Geophysical Imaging of Yellowstone’s Hydrothermal Plumbing System
Abstract Yellowstone National Park’s plumbing system linking deep thermal fluids to legendary thermal features is virtually unknown. Prevailing concepts of Yellowstone’s hydrology and chemistry are that fluids flow laterally from distal sources and emerge at the edges of lava flows and that spring chemistry reflects varying fluid source regions1,2. Here we present the first view of Yellowstone’s hydrothermal system derived from electrical resistivity and magnetic susceptibility models of airborne geophysical data3,4. Groundwater and thermal fluids containing total dissolved solids or low pH significantly reduce resistivities of porous volcanic rocks5. Low susceptibility clay sequences mapped in thermal areas6,7 and boreholes8 typically form over fault-controlled thermal fluid and/or gas conduits9-12. We show that most thermal features are located above high-flux conduits along buried faults and flow paths are similar irrespective of spring chemistry. Lateral outflow from the conduits mixes with upflow and groundwater at shallow levels in the thermal basins. Similarities between our models and those from the Taupo Volcanic Zone highlight the implication of our work beyond Yellowstone and suggest that hydrothermal systems worldwide are vertically-driven and surface geochemical variations are controlled at depth by mixing of local and distal thermal fluids and groundwater and more locally, by shallow permeability.