Fluid inclusions in high-pressure type metamorphic rocks provide direct information of the deep fluid activity. However, their small size occasionally prevent detailed geochemical study of fluid inclusions. To overcome this difficulty, we applied crush-leach method to quartz veins developed during or near the peak metamorphic stage. Another possible solution is a focused ion beam that allows us precise machining of the solid material. The fluid inclusion study combined with conventional petrographic studies revealed the nature of fluid (and related material) cycle in the subduction zone.
Another powerful approach to investigate the material transfer is so-called “data-driven approach” that employs high-dimension dataset and machine-learning techniques. NMF analysis applied to the Sanbagawa metapelite dataset revealed an evolutional change of the whole-rock composition with metamorphic grade.