北海道中軸部の構造帯 : その構成,性格および構造運動  [in Japanese] Structural framework of the axial zone in Hokkaido : its composition, characters and tectonics  [in Japanese]

Three geological provinces, West, Central and East Hokkaido are divided according to the Late Mesozoic and Tertiary geology and tectonic characters in Hokkaido. West Hokkaido is a volcanic and plutonic zone of Early to Middle Cretaceous age which developed along the northeast margin of the Eurasia Plate. Central Hokkaido consists of three major terrains; the Kamuikotan belt, Hidaka belt and Tokoro belt. The Kamuikotan belt is composed of Early to Middle Cretaceous subduction-accretion complex, metaophiolite and forearc sediments (Yezo Group). The westward polarity of the Kamuikotan subduction is inferred from the consistent ages of the West magmatic zone (Rebun-Kabato arc) and the Kamuikotan high P/T metamorphic belt. Another remnant subduction-volcanic arc system is deduced to occur in the east part of central Hokkaido from the evidences that the Tokoro belt consists of oceanic basalts, cherts and limestones which suffered the Sambagawa-type metamorphism and that the volcanogenic forearc sediments were derived from the northeast. The subduction-arc system is called the Circum Paleo-Okhotsuk Land system. The Hidaka belt is the collision zone of the two subduction-arc systems; the Kamuikotan-Rebun Kabato and the Circum Paleo-Okhotsuk Land systems. The collision took place during the Paleogene through Miocene, followed by island arc type magmatic activity and metamorphism, along the collision zone, especially on the eastern side. The accretion complex and forearc sediments belonging to the Circum Paleo-Okhotsuk Land system collided were converted to the metamorphosed island arc crust. The crust thrust at the latest stage of collision on the metaophiolite, a remnant oceanic crust which had been subducted to the west. The crust and the metaophiolite appear as the Hidaka metamorphic belt. East Hokkaido or the Nemuro belt is the western end of the Paleo-Kuril arc which developed in the Late Cretaceous and Paleogene probably along the south margin of the Paleo-Okhotsuk Land.