Fig. 3
From: Seismic evidence for a mantle suture and implications for the origin of the Canadian Cordillera
Seismic velocity gradient and temperature contrast at the Cordillera–craton boundary. a Seismic velocity gradient at 150 km depth from an averaged Vp and Vs velocity model scaled using Vp/Vs ratios in the reference model36. The Cordillera–craton boundary in the upper mantle determined from P-wave and S-wave models are shown by the purple and blue lines, respectively. The shaded region highlights the spatial variation in the Cordillera–craton boundary location measured from this study and three recent tomographic models29,30,35 (Supplementary Fig. 5). The green arrows indicate the direction of the maximum velocity gradient near the transition boundary. Major faults are marked by the gray lines. b S-wave velocity-temperature (Vs-T) relationship at 150 km depth. The horizontal black lines show the respective average S velocities for the Cordillera and craton regions, with the corresponding standard deviations shaded in gray. The solid and dashed curves represent pyrolite (fertile) and dunite (depleted) compositions, respectively, in a dry (50 ppm H/Si; red) and wet (5000 ppm H/Si; blue) mantle. The yellow shaded regions show the variations of Vs-T curves for various frequencies (0.03–0.3 Hz) and grain sizes (0.03–3 cm)
