New Mexico Geological Society Annual Spring Meeting — Abstracts

New Mexico is endowed with relatively high background heat flow and permeable, fractured bedrock. This combination has given rise to numerous low-temperature geothermal systems throughout the state. Conventional geothermometers consistently overestimate temperatures for moderate-to-low temperature geothermal systems. Determination of mineral saturation indices has been found to produce better estimates of known reservoir temperatures than the use of traditional geothermometers. However, there are few geothermal systems with known reservoir temperatures in New Mexico.

We attempted to determine which geothermometers are best at predicting known geothermal reservoir temperatures, as well as determining the likelihood of each geothermometer producing valid temperature estimates in areas with unknown reservoir temperatures. We applied both traditional geothermometers and the mineral-saturation approach to areas of known temperature. We also applied a statistical filtering process to both nonthermal and thermal datasets to weed out conventional geothermometers predicting unlikely temperatures.

No single geothermometer or suite of geothermometers could be considered highly reliable for predicting reservoir temperatures in New Mexico. Traditional geothermometers such as quartz, chalcedony, Na-K-Ca, and Na-K geothermometers work well for predicting high-temperature resources. The mineral speciation approach also worked well for predicting high reservoir temperatures. Though this method is more time-consuming it is useful when there is no agreement between traditional geothermometers. Our screening process determined that four traditional geothermometers are best suited for estimating low-to-moderate temperature resources: two chalcedony, one Na-K-Ca, and the K-Mg. It is also apparent that the mineral speciation approach works well with lower temperature systems. However, these lower temperature systems show less convergence and wider range of predicted temperatures. Our screening process identified several regions of known moderate-temperature geothermal resources (Lightning Dock, NMSU, Jemez Springs). We also identified several moderate-temperature systems that have not previously been identified with geothermometry (Montezuma Hot Springs, Hondo Hot Springs).