Discovery of (Mg,Fe)SiO₃ tetragonal garnet in a shocked chondrite

Abstract

Distorted garnet with a tetragonal symmetry was discovered in fragments of host rock in a melt vein in a shocked chondrite by ATEM. The garnet occurs as aggregates of fine-grained crystals (< 1.5µm in size) with nearly the same chemical composition with the host low-Ca pyroxene. This occurrence indicates the tetragonal garnet has formed a solid-state transformation from the host pyroxene at >1600 °C and 16-22 GPa. Cooling rate of the melt vein was estimated to be larger than 10³ °C/sec based on diffraction intensity analysis of the garnet.