R8: Metamorphic rocks and tectonics

[R8-16] Polyphase metamorphism in migmatite zones caused by pulsed granitoid intrusions into a low-P/T type metamorphic belt: decoding P-T-D-t paths using multi-stage growth of zircon

*Tetsuo Kawakami¹, Tomoe Ichino¹, Keiichi Kazura¹, Shuhei Sakata², Kota Takatsuka¹ (1. Kyoto Uni. Sci., 2. Uni. Tokyo)

Keywords: low P/T type metamorphic belt, zircon, P-T-t path, Ryoke belt, magmatic flare-up

In the Grt-Crd zone of Mikawa area, Ryoke belt, Sil-grade condition prevailed at ca. 97-87 Ma, followed by cooling to ~500 ^oC, ~4 kbar. Intrusion of gneissose granitoids below the Grt-Crd zone reheated the zone to the Sil-grade condition at ca. 84 Ma, followed by ca. 70 Ma contact metamorphism. Ductile deformation that formed migmatitic foliation started before ca. 89 Ma and continued until ca. 84 Ma. The ca. 70 Ma granitoids locally caused partial melting and low-strain ductile deformation.