Sharp 660-km discontinuity controlled by extremely narrow binary post-spinel transition

Takayuki Ishii, Rong Huang, Robert Myhill, Hongzhan Fei, Iuliia Koemets, Zhaodong Liu, Fumiya Maeda, Liang Yuan, Lin Wang, Dmitry Druzhbin, Takafumi Yamamoto, Shrikant Bhat, Robert Farla, Takaaki Kawazoe, Noriyoshi Tsujino, Eleonora Kulik, Yuji Higo, Yoshinori Tange, Tomoo Katsura

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The Earth’s mantle is characterized by a sharp seismic discontinuity at a depth of 660 km that can provide insights into deep mantle processes. The discontinuity occurs over only 2 km—or a pressure difference of 0.1 GPa—and is thought to result from the post-spinel transition, that is, the decomposition of the mineral ringwoodite to bridgmanite plus ferropericlase. Existing high-pressure, high-temperature experiments have lacked the pressure control required to test whether such sharpness is the result of isochemical phase relations or chemically distinct upper and lower mantle domains. Here, we obtain the isothermal pressure interval of the Mg–Fe binary post-spinel transition by applying advanced multi-anvil techniques with in situ X-ray diffraction with the help of Mg–Fe partition experiments. It is demonstrated that the interval at mantle compositions and temperatures is only 0.01 GPa, corresponding to 250 m. This interval is indistinguishable from zero at seismic frequencies. These results can explain the discontinuity sharpness and provide new support for whole-mantle convection in a chemically homogeneous mantle. The present work suggests that distribution of adiabatic vertical flows between the upper and lower mantles can be mapped on the basis of discontinuity sharpness.

Original languageEnglish
Pages (from-to)869-872
Number of pages4
JournalNature Geoscience
Volume12
Issue number10
DOIs
Publication statusPublished - Oct 1 2019

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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    Ishii, T., Huang, R., Myhill, R., Fei, H., Koemets, I., Liu, Z., Maeda, F., Yuan, L., Wang, L., Druzhbin, D., Yamamoto, T., Bhat, S., Farla, R., Kawazoe, T., Tsujino, N., Kulik, E., Higo, Y., Tange, Y., & Katsura, T. (2019). Sharp 660-km discontinuity controlled by extremely narrow binary post-spinel transition. Nature Geoscience, 12(10), 869-872. https://doi.org/10.1038/s41561-019-0452-1