Global receiver function observations of the X-discontinuity reveal recycled basalt beneath hotspots

Abstract The distribution of chemical heterogeneity beneath hotspots provides important constraints on the source magmatism and mantle convection. Chemical heterogeneities in upper produce discontinuities that can be interrogated seismically. One such discontinuity, X-discontinuity (230-350 km depth), is observed intermittently across globe, with multiple possible causal mechanisms. However, to better understand cause its relationship upwellings, we require global short wavelength observations, previously unresolved by reflected phases broad Fresnel zones. Discontinuities resulting from seismically observable impedance contrasts targeted using high frequency P wave receiver functions (RFs) possessing lateral sensitivity (?100 km) structures almost directly station. Thus, below well-instrumented investigate properties constrain mechanisms these locations. Using P-to-s converted teleseismic between 30-90?, stack RFs depth time-slowness domains at 28 6 cratons globally. This reveals 15 robust observations 244-344 depth. A further 10 potential are present hotspots, null cratons. Two remain elevated temperatures expected hotspots. coesite-stishovite phase transition occurs eclogite and/or carbonated silicate melt may form under certain conditions. For either mechanism provide contrasts, must locally enriched basalt. Assessing a correlation Large Low Velocity Provinces, suggesting plumes entrain recycled basalt lowermost mantle.