Widespread Tissintite in Strongly Shock‐Lithified Lunar Regolith Breccias

Abstract

AbstractShock‐lithification is a fundamental process of making rocks from fine‐grained and porous regoliths on the surface of the Moon. Previous investigations have constrained potential shock pressures during shock‐lithification based on experimental and numerical simulations. However, pressure and temperature conditions during shock‐lithification have not been directly inferred from natural lunar breccias. Here, we report the discovery of widespread tissintite in strongly shock‐lithified lunar meteorites, accompanied occasionally by Si‐rich corundum and coesite. The coexistence of tissintite and coesite and the absence of stishovite in molten regions indicate a shock pressure of 4–8 GPa, which might be the pressure boundary between weak and strong shock‐lithification. Meanwhile, the presence of Si‐rich corundum imposes a temperature constraint of ∼2,300 K for the intergranular melts. This temperature constraint has profound significance for interpreting the behaviors of volatile and moderately volatile elements and remanent magnetization records during strongly shock‐lithification of lunar breccias.