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Shock wave compression of single-crystal forsterite

Jackson, Ian and Ahrens, Thomas J. (1979) Shock wave compression of single-crystal forsterite. Journal of Geophysical Research B, 84 (B6). pp. 3039-3048. ISSN 0148-0227. doi:10.1029/JB084iB06p03039.

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Hugoniot equation of state measurements have been performed on pure synthetic single-crystal forsterite (Mg_2SiO_4) in the pressure range 70–160 GPa (0.7–1.6 Mbar). These and earlier data for polycrystalline forsterite are compared with theoretical Hugoniots for the assemblages 2MgO (rocksalt) + SiO_2 (stishovite) and MgO (rocksalt) + MgSiO_3 (perovskite). The densities attained by single-crystal forsterite at pressures in excess of 120 GPa are greater than those expected in the event of shock-induced transformation to the isochemical oxide mixture. A similar test of the hypothesis of shock-induced transformation to the perovskite-bearing assemblage is sensitive to the choice of MgSiO_3 (perovskite) bulk modulus. Recent static compression measurements of Yagi et al. (1978) yield a K_(0T) of 286 GPa (for K_(0T)′ = 5), which, along with other elastic and thermodynamic parameters, suggests that shocked forsterite may be more dense than the perovskite-bearing assemblage. Crystalline phases of up to 5% greater zeropressure density or equally dense short-range-order-only phases may well be involved. Alternatively, the use of an isentropic bulk modulus of 250 GPa (estimated by Liebermann et al., 1977) for MgSiO_3 (perovskite) allows consistency between the data and the calculated MgO + MgSiO_3 (perovskite) Hugoniot for a reasonable choice (∼3.8) of K_(0s)′ for the latter phase. The new forsterite data along with high-pressure Hugoniot data for other olivines and olivinitic rocks define a smooth isobaric variation of Hugoniot density with composition. It is shown that an estimated pyrolite (Ringwood, 1975) Hugoniot density of 5.31 g/cm^3 at 120 GPa is ∼2% less dense than inferred from typical lower mantle density profiles.

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Additional Information:Copyright 1979 by the American Geophysical Union. (Received June 8, 1978; revised October 3, 1978; accepted October 18, 1978.) Paper number 8B1114. This study would not have been possible without the efforts of T. J. Shankland in providing sample material via an NSF-supported program. We are grateful to H. Richeson, E. Gelle, and R. Smith for their expert technical assistance with all facets of the experimental work and to R. Jeanloz, R. S. Anderssen, J. R. Cleary, L. Liu, R. T. Merrill, and A. E. Ringwood for stimulating discussions of many aspects of this work. The experimental work reported in this paper was performed in the Helen and Roland Lindhurst Laboratory of Experimental Geophysics. This paper was written after one of us (I.J.) took an appointment at the Australian National University. Financial support through the U.S. National Science Foundation (DES 75-15006) is gratefully acknowledged. Contribution number 3048, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California
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NSFDES 75-15006
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Caltech Division of Geological and Planetary Sciences3048
Issue or Number:B6
Record Number:CaltechAUTHORS:20141031-123329621
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Official Citation:Jackson, I., and T. J. Ahrens (1979), Shock wave compression of single-crystal forsterite, J. Geophys. Res., 84(B6), 3039–3048, doi:10.1029/JB084iB06p03039.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51125
Deposited By: George Porter
Deposited On:31 Oct 2014 20:07
Last Modified:10 Nov 2021 19:06

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