黒瀬川-古領家-南部北上陸塊の構造的枠組みの復元(古領家帯と黒瀬川帯の構成要素と改変過程)  [in Japanese] Reconstruction of tectonic framework of the Kurosegawa-Paleo-Ryoke-Southern Kitakami continent(Geotectonic evolution of the Paleo-Ryoke and Kurosegawa Terranes)  [in Japanese]

黒瀬川-古領家-南部北上陸塊の枠組みについて, 古地磁気, 白亜紀花崗岩の活動様式, 構造運動の様式, 花崗岩体の放射年代, 付加体群の化石年代・放射年代などを基礎に, 今日課題とされるべき問題を検討した.黒瀬川-古領家-南部北上陸塊の枠組みには, 今日およそ二つのモデルが提示されているようにみえるが, その中で, この陸塊を, 大分-熊本構造線-中央構造線-棚倉構造線にそって移動してきた地質体であると規定するモデルIは否定されることを指摘した.そして, 陸塊と内帯付加体群の縫合線は, 内帯のジュラ紀から最前期白亜紀付加体より古い花崗岩・変成岩の分布域の北限によって規定される…東北日本では御斎所変成岩(内帯付加体)と日立変成岩(陸塊)の間に位置する…とするモデルIIと, 白亜紀における東北日本と西南日本の構造的関係とを, 総合的に研究するのに必要な視点を検討した.

The paleogeographic model of Japanese Islands just before the opening of the sea of Japan is newly drawn on the basis of paleomagnetic data after Torii et al. (1985) for Southwest Japan and Hamano and Toshya (1985) for Northeast Japan. The Inner Zone accretionary complexes (IZA) developed in front of the Precambrian〜Paleozoic continent including the Hida Terrane (H-S continent) was coupled during Early Cretaceous age with the Paleozoic continent (Kurosegawa-Paleo-Ryoke-Southern Kitakami continent=K continent), which was migrated from southwest and associated with the Outer Zone accretionary complexes (=OZA). Their suture zone is placed between the Gozaisyo metamorphic rocks (=IZA) of the Abukuma belt and the K continent (=Hitachi metamorphic rocks with 492Ma granite) in Northeast Japan, while in Southwest Japan it is placed in the southern part of the Ryoke belt. The intrusion of Cretaceous granitoid in Northeast Japan occurred not only in the Abukuma belt but also in the K continent and the OZA accretionary complexes, while in Southwest Japan it occurred in the Ryoke belt and the northern part - middle part of the K continent but not in the southern part of the K continent and the OZA accretionary complexes. On the basis of activity pattern of Cretaceous granitoid, the Asahi belt between the Mino-Ashio Terrane and the Abukuma Terrane may be understood to have occurred as a gradational zone between Southwest Japan and Northeast Japan and to be a geological body almost lost during the opening of the sea of Japan.