A tomographic glimpse of the upper mantle source of magmas of the Jemez lineament, New Mexico

In this study, the lateral variations of the P wave velocity as a function of depth were examined for the regions of the Rio Grande rift and the Jemez lineament, to infer spatial distributions of partial melt in the upper mantle source zones for the rift and the lineament. The method involved measurements of teleismic P wave delays at a 22-station network followed by performing a damped least-squares three-dimensional inversion for these lateral variations. Results indicate that, directly beneath the Jemez lineament (but not beneath the Rio Grande rift), there is a 100-km-wide 1-2-percent low-P-wave-velocity feature in the depth range of 50-160 km. This implies that the volcanic potential of the Jemez lineaments continues to greatly exceed that of the Rio Grande rift.