Shock experiments on quartz targets pre-cooled to 77 K

The influence of temperature on the development of shock deformation effects in quartz single-crystal targets has been investigated in this parameter study. Quartz targets were pre-cooled to 77 K and shocked parallel to their (101;-0) orientation in shock reverberation experiments of microsecond shock duration. Shock deformation effects in quartz were characterized by optical and spectroscopic methods. The degree of shock metamorphism in pre-cooled quartz targets has then been compared with literature data from s-shock reverberation experiments on quartz targets shocked parallel to the same crystallographic orientation but at initial temperatures of 293-903 K. The degree of shock metamorphic overprint in quartz was found to be rather insensitive to temperature variation in the low-temperature region (<548 K), but sensitive to temperature variation in the high-temperature region up to 903 K. This temperature dependence allows to distinguish between different mechanism s that had been proposed to explain the formation of shock deformation effects in quartz. The identified temperature dependence points toward a simple mechanism in which the crystal lattice collapses due to overpressure at low to moderate temperatures. Very high temperatures result in weakening of the silicon-oxygen bonds that support the crystal lattice, leading to a decrease of the onset pressure for structural collapse.