Microstructural shock signatures of major minerals in meteorites

Shock metamorphism is a fundamental process in the solar system. It is evid enced by craters on the surfaces of solid planets and asteroids, as well as by shock-induced microstructural modifications in minerals. This paper pre sents review of the main microstructural characteristics of shock signature s in meteoritic minerals (olivine, enstatite, diopside, plagioclase and met al) as evidenced by transmission electron microscopy (TEM). The nature of t he shock-induced modifications strongly depends on the material and the sho ck conditions (peak pressure and peak temperature). It includes fracturing, dislocations and twins (evidence of plastic deformation), phase transforma tion to high pressure polymorphs, amorphization, recrystallization, melting and volatilization. The influence of shock-induced microstructures during post-shock events is also discussed and further research tracks on the micr ostructural aspect of shock metamorphism are outlined.