Anatomy and genesis of a subduction‐related orogen: A new view of geotectonic subdivision and evolution of the Japanese Islands

摘要: The Japanese Islands represent a segment of 450 million year old subduction-related orogen developed along the western Pacific convergent margin. geotectonic subdivision is newly revised on basis recent progress in 1980s utilizing microfossil and chronometric mapping methods for ancient accretionary complexes their high-P/T metamorphic equivalents. This new based accretion tectonics, it contrasts strikingly with previous schemes 'geosyncline' continent-continent collision-related or terrane tectonics. Most units Japan are composed Late Paleozoic to Cenozoic high-PIT equivalents, except two representing fragments Precambrian cratons, which were detached from mainland Asia Tertiary. These identified using method oceanic plate stratigraphy. comprised 12 units, all noted southwest Japan, five have along-arc equivalents Ryukyus. Northeast has nine these East Hokkaido three units. Recent field observations shown that most primary boundaries demarcated by low-angle faults, sometimes modified second- ary vertical normal and/or strike-slip faults. On observations, tectonic evolution summarized following stages: (i) birth at rifted Yangtze continental margin ca 750-700 Ma; (ii) inversion passive active around 500 (iii) successive subduction beginning Ma continuing present time; (iv) isolation back-arc spreading 20 Ma. In addition, collision occurred between Sino- Korean cratons 250 during stage three. Five characteristic features recognized here: step-wise (not steady-state) growth complexes; subhorizontal piled nappe structure; tectonically downward-younging polarity; intermittent exhumation metamorphosed accre- tionary complex; (v) microplate-induced modification. suggest orogenic resulted highly episodic processes. formation associated granitic batholith (i.e. paired belts) approximately every 100 years, timing such culmination apparently coincides ridge beneath Asia.