The Albuquerque basin, a part of the central Rio Grande rift, is host to a complex fault network that influences deep and shallow fluid migration. This study examines CO2 flux along these faults at the northern and western borders with the Valles caldera and San Juan basin, using a CO2 flux device with an accumulation chamber (PP-Systems). These major and minor Quaternary faults have damage zones that can influence CO2 degassing, hydrocarbon migration, and groundwater flow and mixing, including geothermal waters related to the Valles caldera geothermal system, ultimately acting as conduits or barriers to fluid flow. Rift systems are known to emit significant amounts of CO2 to the atmosphere, and the location of the central Rio Grande rift accompanied by a relatively recent caldera eruption and the Jemez Volcanic Lineament make this area a field laboratory for examining links between the mantle and surface. To test these hypotheses, 8 sites were targeted, the first 6 of which have springs located along faults: 1) The Valles caldera geothermal system at Sulphur Springs, 2) CO2 rich springs in the caldera at Alamo Canyon, 3) The Soda Dam area of the Valles geothermal outflow plume, 4) Travertine springs of Penasco Springs on the Nacimiento fault, 5) Travertine springs at San Ysidro on the Nacimiento fault, and 6) Travertine springs at Carrizo Arroyo on western rift bounding faults in the area of the Socorro magma body. Two cemented fault zone sites were also targeted: 7) Four faults at the Santa Ana Fault network on the Zia Pueblo and 8) the carbonate cemented Sand Hill fault. There were over 600 CO2 flux measurements taken, in units of grams of CO2 per square meter per day (gCO2/m2d). Collectively, these sites provide a set of transects that allows comparison of CO2 flux from springs and faults north (Alamo Canyon) to south (Carrizo Arroyo) with increasing distance away from the Valles caldera (~ 135 km). Cumulative probability plots were utilized to classify CO2 flux in terms of local background, diffuse, and high point source fluxes (HPSF) at each site. Local background at each site ranges from 0.7 -- 4.0 gCO2/m2d (Alamo Canyon), 0.2 -- 2.8 gCO2/m2d (Soda Dam), 0.0 -- 2.5 gCO2/m2d (Penasco Springs), 0.0 -- 1.3 gCO2/m2d (San Ysidro), 0.0 -- 1.7 gCO2/m2d (Zia Pueblo), 0.0 -- 1.1 gCO2/m2d (Sand Hill Fault), and 0.0 -- 1.0 gCO2/m2d (Carrizo Arroyo). Background at Sulphur Springs was uniformly high, possibly the results of an enhanced fault damage zone coupled with an active geothermal system that influences the entire area where measurements were taken. Above background CO2 fluxes are observed in areas around fault zones and are termed diffuse. These moderate CO2 fluxes may be the result of multiple processes surrounding fluid migration and the degassing of CO2 on the surface. A considerable number of these moderate fluxes were measured at most sites except for the carbonate cemented faults at the Zia Pueblo, where one measurement is attributed to a diffuse flux on a silica cemented fault (9.6 gCO2/m2d). Diffuse CO2 flux at each site ranged from 15.5 -- 1,778 gCO2/m2d (Alamo Canyon), 8.6 -- 60.3 gCO2/m2d (Sulphur Springs), 2.8 -- 32.4 gCO2/m2d (Soda Dam), 4.0 -- 13.2 gCO2/m2d (Penasco Springs), 1.3 -- 5.1 gCO2/m2d (San Ysidro), 1.7 -- 9.6 gCO2/m2d (Zia Pueblo), 2.5 -- 7.7 gCO2/m2d (Sand Hill Fault), and 2.5 -- 11.3 gCO2/m2d (Carrizo Arroyo). Relatively high diffuse fluxes measured at most sites attests to fault damage zones providing pathways for volatiles, whereas low or background fluxes measured along faults may indicate barriers to fluid flow. High CO2 fluxes (HPSF) are attributed to the migration of fluids along fault damage zones where the degassing of CO2 occurs directly over the fault or at the intersection of multiple faults. The HPSF are most likely a combination of three types of fluxes (background, diffuse, and HPSF) with a more significant CO2 flux from deeper and/or distal sources. These are typically measured at carbonic springs, but HPSF were also measured on dry surfaces at Sulphur Springs, Soda Dam, Penasco Springs, and San Ysidro. HPSF range from 1,778 - 144, 239 gCO2/m2d (Alamo Canyon), 302 -- 170,122 gCO2/m2d (Sulphur Springs), 200 -- 9,675 gCO2/m2d (Soda Dam), 13.2 -- 2,400 (Penasco Springs), and 42.7 -- 149,322 gCO2/m2d (San Ysidro). No HPSF were measured at Zia Pueblo, Sand Hill fault, or Carrizo Arroyo. The Zia Pueblo site hosts tight carbonate and silica cemented faults that block CO2 degassing on the surface. Sand Hill fault and Carrizo Arroyo may not have any HPSF, however, large amounts of diffuse flux attest to permeability along the fault zones. CO2 flux measurements were conducted across various geologic areas and environments over relatively wide distances. The total annual CO2 flux (in tons/year) for each site was calculated based on fault damage zone areas and distal damage zone areas. The total annual CO2 flux from two areas at the Valles caldera (Alamo Canyon and Sulphur Springs) were calculated to be 9.1x105 t/y (total area of evaluation ~ 3.15x105 m2), at 4 areas in the Albuquerque basin (PS, SY, SHF, and CA) to be 5.4x105 t/y (total area of evaluation ~ 9.1x105 m2), and at 1 area in between these two locations (Soda Dam) to be 1,856 t/y (total area of evaluation ~ 3.2x104 m2). When compared to other geothermal and magmatic sites such as Yellowstone and the East African rift, the Valles caldera and Albuquerque basin faults provide pathways for significant amounts of CO2 degassing from the solid Earth. Gas analyses (3He/4He ratios, carbon isotopes, and whole gas analyses) show there are components of CO2 from a magmatic source (i.e. endogenic). It is clear that the initiation of major extension along the Rio Grande rift and the eruption of volcanoes along the Jemez Volcanic Lineament contribute significantly to the CO2 that is degassing along structures at the Albuquerque basin and Valles caldera, and have been a significant source of CO2 to the atmosphere over millions of years.
Earth and Planetary Sciences
Level of Degree
Department of Earth and Planetary Sciences
First Committee Member (Chair)
CO2 Flux, Fluid Flow, Fault Networks, Fault Cement, Rio Grande Rift, Albuquerque Basin
Smith, Jared. "CO2 Flux Along Faults of the Central Rio Grande Rift, New Mexico." (2016). https://digitalrepository.unm.edu/eps_etds/108