Sangun Metamorphic Belt - Sangun Metamorphic Belt

Japanese: 三郡変成帯 - さんぐんへんせいたい

A metamorphic belt from northern Kyushu to the Chugoku region, as indicated by the distribution of the Sangun Metamorphic Rocks. The Sangun Metamorphic Rocks are characterized by being composed of high-pressure, low-temperature crystalline schist containing lanthanite. Various theories have been presented, including one that states that the Sangun Metamorphic Belt and the Hida Metamorphic Belt form the central metamorphic belt of the Akiyoshi Orogeny, another that states that the Sangun Metamorphic Belt was formed by the Honshu Orogeny along with the Ryoke Metamorphic Belt and the Sanbagawa Metamorphic Belt, and another that the Sangun Metamorphic Belt is a high-pressure, low-temperature metamorphic belt paired with the high-temperature, low-pressure Hida Metamorphic Belt. Many radiometric ages measured in recent years are concentrated around 300 million years ago, 220 million years ago, and 180 million years ago. This shows that there is a problem in treating the Sangun Metamorphic Belt as a single metamorphic belt.

Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

九州北部から中国地方にかけて，三郡変成岩の分布によって示される変成帯。三郡変成岩は，ランセン石を含む高圧低温型の結晶片岩からなることが特徴。飛騨変成帯とともに秋吉造山運動の中軸変成帯をなすとする説，本州造山運動によって領家変成帯や三波川変成帯とともに形成されたとする説，高温低圧型の飛騨変成帯と対をなす高圧低温型の変成帯とする説など，さまざまな見解が発表されてきた。近年数多く測定された放射年代値は約３億年前，約2.2億年前，約1.8億年前に分散して集中する。このことは三郡変成帯を単一の変成帯とするには問題があることを示している。

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