Phase transition and melting in zircon by nanosecond shock loading

In this study, we use laser-driven shock compression coupled with in situ X-ray diffraction to interrogate the phase transition dynamics of shock-compressed zircon (ZrSiO 4 ) for the first time. A phase transition from zircon to the high-pressure reidite phase was observed during the nanosecond timescale of a laser-driven shock. At high laser power, diffraction peaks of zircon and reidite appeared superimposed on two broad features. This diffuse background was ascribed to liquid scattering from a partial melt. At the highest laser power, the diffuse scattering dominated, with minimal evidence for crystal diffraction. On release, the melt recrystallized into a combination of zircon and reidite. Decomposition of zircon to SiO 2 and ZrO 2 was not observed. This study revealed that on laser-shock timescales, the zircon–reidite phase transition readily occurs. However, the decomposition of zircon into ZrO 2 and SiO 2 is kinetically inhibited.