HR: 09:20h
AN: V51F-06    [Abstracts]
TI: Numerical Simulations of Multi-phase, Multi-component Hydrothermal Fluid Flow: Implications for Heat and Mass Transport and Deformation of the Yellowstone Caldera
AU: * Hutnak, M
EM: mhutnak@usgs.gov
AF: U.S Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AU: Hurwitz, S
EM: shaulh@usgs.gov
AF: U.S Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AU: Hsieh, P A
EM: pahsieh@usgs.gov
AF: U.S Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AU: Ingebritsen, S E
EM: seingebr@usgs.gov
AF: U.S Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025, United States
AB: Ground surface displacements in large calderas such as Yellowstone have traditionally been modeled by the volume change of a discrete source embedded in an elastic or viscoelastic half-space, and the contributing roles of aqueous fluids and gases have largely been neglected. Because heat flux, hydrothermal fluid flow, and deformation are coupled in volcanically active areas, discrimination between crustal deformation resulting directly from magmatic intrusion and that induced by the associated injection of magmatic volatiles into the hydrothermal system has a direct impact on estimates of the magma source depth, geometry, and composition. The Yellowstone hydrothermal system contains multi-phase fluid and gas components extending to depths of several km, and has a very high efflux of CO2 (Werner and Brantley, 2003). We extend previous numerical simulations of fluid flow and rock deformation in an elastic porous medium using the coupled code TOUGH2-BIOT2 (Hurwitz et al., 2007) to include the effects of multi-phase (liquid-gas) and multi-component (H2O-CO2) flow. Simulations coupling hydrothermal fluid flow and mechanical deformation are sensitive to several hydrological parameters, including permeability, injection rate and depth of magmatic volatiles, and fluid composition. Phase distributions within the hydrothermal system are influenced by the water and gas depth and rate of injection, the temperature of the injected fluid, and the crustal permeability distribution. In simulations where a gas phase develops, ascent and expansion of a buoyant, high-enthalpy plume migrating towards the ground surface has a significant effect on the rate, magnitude, and geometry of ground surface displacements. For a plausible range of hydrologic parameters, water and gas injection yields simulated ground surface displacement rates (one to tens of mm/yr) and radii of deformation (tens of km) that are similar to those observed in Yellowstone, suggesting that ascent of magmatic gases towards the shallow crust and multi-phase dynamics within the hydrothermal system may explain some of the deformation observed in Yellowstone.
DE: 1847 Modeling
DE: 8045 Role of fluids
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
DE: 8430 Volcanic gases
DE: 8440 Calderas
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting