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Shock-wave equation of state of molten and solid fayalite

Chen, George Q. and Ahrens, Thomas J. and Stolper, E. M. (2002) Shock-wave equation of state of molten and solid fayalite. Physics of the Earth and Planetary Interiors, 134 (1-2). pp. 35-52. ISSN 0031-9201. http://resolver.caltech.edu/CaltechAUTHORS:20120823-103324201

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Abstract

Shock-wave equations of state (EOS) of initially solid (300 K) and molten (1573 K) fayalite (Fe_2SiO_4, Fa) are measured over the pressure ranges of 23–212 and 5–47 GPa, respectively. The 300 K data indicates that Fa undergoes a phase change from the low-pressure olivine structure (Lpp) over the 35–55 GPa range. In agreement with earlier analyses of Rockport fayalite shock data and diamond cell recovery experiments, the high pressure phase (Hpp) data are consistent with an oxide (2FeO+SiO_2, stishovite) mixture. A fit to the Hpp Hugoniot data in the shock velocity (u_S)–particle velocity (u_P) plane yields: u_S = 4.07 (0.22)km/s + 1.43 (0.06)u_P. Here, the initial density, ρ_0 is 4.375 (0.027) Mg/m^3. The 1573 K data yields: u_S = 2.63(0.02) km/s + 1.59 (0.01)u_P. Initial density calculated from temperature data is 3.750 (0.018) Mg/m^3 and K_(0S)=25.9±0.4 GPa, and K_(0S)′=5.36±0.04 GPa. The bulk modulus, K_(0S), compares favorably with Agee’s result [Geophys. Res. Lett. 19 (1992a) 1169], 24.4 GPa, but the pressure derivative is much less than the K_(0T)′=10.1 GPa previously reported. Molten Fa compression data >40 GPa are closely fit with an ideal mixture of oxides, SiO_2 (stishovite) + 2FeO (Lpp), in support of the hypothesis of Rigden et al. [J. Geophys. Res. 94 (1989) 9508]. A model molten basalt incorporating previous molten anorthite (An)–diopside (Di) eutectic and the present molten Fa (EOS) data implies that a zone of basic silicate liquid, could be neutrally buoyant at a depth of ∼250–400 km, upon partial melting of a peridotite mantle as discussed by Rigden et al. [Science 226 (1984) 1071]. This conclusion is based on comparison of the density of the model basalt: (An_(0.36)Di_(0.64))_(0.85)Fa_(0.15), with Dziewonski and Anderson’s Preliminary Reference Earth model [Phys. Earth Planet. Inter. 25 (1981) 297].


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http://dx.doi.org/10.1016/S0031-9201(02)00080-8DOIUNSPECIFIED
http://www.sciencedirect.com/science/article/pii/S0031920102000808PublisherUNSPECIFIED
Additional Information:© 2002 Elsevier Science B.V. Received 18 January 1999. Revised 28 June 2002. Accepted 28 June 2002. Available online 16 September 2002. Research supported by National Science Foundation. We appreciate the helpful comments of Paul Asimow and two reviewers and gifts of fayalite single-crystals from C.A. Finch, Oak Ridge National Laboratory and H. Takei (Tohoku U., Sendai). Contribution #8592, Division of Geological and Planetary Science, California Institute of Technology, Pasadena, California, 91125, USA.
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Subject Keywords:Shock-wave equation; Fayalite; Pressure
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Caltech Division of Geological and Planetary Sciences8592
Record Number:CaltechAUTHORS:20120823-103324201
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120823-103324201
Official Citation:George Q Chen, Thomas J Ahrens, E.M Stolper, Shock-wave equation of state of molten and solid fayalite, Physics of the Earth and Planetary Interiors, Volume 134, Issues 1–2, 28 November 2002, Pages 35-52, ISSN 0031-9201, 10.1016/S0031-9201(02)00080-8. (http://www.sciencedirect.com/science/article/pii/S0031920102000808)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:33472
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:23 Aug 2012 20:43
Last Modified:23 Aug 2012 20:43

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