Luo, Sheng-Nian and Ahrens, Thomas J. and Asimow, Paul D.
Polymorphism, superheating, and amorphization of silica upon shock wave loading and release.
Journal of Geophysical Research B, 108
Art. No. 2421.
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We present a detailed and quantitative examination of the thermodynamics and phase change mechanisms (including amorphization) that occur upon shock wave loading and unloading of silica. We apply Debye-Grüneisen theory to calculate both the Hugoniot of quartz and isentropic release paths. Quartz converts to stishovite (or a stishovite-like phase) between 15 and 46 GPa, and persistence of the solid phase above its liquidus (i.e., superheating) is confirmed between 77 and 110 GPa. Calculations compare favorably to measurements of shock and post-shock temperatures. For silica, the method of measuring post-shock temperature is insensitive to predicting whether phase transitions actually occur during release. Measurements of release states in pressure-particle velocity space are compared to computed frozen-phase release paths. This comparison suggests transformation of a stishovite-like phase to lower density phases including quartz, liquid, or dense amorphous glass. Transformations to liquid or glass occur upon release from peak pressure of 26 GPa and above. The isentropic release assumption appears to be approximately valid. A shock pressure-temperature scale relating metamorphism of silica in shock-loaded quartz is proposed. Neither recovery of coesite nor substantial quantities of crystalline stishovite-like phases upon shock loading of quartz is predicted. Trace amounts of crystalline stishovite-like phases from shock loading between 15 and 26 GPa are expected.
|Additional Information:||© 2003 American Geophysical Union. Received 21 November 2002; revised 12 May 2003; accepted 23 May 2003; published 10 September 2003. S.-N. Luo has been supported by NSF grant
EAR-0207934. We appreciate helpful discussions with Z. R. Wang, D. Andrault, and O. Tschauner. Comments by I. Jackson and two reviewers helped improve the manuscript. Contribution 8916, Division of Geological and Planetary Sciences, California Institute of Technology|
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|Caltech Division of Geological and Planetary Sciences||8916|
|Official Citation:||Luo, S.-N., T. J. Ahrens, and P. D. Asimow, Polymorphism, superheating, and amorphization of silica upon shock wave
loading and release, J. Geophys. Res., 108(B9), 2421, doi:10.1029/2002JB002317, 2003.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited On:||05 Sep 2012 21:20|
|Last Modified:||23 Jul 2013 18:43|
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