Shock Stage

Pressure–temperature fields for shock metamorphism of silicate rocks. Dashed lines represent temperature estimates based on theoretical considerations by Davies (1972). Image Modified from Source: MaPS Volume 53, Issue 1

A petrographic assessment, using features observed in minerals grains, of the degree to which a meteorite has undergone shock metamorphism. The highest stage observed in 25% of the indicator grains is used to determine the stage. Also called “shock level”.

 

 

 

 

 

 

Shock StageDescriptionPressure (GPa)Temperature Increase (K)Features
S1Unshocked< 510Sharp optical extinction viewed in microscope
Small number of irregular fractures
S2Very Weakly Shocked5 - 1020Undulatory extinction
Irregular fractures
S3Weakly Shocked10 - 20100Olivine: fractures
Plagioclase: undulatory extinction
S4Moderately Shocked30 - 35300Olivine: weak mosaicism, planar fractures
Plagioclase: undulatory extinction, isotropic in places, planar deformation features.
S5Strongly Shocked45 - 55600Olivine: strong mosaicism, planar fractures and planar deformation features
Plagioclase: maskelynite
S6Very Strongly Shocked75 - 901500Olivine: solid state recrystallization and staining, presence of ringwoodite, local melting
Plagioclase: shock melted