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Shock compression and adiabatic release of a titaniferous mare basalt

Ahrens, Thomas J. and Jackson, Ian and Jeanloz, Raymond (1977) Shock compression and adiabatic release of a titaniferous mare basalt. In: 8th Lunar Science Conference. Geochimica et cosmochimica acta. Supplement. Vol.3. No.8. Pergamon Press , New York, NY, pp. 3437-3455. ISBN 0080220525. http://resolver.caltech.edu/CaltechAUTHORS:20150903-075903383

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Abstract

Hugoniot and release adiabat data for a high-titanium basalt (70215) of initial density 3.4 g/cm^3, are reported to shock stresses of 120 GPa, at which point a density of 5.7 g/cm^3 is achieved along the Hugoniot. Although only three Hugoniot states were measured in the relatively lowpressure regime (7-16 GPa), this limited data set, which includes some release adiabat measurements, indicates that nearly reversible compression takes place to stress levels of ~14 GPa, above which the post-shock zero-pressure density becomes greater than 3.4 g/cm^3. At shock stresses between ~14GPa and ≳50 GPa an assemblage of low- and high-pressure phases is inferred to exist along the Hugoniot curve, but has not been studied here. Release adiabat states at ~90 GPa, centered at Hugoniot states of 120 GPa, suggest the formation of a shock-induced high-pressure mineral assemblage with a zero-pressure density of ~5.2 g/cm^3. Substantial (~4 GPa) elastic precursors observed in the shock compression of the terrestrial Vacaville basalt and lunar gabbroic anorthosite are absent from the present study of 70215. Our results indicate that the Hugoniot elastic limit for 70215 is ≤0.4 GPa. The large compressions associated with the major phase changes in the principal minerals (Fe-rich pyroxene, calcic plagioclase, and ilmenite) imply that larger craters will be excavated by a given influx spectrum of meteoroid masses and velocities, on mare terranes than on the less compressible, anorthositic highland terranes. Qualitatively, the present results imply either that previous mare cratering ages may have been overestimated relative to mare basin ejecta and highland units or, more probably, that the integrated meteoroid fluxes could have suffered an even sharper decline with time during the first 1.5 G.y. of lunar history than previously inferred.


Item Type:Book Section
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http://adsabs.harvard.edu/full/1977LPSC....8.3437AADSArticle
Additional Information:© 1977 Lunar and Planetary Institute. This research was supported under NASA grant NSG-9019 within the facilities of the Helen and Roland W. Lindhurst Laboratory. We appreciate the careful experimental operation of this facility by H. Richeson, E. Gelle, and R. Smith. Contribution number 2863, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.
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NASANSG-9019
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Caltech Division of Geological and Planetary Sciences 2863
Record Number:CaltechAUTHORS:20150903-075903383
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150903-075903383
Official Citation:Shock compression and adiabatic release of a titaniferous mare basalt Ahrens, T. J., Jackson, I., & Jeanloz, R. In: Lunar Science Conference, 8th, Houston, Tex., March 14-18, 1977, Proceedings. Volume 3. (A78-41551 18-91) New York, Pergamon Press, Inc., 1977, p. 3437-3455.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60041
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:11 Sep 2015 17:51
Last Modified:11 Sep 2015 17:51

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