Paper No. 13
Presentation Time: 4:35 PM


HANSON, Matthew Coombs, OZE, Christopher and HORTON, Travis, Geological Sciences, University of Canterbury, Christchurch, 8140, New Zealand,

Carbon dioxide flux is a widely applied tracer in geothermal and volcanic systems with elevated gaseous emissions at the surface. In an effort to explore the potential of this tracer in relatively low, diffused CO2 systems we completed a survey in the Ngatamariki geothermal field (Taupo Volcanic Zone, NZ). Our results show: (1) CO2 fluxes between 0.247 and 217 gCO2m-2day-1, (2) 10 cm depth temperatures ranging between 12.9 to 50.4 °C, and (3) δ13C of CO2 values of these gases have a range of -26 to -7.3 ‰. Of the 320 measurements 94% of the soil CO2 flux measurements fall below the previously established background of 90 gCO2m-2day-1 and 5.6% of the soil temperatures are greater than 30°C. No significant correlation between increasing soil temperature and CO2 flux is present. The greatest diffuse soil CO2 flux recorded in the Ngatamariki field is associated with an area of recent land disturbance rather than the active thermal features. By coupling δ13C of CO2 and CO2 concentration we were capable of indentifying both active thermal areas at Ngatamariki despite their low CO2 flux. Our findings demonstrate the importance of utilizing diffuse soil gas investigations and high spatial density δ13C of CO2 surveys to identify blind geothermal resource targets in low CO2 flux systems.