REACTIVE MULTIPHASE BEHAVIOR OF CO2 IN SALINE AQUIFERS BENEATH THE COLORADO PLATEAU

摘要

Soil CO{sub 2} flux surveys have been conducted over known CO{sub 2} reservoirs at Farnham Dome, Utah, Crystal Geyser-Ten Mile Graben in Utah and Springerville-St. Johns, Arizona. No anomalous CO{sub 2} flux was detected at the Farnham Dome and Springerville-St. Johns. At Crystal Geyser-Ten Mile Graben, localized areas of anomalously high CO{sub 2} flux ({approx}100 g m{sup -2} day{sup -1}) occur along a fault zone near visibly degassing features. Isotopic measurements on CO{sub 2} collected from nearby springs indicate that it originated at depth. Evidence of widespread vein calcite at the surface (Farnham Dome) and travertine deposits at the other two areas suggests that discharge of CO{sub 2}-rich fluids has occurred in the past. Despite the lack of evidence for significant present day leakage of CO{sub 2} to the atmosphere at Springerville-St. Johns and Crystal Geyser-Ten Mile Graben, there are significant outflows of high-bicarbonate water in both areas suggesting continuous migration of CO{sub 2} in the aqueous phase from depth. The very localized nature of the CO{sub 2} flux anomalies, and the outflow of ground water containing dissolved CO{sub 2} present challenges for effective, long term monitoring of CO{sub 2} leakage.