Seismic Evidence for Olivine Phase Changes at the 410- and 660-Kilometer Discontinuities
Sergei Lebedev,1*
Sébastien Chevrot,2
Rob D. van der Hilst1
The view that the seismic discontinuities bounding the mantle
transition zone at 410- and 660-kilometer depths are caused by
isochemical phase transformations of the olivine structure is debated.
Combining converted-wave measurements in East Asia and Australia with
seismic velocities from regional tomography studies, we observe a
correlation of the thickness of, and wavespeed variations within, the
transition zone that is consistent with olivine structural
transformations. Moreover, the seismologically inferred Clapeyron
slopes are in agreement with the mineralogical Clapeyron slopes of the
(Mg,Fe)2SiO4 spinel and postspinel
transformations.
1 Department of Earth, Atmospheric, and
Planetary Sciences, Room 54-512, Massachusetts Institute of Technology,
Cambridge, MA 02139, USA.
2 Observatoire Midi
Pyrénées,14 Avenue Edouard Belin, Toulouse, France.
*
To whom correspondence should be addressed. E-mail:
sergei{at}quake.mit.edu
