Shock metamorphism

Japanese: 衝撃変成作用 - しょうげきへんせいさよう

① Impact metamorphism : Shock metamorphism caused by a meteorite impact [Spry: 1969]. A similar effect is also produced by the explosion of an atomic bomb.
② Shock metamorphism : Dynamic metamorphism occurs over a relatively short period of time with a very fast deformation rate. Hydrostatic pressure and stress are temporarily very high, and temperatures range from low to very high. Metamorphic rocks found in meteorite craters caused by meteorite impacts are a variety of rocks, ranging from breccia to glassy rocks, and may contain high-pressure, high-density silica (SiO ₂ ) [Chao, et al.: 1960, Chao, et al .: 1962, Carter: 1965, Spry: 1969]. The pressure exerted by shock metamorphism is generally thought to be over 30 Gpa (300,000 atmospheres), and sometimes accompanied by high temperatures of over 1,800°C. Shock metamorphism is a type of metamorphism that does not belong to the conventional types, but it can be considered a type of dynamic metamorphism. Similar rocks have been found not only as a result of meteorite impacts but also as a result of nuclear explosions [Short: 1966], but there is a question as to whether man-made phenomena should be included in metamorphism.

Source: Asakura Publishing Dictionary of Petrology Information

Japanese:

① impact metamorphism: 隕石の衝突で起こった衝撃変成作用（shock metamorphism）［Spry : 1969］．類似の効果は原子爆弾の爆発でも形成される．
② shock metamorphism: 変形速度が非常に速く，比較的短時間に働く動力変成作用である．静水圧も応力も一時的に非常に高く，温度は低温から非常に高温までの範囲である．隕石の衝突による隕石孔で発見された変成岩には，衝撃変成作用によって角礫岩からガラス質の岩石まで変化に富むものが形成され，高圧型の高密度の珪酸（SiO₂）が含まれることがある［Chao, et al. : 1960, Chao, et al. : 1962, Carter : 1965, Spry : 1969］．衝撃変成作用で働いた圧力は一般に30Gpa（30万気圧）以上で，ときに1 800℃以上の高温を伴うこともあると考えられている．衝撃変成作用は従来の型に属さない変成作用であるが，動力変成作用の一種と考えることができる．隕石の衝突ばかりでなく原子力爆発による作用でも同様な岩石が認められたが［Short : 1966］，人工的な現象を変成作用に含めてよいかどうか問題がある．

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