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The equation of state of Mg_(0.6)Fe_(0.4)O to 200 GPa

Vassiliou, M. S. and Ahrens, Thomas J. (1982) The equation of state of Mg_(0.6)Fe_(0.4)O to 200 GPa. Geophysical Research Letters, 9 (2). pp. 127-130. ISSN 0094-8276. doi:10.1029/GL009i002p00127.

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New Hugoniot data on polycrystalline (avg.porosity 6.9%) samples of the magnesiowustite Mg_(0.6)Fe_(0.4)O are presented, covering the pressure range up to 200 GPa. When our data are fit by a single 3rd order Eulerian Hugoniot with K_0 constrained to its ultrasonic value of 161.5 GPa, the required isentropic pressure derivative K_0′ is 4.37 +/− 0.37. This value is significantly lower than the ultrasonic one of 6.18; existing isothermal compression data, however, are in agreement with our value rather than the ultrasonic one. Our data are adequately explained without phase transitions. There is some marginal evidence for a possible phase transition around 120 GPa. If such a transition indeed occurs it is probably of small volume change compared to the transition observed in FeO; we place an extreme upper bound of 3% on the density change such a transformation could involve and still be consistent with the data. Contrary to earlier hypotheses, we believe that a phase transition in magnesiowustite is not a likely explanation of the seismic effects in the D″ region of the lower mantle. The wustite transition may be a more complex phenomenon than initially supposed — perhaps an effect of nonstoichiometry localized to the iron-rich end of the solid solution series.

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Alternate Title:The equation of state of Mg0.6Fe0.4O to 200 GPa
Additional Information:Copyright 1982 by the American Geophysical Union. (Received September 11, 1981; revised November 2, 1981; accepted December 2, 1981.) Paper number 1L1853. We gratefully acknowledge the experimental expertise of E. Gelle and M. Long, who operate the shock-wave facility in the Lindhurst Laboratory of Experimental Geophysics at Caltech. Discussions with Raymond Jeanloz, Don Anderson, and Glen Waychunas were very helpful. We are indebted to Earl Graham of the Pennsylvania State University for providing us with our samples of magnesiowustite. This research was supported by the Earth Sciences Section, National Science Foundation, grant # EAR79-26384. (Contribution # 3700, Division of Geological and Planetary Sciences, California Institute of Technology)
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NSFEAR 79-26384
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Caltech Division of Geological and Planetary Sciences3700
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Official Citation:Vassiliou, M. S., and T. J. Ahrens (1982), The equation of state of Mg0.6Fe0.4O to 200 GPa, Geophys. Res. Lett., 9(2), 127–130, doi:10.1029/GL009i002p00127.
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ID Code:51203
Deposited By: George Porter
Deposited On:04 Nov 2014 00:02
Last Modified:10 Nov 2021 19:07

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