Geothermal resources of southwestern New Mexico and southeastern Arizona
James C. Witcher
A geologic inventory of the discharge sites of convective geothermal systems points to a common geohydrologic setting. Tectonic and erosional stripping of Cenozoic and Mesozoic aquitards has exposed discharge windows which channel outflow of thermal water. Discharge occurs through windows of structurally high and permeable bedrock at low elevations on or near perennial drainage. Discharge is either at the surface or into near-surface aquifers. Low-relief horst blocks which intersect Laramide uplifts and mid-Tertiary cauldron ring-fracture zones are favorable sites. The geologic and physiographic setting of known systems strongly supports forced convection.
Conductive hydrothermal resources are found in late Tertiary basins which contain sediments of low thermal conductivity. As a consequence, temperature gradients between 35 and 45°C/km are typical even with background or regional heat fluxes.
Current uses of convective resources in the region include space heating and hot water for New Mexico State University and heat for more than 15 acres of greenhouses. Conductive resources are mostly subeconomic because of high costs and risks associated with deep wells.
- Witcher, James C., 1988, Geothermal resources of southwestern New Mexico and southeastern Arizona, in: Cretaceous and Laramide tectonic evolution of southwestern New Mexico, Mack, G. H.; Lawton, T. F.; Lucas, S. G., New Mexico Geological Society, Guidebook, 39th Field Conference, pp. 191-197.