Geothermal anomalies along the Rio Grande rift in New Mexico

Heat-flow data suggest that there are regions along the Rio Grande rift where crustal temperatures are above those in neighboring areas. Magma bodies at 15 to 30 km, as predicted by several investigators, seem to provide reasonable sources of heat that could increase heat-flow values from 1.8 to about 2.5 HFU and somewhat higher. However, heat-flow values of 6.0 to 16.0 HFU occur at four locations along the Rio Grande rift; these values occur within geologic environments such as recent volcanic centers and the intersections of cauldron boundaries with large normal faults where upward heat transport by magmatic and/or ground-water movement is plausible. Test drillings of several kilometres are necessary to confirm the continuity with depth of these very high geothermal gradients and to relate them to their possible sources in the upper crust. *Present address: Los Alamos Scientific Laboratory, University of California, P.O. Box 1663, Los Alamos, New Mexico 87545