S2: 岩石-水相互作用 （スペシャルセッション）

[S2P-03] 下部地殻の加水反応に関する実験的研究：斜長石＋単斜輝石系における優先的な斜長石の反応

*中谷 貴之¹、中村 美千彦² (1. 産総研、2. 東北大・院理)

キーワード：下部地殻、加水反応、斜長石、単斜輝石

To simulate the hydration reaction of the lower crustal rocks, we conducted hydration experiments in the plagioclase (pl) + clinopyroxene (cpx) systems at 500degC and 1.0 GPa. Mass balance calculation revealed that plagioclase reacted preferentially in the pl + cpx system. Preferential plagioclase reaction leads to the dominant formation of epidote whose density (~3.4 g/cm3) is much higher than that of the primary plagioclase (~2.7 g/cm3). This leads to ~1% decrease in the overall volume, which is in contrast to the volume-increasing hydration reaction in the ultramafic system.