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单词 shock metamorphism
释义
shock metamorphism

Astronomy
  • The effects of a high-speed impact on a rock. The extreme temperatures and pressures in a meteorite impact produce a wide range of effects, including fracturing and brecciation, the formation of minerals that are stable only at very high pressures, and heating or extensive melting of the material. Such effects are evident in meteorites, as the results of bombardment of their parent body, and in many lunar rocks. Evidence of shock metamorphism in terrestrial rocks is now regarded as proof of meteoritic impact. On Earth, common forms of shock effects include shatter cones and the formation of shock-induced minerals such as coesite and stishovite.


Geology and Earth Sciences
  • Changes included in rocks and minerals when they are subjected to pressures from shock waves travelling at 10–13 km/s resulting from meteorite, cometary, or asteroidal impact. Pressures ranging to more than 50 Mpa are experienced during such events. Materials subjected to less than 10 Mpa are severely disrupted and fractured; between 10 and 25 Mpa, framework silicates exhibit planar deformation features; maskelynite (vitrified plagioclase feldspar) forms between 25 and 40 Mpa; quartz and feldspar melt from 40 to 60 Mpa; while rocks subjected to pressures of more than 60 to 70 Mpa become molten. Peak pressures are sufficient to vaporize material.


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