Sediment deformation and hydrogeology of the Nankai Trough accretionary prism: Synthesis of shipboard results of ODP Leg 131
Sediment deformation and hydrogeology of the Nankai Trough accretionary prism: Synthesis of shipboard results of ODP Leg 131
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南海海槽增生棱柱的沉积物变形和水文地质：ODP 131 段船上结果的综合
DOI：
10.1016/0012-821x(92)90104-4
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发表时间：
1992
影响因子：
5.3
通讯作者：
Jianzhong Zhang
中科院分区：
文献类型：
--
作者：
A. Taira;I. Hill;J. Firth;U. Berner;W. Brückmann;T. Byrne;T. Chabernaud;A. Fisher;J. Foucher;T. Gamo;J. Gieskes;R. Hyndman;D. Karig;M. Kastner;Y. Kato;S. Lallemant;R. Lu;A. Maltman;G. Moore;K. Moran;G. Olaffson;W. Owens;K. Pickering;F. Siena;E. Taylor;M. Underwood;C. Wilkinson;M. Yamano;Jianzhong Zhang
第131航次的主要目的是提供关于南海棱柱体趾部的变形过程和相关水文地质的数据。钻探在海洋钻探史上第一次成功地穿透了整个沉积序列，到达玄武岩基底，达到1 327 mbsf（海底以下米），岩心回收率良好（55%）。岩性和构造，包括前锋逆冲断层和滑脱，与地震反射图像也确定了良好的相关性。分析的核心层倾角，断层和剪切带确认的变形模式，主要是由于西北-东南缩短，从板块构造收敛矢量的预期。滑脱层以下没有明显的变形特征，表明滑脱层是应力传递的一个明显的不连续性，物性数据显示滑脱层处存在较大的不连续性，特别是滑脱层以下孔隙度增加。这可能表明俯冲段和滑脱带存在超孔隙压力。锋面逆冲断层以下孔隙度增加不太明显，可能反映了这一特征的年轻性。不稳定的井眼条件严重阻碍了进行井下测量的尝试，但对热状况进行了有用的限制，并提供了一些实验室物理性质对原位条件的校准，并在最上层沉积物中测量了原位应力和孔隙压力。没有发现明显的地球化学特征或明确的地球化学异常指示通道化的流体flow. Thermal测量是没有显着不同的预测由一个纯粹的传导热流模型。低氯化物孔隙水附近的滑脱签名可能部分与蒙皂石成岩作用，但也可能是由于幕式流体流动事件。我们的结论是，脱水可能主要是通过扩散流在这个网站的增生沉积物。
The main objective of Leg 131 was to provide data on the deformational processes and associated hydrogeology of the Nankai prism toe. Drilling succeeded, for the first time in the history of ocean drilling, in penetrating the complete sedimentary sequence to basaltic basement, reaching 1327 mbsf (metres below seafloor) with good core recovery (55%). Excellent correlation of the lithology and structure, including the frontal thrust and the decollement, with seismic reflection images was also determined.Bedding dips, faults and shear bands analyzed in the cores confirm the pattern of deformation to be mainly due to NW-SE shortening, as expected from the plate tectonic convergence vector. Below the decollement, no significant deformation features were observed, indicating that the decollement is a sharp discontinuity in stress transmission.Physical properties data show major discontinuities at the decollement, notably an increase in porosity below the later. This may indicate excess pore pressure in the subducted section and decollement zone. A less marked increase in porosity below the frontal thrust may reflect the youthfulness of this feature. Attempts to make downhole measurements were severely hampered by unstable hole conditions, but useful constraints have been placed on the thermal regime, and some calibration of laboratory physical properties toin-situconditions has been provided, andin-situstress and pore pressure were measured in the uppermost sediments.Evidence of channelized fluid flows is inconclusive. No sharp geochemical signatures or unequivocal geochemical anomalies indicative of channelized fluid flow were found. Thermal measurements are not significantly different from those predicted by a purely conductive heat flow model. A signature of low chloride pore water near the decollement may partly be related to smectite diagenesis but may also be due to episodic fluid flow events. We conclude that dewatering probably occurred dominantly through diffuse flow throughout the accreted sediments at this site.