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Low-Pressure Metamorphic Rocks


Low-Pressure metamorphic belt


Low-P metamorphic rocks formed by subduction of ocean plates under the east margin of the Eurasian continent. Protoliths of low-P metamorphic rocks are accretionary complexes, but they are composed of at least two accretionary complexes accreted at different ages. As the result, low-P metamorphic rocks distribute crossing accretionary complexes as bands in the island arc. It is considered that low-P metamorphic rocks were formed by intrusion of granitoid after accretionary complexes were settled. Rocks subjected to higher grade of metamorphism than Prehnite-Pumpellyite facies or Greenschist facies are recognized as low-P metamoprhic rocks as they show characteristic structures, and they have been treated with the same importance as accretionary complexes and high-P metamorphic rocks. It may be difficult to distinguish low-P metamorphic rocks from contact metamorphic rocks because low-P metamorphic rocks gradually change to contact metamorphic rocks in some cases.

Ryoke facies series (Low-P)

Greenschist facies > Amphibolite facies > Pyroxene-hornfels facies

Low-Pressure Metamorphic Rocks

Low-P metamorphic rocks distribute crossing accretionary complexes.

Red: Ryoke Belt, Pink: Gosaisho belt, Brown: Hidaka Belt.

Gosaisho belt is considered as a part of Ryoke belt.

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