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Multi-technique equation of state for Fe_(2)SiO_4 melt and the density of Fe-bearing silicate melts from 0 to 161 GPa

Thomas, Claire W. and Liu, Qiong and Agee, Carl B. and Lange, Rebecca A. and Asimow, Paul D. (2012) Multi-technique equation of state for Fe_(2)SiO_4 melt and the density of Fe-bearing silicate melts from 0 to 161 GPa. Journal of Geophysical Research B, 117 . Art. No. B10206 . ISSN 0148-0227.

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We have conducted new equation of state measurements on liquid Fe_(2)SiO_4 in a collaborative, multi-technique study. The liquid density (ρ), the bulk modulus (K), and its pressure derivative (K′) were measured from 1 atm to 161 GPa using 1-atm double-bob Archimedean, multi-anvil sink/float, and shock wave techniques. Shock compression results on initially molten Fe_(2)SiO_4 (1573 K) fitted with previous work and the ultrasonically measured bulk sound speed (C_o) in shock velocity (U_S)-particle velocity (u_p) space yields the Hugoniot: U_S = 1.58(0.03) u_p + 2.438(0.005) km/s. Sink/float results are in agreement with shock wave and ultrasonic data, consistent with an isothermal K_T = 19.4 GPa and K′ = 5.33 at 1500°C. Shock melting of initially solid Fe_(2)SiO_4 (300 K) confirms that the Grüneisen parameter (γ) of this liquid increases upon compression where γ = γ_o(ρ_(o)/ρ)^q yields a q value of –1.45. Constraints on the liquid fayalite EOS permit the calculation of isentropes for silicate liquids of general composition in the multicomponent system CaO-MgO-Al_(2)O_3-SiO_2-FeO at elevated temperatures and pressures. In our model a whole mantle magma ocean would first crystallize in the mid-lower mantle or at the base of the mantle were it composed of either peridotite or simplified “chondrite” liquid, respectively. In regards to the partial melt hypothesis to explain the occurrence and characteristics of ultra-low velocity zones, neither of these candidate liquids would be dense enough to remain at the core mantle boundary on geologic timescales, but our model defines a compositional range of liquids that would be gravitationally stable.

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Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2012 American Geophysical Union. Received 26 April 2012; revised 12 August 2012; accepted 27 August 2012; published 12 October 2012. The authors would like to thank the shock wave lab technical staff—Michael Long, Eprapodito Gelle, and Russell Oliver; additionally, Bjorn Mysen for conducting Mössbauer measurements and Jeff Nguyen for running simulations of our shock wave experiments. C.B.A. acknowledges Michael Spilde for assistance with electron microprobe analyses and Galen Barnett for assistance with multi-anvil experiments. This work was supported by the National Science Foundation through award EAR-0855774.
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Subject Keywords:ULVZ; equation of state; fayalite; magma oceans; shock compression; silicate liquids
Record Number:CaltechAUTHORS:20121116-100605844
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Official Citation:Thomas, C. W., Q. Liu, C. B. Agee, P. D. Asimow, and R. A. Lange (2012), Multi-technique equation of state for Fe2SiO4 melt and the density of Fe-bearing silicate melts from 0 to 161 GPa, J. Geophys. Res., 117, B10206, doi:10.1029/2012JB009403.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35509
Deposited By: Jason Perez
Deposited On:16 Nov 2012 21:19
Last Modified:03 Oct 2019 04:29

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