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Liquid Silicate Equation of State: Using Shock Waves to Understand the Properties of the Deep Earth

Citation

Thomas, Claire Waller (2013) Liquid Silicate Equation of State: Using Shock Waves to Understand the Properties of the Deep Earth. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/8JTY-MQ03. http://resolver.caltech.edu/CaltechTHESIS:04162013-132730413

Abstract

The equations of state (EOS) of several geologically important silicate liquids have been constrained via preheated shock wave techniques. Results on molten Fe2SiO4 (fayalite), Mg2SiO4 (forsterite), CaFeSi2O6 (hedenbergite), an equimolar mixture of CaAl2Si2O8-CaFeSi2O6 (anorthite-hedenbergite), and an equimolar mixture of CaAl2Si2O8-CaFeSi2O6-CaMgSi2O6(anorthite-hedenbergite-diopside) are presented. This work represents the first ever direct EOS measurements of an iron-bearing liquid or of a forsterite liquid at pressures relevant to the deep Earth (> 135 GPa). Additionally, revised EOS for molten CaMgSi2O6 (diopside), CaAl2Si2O8 (anorthite), and MgSiO3 (enstatite), which were previously determined by shock wave methods, are also presented.

The liquid EOS are incorporated into a model, which employs linear mixing of volumes to determine the density of compositionally intermediate liquids in the CaO-MgO-Al2O3-SiO2-FeO major element space. Liquid volumes are calculated for temperature and pressure conditions that are currently present at the core-mantle boundary or that may have occurred during differentiation of a fully molten mantle magma ocean.

The most significant implications of our results include: (1) a magma ocean of either chondrite or peridotite composition is less dense than its first crystallizing solid, which is not conducive to the formation of a basal mantle magma ocean, (2) the ambient mantle cannot produce a partial melt and an equilibrium residue sufficiently dense to form an ultralow velocity zone mush, and (3) due to the compositional dependence of Fe2+ coordination, there is a threshold of Fe concentration (molar XFe ≤ 0.06) permitted in a liquid for which its density can still be approximated by linear mixing of end-member volumes.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:equation of state; liquid silicate; shock wave
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Asimow, Paul David
Thesis Committee:
  • Rossman, George Robert (chair)
  • Jackson, Jennifer M.
  • Stolper, Edward M.
  • Asimow, Paul David
Defense Date:11 April 2013
Funders:
Funding AgencyGrant Number
NSFEAR-0855774
NSFEAR-1119522
Record Number:CaltechTHESIS:04162013-132730413
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:04162013-132730413
DOI:10.7907/8JTY-MQ03
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2012JB009403DOIUNSPECIFIED
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7616
Collection:CaltechTHESIS
Deposited By: Claire Thomas
Deposited On:22 Apr 2013 17:14
Last Modified:26 Apr 2019 18:20

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