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The MgSiO_3 system at high pressure: Thermodynamic properties of perovskite, postperovskite, and melt from global inversion of shock and static compression data

Mosenfelder, Jed L. and Frost, Daniel J. and Rubie, David C. and Ahrens, Thomas J. and Asimow, Paul D. (2009) The MgSiO_3 system at high pressure: Thermodynamic properties of perovskite, postperovskite, and melt from global inversion of shock and static compression data. Journal of Geophysical Research B, 114 . B01203. ISSN 0148-0227. https://resolver.caltech.edu/CaltechAUTHORS:MOSjgrb09

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Abstract

We present new equation-of-state (EoS) data acquired by shock loading to pressures up to 245 GPa on both low-density samples (MgSiO_3 glass) and high-density, polycrystalline aggregates (MgSiO_3 perovskite + majorite). The latter samples were synthesized using a large-volume press. Modeling indicates that these materials transform to perovskite, postperovskite, and/or melt with increasing pressure on their Hugoniots. We fit our results together with existing P-V-T data from dynamic and static compression experiments to constrain the thermal EoS for the three phases, all of which are of fundamental importance to the dynamics of the lower mantle. The EoS for perovskite and postperovskite are well described with third-order Birch-Murnaghan isentropes, offset with a Mie-Grüneisen-Debye formulation for thermal pressure. The addition of shock data helps to distinguish among discrepant static studies of perovskite, and for postperovskite, constrain a value of K' significantly larger than 4. For the melt, we define for the first time a single EoS that fits experimental data from ambient pressure to 230 GPa; the best fit requires a fourth-order isentrope. We also provide a new EoS for Mg_2SiO_4 liquid, calculated in a similar manner. The Grüneisen parameters of the solid phases decrease with pressure, whereas those of the melts increase, consistent with previous shock wave experiments as well as molecular dynamics simulations. We discuss implications of our modeling for thermal expansion in the lower mantle, stabilization of ultra-low-velocity zones associated with melting at the core-mantle boundary, and crystallization of a terrestrial magma ocean.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2008JB005900DOIUNSPECIFIED
http://www.agu.org/pubs/crossref/2009/2008JB005900.shtmlPublisherUNSPECIFIED
ORCID:
AuthorORCID
Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2009 American Geophysical Union. Received 26 June 2008; accepted 3 November 2008; published 14 January 2009. Funding for this work was provided by the Bayerisches Geoinstitut and by National Science Foundation grant EAR- 0207934. We thank H. Fischer for technical support of multianvil experiments in Germany; M. Long, P. Gelle, and R. Oliver for support with the shock wave experiments at Caltech; B. Balta for obtaining microprobe analyses; and T. Schneider for advice on statistics.
Funders:
Funding AgencyGrant Number
Bayerisches GeoinstitutUNSPECIFIED
NSFEAR-0207934
Subject Keywords:EQUATION-OF-STATE; LOWER MANTLE CONDITIONS; V-T EQUATION; X-RAY-OBSERVATION; THERMOELASTIC PROPERTIES; THERMAL-EXPANSION; PHASE-TRANSITION; MULTIANVIL SYSTEM; CRYSTAL-STRUCTURE; SILICATE MELTS
Record Number:CaltechAUTHORS:MOSjgrb09
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:MOSjgrb09
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13552
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:12 May 2009 19:27
Last Modified:03 Oct 2019 00:40

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