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Shock metamorphism of silicate glasses

Gibbons, Rex V. and Ahrens, Thomas J. (1971) Shock metamorphism of silicate glasses. Journal of Geophysical Research, 76 (23). pp. 5489-5498. ISSN 0148-0227. doi:10.1029/JB076i023p05489.

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The changes in refractive index caused by shock compression have been determined for tektite, soda-lime, and silica glasses shocked to pressures up to 460 kb. For shock compression below 80 kb for fused silica and 40 kb for tektite and soda-lime glasses, compression is reversible as the refractive indices are within 0.0025 of the starting values. Index increases of 0.01, 0.04, and 0.06 are observed for soda-lime, tektite, and silica glasses shocked to pressures of 80, 130, and 140 kb respectively. For soda-lime glass subjected to shock pressures between 80 and 230 kb there is a decrease in the postshock refractive index to n=1.5211 at 230 kb. For fused silica shocked to pressures of 140 to 460 kb, refractive index drops from 1.52 to 1.47. The reasons for these decreases in index are not obvious. New values for postshock temperatures for fused silica based on release adiabat data, e.g. ∼1000°C for a shock state at 250 kb, suggest that the decreases in refractive index are caused by a combination of decompression along release adiabats and reconstructive transformation from a shock-induced stishovitelike phase to a low-density glass. Postshock densities calculated from the refractive index data agree closely with those calculated from the release adiabat data.

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Additional Information:Copyright 1971 by the American Geophysical Union. (Received January 7, 1971; revised March 22, 1971.) We especially appreciate E. C. T. Chao's hospitality and assistance in carrying out the interference microscopy and R. L. Fleischer's kindness in providing some of the specimen material. Contributions were made to the experiments by D. Johnson, J. Kleeman, and J. Lower. Discussions of the project with A. L. Albee, E. C. T. Chao, B. Kamb, E. Shoemaker, L. T. Silver, and H. P. Taylor were also helpful. The research was supported at California Institute of Technology by NASA grant NGL-05-002-105. Publication was, in part, supported by NASA contract NSR 09-051-001. Contribution 1957, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena 91109. Lunar Science Institute Contribution 41.
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NASANSR 09-051-001
Subject Keywords:Deformation: Experimental Studies; Metamorphism: Shock
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences1957
Lunar Science Institute41
Issue or Number:23
Record Number:CaltechAUTHORS:20141107-084805316
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Official Citation:Gibbons, R. V., and T. J. Ahrens (1971), Shock metamorphism of silicate glasses, J. Geophys. Res., 76(23), 5489–5498, doi:10.1029/JB076i023p05489.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51415
Deposited By: George Porter
Deposited On:07 Nov 2014 17:47
Last Modified:10 Nov 2021 19:10

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