Progressive metamorphism

Japanese: 累進変成作用 - るいしんへんせいさよう（英語表記）progressive metamorphism

Metamorphism that occurs with increasing temperature [Turner: 1938, Watanabe (ed.): 1935]. This refers to the process by which a metamorphic rock is transformed into a different metamorphic rock by subsequent high-grade metamorphism, and the degree of metamorphism gradually increases. Once all the rocks have been altered by the final metamorphism, it is no longer possible to determine what occurred before. The metamorphic rocks that can usually be observed represent the highest temperature state of each individual rock, so it is not always possible to determine whether a high-temperature metamorphic rock passed through a low-temperature state in the early stages of metamorphism. Progressive metamorphism is generally accompanied by dehydration reactions [Katayama et al.: 1970]. This refers to metamorphism in which the degree of metamorphism formed in a series of metamorphic belts becomes stronger toward the center of metamorphism or the contact points with igneous rocks. Rocks in areas of high metamorphism progress through periods of low metamorphism [Turner: 1938].

Source: Asakura Publishing Dictionary of Petrology Information

Japanese:

温度の上昇に伴って行われる変成作用［Turner : 1938，渡辺編 : 1935］．変成岩がその後引き続いた高度の変成作用によって別な変成岩に変化する作用をいい，変成作用の程度が次第に高くなる場合である．最後の変成作用で岩石がすべて改変されてしまえば，それ以前のことはわからなくなる．通常観察できる変成岩は個々の岩石の最高温度の状態を表すので，高温の変成岩が変成作用の初期に低温状態を経過したかどうかがわかるとは限らない．累進変成作用では一般に脱水反応を伴う［片山他 : 1970］．変成帯の系列で形成される変成作用の程度が，変成の中心あるいは火成岩の接触部に向って強くなるような変成作用をいう．高変成度の地域の岩石は，低変成度の時期を通って順に高くなっている［Turner : 1938］．

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