Tectonic accretion of a subducted intraoceanic remnant arc in Cretaceous Hokkaido, Japan, and implications for evolution of the Pacific northwest
Article first published online: 21 DEC 2005
Volume 14, Issue 4, pages 582–598, December 2005
How to Cite
Ueda, H. and Miyashita, S. (2005), Tectonic accretion of a subducted intraoceanic remnant arc in Cretaceous Hokkaido, Japan, and implications for evolution of the Pacific northwest. Island Arc, 14: 582–598. doi: 10.1111/j.1440-1738.2005.00486.x
- Issue published online: 21 DEC 2005
- Article first published online: 21 DEC 2005
- Received 9 May 2005; accepted for publication 5 September 2005.
- accretionary complex;
- circum-Pacific ophiolite;
- Idonnappu zone;
- intraoceanic remnant arc;
- subduction zone tectonics
Abstract An accretionary complex, which contains fragments of a remnant island arc, was newly recognized in the Cretaceous accretionary terranes in Hokkaido, Japan. It consists of volcanics, volcanic conglomerate, intermediate to ultramafic intrusive rocks with island-arc affinity including boninitic rocks, accompanied by chert and deformed terrigenous turbidites. Compared with the results of modern oceanic surveys, the preserved sequence from island-arc volcanics to chert, via reworked volcanics, is indicative of intraoceanic remnant arc, because the sequence suggests an inactive arc isolated within a pelagic environment before its accretion. The age of a subducting oceanic crust can be discontinuous before and after a remnant-arc subduction, resulting in abrupt changes in accretion style and metamorphism, as seen in Cretaceous Hokkaido. Subduction of such an intraoceanic remnant arc suggests that the subducted oceanic plate in the Cretaceous was not an extensive oceanic plate like the Izanagi and/or Kula Plates as previously believed by many authors, but a marginal basin plate having an arc–back-arc system like the present-day Philippine Sea Plate.