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.