The role of oblique subduction and strike-slip tectonics in the evolution of Japan

Abstract

The pre-Neogene geologic framework of Japan consists of the pre-Jurassic terranes (older terranes) and Jurassic to Tertiary subduction terranes, juxtaposed in a complex manner and bounded by strike-slip mobile zones. Within these strikeslip mobile zones, the exotic tectonic blocks of Devonian to Triassic sedimentary and igneous rocks, metamorphic rocks of 200–400 m.y., and high and low-pressure metamorphosed ophiolites have been emplaced with abundant serpentinite forming serpentinite melange. The slicing and lateral migration of subduction terrane and development of strike-slip mobile zone systems were possibly associated with oblique subduction. The Cretaceous systems of the southwest Japan show two strike-slip zones which developed in- and out-side of the frontal arc, forming boundaries to the fore-arc basin and fore-arc shelf basin respectively. The oblique subduction and related strike-slip zones have played a major role in reorientation of subduction terrane, emplacement of exotic blocks and serpentinite,and development of the fore-arc basin and shelf basin in the geotectonic evolution of Japan.