New Mexico Geological Society Annual Spring Meeting — Abstracts

The Rincon geothermal system is one of the highest temperature geothermal systems in New Mexico with a water table temperature of 81 ^oC. This hydrothermal system is located in the within the discharge area of the Jornada del Muerto proximal to the Rio Grande. It is a blind system, having no surface expression other than opal deposits. Rincon was discovered with the use of shallow thermal wells, self-potential surveys, and radon soil-gas surveys, all of which had anomalies relating to a geothermal system. A geothermal exploration borehole (SLH-1) was drilled in 1993 to a depth of 371 m and a bottom hole temperature of 99 ^oC . Its temperature-depth profile did not display typical linear characteristics of stead-state geothermal systems; instead, it had higher temperatures at shallower depths, which suggested a short-term high flow rate transient system.

We remeasured temperature in SLH-1 in Sept. 2018 and found the temperature fully equilibrated from lost drilling fluid, but otherwise unchanged in the intervening 25 years. We hypothesize that the temperature overturn in SLH-1 is due to three-dimensional flow effects related to the interaction of the geothermal upflow zone and the regional flow field. We have built a three-dimensional groundwater flow and heat transport model of the Rincon upflow zone to test our hypothesis. We also completed three transects of transient electromagnetics (TEM), which provide vertical profiles of formation resistivity up to 500 m depth. The TEM surveys reveal a zone of high formation electrical conductivity at the water table that correspond to the geothermal system.