Formation of cratonic mantle keels by arc accretion: Evidence from S receiver functions

Delineating mantle interfaces can provide important clues for understanding the formation of continents. We use S-wave receiver functions to investigate lithospheric structure along a transect extending from Vancouver Island to Baffin Island. Observed Sp converted waves allow for interpretation of boundaries in the depth range expected for tectonic plates. Receiver functions show a distinct negative amplitude feature, interpreted as the lithosphere-asthenosphere boundary, at shallow depths beneath British Columbia (similar to 85km), deepening abruptly at the eastern edge of the Cordillera to similar to 260km beneath the Canadian Shield. Dipping mid-lithospheric discontinuities extend beneath several giant ca. 1.8 Ga epicontinental magmatic arcs, consistent with formation of cratonic lithosphere by arc accretion. This model provides a plausible explanation for global mid-lithospheric discontinuities within cratons and aids in understanding their formation. Citation: Miller, M. S., and D. W. Eaton (2010), Formation of cratonic mantle keels by arc accretion: Evidence from S receiver functions, Geophys. Res. Lett., 37, L18305, doi: 10.1029/2010GL044366.