New Mexico Geological Society Annual Spring Meeting — Abstracts

Uranium dissolved in stream water of the Rio Ojo Caliente in southwestern Taos County and groundwater recharging from it approach or exceed the Federal and State drinking water standards. Nearly all domestic and public water wells in the area approach or exceed the NM drinking water standard of 30ppb. The source of uranium and other trace ions appears to be deep-sourced hot springs emanating from faults at the base of La Madera Mountains to the north in Rio Arriba County. These hot springs have been depositing travertine terraces over the past 100,000 years. Uranium concentrations in these travertine deposits approach 250ppm, comparable to the levels mined in the Hopi Buttes volcanic maar fields in northeastern Arizona. Solution weathering of the travertine releases uranium ions to the Rio Ojo Caliente which recharges ground water downstream in the Ojo Caliente area. Additional uranium and other elements are added to groundwater from the Ojo Caleinte Hot Springs, raising ion levels downstream to the south in Rio Arriba County.