Tectonic relationship between the Median Tectonic Line and the Tanakura Tectonic Line viewed from isotopic ages and Sr isotopes of granitic rocks in the northern Kanto Mountains

Initial ⁸⁷Sr/⁸⁶Sr ratios have been determined for Permian and Early Cretaceous allochthonous granitic rocks and Late Cretaceous ones from the northern marginal areas of the Kanto Mountains, and for granitic rocks from the Yamizo Mountains and granitic clasts from the Usuginu conglomerate in Northeast Japan. Ages and Sr isotopic data of granitic rocks from the Kanto Mountains suggest that the Okitano-Iwayama Line and the Naranashi Fault are the eastern extension of the Median Tectonic Line. In addition, the components of the Abukuma-South Kitakami Belt are now shown to be distributed in the northern marginal areas of the Kanto Mountains between the Ryoke and Sambagawa Belts, and thus the Median Tectonic Line can be extended to the Tanakura Tectonic Line. -from English summary