DEFLECTION OF THE YELLOWSTONE PLUME IN LARGE-SCALE MANTLE FLOW

A shear flow field in the sublithospheric upper mantle will deflect the Yellowstone plume. Here we show predictions for the shape of the tilted plume conduit in the upper mantle. Results depend on both large-scale flow field and plume buoyant rising speed. Large-scale flow depends on mantle density and viscosity structure. Mantle density can be inferred from seismic tomography or from subduction history. We use different density models and vary viscosity within realistic bounds in order to estimate uncertainties in the large-scale flow. We predict eastward asthenospheric flow in the vicinity of Yellowstone, driven by large-scale upwelling beneath the Pacific and the remains of subducted slabs in the lower mantle beneath central and eastern North America. Based on plume anomalous mass flux and viscosity in both the plume and surrounding mantle, we estimate a plume buoyant rising speed of 5-10 cm/yr in the sublithospheric upper mantle. Hence a substantially tilted plume conduit, displaced towards the west in the transition zone relative to the surface hotspot, is predicted. We compare our model predictions with seismological results, and discuss implications of a tilted conduit on the asymmetry of the Yellowstone hotspot track.