Microstructural shock signatures of major minerals in meteorites

Shock metamorphism is a fundamental process in the solar system. It is evidenced by craters on the surfaces of solid planets and asteroids, as well as by shock-induced microstructural modifications in minerals. This paper presents review of the main microstructural characteristics of shock signatures in meteoritic minerals (olivine, enstatite, diopside, plagioclase and metal) as evidenced by transmission electron microscopy (TEM). The nature of the shock-induced modifications strongly depends on the material and the shock conditions (peak pressure and peak temperature). It includes fracturing, dislocations and twins (evidence of plastic deformation), phase transformation 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 microstructural aspect of shock metamorphism are outlined.