This project investigates the novel hypothesis that the Quaternary travertines and CO2-rich springs of the western US are a consequence of the interplay between tectonic activity (magmatism and seismicity) and hydrology. Previous work has shown that travertine-depositing cool springs and hydrothermal springs of the western U.S. have 3He/4He ratios indicative of mantle out-gassing and hence are surface manifestations of mantle inputs. Deeply-sourced fluids include high salt contents and deleterious trace elements such as arsenic and uranium, and may naturally mix into aquifer systems on the Colorado Plateau and the Rio Grande Rift. Observation of the geochemistry of water and gas from active springs, combined with groundwater modeling, will assist in understanding the connections between deep-sourced and shallow-sourced hydrologic inputs. We will examine water and gases in the Colorado Plateau and surrounding tectonic provinces to; 1) evaluate endogenic hydrologic end members that may correspond to heterogeneity in mantle inputs and proximity to young basaltic volcanism; 2) quantify mixing parameters between deeply-sourced and shallow-sourced groundwaters via hydrologic modeling; 3) conduct neotectonic studies on Quaternary faults, travertines, travertine-depositing springs, and CO2 fields to establish the link between tectonism and water quality. We are using natural geochemical tracers (major and trace elements in water including Sr, Cl/Br, As, and stable isotopes of C, H and O) integrated with gas chemistry (3He/4He, CO2, % He, N2/He, N2/CO2, CO2/3He). The spatial scale of the proposed study is from local to regional; the temporal scale ranges from modern to the late Neogene geologic record of CO2 outgassing encoded in travertine deposits. This project includes education and outreach effort at the graduate and undergraduate levels, an integration of research and teaching, informal public education through the Trail of Time project at Grand Canyon, and involvement of minority populations, including Native American. We are working closely with the National Park Service and with various Native American tribes (Hualapai, Havasupai, and Navajo) whose waters are directly impacted by deeply sourced contaminants.
