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Title: Hydrogen self-diffusion in single crystal olivine and electrical conductivity of the Earth’s mantle

Nominally anhydrous minerals formed deep in the mantle and transported to the Earth’s surface contain tens to hundreds of ppm wt H 2O, providing evidence for the presence of dissolved water in the Earth’s interior. Even at these low concentrations, H 2O greatly affects the physico-chemical properties of mantle materials, governing planetary dynamics and evolution. The diffusion of hydrogen (H) controls the transport of H 2O in the Earth’s upper mantle, but is not fully understood for olivine ((Mg, Fe) 2SiO 4) the most abundant mineral in this region. Here we present new hydrogen self-diffusion coefficients in natural olivine single crystals that were determined at upper mantle conditions (2 GPa and 750–900 °C). Hydrogen self-diffusion is highly anisotropic, with values at 900 °C of 10 -10.9, 10 -12.8 and 10 -11.9 m 2/s along [100], [010] and [001] directions, respectively. Combined with the Nernst-Einstein relation, these diffusion results constrain the contribution of H to the electrical conductivity of olivine to be σH = 10 2.12S/m·C H2O·exp -187kJ/mol/(RT). Comparisons between the model presented in this study and magnetotelluric measurements suggest that plausible H 2O concentrations in the upper mantle (≤250 ppm wt) can account for high electrical conductivity values (10 -2–10more » -1 S/m) observed in the asthenosphere.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [2] ;  [2]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Cambridge (United Kingdom). Department of Earth Sciences
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Arizona State Univ., Tempe, AZ (United States). School of Earth and Space Exploration
Publication Date:
Report Number(s):
LLNL-JRNL-706280
Journal ID: ISSN 2045-2322; PII: 5113
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1393347

Novella, Davide, Jacobsen, Benjamin, Weber, Peter K., Tyburczy, James A., Ryerson, Frederick J., and Du Frane, Wyatt L.. Hydrogen self-diffusion in single crystal olivine and electrical conductivity of the Earth’s mantle. United States: N. p., Web. doi:10.1038/s41598-017-05113-6.
Novella, Davide, Jacobsen, Benjamin, Weber, Peter K., Tyburczy, James A., Ryerson, Frederick J., & Du Frane, Wyatt L.. Hydrogen self-diffusion in single crystal olivine and electrical conductivity of the Earth’s mantle. United States. doi:10.1038/s41598-017-05113-6.
Novella, Davide, Jacobsen, Benjamin, Weber, Peter K., Tyburczy, James A., Ryerson, Frederick J., and Du Frane, Wyatt L.. 2017. "Hydrogen self-diffusion in single crystal olivine and electrical conductivity of the Earth’s mantle". United States. doi:10.1038/s41598-017-05113-6. https://www.osti.gov/servlets/purl/1393347.
@article{osti_1393347,
title = {Hydrogen self-diffusion in single crystal olivine and electrical conductivity of the Earth’s mantle},
author = {Novella, Davide and Jacobsen, Benjamin and Weber, Peter K. and Tyburczy, James A. and Ryerson, Frederick J. and Du Frane, Wyatt L.},
abstractNote = {Nominally anhydrous minerals formed deep in the mantle and transported to the Earth’s surface contain tens to hundreds of ppm wt H2O, providing evidence for the presence of dissolved water in the Earth’s interior. Even at these low concentrations, H2O greatly affects the physico-chemical properties of mantle materials, governing planetary dynamics and evolution. The diffusion of hydrogen (H) controls the transport of H2O in the Earth’s upper mantle, but is not fully understood for olivine ((Mg, Fe)2SiO4) the most abundant mineral in this region. Here we present new hydrogen self-diffusion coefficients in natural olivine single crystals that were determined at upper mantle conditions (2 GPa and 750–900 °C). Hydrogen self-diffusion is highly anisotropic, with values at 900 °C of 10-10.9, 10-12.8 and 10-11.9 m2/s along [100], [010] and [001] directions, respectively. Combined with the Nernst-Einstein relation, these diffusion results constrain the contribution of H to the electrical conductivity of olivine to be σH = 102.12S/m·CH2O·exp-187kJ/mol/(RT). Comparisons between the model presented in this study and magnetotelluric measurements suggest that plausible H2O concentrations in the upper mantle (≤250 ppm wt) can account for high electrical conductivity values (10-2–10-1 S/m) observed in the asthenosphere.},
doi = {10.1038/s41598-017-05113-6},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = {2017},
month = {7}
}