Confined ductile deformation in the Japan arc inferred from paleomagnetic studies
Confined ductile deformation in the Japan arc inferred from paleomagnetic studies
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从古地磁研究推断日本的受限延性变形
DOI：
10.1016/0040-1951(89)90294-1
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发表时间：
1989
期刊：
影响因子：
2.9
通讯作者：
Yoshihiko Ito
中科院分区：
文献类型：
--
作者：
Y. Itoh;Yoshihiko Ito
为了阐明以丝属川-静冈构造线（ISTL）东侧为界的日本岛弧南部连续花岗质长条体的变形模式，采用古地磁和生物地层学方法，对丝属川-静冈构造线（ISTL）西侧金泽和大正寺地区的中新世岩石进行了研究。七个站点在金泽地区和9个站点在Daishoji地区被发现保持稳定的特征剩磁（ChRM），通过热和交变磁场方法的渐进退磁。ChRM方向的时空变化表明，这些地区经历了与伊豆-小笠原弧的中中新世碰撞有关的弧内构造变形，该碰撞继承了与15 Ma左右弧后开口相关的日本弧南部的一致顺时针旋转。表明相对逆时针旋转角度向东逐渐增大，是中中新世弧-弧碰撞作用的结果。这一结果和缺乏可识别的故障，可以补偿差异旋转，意味着弧在碰撞事件中的韧性变形。也有人建议，显着的旋转发生在东部，局限，部分均匀的大陆地壳银。日本岛弧地壳的局限性韧性变形是由菲律宾海板块俯冲时在弧前一侧产生的不规则挤压力和在弧后一侧产生的可能的抵抗力共同作用的结果。
Miocene rocks collected from the Kanazawa and Daishoji areas in the western vicinity of the Itoigawa-Shizuoka tectonic line (ISTL) were investigated using paleomagnetic and biostratigraphic methods in order to clarify the deformation mode of a continuous granitic sliver in the southern part of the Japan arc which was bounded on east side by the ISTL. Seven sites in the Kanazawa area and nine sites in the Daishoji area were found to preserve stable characteristic remanent magnetization (ChRM) through progressive demagnetization by thermal and alternating field methods. Temporal and spatial changes in ChRM directions suggest that the areas were subjected to intra-arc tectonic deformation linked with the middle Miocene collision of the Izu-Bonin arc which succeeded to coherent clockwise rotation of the southern part of the Japan arc associated with the back-arc opening around 15 Ma.The data in this study, together with data previously obtained, indicate that the angle of relative counterclockwise rotation increases gradually toward the east, which was caused by the middle Miocene arc-arc collision. This result and the absence of identifiable faults which could compensate differential rotations, imply that the arc was ductilely deforming during the collision event. It is also suggested that significant rotation occurred in the eastern, confined, portion of the uniform sliver of continental crust. The confined ductile deformation of the crust observed in the Japan arc can be achieved by the irregular compressive force on the fore-arc side generated by landmasses on the subducting Philippine Sea plate and the plausible resisting force induced on the back-arc side.