2D and 3D coexisting modes of thermal convection in fractured hydrothermal systems - Implications for transboundary flow in the Lower Yarmouk Gorge
2D and 3D coexisting modes of thermal convection in fractured hydrothermal systems - Implications for transboundary flow in the Lower Yarmouk Gorge
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DOI：
10.1016/j.marpetgeo.2016.10.002
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发表时间：
2016-12
影响因子：
4.2
通讯作者：
F. Magri;S. Möller;N. Inbar;P. Möller;M. Raggad;T. Rödiger;E. Rosenthal;C. Siebert
中科院分区：
文献类型：
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作者：
F. Magri;S. Möller;N. Inbar;P. Möller;M. Raggad;T. Rödiger;E. Rosenthal;C. Siebert
数值研究的2D和3D模式的大规模对流断层含水层的目的是推断可能的运输机制，支持通过断裂含水层形成温泉。瞬态有限元模型是基于理想化的结构特征，可以表征许多热液系统。断层渗透率的敏感性分析表明，断层横切主要区域流动方向，使地下水被横向驱动的对流力在断层面。在那里，热沃茨可以沿着断层痕迹排出，或者通过相邻的可渗透含水层排出断层。在后一种情况下，产生的流动是螺旋形的和瞬态的。放电区的位置和间距可以随时间推移而迁移，不严格限制于损伤区，而是反映了断层带多细胞机制的波长。基于简化的耶尔穆克峡谷下游（LYG）结构数据给出了一个说明性例子。数值计算表明，交叉流动路径是断层对流与附加流场共存的结果，断层对流例如沿峡谷内的沿着NE-SW向断层发展。后者是由地形引起的，例如垂直于峡谷主轴的梯度，或由始新世隔水层以下渗透性含水层中的局部热对流引起的。断层导水率（K）的敏感性分析和基于粘性相关瑞利理论的解析解表明，K值在2.3e-7 m/s和9.3e-7 m/s之间（即分别为7 m/yr和30 m/yr）有利于共存的输运过程。上升的热羽流蔓延了几百米，形成了一串泉水，与观测结果一致，温度在测量范围内，即20 °C-60 °C。在一定程度上，模型还再现了弹簧温度的瞬态行为。由于所提出的模型的理想化性质，数值结果和相关的解析解可以应用于研究热对流的发生和由此产生的任何裂缝热液盆地的流型。
Numerical investigations of 2D and 3D modes of large-scale convection in faulted aquifers are presented with the aim to infer possible transport mechanisms supporting the formation of thermal springs through fractured aquicludes. The transient finite elements models are based on idealized structural features that can characterize many hydrothermal systems. The sensitivity analysis of the fault permeability showed that faults cross-cutting the main regional flow direction allow groundwater to be driven laterally by convective forces within the fault planes. Therein thermal waters can either discharge along the fault traces or exit the fault through adjacent permeable aquifers. In the latter case, the resulting flow is helicoidally and transient. The location and the spacing between discharge areas can migrate with time, is not strictly constrained to the damage zones and reflects the wavelength of the multicellular regime in the fault zone.An illustrative example based on simplified structural data of the Lower Yarmouk Gorge (LYG) is presented. The numerical calculations indicate that crossing flow paths result from the coexistence of fault convection, developing for example along NE-SW oriented faults within the Gorge, and additional flow fields. The latter are induced either by topography Nsingle bondS gradients, e.g. perpendicular to the major axe of the Gorge, or by local thermal convection in permeable aquifers below the Eocene aquiclude. Sensitivity analysis of fault hydraulic conductivity (K) and the analytical solutions based on viscous-dependent Rayleigh theory show thatKvalues between 2.3e−7m/s and 9.3e– 7m/s (i.e. 7 m/yr and 30 m/yr, respectively) favor coexisting transport processes. The uprising thermal plumes spread over several hundred meters forming clusters of springs, in agreement with observation, and which temperature fall within the measured ranges, i.e. 20 °C−60 °C. To some extent the models also reproduced the transient behavior of the spring temperature. Owing to the idealized nature of the presented models, the numerical results and the associated analytical solution can be applied to study the onset of thermal convection and resulting flow patterns of any fractured hydrothermal basin.