Shocked quartz

Studies of the impact crater were investigated using signals of sands at the crater. ESR spectrum in shocked quartz from western rim of Wolfe Creek meteorite crater Australia, showed Ef centres in normal quartz sand at 0.001 mW. The same crater sample showed signals of peroxy centres at g = 2.0074 and an intense new ones ascribed to CCE" in SiOj at 5 mW, where E centre is saturated. 

Retallack [2] computed relative acidification for the Brownie Butte boundary bed by using the impact bed as the parent material, and obtained a value of 0.054 meq cm. Since typical late Cretaceous/early Paleocene paleosols have acid consmnption rates of 0.01-0.02 meq cm yr" , this is evidence for enhanced leaching from the boundary bed relative to the impact bed. Because the boundary bed was emplaced -minutes to hours after tlie impact [33] and the bulk of the impact bed (including shocked quartz) was emplaced -hours to days after tlie impact bed, the boundary bed may have experienced somewhat greater acid deposition. This was true only if significant acid deposition occurred in tlie interval between boundary and impact bed emplacement. In the normal atmosphere rainout of acid in the troposphere occurs on timescales of days in the post-impact atmosphere rainout may have occurred soon after the unpack once the atmosphere cooled. Because of the uncertainties in such timescales and the possibility of different parent material compositions for the impact and boundary beds, we do not consider tlie relative acidification of the two beds further. 

W. Alvarez, P. Claeys, and S.W. Kieffer, Emplacement of Cretaceous-Tertiary boundary shocked quartz from Chicxulub crater. Science 269, pp. 930-935 (1995). 

Retallack et al. (1998) briefly reviewed the literature concerning the causes of the Permo-Triassic extinction event as an introduction to their own study to determine whether boundary clays at Graphite Peak between the Buckley and Fremouw formations contain shocked quartz and anomalously high concentrations of iridium of meteoritic origin. Although they found shocked... 

Shock Luminescence. Some transparent materials give off copious amounts of light when shocked to a high pressure, and thus they can serve as shock arrival-time indicators. A technique used by McQueen and Fritz (1982) to measure arrival times of release waves is based on the reduction of shock-induced luminescence as the shock pressure is relieved. Bromoform, fused quartz, and a high-density glass have been used for their shock luminescence properties. 

Of all the piezoelectric crystals that are available for use as shock-wave transducers, the two that have received the most attention are x-cut quartz and lithium-niobate crystals (Graham and Reed, 1978). They are the most accurately characterized stress-wave transducers available for stresses up to 4 GPa and 1.8 GPa, respectively, and they are widely used within their stress ranges. They are relatively simple, accurate gauges which require a minimum of data analysis to arrive at the observed pressure history. They are used in a thick gauge mode, in which the shock wave coming through the specimen is... 

Chhabildas, L.C. and D.E. Grady (1984), Shock Loading Behavior of Fused Quartz, in Shock Waves in Condensed Matter—1983 (edited by J.R. Asay, R.A. Graham, and G.K. Straub), Elsevier Science, New York, pp. 175-178. 

Figure 4.12. Shock velocity versus particle velocity for fused quartz. Three regimes are indicated low pressure, fused quartz regime, the mixed phase regime, and the high-pressure phase, stishovite regime.

Figure 4.14. Shock pressure versus particle velocity for calcia and fused quartz in three regimes.

Figure 4.15. Shock pressure versus specific volume for calcia and fused quartz indicating three regimes fused quartz, low-pressure regime is fused quartz, mixed phase regime, and high-pressure regime representing stishovite. In the case of calcia, the low-pressure phase is the B1 structure, mixed phase is indicated, and the high-pressure phase regime is in the B2 structure.

Figure 4.19. Shock pressure versus density Hugoniot states for initially porous quartz. Density of starting material is indicated on various curves. Porous properties of stishovite are represented by curves with 1.75, 2.13, and 2.65 Mg/m, initial density, whereas coesitelike properties are represented by 0.2-0.8 Mg/m curves (after Simakov and Trunin (1990)).

In 1963, McQueen, Fritz, and Marsh (J. Geophys. Res. 68, p. 2319) suggested that the high-pressure shock-wave data for fused quartz (Table 1) and the data for crystal quartz pg = 2.65 g/cm, Co = 1.74 km/s and s = 1.70, both described the shock-induced high-pressure phase of SiOj, stishovite pg = 4.35 g/cm ), above 50 GPa. Assume Ej-j, = 1.5 kJ/g show that these shock data are consistent with a constant value of y = 0.9 in the 50-100 GPa range. 

Trunin, R.F., Simakov, G.V., and Podurets, M.A. (1971), Compression of Porous Quartz by Strong Shock Waves, Izv. Earth Phys. English Transl., 2, 102-106. 

Wackerle, J. (1962), Shock-Wave Compression of Quartz, J. Appl. Phys. 33,922-937. 

Fig. 2.17. Fused quartz is known to have an anomalous softening with stress or pressure in both static and shock loading. The time-resolved wave profile measured with a VISAR system shows the typical low pressure ramp followed by a shock at higher pressure. The release to zero pressure is with a shock, in agreement with the shape of the pressure-volume curve (after Setchell [88S01]).

The ramp of pressure to about 3 GPa observed in shock-loaded fused quartz has been used very effectively in acceleration-pulse loading studies of viscoelastic responses of polymers by Schuler and co-workers. The loading rates obtained at various thicknesses of fused quartz have been accurately characterized and data are summarized in Fig. 3.6. At higher peak pressures there are no precise standard materials to produce ramp loadings, but materials such as the ceramic pyroceram have been effectively employed. (See the description of the piezoelectric polymer in Chap. 5.)... 

The development of devices that provide a direct measure of stress or particle velocity led to observations of new rate-dependent mechanical responses and showed the power of such time-resolved measurements. The quartz gauge was the first of these devices with nanosecond time resolution, but its upper operating limit of 4 GPa limited its application. The development of the VISAR has had the most substantial impact on capabilities. VISAR systems, with time-resolution approaching 1 ns and the ability to work to pressures of 100 GPa, provide capabilities that have substantially altered the scientific descriptions of shock-compressed matter. 

Fig. 4.2. The technique used to study the piezoelectric behavior of the crystals quartz and lithium niobate used controlled, precise impact loading. The impact velocity can be measured to an accuracy of 0.1%, leading to the most precisely known condition in shock-compression science (after Davison and Graham [79D01]).

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