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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新西兰希库朗吉边缘近海底逆冲断层的物理性质和天然气水合物
DOI：
10.1002/essoar.10503197.1
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Cook A
中科院分区：
文献类型：
--
作者：
Cook A
在国际大洋发现计划U1518站点钻探的Pāpaku断裂带是一条活动的伸展断裂，位于Hikurangi边缘的前缘增生楔中。在随钻测井数据中，33米厚的断裂带表现出混合的变形模式，并伴随着密度、P波速度和电阻率下降的趋势。甲烷水合物在海底以下约30至585米处(MBsf)观察到，包括断裂带及其周围。水合物的聚集是垂直不连续的，在整个测井段中低到中等饱和度的粉质和砂质厘米厚的层中都有水合物聚集。我们认为，水合物的分布意味着甲烷不是来自沿断层的流体流动，而是来自局部扩散。这结合U1518现场的地球物理观测和地球化学测量，表明该断裂不是深源流体的集中运移通道，近海底Pāpaku断裂带几乎没有活动的流体流动。
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.