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Journal of Geophysical Research

Shock compression of crustal rocks: Data for quartz, calcite, and plagioclase rocks

Authors

  • Thomas J. Ahrens,

  • V. G. Gregson Jr.


Abstract

Hugoniot data in the 4- to 250-kb stress range were obtained for quartzite and novaculite, sandstones of varying porosity, single-crystal calcite, marble, porous and nonporous limestone, several plagioclases of varying composition, and a basalt. Conventional plane-wave, in-contact explosive assemblies were used; the shock state was computed from measured shock velocities; particle velocities are inferred from either specimen or driver plate free-surface motion. Impedence-match solutions were obtained for porous rock. High values of the Hugoniot elastic limit were observed in nonporous rocks—approximately 40 to 90 kb in quartzite and novaculite, 40 to 50 kb in the plagioclase rocks, and 15 to 25 kb in calcite and marble. Reduced values were found for porous rocks, approximately 5 kb in sandstone and limestone. Phase transitions are inferred at 30, 45, and 95 kb in calcite, and 22, 45, and 90 kb in marble and limestone. For calcite these are indicated by multiple shock fronts. Anomalously low volumes achieved by sandstone shocked to above approximately 40 kb, and high calculated shock temperatures, suggest partial conversion to coesite or stishovite. High-pressure states observed in basalt and plagioclase agree with previously reported states for gabbro [Hughes and McQueen, 1958] above 300 kb when both data are plotted in terms of relative volume. The previously observed slope-change of the gabbro Hugoniot is believed to result from an elastic wave of perhaps 50-kb amplitude which is overdriven at 300 kb.

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