Physical Properties and Gas Hydrate at a Near‐Seafloor Thrust Fault, Hikurangi Margin, New Zealand
Physical Properties and Gas Hydrate at a Near‐Seafloor Thrust Fault, Hikurangi Margin, New Zealand
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DOI：
10.1029/2020gl088474
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发表时间：
2020-08
影响因子：
5.2
通讯作者：
A. Cook;M. Paganoni;M. Clennell;D. Mcnamara;M. Nole;Xiujuan Wang;Shuoshuo Han;R. Bell;E. Solomon;D. Saffer;P. Barnes;I. Pecher;L. Wallace;L. Levay;K. Petronotis
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文献类型：
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作者：
A. Cook;M. Paganoni;M. Clennell;D. Mcnamara;M. Nole;Xiujuan Wang;Shuoshuo Han;R. Bell;E. Solomon;D. Saffer;P. Barnes;I. Pecher;L. Wallace;L. Levay;K. Petronotis
在国际海洋发现计划（IODP）U1518站点钻探的Pāpaku断层带是位于希库朗吉边缘前缘增生楔中的活动展状断层。在随钻测井数据中，33 m厚的断层带显示出与密度、P波速度和电阻率下降趋势相关的混合变形模式。甲烷水合物可在海底以下约30至585米处观察到，包括断层带内部和周围。海积灰堆积在垂直方向上是不连续的，在整个测井剖面中，在低至中等饱和度下，在粉砂和桑迪厘米厚的地层中出现。我们认为，水合物的分布意味着甲烷不是来源于流体流动沿着断层，而是通过局部扩散。这与U1518站点的地球物理观测和地球化学测量相结合，表明该断层不是深源流体的集中迁移通道，并且近海底的Pāpaku断层带几乎没有活跃的流体流动。
The Pāpaku Fault Zone, drilled at International Ocean Discovery Program (IODP) Site U1518, is an active splay fault in the frontal accretionary wedge of the Hikurangi Margin. In logging‐while‐drilling data, the 33‐m‐thick fault zone exhibits mixed modes of deformation associated with a trend of downward decreasing density, P‐wave velocity, and resistivity. Methane hydrate is observed from ~30 to 585 m below seafloor (mbsf), including within and surrounding the fault zone. Hydrate accumulations are vertically discontinuous and occur throughout the entire logged section at low to moderate saturation in silty and sandy centimeter‐thick layers. We argue that the hydrate distribution implies that the methane is not sourced from fluid flow along the fault but instead by local diffusion. This, combined with geophysical observations and geochemical measurements from Site U1518, suggests that the fault is not a focused migration pathway for deeply sourced fluids and that the near‐seafloor Pāpaku Fault Zone has little to no active fluid flow.