Martian meteorite Tissint records unique petrogenesis among the depleted shergottites

Abstract

Tissint, a new unaltered piece of Martian volcanic materials, is the most silica-poor and Mg-Fe-rich igneous rock among the “depleted” olivine-phyric shergottites. Fe-Mg zoning of olivine suggests equilibrium growth (<0.1 °C h−1) in the range of Fo80–56 and olivine overgrowth (Fo55–18) through a process of rapid disequilibrium (~1.0–5.0 °C h−1). The spatially extended (up to 600 μm) flat-top Fe-Mg profiles of olivine indicates that the early-stage cooling rate of Tissint was slower than the other shergottites. The chemically metastable outer rim of olivine (