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Title: Composition dependence of spin transition in (Mg,Fe)SiO 3 bridgmanite

Spin transitions in (Mg,Fe)SiO 3 bridgmanite have important implications for the chemistry and dynamics of Earth’s lower mantle, but have been complex to characterize in experiments. We examine the spin state of Fe in highly Fe-enriched bridgmanite synthesized from enstatites with measured compositions (Mg 0.61Fe 0.38Ca 0.01)SiO 3 and (Mg 0.25Fe 0.74Ca 0.01)SiO 3. Bridgmanite was synthesized at 78-88 GPa and 1800-2400 K and X-ray emission spectra were measured on decompression to 1 bar (both compositions) and compression to 126 GPa ((Mg 0.61Fe 0.38Ca 0.01)SiO 3 only) without additional laser heating. Observed spectra confirm that Fe in these bridgmanites is dominantly high spin in the lower mantle. However, the total spin moment begins to decrease at ~50 GPa in the 74% FeSiO 3 composition. Lastly, these results support density functional theory predictions of a lower spin transition pressure in highly Fe-enriched bridgmanite and potentially explain the high solubility of FeSiO 3 in bridgmanite at pressures corresponding to Earth’s deep lower mantle.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [1]
  1. Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland)
  2. Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland); Univ. Paris Diderot, Paris (France)
  3. Synchrotron SOLEIL, Gif-sur-Yvette (France)
  4. Carnegie Inst. of Washington, Argonne, IL (United States)
Publication Date:
Grant/Contract Number:
NA0002006
Type:
Accepted Manuscript
Journal Name:
American Mineralogist
Additional Journal Information:
Journal Volume: 100; Journal Issue: 10; Journal ID: ISSN 0003-004X
Publisher:
Mineralogical Society of America
Research Org:
Carnegie Institution of Washington, Washington, D.C. (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; bridgmanite; spin transition; iron-bearing silicates; lower mantle
OSTI Identifier:
1335651

Dorfman, Susannah M., Badro, James, Rueff, Jean -Pascal, Chow, Paul, Xiao, Yuming, and Gillet, Philippe. Composition dependence of spin transition in (Mg,Fe)SiO3 bridgmanite. United States: N. p., Web. doi:10.2138/am-2015-5190.
Dorfman, Susannah M., Badro, James, Rueff, Jean -Pascal, Chow, Paul, Xiao, Yuming, & Gillet, Philippe. Composition dependence of spin transition in (Mg,Fe)SiO3 bridgmanite. United States. doi:10.2138/am-2015-5190.
Dorfman, Susannah M., Badro, James, Rueff, Jean -Pascal, Chow, Paul, Xiao, Yuming, and Gillet, Philippe. 2015. "Composition dependence of spin transition in (Mg,Fe)SiO3 bridgmanite". United States. doi:10.2138/am-2015-5190. https://www.osti.gov/servlets/purl/1335651.
@article{osti_1335651,
title = {Composition dependence of spin transition in (Mg,Fe)SiO3 bridgmanite},
author = {Dorfman, Susannah M. and Badro, James and Rueff, Jean -Pascal and Chow, Paul and Xiao, Yuming and Gillet, Philippe},
abstractNote = {Spin transitions in (Mg,Fe)SiO3 bridgmanite have important implications for the chemistry and dynamics of Earth’s lower mantle, but have been complex to characterize in experiments. We examine the spin state of Fe in highly Fe-enriched bridgmanite synthesized from enstatites with measured compositions (Mg0.61Fe0.38Ca0.01)SiO3 and (Mg0.25Fe0.74Ca0.01)SiO3. Bridgmanite was synthesized at 78-88 GPa and 1800-2400 K and X-ray emission spectra were measured on decompression to 1 bar (both compositions) and compression to 126 GPa ((Mg0.61Fe0.38Ca0.01)SiO3 only) without additional laser heating. Observed spectra confirm that Fe in these bridgmanites is dominantly high spin in the lower mantle. However, the total spin moment begins to decrease at ~50 GPa in the 74% FeSiO3 composition. Lastly, these results support density functional theory predictions of a lower spin transition pressure in highly Fe-enriched bridgmanite and potentially explain the high solubility of FeSiO3 in bridgmanite at pressures corresponding to Earth’s deep lower mantle.},
doi = {10.2138/am-2015-5190},
journal = {American Mineralogist},
number = 10,
volume = 100,
place = {United States},
year = {2015},
month = {10}
}