Chemistry and Physics of Minerals and Rocks/Volcanology
Shock-compressed MgSiO3 glass, enstatite, olivine, and quartz: Optical emission, temperatures, and melting
Article first published online: 11 MAY 2004
Copyright 2004 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 109, Issue B5, May 2004
How to Cite
2004), Shock-compressed MgSiO3 glass, enstatite, olivine, and quartz: Optical emission, temperatures, and melting, J. Geophys. Res., 109, B05205, doi:10.1029/2003JB002860., , , and (
- Issue published online: 11 MAY 2004
- Article first published online: 11 MAY 2004
- Manuscript Accepted: 10 MAR 2004
- Manuscript Revised: 3 MAR 2004
- Manuscript Received: 20 OCT 2003
- shock temperature;
- equation of state;
 Optical emission of MgSiO3 glass, enstatite, olivine, and quartz under shock wave compression was investigated with optical pyrometry at discrete wavelengths ranging from visible to near infrared. We develop a new analysis of optical emission that does not require a gray body assumption. Instead, at each wavelength, the optical linear absorption coefficients (a) and blackbody spectral radiances (Lλb) of shocked and unshocked materials were obtained by nonlinear fitting to the time-resolved radiance from the target assembly. The absorption spectra of unshocked samples corresponding to the measured values of a reproduce those from independent static optical spectroscopic measurements. The measured values of a (ranging from 7 to 56 mm−1) for shocked samples indicate that shock-induced high-pressure phases (including melt) can be regarded essentially as black bodies in the optical range investigated, although starting phases such as enstatite and olivine have band-like spectra at ambient conditions. The effect of emission from the air gap at the driver sample interface on the recorded radiance can be resolved, but a and Lλb cannot be separated for this component of the signal. The shock velocity-particle velocity relationships of these silicates derived from radiance history are in accord with previous investigations using independent techniques. Given the limited amount of shock wave data, possible high-pressure melting curves of Mg-perovskite and its assemblage with periclase are deduced; their melting temperatures near the core-mantle boundary (CMB) being 6000 ± 500 K and 4000 ± 300 K, respectively. It is proposed that Mg-perovskite melts with density increase at the CMB pressure.