Little is known about the local plumbing systems that fuel Yellowstone's famous hot springs, geysers and mud pots. A multi-method, multi-scale geophysical investigation was carried out in the Obsidian Pool Thermal Area (OPTA) to: (a) delineate the lateral extent of the hydrothermal area and associated surface features; (b) estimate the dimensions of the upflow zone and identify its main controlling structures; (c) assess fluids circulation pathways from depth to surface. Ground and airborne geophysical data were acquired to connect local and regional scales, from shallow to large depths. Maps of surface electrical resistivity show a strong correlation with hydrothermal features. At intermediate depths, electrical resistivity permits delineating the upper limit of the upflow zone, while Poisson's ratio highlights differences in subsurface fluid content. Combining these results with surface observations and topographic information, we speculate that differential mixing of hydrothermal and fresh water could explain the wide diversity of features observed at OPTA. Low electrical resistivity observed at large depths also suggest that a vast upflow zone, controlled by rhyolite flows and conjugate faults, underlies the OPTA. We speculate that hydrothermal fluids rise along fractures and reach the surface in topographic lows to form hydrothermal features. Our results show that synoptic, multi-scale geophysical measurements provide a roadmap for understanding where and how geologic heterogeneity, topography, fluid-gas separation, and the mixing of thermal and meteoric waters conspire to produce the wide variety of Yellowstone's renowned hydrothermal features.

中文翻译：

---

美国黄石国家公园热液系统的多尺度地球物理成像


人们对为黄石公园著名的温泉、间歇泉和泥浆罐提供燃料的当地管道系统知之甚少。在黑曜石池热区 （OPTA） 进行了多方法、多尺度的地球物理调查，以：（a） 划定热液区的横向范围和相关表面特征;（b） 估计上游流出区的尺寸并确定其主要控制结构;（c） 评估从深处到表面的流体循环途径。获取地面和航空地球物理数据以连接从浅到大的局部和区域尺度。表面电阻率图显示与热液特征具有很强的相关性。在中间深度，电阻率允许划定上流区的上限，而泊松比则突出了地体含量的差异。将这些结果与地表观测和地形信息相结合，我们推测热液和淡水的差异混合可以解释在 OPTA 观察到的广泛特征多样性。在大深度观察到的低电阻率也表明，OPTA 下方存在一个巨大的上升带，由流纹岩流和共轭断层控制。我们推测热液流体沿着裂缝上升，并在地形低处到达地表，形成热液特征。我们的结果表明，天气、多尺度地球物理测量为了解地质非均质性、地形、液气分离以及热水和陨石水的混合共同产生黄石公园各种著名的热液特征提供了路线图。