New Mexico Geological Society Annual Spring Meeting — Abstracts

Heat flow data in the Albuquerque Basin and along La Ristra seismic line, which crosses New Mexico from NW to SE, show high values associated with the Rio Grande rift and the Jemez lineament. The data profile is interpreted to indicate a thermal source under the rift axis having a mid-step depth of ~ 65 km, coincident with the mid-depth of the lowest seismic velocity anomaly along La Ristra. The heat flow anomaly and recent volcanism show the low seismic velocity region at depth under the Rio Grande rift is caused both by increased temperature as well as partial melting.

A second thermal source is suggested at ~ 33 km depth, near the Moho. Along La Ristra profile a wedge of the Colorado Plateau lies between the Rio Grande rift and the Jemez Lineament, as indicated by lower heat flow values. Heat flow returns to intermediate values near the eastern boundary of the Rio Grande rift, suggesting a thermal regime somewhat similar to the Colorado Plateau. Seismic studies indicate slow seismic velocities extend across the southeastern flank of the rift (e.g. the northern Tularosa Basin). Perhaps ray paths, which traverse the southward broadening Rio Grande rift, influence the seismic analysis, or perhaps the deep seismic anomalies are too young to be recognized in near surface geothermal gradients. More recent heat flow data in the Albuquerque Basin indicates an axial thermal anomaly that significantly narrows north of ~ 35 o N. These data suggest mid and upper crustal heat sources associated with deeply penetrating faults and/or crustal intrusions.