On the Kamiyakawa-Ikegawa Tectonic Line

The Kamiyakawa-Ikegawa tectonic line is a fault situated on the boundary between the Sambagawa southern marginal belt and the Chichibu northern zone, also through the body of the Mikabu greenrocks, in Central Shikoku. It can be traced about 80 km in the direction of its trend. The position of the fault corresponds to the tension part at the axis of an anticlinal structure. Since the tectonic line had intimate relation with the swelling of the zone of the Sambagawa metamorphism, it is certain that the tectonic line was initiated immediately after the Sambagawa metamorphism.
Acidic igneous rocks are exposed along the tectonic line in the districts characterized by psammitic and pelitic rocks, while, ultrabasic rocks are distributed along it in the Mikabu green rocks.
Judging from structure, stratigraphy and mineral assemblage, the author believes that the tectonic line was formed either along the axial part of the anticline, of which the Sambagawa southern marginal belt and the Chichibu northern zone form the northern and southern limbs, respectively, or in the Mikabu green rocks which lie upon those formations conformably. The movement amount of the tectonic line is proved to be insignificant. The author concludes that the boundary between the Sambagawa and the Chichibu zones is not a tectonic line, but an original anticlinal structure, to which the tectonic line is related.