Cham. https://doi.org/10.1007/978-3-030-10475-7_41-1
Download citation
DOI: https://doi.org/10.1007/978-3-030-10475-7_41-1
Received:
Accepted:
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-030-10475-7
Online ISBN: 978-3-030-10475-7
eBook Packages: Springer Reference Earth and Environm. ScienceReference Module Physical and Materials ScienceReference Module Earth and Environmental Sciences