Disproportionation of (Mg,Fe)SiO₃ perovskite in Earth's deep lower mantle

Li Zhang; Yue Meng; Wenge Yang; Lin Wang; Wendy L Mao; Qiao-Shi Zeng; Jong Seok Jeong; Andrew J Wagner; K Andre Mkhoyan; Wenjun Liu; Ruqing Xu; Ho-kwang Mao

doi:10.1126/science.1250274

Disproportionation of (Mg,Fe)SiO₃ perovskite in Earth's deep lower mantle

Science. 2014 May 23;344(6186):877-82. doi: 10.1126/science.1250274.

Authors

Li Zhang¹, Yue Meng², Wenge Yang³, Lin Wang³, Wendy L Mao⁴, Qiao-Shi Zeng⁵, Jong Seok Jeong⁶, Andrew J Wagner⁶, K Andre Mkhoyan⁶, Wenjun Liu⁷, Ruqing Xu⁷, Ho-kwang Mao⁸

Affiliations

¹ Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203, China. Geophysical Laboratory, Carnegie Institution of Washington (CIW), Washington, DC 20015, USA. [email protected].
² High Pressure Collaborative Access Team (HPCAT), Geophysical Laboratory, CIW, Argonne, IL 60439, USA.
³ Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203, China. High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, CIW, Argonne, IL 60439, USA.
⁴ Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, USA. Photon Science, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
⁵ Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, USA.
⁶ Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455 USA.
⁷ Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
⁸ Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203, China. Geophysical Laboratory, Carnegie Institution of Washington (CIW), Washington, DC 20015, USA.

PMID: 24855264
DOI: 10.1126/science.1250274

Abstract

The mineralogical constitution of the Earth's mantle dictates the geophysical and geochemical properties of this region. Previous models of a perovskite-dominant lower mantle have been built on the assumption that the entire lower mantle down to the top of the D″ layer contains ferromagnesian silicate [(Mg,Fe)SiO3] with nominally 10 mole percent Fe. On the basis of experiments in laser-heated diamond anvil cells, at pressures of 95 to 101 gigapascals and temperatures of 2200 to 2400 kelvin, we found that such perovskite is unstable; it loses its Fe and disproportionates to a nearly Fe-free MgSiO3 perovskite phase and an Fe-rich phase with a hexagonal structure. This observation has implications for enigmatic seismic features beyond ~2000 kilometers depth and suggests that the lower mantle may contain previously unidentified major phases.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.