Middle Miocene swift migration of the TTT triple junction and rapid crustal growth in southwest Japan: A review

• Published in: Tectonics (Washington, D.C.) D.C.), 2014-07, Vol.33 (7), p.1219-1238
• Main Authors: Kimura, Gaku, Hashimoto, Yoshitaka, Kitamura, Yujin, Yamaguchi, Asuka, Koge, Hiroaki
• Format: Article
• Language: English
• Subjects: accretionary complex; Calderas; collision; Cretaceous; Crystallization; Geology; Hypotheses; Igneous rocks; Island arcs; Magma; Miocene; Nankai Trough; Philippine Sea Plate; Seamounts; Shimanto; subduction zone
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1002/2014TC003531

We review recent progress in geological and geophysical investigation in SW Japan, Nankai Trough, and Philippine Sea Plate (PSP), and propose a hypothesis for the Miocene tectonics in SW Japan driven by middle Miocene swift migration of the TTT (trench‐trench‐trench) triple junction. The new hypothesis is based on the new interpretations as follows. Near‐trench magmatism in the outer zone of SW Japan is ascribed to a collision of proto‐Izu arc in addition to the previous model of an oceanic ridge of the Shikoku Basin and hot PSP subduction. The indentation structures at Capes Ashizuri, Muroto in Shikoku, and Shiono on the Kii Peninsula were previously explained by “kink folding” due to recent E‐W compression. We alternatively suppose the collision of the active arc or topographic peaks such as seamounts inferred from geological and experimental observations. The main crustal component in SW Japan is suggested to be of igneous plutonic rocks rather than the previous interpretation of Cretaceous to Tertiary accretionary complexes. This is typically illustrated in the outer zone to the north of Capes Ashizuri, Muroto, and Shiono from geophysical observation of gravity anomalies, velocity and resistivity, together with geological estimations of caldera age and the size of its root pluton. Episodic crustal growth due to intrusion of igneous rock and subduction of the PSP may have stopped after approximately 12 Ma and restarted at approximately 6 Ma. Our emphasis for this gap is a cessation and resurgence of subduction rather than the previous interpretation, i.e., decreasing of subduction rate. Key Points A comprehensive model of Miocene arc collision in SW Japan is proposed Izu island arc and TTT triple junction swept across the SW Japan to the east Topographic indentations are of collision‐induced pluton emplacement