New Mexico Geological Society Annual Spring Meeting — Abstracts

Groundwater salinity and ³He/⁴He anomalies (RA values between 0.3 and 0.5) reported in the Albuquerque Basin is a probable indication of complex mixing of mantle and crustal fluids. A suite of new noble gas and water samples were recently collected from Socorro and Sedillo Springs in the Socorro Basin as well as from the recently completed geothermal slim hole near the NMT campus to help determine the flux of mantle derived fluids. High CO₂ levels measured at the travertine depositing spring at Tierra Amarilla near San Yisidro on the Nacimiento fault provide further indication of mantle degassing. A series of east-west and north-south basin-scale, cross-sectional hydrologic models were constructed along the Rio Grande Rift in the Albuquerque and Socorro Basins to assess the relative importance of a faults as conduits for meteoric and deep endogenic fluids. The north-south cross sectional model was developed from geologic maps, well bore lithologic logs, as well as gravity and seismic-surveys. Separate east-west cross sectional models were developed for the sub-vertical normal faults and lystric faults in the Albuquerque Basin to quantify how differently CO₂ and helium transport responds in each fault system using the same hydrologic parameters. Groundwater salinity, temperature, ³He/⁴He, and ¹⁴C data provide the ground truth to calibrate these models. The cross-sectional models used in this study illustrate the importance of deeply penetrating, moderately permeable fault zones (10-14 to 10-16 m² ) in advective transport of groundwater and mantle volatiles to shallow crustal levels.