Experimentally Shock‐Induced Melt Veins in Basalt: Improving the Shock Classification of Eucrites
Haruka Ono, Kosuke Kurosawa, Takafumi Niihara, T. Mikouchi, Naotaka Tomioka, J. Isa, Hiroyuki Kagi, Takuya Matsuzaki, Hiroshi Sakuma, Hidenori Genda, Tatsuhiro Sakaiya, Tadashi Kondo, Masahiro Kayama, Mizuho Koike, Yuji Sano, Masafumi Murayama, Wataru Satake, Takafumi Matsui
Abstract
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 the 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.