SiO2 Glass Density to Lower-Mantle Pressures

Sylvain Petitgirard, Wim J. Malfait, Baptiste Journaux, Ines E. Collings, Eleanor S. Jennings, Ingrid Blanchard, Innokenty Kantor, Alexander Kurnosov, Marine Cotte, Thomas Dane, Manfred Burghammer, and David C. Rubie
Phys. Rev. Lett. 119, 215701 – Published 21 November 2017
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Abstract

The convection or settling of matter in the deep Earth’s interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past and present Earth. SiO2 is the main constituent of Earth’s mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60 GPa. The density data present two discontinuities at 17 and 60GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at 40GPa, and its density becomes identical to that of MgSiO3 glass above 80 GPa. Our results on SiO2 glass may suggest that a variation of SiO2 content in a basaltic or pyrolitic melt with pressure has at most a minor effect on the final melt density, and iron partitioning between the melts and residual solids is the predominant factor that controls melt buoyancy in the lowermost mantle.

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  • Received 22 November 2016

DOI:https://doi.org/10.1103/PhysRevLett.119.215701

© 2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Sylvain Petitgirard1,*, Wim J. Malfait2, Baptiste Journaux3, Ines E. Collings4,6, Eleanor S. Jennings1, Ingrid Blanchard1, Innokenty Kantor5, Alexander Kurnosov1, Marine Cotte6,7, Thomas Dane6, Manfred Burghammer6, and David C. Rubie1

  • 1Bayerisches Geoinstitut, University of Bayreuth, Bayreuth D-95440, Germany
  • 2Laboratory for Building Energy Materials and Components, Swiss Federal Laboratories for Materials Science and Technology, Empa, 8600 Dübendorf, Switzerland
  • 3Institut des Géosciences de l’Environnement-UMR 5001, Université Grenoble Alpes CS 40700, 38 058 Grenoble Cedex 9, France
  • 4Laboratory of Crystallography, University of Bayreuth, Bayreuth D-95440, Germany
  • 5Danmarks Tekniske Universitet, 2800 Kgs. Lyngby, Denmark
  • 6European Synchrotron Radiation Facility, BP 220, Grenoble F-38043, France
  • 7Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8220, Laboratoire d’archéologie moléculaire et structurale (LAMS), 4 Place Jussieu 75005 Paris, France

  • *Corresponding author. Sylvain.Petitgirard@uni-bayreuth.de

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Issue

Vol. 119, Iss. 21 — 24 November 2017

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