Microstructure and metamorphy: phase of argillaceous rocks of Chichibu Belt.

复式逆冲断层和序外逆冲断层是增生杂岩的重要内部结构。在关东山脉的西部，南部秩父带的滨平群分布良好。双工经常在各种尺度下观察到;双工有三个尺度等级，从几厘米到几米，从几十米到几百米，从几百米到几公里。研究区的地层具有双重性，并被双重体加厚。另一方面，在研究区域中识别出三个序列外逆冲断层，即大须高山逆冲断层、三邦山逆冲断层和良上山逆冲断层。这些逆冲断层截断了顺冲断层，并干扰了研究区的古构造。根据泥质岩的1C值估算，三国山逆冲断层上盘的垂直位移对应于.逆冲断层东半部为2km，西半部为0.5km。滨平群中发育不对称构造，即不对称尾迹、S 'C构造和双重构造。从这些构造中可以确定滑动方向：在研究区，以滑动方向定义的变形过程可分为五个阶段。第一阶段是顶部到WSW-SW，第二阶段是顶部到SW，第三阶段是顶部到SSE-SE，第四阶段是顶部到SSW。从第二相位到第四相位，相位的滑移方向至少发生了两次变化。由于古增生杂岩中逆冲作用形成的滑动方向与古板块间的相对运动密切相关，这些滑动方向可能指示了伊那木板块中侏罗世至早白垩世的古板块运动。

Duplex and out-of sequence thrust can be regarded as the important internal structures of the accretionary complex. In the western part of the Kanto Mountains, the Hamadaira Group of the Southern Chichibu Belt is well distributed. Duplexes are frequently observable at various scales ; duplex has three scale classes, from several centimeters to several meters, from several tens to several hundreds of meters, and from several hundreds of meters to several kilometers. The strata of the investigated area have been duplicated and thickened by duplexes. On the other hand, three out-of-sequence thrusts, the Osutaka-yama, Mikuni-yama, and Ryokami-yama Thrusts, are recognized in the investigated area. These thrusts truncate in-sequence thrusts, and disturb the paleothermal structure of the investigated area. Estimating from the 1C values of argillaceous rocks, it is inferred that the vertical displacement of hanging wall of the Mikuni-yama Thrust corresponds to.2. 2 km in the eastern halfofthis thrust, and is 0.5 km in the western half. Asymmetrical structures, that is, asymmetric trail, S'C structure and duplex are developed in the Hamadaira Group. The slip senses could be determined from these structures : In the investigated area, the deformation pbfese, which is defined by the slip sense, is classified into five phases. Firstphase is top to WSW-SW, second is top to SW, third is top to SSE-SE, and fourth is top to SSW. The slip sense of the phases had been changed twice at least from second phase to fourth one. As the slip sense, which was formed by thrusting in the ancient accretionary complex, was in close association with the relative motion between ancient plates, these slip senses may indicate the ancient plate motion of Izanagi Plate from Middle Jurassic to Early Cretaceous.