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Title: Phase transitions in MgSiO 3 post-perovskite in super-Earth mantles

Abstract

The highest pressure form of the major Earth-forming mantle silicate is MgSiO 3 post-perovskite (PPv). Understanding the fate of PPv at TPa pressures is the first step for understanding the mineralogy of super-Earths-type exoplanets, arguably the most interesting for their similarities with Earth. Modeling their internal structure requires knowledge of stable mineral phases, their properties under compression, and major element abundances. Several studies of PPv under extreme pressures support the notion that a sequence of pressure induced dissociation transitions produce the elementary oxides SiO 2 and MgO as the ultimate aggregation form at ~3 TPa. However, none of these studies have addressed the problem of mantle composition, particularly major element abundances usually expressed in terms of three main variables, the Mg/Si and Fe/Si ratios and the Mg#, as in the Earth. Here we show that the critical compositional parameter, the Mg/Si ratio, whose value in the Earth’s mantle is still debated, is a vital ingredient for modeling phase transitions and internal structure of super-Earth mantles. Specifically, we have identified new sequences of phase transformations, including new recombination reactions that depend decisively on this ratio. This is a new level of complexity that has not been previously addressed, but proves essentialmore » for modeling the nature and number of internal layers in these rocky mantles.« less

Authors:
 [1];  [2];  [3];  [4];  [4];  [4]
  1. Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo (Japan). Earth-Life Science Institute; University of Minnesota, Minneapolis, MN (United States). Department of Earth Sciences; Iowa State University, Ames, IA (United States). Ames Laboratory, US DOE and Department of Physics and Astronomy
  2. Columbia University, New York, NY (United States). Department of Applied Physics and Applied Mathematics, Department of Earth and Environmental Sciences; Columbia University, Palisades, NY (United States). Lamont–Doherty Earth Observatory
  3. Iowa State University, Ames, IA (United States). Ames Laboratory, US DOE and Department of Physics and Astronomy; Xiamen University, Xiamen (China). Department of Physics
  4. Iowa State University, Ames, IA (United States). Ames Laboratory, US DOE and Department of Physics and Astronomy
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory, Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC).
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21)
OSTI Identifier:
1463298
DOE Contract Number:  
AC02-07CH11358
Resource Type:
Journal Article
Journal Name:
Earth and Planetary Science Letters
Additional Journal Information:
Journal Volume: 478; Journal Issue: C; Journal ID: ISSN 0012-821X
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Umemoto, Koichiro, Wentzcovitch, Renata M., Wu, Shunqing, Ji, Min, Wang, Cai-Zhuang, and Ho, Kai-Ming. Phase transitions in MgSiO3 post-perovskite in super-Earth mantles. United States: N. p., 2017. Web. doi:10.1016/j.epsl.2017.08.032.
Umemoto, Koichiro, Wentzcovitch, Renata M., Wu, Shunqing, Ji, Min, Wang, Cai-Zhuang, & Ho, Kai-Ming. Phase transitions in MgSiO3 post-perovskite in super-Earth mantles. United States. doi:10.1016/j.epsl.2017.08.032.
Umemoto, Koichiro, Wentzcovitch, Renata M., Wu, Shunqing, Ji, Min, Wang, Cai-Zhuang, and Ho, Kai-Ming. Wed . "Phase transitions in MgSiO3 post-perovskite in super-Earth mantles". United States. doi:10.1016/j.epsl.2017.08.032.
@article{osti_1463298,
title = {Phase transitions in MgSiO3 post-perovskite in super-Earth mantles},
author = {Umemoto, Koichiro and Wentzcovitch, Renata M. and Wu, Shunqing and Ji, Min and Wang, Cai-Zhuang and Ho, Kai-Ming},
abstractNote = {The highest pressure form of the major Earth-forming mantle silicate is MgSiO3 post-perovskite (PPv). Understanding the fate of PPv at TPa pressures is the first step for understanding the mineralogy of super-Earths-type exoplanets, arguably the most interesting for their similarities with Earth. Modeling their internal structure requires knowledge of stable mineral phases, their properties under compression, and major element abundances. Several studies of PPv under extreme pressures support the notion that a sequence of pressure induced dissociation transitions produce the elementary oxides SiO2 and MgO as the ultimate aggregation form at ~3 TPa. However, none of these studies have addressed the problem of mantle composition, particularly major element abundances usually expressed in terms of three main variables, the Mg/Si and Fe/Si ratios and the Mg#, as in the Earth. Here we show that the critical compositional parameter, the Mg/Si ratio, whose value in the Earth’s mantle is still debated, is a vital ingredient for modeling phase transitions and internal structure of super-Earth mantles. Specifically, we have identified new sequences of phase transformations, including new recombination reactions that depend decisively on this ratio. This is a new level of complexity that has not been previously addressed, but proves essential for modeling the nature and number of internal layers in these rocky mantles.},
doi = {10.1016/j.epsl.2017.08.032},
journal = {Earth and Planetary Science Letters},
issn = {0012-821X},
number = C,
volume = 478,
place = {United States},
year = {2017},
month = {11}
}