変成泥質岩の部分溶融とメルト排出による高圧グラニュライトの形成

抄録

This study first reports Ca-rich garnet-bearing metapelitic rocks with high pressure granulite facies mineral assemblages in the low P/high T Higo metamorphic rocks. Peak pressure and temperature condition of the metapelitic rocks is estimated to be 12 kbar and 800^oC. The peak P-T condition almost corresponds to extrapolated P-T conditions of metamorphic rocks of GCII zone. Whole-rock major elements analyses and mineral equilibria modeling show that the Ca-rich garnet-bearing metapelitic rocks were formed by effective melt extraction from the lowest crust. The modeling also shows that influx of H₂O in the mid- to lower crust was required for high proportion of melt needed to form the diatexite, and that the metatexite did not involve little added H₂O.