A new finding of mylonite along the Median Tectonic Line near Sakurabuchi Park in Shinshiro City, Aichi Prefecture

Abstract

We report an outcrop of tonalitic mylonite along the Median Tectonic Line (MTL) in the Ryoke Belt near Sakurabuchi Park in Shinshiro City, Aichi Prefecture. The mylonite has a foliated porphyroclastic texture with coarse (up to a few millimeters) feldspar grains in a greenish/brownish matrix. The strike of the foliation is approximately parallel to that of the MTL. The mylonite consists of plagioclase (locally K-feldspar) porphyroclasts in a fine-grained foliated matrix that consists mainly of dynamically recrystallized quartz aggregates, along with plagioclase and biotite/chlorite. The feldspar porphyroclasts contain quartz-filled fractures and have a asymmetric shape that indicates dextral shear. The quartz c-axis fabric has an intense Y-maxima with a weak cross-girdle pattern. These features of the mylonite fabric are similar to those of porphyroclastic mylonites, such as the Kashio mylonite, which occur along the MTL in other regions.