Amalgamation process of geological units in the Hida Belt-inferred from paleomagnetism and fission-track chronology.

1.测定了侏罗纪下本型花岗岩类的裂变径迹年龄：磷灰石39~49 Ma，锆石99~172 Ma，辉石121~146 Ma。这些年龄数据结合全岩等时线Rb-Sr年龄和角闪石和黑云母K-Ar年龄，表明花岗岩类在大约200~150 Ma的侵位年龄后迅速冷却到300ﾟC，然后从150 Ma开始以恒定的速度缓慢冷却到现在。测定了横山逆冲断层规范角砾岩的磷灰石和锆石裂变径迹年龄，认为该断层规范角砾岩与日达推覆构造在米诺带上的逆冲运动有关。花岗岩块的磷灰石年龄约为40 Ma。花岗岩和砂岩角砾岩的锆石年龄分别为118~125 Ma和140~180 Ma的混合年龄。这些年龄表明，在逆冲形成过程中，温度升高到110ﾟC，温度上升到240ﾟC，逆冲运动一直持续到古生代中期。西诺莫托型花岗岩类的古地磁方向表现为浅倾斜(30ﾟ~40ﾟ)和不同的偏角。他们的Vgp分布在围绕北极的一个小圆圈上，这意味着在他们入侵或早期冷却阶段，日达地区位于纬度约20ﾟN。日达边缘带内及附近的早白垩世至早古近纪火山岩的古地磁研究表明，大部分火山岩为东偏，而米诺带的古地磁研究表明，小规模的东偏偏转。这些数据表明，白垩纪以后，日达带和米诺带之间的相对运动沿着日达边缘带发生。

1. Fission-track ages of the Jurassic Shimonomoto-type granitoids are determined as follows ; apatite : 39 to 49 Ma, zircon : 99 to 172 Ma, sphene : 121 to 146 Ma. These age data conbined with whole rock isochron Rb-Sr ages and hornblende and biotite K-Ar ages imply that the granitoids were rapidly cooled to 300ﾟC from their intrusion ages at about 200 Ma to 150 Ma and were slowly cooled from 150 Ma to the present in a constant rate.2. Apatite and zircon fission-track ages of fault gauge breccia of the Yokoyama thrust which has been considered to be related to the thrust movement of the Hida Nappe on the Mino Belt, were determined. The apatite ages of granite blocks show about 40 Ma. The zircon ages of granite and sandstone breccia are 118 to 125 Ma and mixed ages from 140 to 180 Ma, respectively. These ages imply that temperatrue rised up to 110ﾟC and blow 240ﾟC during the thrust formation, and suggest that the thrust movement was continued was continued until the middle paleogene.Paleomagnetic directions of the Simonomoto-type granitoids show shallow inclination (30ﾟ to 40ﾟ) and diverse declination. Their VGP distributes on a small circle around the North Pole to imply that the Hida area was situated at around 20ﾟ N in latitude during their intrusion or early cooling stages.4. Paleomagnetic studies of Lat Crataceous to Early Paleogene volcanic rocks in and near the Hida Marginal Belt show largely easterly deflected declination, while those in the Mino Belt show that small easterly deflected declination. These data imply that ralative motion between the Hida Belt and Mino Belt occurred along the Hida Marginal Belt after the Cretaceous.