Study on the Tectonics and Sedimentation of the Arc-arc Collision Type sedimentary Basins

众所周知，南大沟是由属于古伊豆-小笠原岛弧的岛屿组成的区域，由于菲律宾海板块向西北方向运动，这些岛屿碰撞并增生到本州岛弧。15 Ma后有4次。本研究的目的是阐明多次碰撞构造与南大窝沉积的关系。结果总结如下。(1)与丹泽地块碰撞有关的槽填沉积物主要由浊积岩和碎屑岩组成。它们表现出碎屑类型的变化趋势和向上变粗的层序，反映了丹泽地块碰撞后腹地的隆升运动。(2)Misaka地块（第二次碰撞）的地质特征尚未得到很好的了解。沉积学研究表明，Misaka地块由一套弧前、火山弧和弧后裂谷带组成。(3)被认为是南马格纳窝第一次碰撞碰撞的串谷山地块主要由再沉积的玻璃碎屑岩和块状流沉积物组成。这些事实表明，串谷山地块应是一个弧前或弧后地区。(4)古地磁研究表明，分布在Tonoki-Aikawa构造线以北的一些年龄大于2 Ma的岩墙顺时针旋转约34 °。这表明本州岛弧的一部分顺时针旋转伴随着块。

The south Fossa Magna is well known as a zone consisting of islands which belonged to the paleo-Izu-Bonin arc and collided and accreted to the Honshu arc due to the movement of the Philippine Sea plate in a north-west direction. There were four times after 15Ma. The purpose of this study is to clarify the relationship between multiple collision tectonics and sedimentation in the South Fossa Magna. The results are summarized as follows.(1) The trough-fill sediments related to the collision of the Tanzawa block are mainly composed of turbidite and debrite. They show a trend of change of clast type and upward coarsening sequences reflecting the upheaval movement of the hinterland according to the collision of the Tanzawa block.(2) The geological features of the Misaka block (second collision) was not well understood. Sedimentological studies clarified that the Misaka block constitutes a set of forearc, volcanic arc and backarc rift zone.(3) The Kushigatayama block that was thought to be the first collided massif in the South Fossa Magna is mainly composed of re-sedimented hyaloclastite and mass flow deposits. These facts show that the Kushigatayama block must have been a forearc or backarc region.(4) some of the dykes older than 2Ma, distributed in the area to the north of the Tonoki-Aikawa tectonic line, rotated clockwise about 34 degrees based on paleo-magnetic studies. This indicates that part of the Honshu arc rotated clockwise accompanied by the blocks.