In marine rift basins, deep-water clastics (>200 m) in the hanging wall of rift- or basin-bounding fault systems are commonly juxtaposed against crystalline “basement” rocks in the footwall. A distinct feature of such fault systems is therefore the juxtaposition of relatively highly permeable, unconsolidated sediments against relatively low-permeable basement rocks. Due to limited surface exposure of such fault zones, studies elucidating their structure and evolution are rare. Consequently, their impact on fluid circulation and diagenesis within and proximal to the fault zone as well as into the hanging wall strata are also poorly understood. Motivated by this, we here investigate a well-exposed strand of a major basin-bounding fault system in the East Greenland rift system, namely the Dombjerg Fault which bounds the Wollaston Forland Basin, northeast (NE) Greenland. Here, syn-rift deep-water clastics of Late Jurassic to Early Cretaceous age are juxtaposed against Caledonian metamorphic basement. Previously, a ∼ 1 km wide zone of pervasive pore-filling calcite cementation of the hanging wall sediments along the Dombjerg Fault core was identified (Kristensen et al., 2016). In this study, based on U–Pb calcite dating, we show that cementation and formation of this cementation zone started during the rift climax in Berrisian–Valanginian times. Using clumped isotope analysis, we determined cement formation temperatures of ∼ 30–70 ^∘C. The spread in the formation temperatures at similar formation age indicates variable heat flow of upward fluid circulation along the fault in the hanging wall sediments, which may root in permeability variations in the sediments. Calcite vein formation, postdating and affecting the cementation zone, clusters between ∼ 125 and 100 Ma in the post-rift stage, indicating that fracturing in the hanging wall is not directly related to the main phase of activity of the adjacent Dombjerg Fault. Vein formation temperatures at ∼ 30–80 ^∘C are in a similar range as cement formation temperatures. Further, similar minor element concentrations of veins and adjacent cements indicate diffusional mass transfer into fractures, which in turn infers a subdued fluid circulation and low permeability of the fracture network. These results imply that the cementation zone formed a near-impermeable barrier soon after sediment deposition, and that low effective permeabilities were maintained in the cementation zone even after fracture formation, due to poor fracture connectivity. We argue that the existence of such a cementation zone should be considered in any assessments that target basin-bounding fault systems for, e.g., hydrocarbon, groundwater, geothermal energy, and carbon storage exploration. Our study highlights that the understanding of fluid flow properties as well as fault-controlled diagenesis affecting the fault itself and/or adjacent basinal clastics is of great fundamental and economic importance.

中文翻译：

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裂谷盆地边界断层系统的断层控制流体循环和成岩作用–东格陵兰裂谷系统的见解

在海洋裂谷盆地，深水碎屑（> 200 m）在裂谷或盆地边界断层系统的悬挂壁中，通常与底盘中的结晶“基底”岩石并列。因此，这种断层系统的一个显着特征是将相对高渗透率的未固结沉积物与相对低渗透率的基底岩石并置。由于此类断层带的有限的表面暴露，阐明其结构和演化的研究很少。因此，人们对它们对断层带内部和附近以及悬壁地层中的流体循环和成岩作用的影响了解甚少。因此，我们在此调查了东格陵兰裂谷系统中一个主要的盆地边界断层系统，即Dombjerg断层的一条暴露良好的断层，该断层系东北格陵兰东北部的沃拉斯顿福兰德盆地。这里，侏罗纪晚期至白垩纪早期的同裂隙深水碎屑与喀里多尼亚变质基底并列。以前， 沿着Dombjerg断层岩心确定了约1 km宽的悬垂方解石胶结物普遍渗透的充填区（Kristensen等，2016）。在这项研究中，基于U–Pb方解石年代，我们证明了该胶结带的胶结作用和形成始于Berrisian–Valanginian时代的裂谷高潮。使用成群同位素分析，我们确定的水泥形成温度〜  30-70  ^∘ C.在地层温度下形成类似年龄的传播指示沿在挂壁沉积物故障向上流体循环的变量的热流，其可渗透性根沉积物中的变化。方解石脉形成，过时并影响胶结带 在裂谷后阶段约为125 Ma和100 Ma，这表明悬壁的破裂与相邻的Dombjerg断层的活动主相没有直接关系。静脉形成温度在〜  30-80  ^∘C在与水泥地层温度相似的范围内。此外，相似的次要元素浓度的静脉和邻近的胶结物表明扩散质量转移到裂缝中，这又导致流体循环减弱和裂缝网络的渗透率低。这些结果表明，胶结区在沉积物沉积后不久就形成了一个几乎不可渗透的屏障，并且由于裂缝的连通性差，即使在裂缝形成之后，胶结区也保持了较低的有效渗透率。我们认为，在以盆地为界的断层系统为目标的任何评估中，都应考虑存在这种胶结带，例如碳氢化合物，地下水，地热能和碳储量勘探。我们的研究 强调指出，对流体流动特性以及影响断层自身和/或邻近盆地碎屑的断层控制成岩作用的理解具有重要的基础和经济意义。