[S-MP24] Deformed rocks, Metamorphic rocks and Tectonics

[SMP24-P11] Microstructural characteristics of mylonite occurred in the Ryoke Belt beside the Median Tectonic Line in the Shinshiro area, Aichi Prefecture

*Miharu Niwa^1,2, Katsuyoshi Michibayashi^1,3, Kenichiro Tani⁴, Takuma Nishimura⁵ (1.Department of Earth and Planetary Sciences, GSES, Nagoya University, 2.Toyohashi Museum of Natural History, 3.Volcanoes and Earth’s Interior Research, IMG, JAMSTEC, 4.National Museum of Nature and Science, 5.Houraijisan Museum of Natural History)

Keywords:mylonite, Median Tectonic Line, Ryoke belt, fault rock

In the vicinity of the Median Tectonic Line in Shinshiro City, Aichi Prefecture, there are a certain number of outcrops in good condition, which consist of the Ryoke metamorphic and igneous rocks in the inner zone, Sanbagawa metamorphic rocks in the outer zone, and even non-metamorphic layers such as Shitara Group and Atera-Nanadaru Conglomerate overlying these basement rocks. However, although fault rocks along the Median Tectonic Line in the Mikawa area have been identified near Horai-cho, Shinshiro City, Aichi Prefecture, few studies have been reported in terms of deformation microstructure. In this study, an outcrop of mylonite was discovered near the Median Tectonic Line that crosses Sakurabuchi Park in Shinshiro City, located further southwest of Horai-cho. In the outcrops, mylonite is greenish-white in color and characterized by white plagioclase porphyroclasts. Rock thin sections were made in the XZ plane, which is perpendicular to the foliation and parallel to the lineation. Mylonite is tonalitic, with quartz, plagioclase, and biotite as the main constituent minerals. Microstructural observations were made using a polarizing microscope, the crystal orientation of quartz was measured using an SEM-EBSD system, and some samples were also dated by zircon U-Pb geochronoloty. In this presentation, the results will be reported.