New insights into deformation and fluid flow processes in the Nankai Trough accretionary prism: Results of Ocean Drilling Program Leg 190
New insights into deformation and fluid flow processes in the Nankai Trough accretionary prism: Results of Ocean Drilling Program Leg 190
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DOI：
10.1029/2001gc000166
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发表时间：
2001-10
期刊：
影响因子：
3.7
通讯作者：
G. Moore;A. Taira;A. Klaus;L. Becker;B. Boeckel;B. Cragg;A. Dean;C. Fergusson;P. Henry;S. Hirano;T. Hisamitsu;S. Hunze;M. Kastner;A. Maltman;J. Morgan;Y. Murakami;D. Saffer;M. Sánchez-Gómez;E. Screaton;David C. Smith;A. Spivack;J. Steurer;H. Tobin;K. Ujiie;M. Underwood;M. Wilson
中科院分区：
文献类型：
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作者：
G. Moore;A. Taira;A. Klaus;L. Becker;B. Boeckel;B. Cragg;A. Dean;C. Fergusson;P. Henry;S. Hirano;T. Hisamitsu;S. Hunze;M. Kastner;A. Maltman;J. Morgan;Y. Murakami;D. Saffer;M. Sánchez-Gómez;E. Screaton;David C. Smith;A. Spivack;J. Steurer;H. Tobin;K. Ujiie;M. Underwood;M. Wilson
南开海槽增生三棱镜被认为是一个“端元”三棱镜，在构造简单、地震和其他地球物理技术分辨率无与伦比、历史大地震的背景下，增生了粗糙的陆源沉积剖面。因此，海洋钻探计划（ODP）一直致力于解决有关吸积过程和棱镜演化的几个未解决的问题。在ODP Leg 190期间沿南开海槽增生棱镜的两条样带取心的6个地点，岩石地层和沉积成岩作用有显著差异。在两个样带的向海端，首次确定了四国盆地沉积剖面的加/俯冲地层格架。一厚层中新世浊积岩和富含蒙脱石的泥岩存在于Ashizuri遗址的俯冲剖面中。Muroto遗址相关剖面未见浊积岩和泥岩；传入沉积物的岩性、矿物学和水文性质的变化可能导致两个样带之间棱柱楔锥度的差异，同时可能控制着活动板块边界的地震特征。在这两个样带中的胞质结均位于四国盆地下部相的一个共同地层单元内（~ 5.9-7 Ma）。胞体也是物理和机械性能的主要边界。在四国盆地下部单元，首先在808站点发现了一个广泛的低氯化物孔隙水异常，沿着Muroto样带，从棱柱到盆地的幅度逐渐减小。物理性质关系、沉积物矿物学变化的证据以及孔隙流体化学表明，氯化物异常主要是由沉积物中的原位成岩反应引起的，可能还受到来自深处的新鲜流体流动的增强。对Muroto样带更靠近陆地部分的地层和单元年龄的新限制，极大地改变了我们对该地区棱柱构造演化的看法。棱镜向海的大部分的增长速度非常快，在过去的200万年里有40公里的增长。这个速率至少是在一个可比的棱镜生长速率的3倍。
The Nankai Trough accretionary prism is considered an “end‐member” prism accreting a coarse terrigenous sediment section in a setting with structural simplicity, unparalleled resolution by seismic and other geophysical techniques, and large historic earthquakes. It therefore has been the focus of Ocean Drilling Program (ODP) drilling to address several unresolved questions concerning accretionary processes and prism evolution. At six sites cored along two transects across the Nankai Trough accretionary prism during ODP Leg 190, lithostratigraphy and sediment diagenesis vary markedly. For the first time, reference sites at the seaward ends of the two transects defined the stratigraphic framework of the accreting/subducting Shikoku Basin sedimentary section. A thick section of Miocene turbidites and smectite‐rich mudstone is present within the subducting section at the Ashizuri site. The turbidites and mudstones are absent in the correlative section at the Muroto site; variations in lithology, mineralogy, and hydrologic properties of the incoming sediments probably contribute to the difference in prism wedge taper between the two transects, while possibly controlling the seismic character of the active plate boundary. The décollement in both transects is localized within a common stratigraphic unit (∼5.9–7 Ma) within the lower Shikoku Basin facies. The décollement is also a major boundary for both physical and mechanical properties. A broad low‐chloride pore water anomaly in the lower Shikoku Basin unit, first identified at Site 808, progressively decreases in magnitude from prism to basin along the Muroto Transect. Physical properties relationships, evidence for mineralogic changes in the sediments, and pore fluid chemistry suggest that the chloride anomaly results primarily from in situ diagenetic reactions in the sediments, possibly augmented by flow of freshened fluid from depth. New constraints on stratigraphy and age of units along more landward parts of the Muroto Transect have dramatically changed our ideas about the tectonic evolution of the prism in this area. Growth of the seaward‐most part of the prism took place very rapidly, with 40 km of accretion within the past 2 Myr. This rate is at least 3 times greater than growth rates in a comparable prism.