Seafloor overthrusting causes ductile fault deformation and fault sealing along the Northern Hikurangi Margin
Seafloor overthrusting causes ductile fault deformation and fault sealing along the Northern Hikurangi Margin
复制标题
海底逆冲导致北希库朗吉边缘的延性断层变形和断层封闭
DOI：
10.1016/j.epsl.2022.117651
复制
发表时间：
2022
影响因子：
5.3
通讯作者：
Morgan J
中科院分区：
文献类型：
--
作者：
Morgan J
在IODP第372次和第375次探险期间钻探的U1518 IODP站点穿过了一个大偏移量(∼6公里)的逆冲断层--Pāpaku断层，它从沿Hikurangi边缘反复发生慢滑事件的巨型逆冲中升起。尽管钻探仅在海底以下∼300m处的多孔粉质泥岩内穿过断裂带，但它显示出强烈的构造韧性变形，包括扭曲成分米级褶皱的细带泥岩；具有颗粒尾部复合体的细长泥岩碎屑；变形泥岩中的堆积和截断的粉砂层；以及软沉积物注入。在局部，这些韧性特征被脆性变形叠加，包括正断层、裂缝阵列和角砾岩。固结程度较高的上盘以脆性结构为主，而下盘则表现出韧性和脆性变形，其强度随深度降低。U1518断裂带强烈的构造韧性变形和构造的不对称分布可以用海底推覆作用来解释。上盘在下盘平地上的侵位覆盖了高孔隙度、未变形和以前未被埋藏的沉积物，使这些弱沉积物中的剪切变形局部化。相反，超固结上盘在褶皱和位移过程中优先经历脆性变形。U1518站位的间隙孔隙水地球化学剖面显示断层下方的近海底成岩序列重复，与先前未埋藏地层的逆冲推覆一致。保存下来的下盘成岩剖面表明，逆冲推覆作用发生在最近50-100KYR内，并表明U1518地点沿断层或跨断层的流体流动很少。因此，PāPaku断层似乎定义了一种低渗透封闭性，限制了下盘固结，保持了局部高的孔隙流体压力和低的断层强度。如果边缘其他地方也存在类似的低渗透结构，它们可能支持区域高孔压条件，有利于在Hikurangi巨型逆冲断裂上出现SSE。
IODP Site U1518, drilled during IODP Expeditions 372 and 375, penetrated a large-offset (∼6 km) thrust, the Pāpaku fault, rising from a megathrust that hosts recurring slow slip events along the Hikurangi margin. Although drilling intersected the fault zone at only ∼300 m below the seafloor within porous silty mudstone, it exhibits intense tectonic ductile deformation, including finely banded mudstones contorted into decimeter-scale folds; elongate mudstone clasts with grain tail complexes; stacked and truncated silt beds in distorted mudstones; and soft sediment injections. Locally, these ductile features are overprinted by brittle deformation, including normal faults, fracture arrays, and breccias. The more consolidated hanging wall is dominated by brittle structures, whereas the footwall exhibits ductile and brittle deformation that decreases in intensity with depth. The intense tectonic ductile deformation and asymmetric distribution of structures across the fault zone at Site U1518 can be explained by seafloor overthrusting. The emplacement of the hanging wall upon the footwall flat overrode high-porosity, undeformed, and previously unburied sediments, localizing shear deformation within these weak sediments. In contrast, the overconsolidated hanging wall preferentially experienced brittle deformation during folding and displacement. Interstitial pore water geochemical profiles at Site U1518 show a repetition of near-seafloor diagenetic sequences below the fault, consistent with overthrusting of previously unburied strata. The preserved diagenetic profiles in the footwall suggest that overthrusting occurred within the last 50-100 kyr, and indicate little along- or across-fault fluid flow at the location of Site U1518. Thus the Pāpaku fault appears to define a low-permeability seal that restricts footwall consolidation, maintaining locally high pore fluid pressures and low fault strength. If similar low permeability structures occur elsewhere along the margin, they could support regionally high pore pressure conditions favorable to the occurrence of SSEs on the Hikurangi megathrust fault.
登录
查看更多内容
构造与岩性
影响因子：
5.8
作者：
D. Craw;D. MacKenzie
通讯作者：
D. MacKenzie
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
影响因子：
5.3
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
通讯作者：
Jianzhong Zhang
影响因子：
5.8
作者：
J. Morgan;N. Bangs
通讯作者：
J. Morgan;N. Bangs
影响因子：
5.2
作者：
A. Spivack;M. Kastner;B. Ransom
通讯作者：
A. Spivack;M. Kastner;B. Ransom
影响因子：
2.8
作者：
Antriasian, Anson;Harris, Robert N.;Barker, Dan
通讯作者：
Barker, Dan