TY - JOUR
T1 - Formation of bridgmanite-enriched layer at the top lower-mantle during magma ocean solidification
AU - Xie, Longjian
AU - Yoneda, Akira
AU - Yamazaki, Daisuke
AU - Manthilake, Geeth
AU - Higo, Yuji
AU - Tange, Yoshinori
AU - Guignot, Nicolas
AU - King, Andrew
AU - Scheel, Mario
AU - Andrault, Denis
N1 - Funding Information:
We thank T. Yoshino, F. Xu, E. Boulard, N. Tsujino, H. Gomi, C. Zhao, Y. Zhang, M. Sakurai, V. Jaseem, and C. Oka for their assistance in high-pressure, high-temperature experiments. We thank R. Njul, D. Wiesner, D. Krauße for the help on polishing sample, measuring SEM and Microprobe, respectively. Discussions with E. Ito, M. Kanzaki, A. Suzuki, and C. Wang helped design the project, and with F. Noritake, S. Ohmura, T. Tsuchiya, X. Xue, S. Yamashita, Y. Wang, and D. Dobson improved knowledge of silicate melt. We thank J. Monteux for the discussion on the adiabats of a magma ocean, S. Karato for the discussion on fitting of the experimental data and D.J. Stevenson for the discussion on viscous drag for different flow patterns. We thank M. Izawa for the proof reading of the paper and T. Katsura for suggestions on improving figures. The BDD powder was grinded at the Geodynamic Research Center, Ehime University under the PRIUS program with T. Irifune and T. Shinmei (Project Nos. A48, 2016-A02, 2017-A01, 2017-A21, and 2018-B30). This work was supported by JSPS Research Fellowship for Young Scientists (DC2-JP17J10966 to L. Xie) and Grants-in-Aid for Scientific Research (Nos. 22224008 and 15H02128 to A.Y.). This is a contribution n°383 to the ClerVolc program. The in-situ falling sphere experiments were performed under SPring-8 Budding Researcher Support Program (Nos. 2015A1771, 2016A1651, 2016B1686, 2017B1686, and 2018A1637) and SOLEIL research proposals (20160333, 20170194).
Publisher Copyright:
© 2020, The Author(s).
PY - 2020/12/1
Y1 - 2020/12/1
N2 - Thermochemical heterogeneities detected today in the Earth’s mantle could arise from ongoing partial melting in different mantle regions. A major open question, however, is the level of chemical stratification inherited from an early magma-ocean (MO) solidification. Here we show that the MO crystallized homogeneously in the deep mantle, but with chemical fractionation at depths around 1000 km and in the upper mantle. Our arguments are based on accurate measurements of the viscosity of melts with forsterite, enstatite and diopside compositions up to ~30 GPa and more than 3000 K at synchrotron X-ray facilities. Fractional solidification would induce the formation of a bridgmanite-enriched layer at ~1000 km depth. This layer may have resisted to mantle mixing by convection and cause the reported viscosity peak and anomalous dynamic impedance. On the other hand, fractional solidification in the upper mantle would have favored the formation of the first crust.
AB - Thermochemical heterogeneities detected today in the Earth’s mantle could arise from ongoing partial melting in different mantle regions. A major open question, however, is the level of chemical stratification inherited from an early magma-ocean (MO) solidification. Here we show that the MO crystallized homogeneously in the deep mantle, but with chemical fractionation at depths around 1000 km and in the upper mantle. Our arguments are based on accurate measurements of the viscosity of melts with forsterite, enstatite and diopside compositions up to ~30 GPa and more than 3000 K at synchrotron X-ray facilities. Fractional solidification would induce the formation of a bridgmanite-enriched layer at ~1000 km depth. This layer may have resisted to mantle mixing by convection and cause the reported viscosity peak and anomalous dynamic impedance. On the other hand, fractional solidification in the upper mantle would have favored the formation of the first crust.
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U2 - 10.1038/s41467-019-14071-8
DO - 10.1038/s41467-019-14071-8
M3 - Article
C2 - 31992697
AN - SCOPUS:85078423837
VL - 11
JO - Nature Communications
JF - Nature Communications
SN - 2041-1723
IS - 1
M1 - 548
ER -