Studies on Orogeny based on Plate Tectonics in Japan and New Geotectonic Subdivision of the Japanese Islands
Studies on Orogeny based on Plate Tectonics in Japan and New Geotectonic Subdivision of the Japanese Islands
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基于日本板块构造的造山运动及日本列岛新大地构造划分研究
DOI：
10.5026/jgeography.100.5_697
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发表时间：
1991
影响因子：
3.1
通讯作者：
S. Maruyama
中科院分区：
文献类型：
--
作者：
Y. Isozaki;S. Maruyama
日本列岛基本上是由沿着东亚大陆边缘的俯冲带（2.0Ga扬子克拉通（华南）和450Ma弧前蛇绿岩）原地形成的晚古生代-新生代增生杂岩组成。最近的研究利用微体化石和放射性测年区分了几个主要的增生杂岩，包括高P/T变质部分，和下属蛇绿岩。特别是，认识到海洋板块地层和年龄的俯冲有关的变质作用的个人增生杂岩允许的大地构造划分的日本群岛进行修订与大地构造单元和它们的相互边界的新定义。排除弧后岩浆活动和弧后盆地张开、弧前银片运动、弧碰撞等微板块活动对次级构造改造的影响，增生杂岩具有明显的向洋向俯冲极性。这种增长的极性在日本西南部很好地观察到，那里有七个不同的单元，即从日本海一侧到太平洋一侧：400 - 300 Ma高P/T片岩，二叠纪（250 Ma）增生杂岩，230 - 180 Ma高P/T片岩，侏罗纪（180 - 140 Ma）增生杂岩、100 Ma高P/T片岩、晚白垩世（80 Ma）增生杂岩和第三纪（50 - 20 Ma）增生杂岩。这些大地构造边界的弯曲表面轨迹和几个构造异常点和窗口的出现表明，所有这些杂岩，包括高P/T片岩，都是作为近水平（或轻微北倾）的薄构造单元，即。e.推覆体因此，日本诸岛形成了一个巨大的推覆体堆，这些推覆体在结构上变得越来越年轻，一直到现代的南海增生杂岩。值得注意的是，在这个近水平造山带中，高P/T单元被构造夹在低P单元之间，即高P/T单元。G.薄推覆体为100 Ma的三坝川蓝片岩，介于侏罗纪和晚白垩世的绿帘石-绿帘石相增生杂岩之间。Sanbagawa高P/T单元的隆起似乎与库拉/太平洋扩张脊到达海沟相关，这表明高P/T增生杂岩可能已被挤压并抬升到弧前低P域，通过扩张脊在海沟的浮力俯冲。当时洋脊俯冲的证据得到了重建的古板块运动和与低P/T区域变质作用有关的弧相关Ryoke岩浆活动的同时代高潮的支持。夹在低磷单元之间的较老的高磷温比蓝片岩推覆体的形成也可以用同样的方法来解释。主扩张脊的俯冲作用似乎对近水平高P/T推覆体和大陆侧花岗岩带的幕式向洋发展最为关键。
The Japanese Islands consist fundamentally of late Paleozoic to Cenozoic accretionary complexes that formed in situ in a subduction zone along the East Asian continental margin, i.e. 2.0 Ga Yangtze craton (South China) and 450 Ma fore-arc ophiolite. Recent research utilizing microfossil and radiometric dating has distinguished several major accretionary complexes, including high-P/T metamorphosed parts, and subordinate ophiolites. In particular, recognition of oceanic plate stratigraphy and age of subduction-related metamorphism for individual accretionary complex allows the geotectonic subdivision of the Japanese Islands be emended with a new definition of geotectonic units and their mutual boundaries. Removing the effect of arcrelated magmatism and secondary tectonic modification by microplate activities such as backarc basin opening, fore-arc sliver movement, and arc-collision, a remarkable oceanward younging polarity is recognized among the accretionary complexes. This polarity in growth is well observed in Southwest Japan where seven distinct units occur, i.e. from the Japan Sea side to the Pacific side: 400-300 Ma high-P/T schists, Permian (250 Ma) accretionary complex, 230-180 Ma high-P/T schists, Jurassic (180-140 Ma) accretionary complex, 100 Ma high-P/T schists, Late Cretaceous (80 Ma) accretionary complex, and Tertiary (50-20 Ma) accretionary complex. The sinuous surface trajectories of these geotectonic boundaries and occurrence of several tectonic outliers and windows indicate that all these complexes, including high-P/T schists, occur as subhorizontal (or gently northward dipping) thin tectonic unit, i. e. nappe. Thus the Japanese Islands form a huge pile of nappes that become younger structurally downward to the modern Nankai accretionary complex. What is remarkable in this subhorizontal orogen is that high-P/T units are tectonically intercalated between low-P units, e. g. the thin nappe of 100 Ma Sanbagawa blueschists between Jurassic and Late Cretaceous accretionary complexes of the prehnite-pumpellyite facies. Uplift of the Sanbagawa high-P/T unit appears to correlate with the arrival of the Kula/Pacific spreading ridge at the trench, suggesting that this high-P/T accretionary complex may have been extruded and uplifted into low-P domain in fore-arc by buoyant subduction of the spreading ridge at the trench. Evidence of ridge subduction at that time is supported by reconstructed paleoplate motion and the coeval climax of arc-related Ry-oke magmatism associated with low-P/T regional metamorphism. Formation of older high-P/T blueschist nappes sandwiched between low-P units can be explained likewise. Subduction of major spreading ridges seems most critical for the episodic oceanward development not only of subhorizontal high-P/T nappes but also of continent side granitic belts.
影响因子：
4.2
作者：
MATSUDA, T;ISOZAKI, Y
通讯作者：
ISOZAKI, Y