Ultrafast structural response of shock-compressed plagioclase

Abstract

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.