New Mexico Geological Society Annual Spring Meeting — Abstracts

The Rio Grande runs through White Rock Canyon in North-Central New Mexico. White Rock Canyon is positioned on the East flank of the Jemez Mountains on the edge of Pajarito Plateau and exposes volcanic rocks related to both the Bandelier tuff eruptions and basalts of the Cerros del Rio volcanic field. Numerous springs emerge along the Rio Grande and along canyon tributaries. Previous workers examined spring water chemistry to inspect the possibility of environmental contamination from anthropogenic activities on the Pajarito Plateau. The purpose of this study was to resample springs and gases at selected sites to deduce likely groundwater flow paths based on geochemical parameters. This study is part of a regional examination of the extent of the Valles Caldera geothermal system and regional fault zones in influencing ground and surface water quality. We also compare results to previous studies. Samples were taken in March, 2015. The samples were analyzed for major ions, trace elements, and stable isotopes of water. In addition to the examination of this chemistry, gas chemistry will also be analyzed. Spring temperatures ranged from 11 to 20 degrees C. The pH ranged from 6.2 to 8.35 and total dissolved solids (TDS) are generally low (100-300 mg/L). Alkalinity ranges from a low of 80 ppm to a high of over 200 ppm as bicarbonate. The springs are uniformly higher in Br, F and silica concentration relative to the Rio Grande, although Li concentrations are similar. Sulfate concentrations are uniformly low in the spring waters relative to the Rio Grande. As gas and stable isotope data become available, multiple tracers can be applied to examine reasonable end-member mixing models to ascertain whether the waters mix with a geothermal component. Preliminary examination of major ion chemistry indicates that the waters are calcium-bicarbonate dominated and dominated by meteoric recharge.