Tectonic context of fluid venting at the toe of the eastern Nankai accretionary prism: Evidence for a shallow detachment fault
Tectonic context of fluid venting at the toe of the eastern Nankai accretionary prism: Evidence for a shallow detachment fault
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南开东部增生棱柱趾部流体喷发的构造背景：浅层滑脱断层的证据
DOI：
10.1016/0012-821x(92)90095-d
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发表时间：
1992
影响因子：
5.3
通讯作者：
H. Tokuyama
中科院分区：
文献类型：
--
作者：
N. Chamot‐Rooke;S. Lallemant;X. Pichon;P. Henry;M. Sibuet;J. Boulègue;J. Foucher;T. Furuta;T. Gamo;G. Glacon;Kyoko Kobayashi;S. Kuramoto;Y. Ogawa;P. Schultheiss;J. Segawa;A. Takeuchi;P. Tarits;H. Tokuyama
在Kaiko-Nankai潜水巡航期间，排气活动的高峰位于第一个背斜的顶部附近。中坡（3870 m）和褶皱顶点（3770 m）之间最显著的形态特征是一个20 m高的悬崖，该悬崖穿过受众多节理影响的近水平块状泥岩。该陡坎的走向与褶皱轴斜交，并沿沿着两个明显的NNE-SSE和E-W方向受构造控制。在当地发现的新的岩屑堆和岩块表明了活跃的构造和近期的侵蚀作用。强烈的变形是明显的强烈倾斜的地层限制在悬崖的基础上，我们解释为一个上坡推力。按照Seabeam制图的比例尺，这一逆冲可沿3 820米等深线向东延伸沿着多公里。在一次现场前勘测期间记录的两条地震测线显示，浅层有变形，包括小规模的褶皱和冲断作用，只影响楔形顶部层序。在这个层序之下可以连续追踪到更深的层。我们的结论是“背驮式”盆地和前缘褶皱浊积岩之间的边界作为一个浅拆离断层，并解释的悬崖底部的断层露头。密集的菌落ofCalyptogenaclams和强烈的非线性热梯度位于主要悬崖上方的高原边缘的流体活动的主要高峰。在沿着悬崖底部的狭窄地带还发现了分散的生物菌落以及白色细菌垫和水泥烟囱。因此，流体活动与浅层拆离断层密切相关，流体在断层露头处和其上方通过上覆地层排出，可能使用非常密集的节理网络。
During the Kaiko-Nankai diving cruise the peak of the venting activity was located near the top of the very first anticline. The most prominent morphological feature between the mid-slope (3870 m) and the apex of the fold (3770 m) is a 20 m high cliff cutting through subhorizontal massive mudstones affected by numerous joints. The trend of this scarp is oblique to the fold axis and structurally controlled along two sharply defined NNE-SSE and E-W directions. Fresh talus and blocks found locally suggest active tectonics and recent erosion. Intense deformation is evident from strongly tilted strata restricted to the base of the cliff that we interpret as an upslope thrust. At the scale of Seabeam mapping, this thrust can be followed eastward for more than 5 km along the 3820 m isobath. Two seismic lines recorded during one of the pre-site surveys show deformation at shallow depth, including small-scale folding and thrusting affecting only the wedge-shaped top sequence. Deeper layers can be traced continuously below this sequence. We conclude that the boundary between the “piggy-back” basin and the frontal fold turbidites acts as a shallow detachment fault, and interpret the base of the cliff as the outcrop of the fault. Dense colonies ofCalyptogenaclams and strongly nonlinear thermal gradients locate the major peak of fluid activity at the edge of the plateau above the main cliff. Scattered biological colonies as well as white bacterial mats and cemented chimneys were also found in a narrow belt along the base of the cliff. Fluid activity is thus closely related to the shallow detachment fault, fluid being expelled both at the outcrop of the fault and above it through the overlying strata, possibly using the very dense joint network.