Collisional and collapse processes of reef-seamount complex

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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.