K-Ar ages of fault gouges and felsite dykes from the Median Tectonic Line in Chubu region, central Japan

The K-Ar ages were determined on fine fractions (<2 μm) extracted from six fault gouges at outcrops of the Median Tectonic Line (MTL) in the Kami-ina and Sakuma areas in Chubu Region. The K-Ar ages range from 11.1 to 45.2 Ma and can be divided into three groups, namely 11.1-13.8 Ma, 21.1 Ma and 45.2 Ma. The first age group probably represents the rejuvenation by intrusion of felsite dykes which give the ages of 12.3-15.6 Ma. The second age together with our previous result (19-23 Ma) probably represents the time of hydrothermal alteration. The third age is similar to the data of the fault gouges from Kinki Region. It probably represents the time of major fault movement during the Paleogene in this area. -from English summary