Collaborative Research: Modeling hydrothermal recharge and outflow in oceanic crust analogs with sharp permeability gradients

合作研究：模拟具有尖锐渗透率梯度的洋壳类似物的热液补给和流出

• 批准号: 1537650
• 负责人: Eric Mittelstaedt
• 金额: $ 6.82万
• 依托单位: Regents of the University of Idaho
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1537650&HistoricalAwards=false
• 关键词: Collaborative; Research; Modeling; hydrothermal; recharge

Fluid circulation through the oceanic crust at the axis of mid-ocean ridges is a primary mechanism through which the Earth loses its internal heat. At the seafloor, this circulation releases hot fluids into the deep ocean. These hydrothermal sites typically host ecosystems and life forms found nowhere else on the planet and are thought to be one of the places on Earth where life may have originated. Hydrothermal fluid venting often occurs at or near major fault or fracture zones, suggesting that these breaks in the ocean crust can act as highly permeable conduits for fluids escape. It is unclear, however, to what extent these breaks in Earth's crust enable fluids to enter and move downward into the seafloor where they get heated. This research uses analog experiments, using a 3-D printer, and modeling to explore how fluid circulation at mid-ocean ridges spontaneously organizes itself and transports heat in highly fractured and faulted crust. By allowing exploration of the relation between venting sites and major tectonic features, the research facilitates our understanding of geothermal processes and the search for new hydrothermal sites on the seafloor. Broader impacts of the work include integration of research and education and support of three early career investigators, one from an institution in an EPSCoR state (Idaho). Results have applications ranging from terrestrial groundwater hydrology to geothermal energy, carbon sequestration, and the oil industry.This research employs numerical and analog experiments to describe and quantitatively explain the effect of heterogeneous permeability on subsurface flow geometry and heat extraction. Using a 3-D printer, we will generate plastic analogs of oceanic crust, containing a series of regularly spaced tubes that will act as fluid pathways of defined permeability. Within this permeable matrix, a planar slot of prescribed width, inclination, and greater permeability (achieved through wider tubes) will be created, representing the damage zone that typically surrounds active faults. The printed volume will be placed in a glass-walled tank containing a mixture of glucose and water. The fluid will be heated from below to initiate porous convection. A combination of particle image velocimetry, thermo-chromic liquid crystals, and temperature sensors at the top and bottom of the volume will allow quantification of the locations of fluid recharge and discharge and the heat output of the convective system as the permeability contrast and geometry of the slot is varied. Results will be compared to numerical models of porous convection in heterogeneous media and then extrapolated to natural conditions. The research will focus on predicting the conditions under which high-permeability fault zones can trap and focus hydrothermal convection rolls. The combined experimental and theoretical approach will greatly inform the investigation of targeted hydrothermal sites on slow-spreading mid-ocean ridges that sit next to major fault systems or near major crustal heterogeneities.

通过海洋脊的轴线穿过海洋壳的流体循环是一种主要的机制，地球通过该机制失去其内部热量。在海底，这种循环将热液释放到深海中。这些水热遗址通常是地球上没有其他地方的生态系统和生命形式，被认为是地球上生命可能产生的地方之一。水热流体通常发生在主要断层或断裂区域，这表明海壳中的这些断裂可以充当液体逸出的高度渗透导管。然而，尚不清楚地球地壳​​中的这些断裂在多大程度上使液体能够进入并向下移动到海底，在那里它们被加热。这项研究使用模拟实验，使用3D打印机和建模来探索中山脊的流体循环如何自发地组织自身并在高度断裂和断层的外壳中运输热量。通过允许探索通风站点与主要构造特征之间的关系，该研究促进了我们对地热过程的理解，并寻找海底上新的热液地点。 这项工作的更广泛的影响包括研究和教育的整合以及三名早期职业研究者的支持，其中一名来自EPSCOR州（爱达荷州）的机构。 结果的应用包括从陆地地下水水文到地热能，碳固执以及石油工业。这项研究采用数值和模拟实验来描述和定量解释异质渗透性对地下流量几何形状和热量提取的影响。使用3-D打印机，我们将生成海洋外壳的塑料类似物，其中包含一系列定期间隔的管，这些管将充当定义的渗透性的流体途径。在此渗透的矩阵中，将创建一个规定的宽度，倾斜度和更大的渗透率（通过更宽的管实现）的平面插槽，代表通常围绕着活动故障的损伤区。印刷体积将放置在玻璃壁油箱中，其中包含葡萄糖和水的混合物。流体将从下方加热以引发多孔对流。粒子图像速度法，体积顶部和底部的温度传感器的组合将允许定量流体充值和放电的位置以及对流系统的热量输出，因为插槽的渗透率对比度和几何形状的几何形状是变化的。 结果将与异质培养基中多孔对流的数值模型进行比较，然后推断为自然条件。这项研究将重点介绍预测高渗透性断层区域可以捕获并集中热液对流掷骰的条件。合并的实验和理论方法将在慢慢地散布的中端脊或靠近主要的地壳异质性的较慢的中山脊上对有针对性的水热位点的研究。