New Mexico Geological Society Annual Spring Meeting — Abstracts

The Rincon geothermal system is located in the East Rincon Hills 56 km north of Las Cruces, at a topographic high dividing the Rio Grande and Jornada del Muerto basins. Rincon is a blind geothermal system that has no surface expression, and its exact size and extent are unknown. Temperatures are as high as 96 °C at 310 m depth on the hanging wall of an east-dipping normal fault known as the East Rincon Hills Fault (ERHF). Five thin (<1 m thick) opal beds have been mapped adjacent to the ERHF. An overturned temperature profile (from well-bore SLH-1) and the distribution of opal deposits indicate that the geothermal system has been active episodically for at least 2 Ma. We have completed two transient electromagnetic (TEM) transects that extend across the foot- and hanging-wall of the ERHF. An additional magnetotelluric (MT) survey is planned for the Fall of 2018. Formation resistivity maps based on 1D TEM inversions collected from our two transects have identified a laterally extensive conductive feature near the water table that may be associated with a geothermal outflow plume of hot, brackish water. We hypothesize that fault permeability increases following relatively low magnitude (< M 5) seismic events and then gradually declines due to silica mineralization. Future work will focus on integrating MT surveys into our study.