Experimentally shock-induced melt veins in basalt: Improving the shock classification of eucrites

TL;DR

This study experimentally investigates shock-induced melt veins in basalt, establishing a new pressure threshold for localized melting and refining shock classification criteria for basaltic eucrites.

Contribution

It provides a new pressure scale for shock classification of basaltic eucrites based on experimental data and shock physics modeling.

Findings

Localized melting occurs at ~10 GPa, lower than previous estimates.

Shock degree C corresponds to shock features at this new pressure scale.

Approximately 15% of basaltic eucrites are classified as shock degree C based on impact velocity estimates.

Abstract

Basaltic rocks occur widely on the terrestrial planets and differentiated asteroids, including the asteroid 4 Vesta. We conducted a shock recovery experiment with decaying compressive pulses on a terrestrial basalt at Chiba Institute of Technology, Japan. The sample recorded a range of pressures, and shock physics modeling was conducted to add a pressure scale to the observed shock features. The shocked sample was examined by optical and electron microscopy, electron back-scattered diffractometry, and Raman spectroscopy. We found that localized melting occurs at a lower pressure (~10 GPa) than previously thought (>20 GPa). The shocked basalt near the epicenter represents shock degree C of a recently proposed classification scheme for basaltic eucrites and, as such, our results provide a pressure scale for the classification scheme. Finally, we estimated the total fraction of the basaltic eucrites classified as shock degree C to be ~15% by assuming the impact velocity distribution onto Vesta.