Time-resolved diffraction of shock-released SiO₂ and diaplectic glass formation

Area of Science:

• Geophysics
• Materials Science
• Mineral Physics

Background:

• Understanding shock-induced mineral transformations is vital for planetary impact modeling.
• Current knowledge relies on ex situ analysis, leaving formation mechanisms for features like diaplectic glass unresolved.
• Diaplectic glass is a common shock feature, but its origin remains debated.

Purpose of the Study:

• To investigate the in situ real-time transformation of fused silica under shock compression and release.
• To determine the formation mechanism of diaplectic glass under shock loading.
• To provide new insights into shock metamorphism processes.

Main Methods:

• In situ pump-probe X-ray diffraction measurements were performed on fused silica.
• Shock compression and release experiments were conducted at 33.6 GPa.
• Analysis of recovered glass fragments was performed.

Main Results:

• Fused silica crystallized to stishovite under shock compression.
• Stishovite converted to an amorphous phase (diaplectic glass) upon shock release within nanoseconds.
• Recovered glass showed evidence of permanent densification.

Conclusions:

• Diaplectic glass formation is a real-time back-transformation product of stishovite.
• These findings challenge traditional stages of shock metamorphism.
• The study provides critical data for understanding impact events and planetary geology.