Structural architecture and active deformation of the Nankai Accretionary Prism, Japan: Submersible survey results from the Tenryu Submarine Canyon
Structural architecture and active deformation of the Nankai Accretionary Prism, Japan: Submersible survey results from the Tenryu Submarine Canyon
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日本南海增生棱镜的结构结构和主动变形：天龙海底峡谷的潜水测量结果
DOI：
10.1130/b26219.1
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发表时间：
2009
影响因子：
4.9
通讯作者：
Yk Shipboard Scientific Parties
中科院分区：
文献类型：
--
作者：
K. Kawamura;Y. Ogawa;R. Anma;Shunji Yokoyama;S. Kawakami;Y. Dilek;G. Moore;S. Hirano;A. Yamaguchi;Tomoyuki Sasaki;Yk Leg;Yk Shipboard Scientific Parties
沿着天龙海底峡谷进行了两次研究航行，部署了潜水调查，以直接观察日本南部海岸外的东海增生棱镜的结构体系。研究表明，加积沉积物是发生在重复逆冲-背斜构造中的强烈变形浊积岩序列。从海沟附近的棱柱体前缘到弧形，在棱柱体内识别出以下变形带：前缘冲断带、棱柱体趾带、叠瓦状冲断带和东海冲断带（或序列外冲断带或OOST带）。前缘冲断带的特征是上盘内的碎屑沉积，根据放射虫生物地层学的测定，其年龄为0-0.43 Ma。Prism Toe带的特征是1.98-3.4 Ma的未固结浊积岩序列;这些序列被正断层和逆冲断层切割。叠瓦状冲断带包括固结泥质层和松散桑迪层，其中含有大量裂缝劈理。OOST区由高度变形的固结沉积物组成，年龄范围为0.18至1.03 Ma。从棱趾带到叠瓦状冲断带，岩石的单轴抗压强度从0.5-3.0 MPa逐渐增大到1.0-6.0 MPa，磁化率各向异性从扁圆形变为长圆形，孔隙度从40%~ 50%减小到30%~ 50%。这些数据表明，东南开增生棱镜似乎已经朝着叠瓦冲断带南部的东方东变形。对东海冲断带砂岩样品中方解石脉和方解石胶结物的稳定同位素分析表明，东方东太平洋地区方解石沉淀的流体温度为24-63 °C。南海增生棱柱体内高度变形和固结的岩石的出现可能是由于深埋岩石沿主要的序列外逆冲断层（如东海东部）沿着的构造搬运。因此，我们推断，顺序逆冲断层发挥了重要作用，在运输深埋，变形岩石增生棱镜到较浅的深度，甚至在正在进行的俯冲作用的海底。
Two research cruises that deployed submersible surveys were undertaken along the Tenryu Submarine Canyon to directly observe the structural architecture of the eastern Nankai Accretionary Prism off the coast of southern Japan. The surveys have demonstrated that the accreted sediments are strongly deformed turbidite sequences that occur in repeated thrust-anticline structures. From the leading edge of the prism near the trench toward the arc, the following deformation zones have been identified within the prism: Frontal Thrust zone, Prism Toe zone, Imbricate Thrust zone, and Tokai Thrust zone (or out-of-sequence thrust or OOST zone). The Frontal Thrust zone is characterized by debris deposits within the hanging wall that have an age of 0–0.43 Ma, as determined from radiolarian biostratigraphy. The Prism Toe zone is characterized by unconsolidated turbidite sequences that are 1.98–3.4 Ma; these sequences are cut by normal and thrust faults. The Imbricate Thrust zone includes consolidated muddy layers and unconsolidated sandy layers that contain numerous fracture cleavages. The OOST zone consists of highly deformed consolidated sediments, ranging in age from 0.18 to 1.03 Ma. From the Prism Toe zone to the Imbricate Thrust zone, the uniaxial compressive strength increases gradually from 0.5–3.0 to 1.0–6.0 MPa, while the anisotropy of magnetic susceptibility changes from oblate to prolate shapes, and porosity decreases from 40%–50% to 30%–50%. These data indicate that the eastern Nankai Accretionary Prism appears to have been deformed toward the Imbricate Thrust zone just south of the OOST. Stable isotope analyses of calcite veins and calcite cement of the sandstone samples from the Tokai Thrust zone have shown that fluid temperatures for calcite precipitation were 24–63 °C in the OOST zone. The occurrence of highly deformed and consolidated rocks within the Nankai Accretionary Prism likely resulted from tectonic transportation of deeply buried rocks along major out-of-sequence thrust faults, such as the Tokai OOST. We infer therefore that out-of-sequence thrust faults play a major role in transporting deeply buried, deformed rocks in accretionary prisms to the shallower depths and even to the seafloor during ongoing subduction.