Mantle transition zone topography and low-velocity zone locations in the Yellowstone Region

Earth’s mantle transition zone (MTZ) is a possible global water reservoir and may be responsible for long-term (~100 Ma) ocean-mass regulation. Estimates of water capacities in MTZ minerals are ~1 wt%, far greater than that of rocks of the surrounding mantle. When water-rich material is displaced from the MTZ, partial melting occurs, generating a sharp reduction in seismic velocities detectable with seismic receiver functions (RFs). We estimated RFs for the MTZ beneath the Yellowstone region using earthquakes recorded by ~200 stations of the Earthscope Transportable Array. We found many LVZs both above and below the MTZ, consistent with water release upon phase transformation of hydrated MTZ rock into upper- and lower-mantle mineral assemblages with low water capacities. The locations of LVZs are consistent with mid-mantle flow induced by descent of a Farallon-slab fragment and ascent of the deeply-rooted Yellowstone plume as imaged by seismic tomography.