The thicknesses and Clapeyron slopes of mantle phase boundaries strongly influence the seismic detectability of the boundaries and convection in the mantle. The unusually large positive Clapeyron slope found for the boundary between perovskite (Pv) and post-perovskite (pPv)1,2,3 (the ‘pPv boundary’) would destabilize high-temperature anomalies in the lowermost mantle4, in disagreement with the seismic observations5. Here we report the thickness of the pPv boundary in (Mg0.91Fe2+0.09)SiO3 and (Mg0.9Fe3+0.1)(Al0.1Si0.9)O3 as determined in a laser-heated diamond-anvil cell under in situ high-pressure (up to 145 GPa), high-temperature (up to 3,000 K) conditions. The measured Clapeyron slope is consistent with the D′′ discontinuity6. In both systems, however, the pPv boundary thickness increases to 400–600 ± 100 km, which is substantially greater than the thickness of the D′′ discontinuity (<30 km)7. Although the Fe2+ buffering effect of ferropericlase8,9,10 could decrease the pPv boundary thickness, the boundary may remain thick in a pyrolitic composition because of the effects of Al and the rapid temperature increase in the D′′ layer. The pPv boundary would be particularly thick in regions with an elevated Al content and/or a low Mg/Si ratio, reducing the effects of the large positive Clapeyron slope on the buoyancy of thermal anomalies and stabilizing compositional heterogeneities in the lowermost mantle. If the pPv transition is the source of the D′′ discontinuity, regions with sharp discontinuities may require distinct compositions, such as a higher Mg/Si ratio or a lower Al content.
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Oganov, A. R. & Ono, S. Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth’s D′′ layer. Nature 430, 445–448 (2004)
Tsuchiya, T., Tsuchiya, J., Umemoto, K. & Wentzcovitch, R. M. Phase transition in MgSiO3 perovskite in the Earth’s lower mantle. Earth Planet. Sci. Lett. 224, 241–248 (2004)
Tateno, S., Hirose, K., Sata, N. & Ohishi, Y. Determination of post-perovskite phase transition boundary up to 4400 K and implications for thermal structure in D′′ layer. Earth Planet. Sci. Lett. 277, 130–136 (2009)
Nakagawa, T. & Tackley, P. J. Effects of a perovskite-post perovskite phase change near core-mantle boundary in compressible mantle convection. Geophys. Res. Lett. 31, L16611 (2004)
Garnero, E. J., Lay, T. & McNamara, A. in Plates, Plumes, and Planetary Processes (eds Foulger, G. R. & Jurdy, D. M.) 79–101 (Geological Society of America, 2007)
Sidorin, I., Gurnis, M. & Helmberger, D. V. Evidence for a ubiquitous seismic discontinuity at the base of the mantle. Science 286, 1326–1331 (1999)
Lay, T. Sharpness of the D'' discontinuity beneath the Cocos Plate: implications for the perovskite to post-perovskite phase transition. Geophys. Res. Lett. 35, L03304 (2008)
Kobayashi, Y. et al. Fe-Mg partitioning between (Mg,Fe)SiO3 post-perovskite, perovskite, and magnesiowüstite in the Earth’s lower mantle. Geophys. Res. Lett. 32, L19301 (2005)
Auzende, A.-L. et al. Element partitioning between magnesium silicate perovskite and ferropericlase: new insights into bulk lower-mantle geochemistry. Earth Planet. Sci. Lett. 269, 164–174 (2008)
Ono, S. & Oganov, A. R. In situ observations of phase transition between perovskite and CaIrO3-type phase in MgSiO3 and pyrolitic mantle composition. Earth Planet. Sci. Lett. 236, 914–932 (2005)
Lay, T., Williams, Q. & Garnero, E. J. The core–mantle boundary layer and deep Earth dynamics. Nature 392, 461–468 (1998)
Garnero, E. J. Heterogeneity of the lowermost mantle. Annu. Rev. Earth Planet. Sci. 28, 509–537 (2000)
Murakami, M., Hirose, K., Kawamura, K., Sata, N. & Ohishi, Y. Post-perovskite phase transition in MgSiO3 . Science 304, 855–858 (2004)
Shim, S.-H., Duffy, T. S., Jeanloz, R. & Shen, G. Stability and crystal structure of MgSiO3 perovskite to the core-mantle boundary. Geophys. Res. Lett. 31, L10603 (2004)
Wookey, J., Stackhouse, S., Kendall, J.-M., Brodholt, J. & Price, G. D. Efficacy of the post-perovskite phase as an explanation for lowermost-mantle seismic properties. Nature 438, 1004–1007 (2005)
Lay, T., Hernlund, J., Garnero, E. J. & Thorne, M. S. A post-perovskite lens and D'' heat flux beneath the central Pacific. Science 314, 1272–1276 (2006)
van der Hilst, R. D. et al. Seismostratigraphy and thermal structure of Earth’s core-mantle boundary region. Science 315, 1813–1817 (2007)
Hirose, K., Sinmyo, R., Sata, N. & Ohishi, Y. Determination of post-perovskite phase transition boundary in MgSiO3 using Au and MgO pressure standards. Geophys. Res. Lett. 33, L01310 (2006)
Mao, W. L. et al. Ferromagnesian postperovskite silicates in the D'' layer of the Earth. Proc. Natl. Acad. Sci. USA 101, 15867–15869 (2004)
Tateno, S., Hirose, K., Sata, N. & Ohishi, Y. Phase relations in Mg3Al2Si3O12 to 180 GPa: effect of Al on post-perovskite phase transition. Geophys. Res. Lett. 32, L15306 (2005)
Nishio-Hamane, D., Fujino, K., Seto, Y. & Nagai, T. Effect of the incorporation of FeAlO3 into MgSiO3 perovskite on the post-perovskite transition. Geophys. Res. Lett. 34, L12307 (2007)
Stixrude, L. Structure and sharpness of phase transitions and mantle discontinuities. J. Geophys. Res. 102, 14835–14852 (1997)
Sinmyo, R. et al. Partitioning of iron between perovskite/postperovskite and ferropericlase in the lower mantle. J. Geophys. Res. 113, B11204 (2008)
McCammon, C. Perovskite as a possible sink for ferric iron in the lower mantle. Nature 387, 694–696 (1997)
Sinmyo, R., Hirose, K., O’Neill, H. S. C. & Okunishi, E. Ferric iron in Al-bearing post-perovskite. Geophys. Res. Lett. 33, L12S13 (2006)
Hirose, K., Fei, Y., Ma, Y. Z. & Mao, H.-K. The fate of subducted basaltic crust in the Earth’s lower mantle. Nature 397, 53–56 (1999)
Murakami, M., Hirose, K., Sata, N. & Ohishi, Y. Post-perovskite phase transition and mineral chemistry in the pyrolitic lowermost mantle. Geophys. Res. Lett. 32, L03304 (2005)
Hutko, A. R., Lay, T., Revenaugh, J. & Garnero, E. J. Anticorrelated seismic velocity anomalies from post-perovskite in the lowermost mantle. Science 320, 1070–1074 (2008)
Ni, S., Tan, E., Gurnis, M. & Helmberger, D. Sharp sides to the African superplume. Science 296, 1850–1852 (2002)
Shim, S.-H. et al. Crystal structure and thermoelastic properties of (Mg0. 91Fe0. 09)SiO3 postperovskite up to 135 GPa and 2700 K. Proc. Natl. Acad. Sci. USA 105, 7382–7386 (2008)
Tangeman, J. A. et al. Vitreous forsterite (Mg2SiO4): synthesis, structure, and thermochemistry. Geophys. Res. Lett. 28, 2517–2520 (2001)
Hammersley, A. P. Fit2d: An Introduction and Overview. ESRF Internal Report (European Synchrotron Radiation Facility, 1997)
Tsuchiya, T. First-principles prediction of the P–V–T equation of state of gold and the 660-km discontinuity in Earth’s mantle. J. Geophys. Res. 108, 2462 (2003)
Jeanloz, R. & Heinz, D. L. Experiments at high temperature and pressure: laser heating through the diamond cell. J. Phys. (Paris) 45, C8–83–C8-92 (1984)
This work is supported by the US National Science Foundation (NSF) grant EAR0738655 (S.-H.S.) and a US Department of Energy (DOE) National Nuclear Security Administration Stewardship Science Graduate Fellowship (K.C.). A. Kubo and B. Grocholski assisted in X-ray measurements. Discussion with T. L. Grove and R. D. van der Hilst improved the paper. This work was performed in the GeoSoilEnviroCARS sector of the Advanced Light Source (APS), Argonne National Laboratory. GeoSoilEnviroCARS is supported by the NSF and the DOE. Use of the APS is supported by the DOE.
Author Contributions K.C. and S.-H.S. prepared and made the measurements on (Mg0.9Fe0.1)(Al0.1Si0.9)O3 and (Mg0.91Fe0.09)SiO3, respectively. V.P. assisted in the synchrotron measurements. K.C. and S.-H.S. conducted the data analysis and calculations. S.-H.S. and K.C. wrote the paper. All authors discussed the results and commented on the manuscript.
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Catalli, K., Shim, SH. & Prakapenka, V. Thickness and Clapeyron slope of the post-perovskite boundary. Nature 462, 782–785 (2009). https://doi.org/10.1038/nature08598