Compactive deformation of incoming calcareous pelagic sediments, northern Hikurangi subduction margin, New Zealand: Implications for subduction processes
Compactive deformation of incoming calcareous pelagic sediments, northern Hikurangi subduction margin, New Zealand: Implications for subduction processes
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新西兰希库朗吉俯冲边缘北部石灰质远洋沉积物的压实变形：对俯冲过程的影响
DOI：
10.1016/j.epsl.2023.118022
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发表时间：
2023
影响因子：
5.3
通讯作者：
Harris, Robert N.
中科院分区：
文献类型：
--
作者：
Wang, Maomao;Barnes, Philip M.;Morgan, Julia K.;Bell, Rebecca E.;Moore, Gregory F.;Wang, Ming;Fagereng, Ake;Savage, Heather;Gamboa, Davide;Harris, Robert N.
钙质岩石普遍存在于俯冲带中，但很少有人研究这些岩石在俯冲前的固结和压实变形，因此对其对俯冲和增生过程的潜在影响知之甚少。利用国际大洋发现计划(IODP)第372次和第375次探险期间获得的钻井资料，结合二维和三维地震反射资料，研究了Hikurangi边缘进入的远洋沉积序列中识别出的正断层的构造、生长历史和滑动速率。地震相干深度切片和垂直剖面显示，这些断层呈现出在俯冲边缘很少有记录的多边形结构。多边形断层排列紧密、层序分明，层序以古新世-上新世的远洋碳酸盐和钙质泥岩为主。运动学模拟和二维位移分析表明，断层活动向上、下断线方向减少。具体来说，两组抛掷剖面由位移极大值的位置定义，可能反映了物理性质的横向变化。多边形断层系统(PFS)可能是由成岩作用引起的剪切破坏和与流体逃逸有关的远洋单元的体积收缩过程形成的。断层生长序列揭示了同期海底变形和沉积的多个弱相关区间，并可以估计断层滑动速率。我们发现了典型滑动速率显著增加的证据，从远洋沉积时的0.5-3m/Ma到陆源沉积开始后的20m/Ma。这些观察表明，海沟-楔形相对远洋沉积物的快速加载与PFS的更新和快速增长有关。PFS最终将被输送到沉积楔形的底部，增强巨型逆冲带沿线材料的几何粗糙度和不均一性，并提供继承的薄弱地带。断层的选择性再活动可能促进与微震、震颤和慢滑事件有关的下楔形变和幕式垂直流体运移。
Calcareous rocks are commonly found in subduction zones, but few studies have investigated the consolidation and compactive deformation of these rocks prior to subduction, and their potential effects on subduction and accretionary processes are thus poorly understood. Using drilling data obtained during International Ocean Discovery Program (IODP) Expeditions 372 and 375 combined with 2D and 3D seismic reflection data, the structure, growth history, and slip rates of normal faults identified in the incoming pelagic sedimentary sequences of the Hikurangi Margin were investigated. A seismic coherence depth slice and vertical profiles show that these faults exhibit polygonal structure that has rarely been documented at subduction margins. The polygonal faults are closely spaced and layer-bound within sequences dominated by pelagic carbonate and calcareous mudstone of Paleocene-Pliocene age. Kinematic modeling and 2D displacement analysis reveal that fault throws decrease toward the upper and lower tipline. In detail, two groups of throw profiles are defined by locations of displacement maxima, possibly reflecting lateral variations in physical properties. The polygonal fault system (PFS) likely formed by syneresis processes that involve diagenetically induced shear failure and volumetric contraction of the pelagic unit associated with fluid escape. Fault growth sequences reveal multiple, weakly correlated intervals of contemporaneous seafloor deformation and sedimentation and allow estimates of fault slip rates. We find evidence for a significant increase in typical slip rates from 0.5-3 m/Ma during pelagic sedimentation to >20 m/Ma following the onset of terrigenous sedimentation. These observations suggest that rapid loading of the pelagic sediments by the trench-wedge facies was associated with renewed and faster growth of the PFS. The PFS will eventually be transported into the base of the accretionary wedge, enhancing geometric roughness and heterogeneity of materials along the megathrust, and providing inherited zones of weakness. Selective fault reactivation may facilitate deformation and episodic vertical fluid migration in the lower wedge associated with microearthquakes, tremor, and slow slip events.