La Bajada uranium-base-metal deposit, Santa Fe County, New Mexico
Virginia T. McLemore
The La Bajada (Lone Star) deposit is an unusual, low-temperature, uranium-base-metal vein deposit in Santa Fe County that formed during the Oligocene or Miocene. Haji-Vassiliou and Kerr (1972) proposed a two-stage process of formation after faulting and fracturing of the host rocks. During faulting, they suggest that petroleum derivatives migrated along the fault, possibly even forming an oil seep on the surface. Then, rising hydrothermal solutions carrying uranium and base metals moved through the fault and mixed with the older petroleum derivatives. Alternatively, the mineralization at the La Bajada may have formed by dewatering of rift basins. During the Miocene, meteoric waters within the Tertiary and older sediments of the rift evolved chemically as they became warmer with depth due to burial and/or basin compaction, by dissolving rock constituents to produce waters of varying salinities and metal concentrations. As the rift developed, favorable discharge zones such as the La Bajada fault allowed the mineralizing fluids to migrate up along fractures and faults. The organic material could have been deposited prior to or during deposition of the metals. Once the deposit was emplaced, oxidation, dissolution, and downward reprecipitation and enrichment of the deposit occurred as the groundwater level dropped in the area.
- McLemore, Virginia T., 1999, La Bajada uranium-base-metal deposit, Santa Fe County, New Mexico, in: Albuquerque Country, Pazzaglia, Frank J.; Lucas, S. G.; Austin, G. S., New Mexico Geological Society, Guidebook, 50th Field Conference, pp. 445-448.