Ultrafast structural response of shock-compressed plagioclase

Meteor impacts can induce unique pressure-dependent structural changes in minerals due to the propagation of shock waves. Plagioclase-ubiquitous throughout the Earth's crust, extraterrestrial bodies, and meteorites-is commonly used for reconstructing the impact history and conditions of the parent bodies. However, there have been unresolved inconsistencies in the interpretation of shock transformations across previous studies: The pressure at which amorphization begins and the process by which it occurs is the subject of ongoing debate. Here, we utilize time-resolved in situ X-ray diffraction (XRD) to probe the phase transformation pathway of plagioclase during shock compression at a sub-nanosecond timescale. Direct amorphization begins at pressures much lower than what was previously assumed, just above the Hugoniot elastic limit of 5 GPa, with full amorphization to a high-density amorphous phase, observed at 32(10) GPa and 20 ns. Upon release, the material partially recrystallizes back into the original structure, demonstrating a memory effect.