R8：変成岩とテクトニクス

[R8-12] 青色片岩相Na輝石の非圧力依存的挙動

*薮田 渉¹、平島 崇男² (1. 無所属、2. 京大)

キーワード：Na輝石、青色片岩相、地質圧力計、Schreinemakers分析

We report chemical compositions of Na pyroxenes in blueschist facies metamorphic rocks in the Kurosegawa Belt in Kyushu, Japan. They are characterised by low Di component and microscopic variation (Xjd = 0.2 – 0.6) within hand-specimen size. Of the constraints, the coexisting Na amphibole is notable as it effectively reduces Jd contents of Na pyroxene, even when coexisting quartz and albite. In this sense, Jd contents are detached from pressure in blueschist facies.