Collisional and collapse processes of reef-seamount complex

通过实地和显微检查，我们确定了筑水石灰岩中普遍存在的内部结构破坏。我们的研究表明，石炭纪-二叠纪Tsukumi灰岩在秩父地体的碰撞和增生最令人满意地解释了Sano和Kanmera（1991）的工作假设。筑水灰岩的碰撞和增生事件顺序总结如下：建在海山上的筑水洋体侵入海沟区，正断层沿外海沟坡将筑水洋体分裂并产生断层诱发的裂缝，筑水洋体及其基座的大规模崩塌和崩塌块体内部的结构破坏，崩塌产物的楔向海沟移动及其与楔的混合。崩塌产物的位移及其与沟填沉积物的混合，碰撞产物与沟填沉积物的刮积并合并成一个增生棱镜。所有这些事件都发生在早侏罗世到中侏罗世早期。值得注意的是，堆积的玄武岩基座也参与了碰撞崩塌事件。除Tsukumi灰岩外，还研究了秋吉地体晚古生代灰岩。虽然需要进一步的检查，内部结构破坏也普遍存在于这些石灰石中。结果表明，它们的吸积可以用碰撞坍缩模型来解释。我们的研究结果表明，Sano和Kanmera（1991）提出的工作假设适用于另一种吸积的海洋灰岩，在吸积构造中没有太大意义。

We identified the prevailing internal textural destruction in the Tsukumi Limestone through the field and microscopic examinations. Our research revealed that the collisional and accretion of the Carboniferous-Permian Tsukumi Limestone in the Chichibu terrane is most satisfactorily explained by the working hypothesis by Sano and Kanmera(1991). The sequence of the collisional and accretionary events of the Tsukumi Limestone is summarized as follows ; encroachment of the Tsukumi oceanic buildup resting on a seamount into a trench area, split of the buildup by normal faults along the outer trenchslope and generation of fault-induced fractures, large scale collapse of the buildup along with its pedestal and internal textural destruction of the collapse blocks, trenchward-movement of a wedge of the collapse products and their intermixing with the wedge, displacement of the collapse products and their mixing with trench-fill sediments and offscraping accretion of the collisional products fogether with the trench-fill sediments and their incorporation into an accretionary prism. All these events took place in early Early to early Middle Jurassic time. Worthy to note is that the basaltic pedestal of the buildup was also involved into the collisional collapse events.Addition to the Tsukumi Limestone, the late Paleozoic limestones in the Akiyoshi terrane were examined. Though the further examination is needed, internal textural destruction is also widespread in these limestones. The results imply that their accretion can be explained by the collisional collapse model avobe described.The whole of our results mean that the working hypothesis proposed by Sano and Kanmera(1991) is applicable to another accreted oceanic limestones and is ot great significance in the accretion tectonics.