PLUME-LITHOSPHERE INTERACTION AND DELAMINATION: THE YELLOWSTONE PLUME’S INFLUENCE ON THE EVOLUTION OF WESTERN N. AMERICA

Delamination of the lower lithosphere can occur under different tectonic settings, sometimes leading to strong lateral strength heterogeneities. Here, we examine plume-induced lithosphere delamination associated with the Yellowstone plume. We propose that interaction between the Yellowstone plume and western North American lithosphere led to delamination of the lower lithosphere beneath the Columbia River Basalt (CRB). The excess melting that occurred when this ‘hole’ was being filled by Yellowstone plume material was the trigger for the CRB melting event. The lower lithosphere that was delaminated currently lies to the northeast of the CRB; it can be clearly identified in recent seismic tomographic models. We suggest that weak zones, either lithosphere-crossing faults or suture zones, or vertical weaknesses associated with hotspot tracks, have acted as lateral boundaries for delamination of the lower lithosphere. Numerical model results indicate that the stronger regions where a weak Mid-Lithospheric Discontinuity layer is absent also act as a barrier for delamination. Low stress ( 1MPa) and high strain rate at the Mid-Lithospheric Discontinuity promote delamination while higher stresses ( 100 MPa) in this region stop delamination.