Upper and middle crustal deformation of an arc - Arc collision across Hokkaido, Japan, inferred from seismic refraction/wide-angle reflection experiments
Upper and middle crustal deformation of an arc - Arc collision across Hokkaido, Japan, inferred from seismic refraction/wide-angle reflection experiments
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DOI：
10.1016/j.tecto.2004.03.025
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发表时间：
2004-09
期刊：
影响因子：
2.9
通讯作者：
T. Iwasaki;K. Adachi;T. Moriya;H. Miyamachi;T. Matsushima;K. Miyashita;T. Takeda;T. Taira;Tomoaki Yamada;K. Ohtake
中科院分区：
文献类型：
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作者：
T. Iwasaki;K. Adachi;T. Moriya;H. Miyamachi;T. Matsushima;K. Miyashita;T. Takeda;T. Taira;Tomoaki Yamada;K. Ohtake
日本北海道中部的日高碰撞带（HCZ）是研究与弧-弧碰撞有关的地壳演化和变形过程的一个很好的目标。中中新世开始的千岛岛弧（KA）与日本东北岛弧（NJA）的碰撞被认为是日高山脉形成、KA中下地壳岩石向西仰冲（日高变质带）和NJA一侧前陆褶皱冲断带发育的控制因素。1998年至2000年进行的“北海道样带”项目是一项多学科努力，目的是通过综合地球物理/地质研究，包括地震折射/反射勘测和地震观测，揭示整个碰撞区的结构异质性。一个东西走向的227公里长的折射/广角反射剖面发现了一个复杂的结构变化，从KA到NJA整个HCZ。在HCZ的东部，腹地区域被4-4.5 km厚的高度起伏的新近纪沉积层覆盖，在该沉积层之下，在10-25 km的深度范围内成像了两个向东倾斜的反射层，可能代表KA的仰冲中/下地壳的层边界。HMB出露在这些反射体的向西延上，具有较高的Vp（> 6.0km/s）和Vp/Vs（>1.80），与中、下地壳岩石相一致。在这些反射层之下，在25-27 km深度处有较平坦和向西倾斜的反射层序列，形成楔形几何形状。这种分布模式表明，KA地壳已分层成两个以上的部分下，我们的配置文件。在断面的西部，褶皱冲断带的结构特征是沉积物包非常厚（5-8公里），速度为2.5-4.8公里/秒。该包在古近系沉积层中显示了一个或两个速度反转，可能是由碰撞过程相关的叠瓦作用形成的。根据这些速度反转的水平分布和其他地球物理/地质数据，估计该地区的地壳缩短速率大于3-4毫米/年，相当于NJA和欧亚板块之间总会聚速率的40-50%。这意味着HCZ以西的褶皱冲断带吸收了大量与北海道岛板块相互作用有关的地壳变形。
The Hidaka Collision Zone (HCZ), central Hokkaido, Japan, is a good target for studies of crustal evolution and deformation processes associated with an arc–arc collision. The collision of the Kuril Arc (KA) with the Northeast Japan Arc (NJA), which started in the middle Miocene, is considered to be a controlling factor for the formation of the Hidaka Mountains, the westward obduction of middle/lower crustal rocks of the KA (the Hidaka Metamorphic Belt (HMB)) and the development of the foreland fold-and-thrust belt on the NJA side. The “Hokkaido Transect” project undertaken from 1998 to 2000 was a multidisciplinary effort intended to reveal structural heterogeneity across this collision zone by integrated geophysical/geological research including seismic refraction/reflection surveys and earthquake observations. An E–W trending 227 km-long refraction/wide-angle reflection profile found a complicated structural variation from the KA to the NJA across the HCZ. In the east of the HCZ, the hinterland region is covered with 4–4.5 km thick highly undulated Neogene sedimentary layers, beneath which two eastward dipping reflectors were imaged in a depth range of 10–25 km, probably representing the layer boundaries of the obducting middle/lower crust of the KA. The HMB crops out on the westward extension of these reflectors with relatively high Vp (>6.0 km/s) and Vp/Vs (>1.80) consistent with middle/lower crustal rocks. Beneath these reflectors, more flat and westward dipping reflector sequences are situated at the 25–27 km depth, forming a wedge-like geometry. This distribution pattern indicates that the KA crust has been delaminated into more than two segments under our profile. In the western part of the transect, the structure of the fold-and-thrust belt is characterized by a very thick (5–8 km) sedimentary package with a velocity of 2.5–4.8 km/s. This package exhibits one or two velocity reversals in Paleogene sedimentary layers, probably formed by imbrication associated with the collision process. From the horizontal distribution of these velocity reversals and other geophysical/geological data, the rate of crustal shortening in this area is estimated to be greater than 3–4 mm/year, which corresponds to 40–50% of the total convergence rate between the NJA and the Eurasian Plate. This means that the fold-and-thrust belt west of the HCZ is absorbing a large amount of crustal deformation associated with plate interaction across Hokkaido Island.