Suchergebnisse

The nature of Yellowstone National Parks plumbing system linking deep thermal fluids to its legendary thermal features is virtually unknown. The prevailing concepts of Yellowstone hydrology and chemistry are that fluids reside in reservoirs with unknown geometries, flow laterally from distal sources and emerge at the edges of lava flows. Here we present a high-resolution synoptic view of pathways of the Yellowstone hydrothermal system derived from electrical resistivity and magnetic susceptibility models of airborne geophysical data. Groundwater and thermal fluids containing appreciable total dissolved solids significantly reduce resistivities of porous volcanic rocks and are differentiated by their resistivity signatures. Clay sequences mapped in thermal areas and boreholes typically form at depths of less than 1,000 metres over fault-controlled thermal fluid and/or gas conduits. We show that most thermal features are located above high-flux conduits along buried faults capped with clay that has low resistivity and low susceptibility. Shallow subhorizontal pathways feed groundwater into basins that mixes with thermal fluids from vertical conduits. These mixed fluids emerge at the surface, controlled by surficial permeability, and flow outwards along deeper brecciated layers. These outflows, continuing between the geyser basins, mix with local groundwater and thermal fluids to produce the observed geochemical signatures. Our high-fidelity images inform geochemical and groundwater models for hydrothermal systems worldwide. ; This work was supported by the US Geological Survey Mineral and Energy Resources and Volcanic Hazards Programs, NSF grant no. EPS-1208909 and the University of Wyoming Office of Research and Economic Development. ; Published version ; Authored by U.S. government employees and therefore in the public domain.

Seismic anisotropy measurements show that upper mantle hydration at the Middle America Trench (MAT) is limited to serpentinization and/or water in fault zones, rather than distributed uniformly. Subduction of hydrated oceanic lithosphere recycles water back into the deep mantle, drives arc volcanism, and affects seismicity at subduction zones. Constraining the extent of upper mantle hydration is an important part of understanding many fundamental processes on Earth. Substantially reduced seismic velocities in tomography suggest that outer rise plate-bending faults provide a pathway for seawater to rehydrate the slab mantle just prior to subduction. Estimates of outer-rise hydration based on tomograms vary significantly, with some large enough to imply that, globally, subduction has consumed more than two oceans worth of water during the Phanerozoic. We found that, while the mean upper mantle wavespeed is reduced at the MAT outer rise, the amplitude and orientation of inherited anisotropy are preserved at depths >1 km below the Moho. At shallower depths, relict anisotropy is replaced by slowing in the fault-normal direction. These observations are incompatible with pervasive hydration but consistent with models of wave propagation through serpentinized fault zones that thin to 1 km below Moho. Confining hydration to fault zones reduces water storage estimates for the MAT upper mantle from similar to 3.5 wt% to <0.9 wt% H(2)0. Since the intermediate thermal structure in the similar to 24 Myr-old MAT slab favors serpentinization, limited hydration suggests that fault mechanics are the limiting factor, not temperatures. Subducting mantle may be similarly dry globally. ; US Ocean Bottom Seismograph Instrument Pool facilities at the Woods Hole Oceanographic Institution; Scripps Institution of OceanographyUniversity of California System ; Published version ; We are grateful for the hard work and dedication of the technicians, crews, officers, and science party of R/V Langseth cruise MGL0807, who overcame many obstacles during Langseth's first science program, and also Trish Gregg and everyone aboard R/V New Horizon cruise TC2NH, which handled OBS operations. The OBS were provided and supported by the US Ocean Bottom Seismograph Instrument Pool (http://www.obsip.org) facilities at the Woods Hole Oceanographic Institution and the Scripps Institution of Oceanography. We thank D. Shillington, S. Naif, F. Klein, and U. ten Brink for many productive discussions and J. Kluesner, C. Ruppel, A. Trehu, and J. Korenaga for reviews of this manuscript. ; Public domain authored by a U.S. government employee

The Reynolds Creek Experimental Watershed (RCEW) was established in 1960 as an "outdoor hydrological laboratory" to investigate hydrological processes of interest in the interior northwestern part of the United States. Initial emphasis was on installing and testing instrumentation and data collection and dissemination. The initial instrumentation network sampled the climatic gradient within the 239-km(2) watershed and focused on specific subwatersheds for intensive instrumentation. This network has expanded and supported ad hoc research and provides a stable platform for the development of long-term programs supporting research and model development in snow hydrology, climate change, water and energy balance, land management, carbon cycling, and critical zone hydrology. Recently, the challenge taken up at the RCEW is to integrate different processes over space for applications to larger areas outside the watershed. The presence of steep local environmental gradients associated with topography in addition to more gradual, elevational gradients requires high-resolution modeling. The snow hydrology program has demonstrated the potential for high-resolution, process-based modeling across large landscapes. The direct linkage of biogeochemical processes with hydrological processes ultimately requires a multidisciplinary approach that has been adopted at the RCEW since inclusion in the Critical Zone Observatory program. We think that coupling of these processes will lead to a better understanding and management of natural resources on the landscape. ; NSF RC CZO [EAR 1331872] ; This work was partially funded by NSF RC CZO Cooperative Agreement no. EAR 1331872. ; Public domain authored by a U.S. government employee