日本鉱物科学会年会

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.