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A shock-induced phase change in iron-silicate garnet

Ahrens, Thomas J. and Graham, E. K. (1972) A shock-induced phase change in iron-silicate garnet. Earth and Planetary Science Letters, 14 (1). pp. 87-90. ISSN 0012-821X. doi:10.1016/0012-821X(72)90086-6.

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Hugoniot measurements on iron-silicate garnet (Fe_(0.79), Mg_(0.14), Ca_(0.04), Mn_(0.03))_3 Al_2Si_3O_(12) initial density 4.18 g/cm^3, demonstrate that above a shock pressure of 205 ± 20 kbar transition to a high-pressure phase(s), having an apparent zero-pressure density and bulk modulus of 4.44 ± 0.06g/cm^3 and 3.3 ± 0.3 Mbar, occurs. Crystal chemical systematics and Debye-Scherrer X-ray patterns of a recovered phase(s), which may be the shock-induced high-pressure form, suggest possible formation of a phase with a density of∼ 4.48/cm^3. Occurrence of such a polymorph of garnet in the mantle would give rise to an increase in density and seismic velocity below ∼ 600km in the earth.

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Additional Information:© 1972 Published by Elsevier B.V. Received 6 September 1971; Revised version received 22 November 1971. We appreciate the assistance of John F Lower and Rex V. Gibbons in carrying out the Hugomot and shock recovery experiments Rex V Gibbons' review of the manuscript is also appreciated This research was supported under NSF Grant GA 21396 and NASA Grant NGL 05-002-105.
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NSFGA 21396
NASANGL 05-002-105
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Caltech Division of Geological and Planetary Sciences2049
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Record Number:CaltechAUTHORS:20150107-133724965
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Official Citation:Thomas J. Ahrens, E.K. Graham, A shock-induced phase change in iron-silicate garnet, Earth and Planetary Science Letters, Volume 14, Issue 1, February 1972, Pages 87-90, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53292
Deposited By: Tony Diaz
Deposited On:08 Jan 2015 02:51
Last Modified:10 Nov 2021 20:00

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