Helium isotopic and rare gas measurements in the Dogger Aquifer of the Paris Basin have shown the helium concentration and helium isotopic ratio to be homogeneous to first order, with only slight differences in relation to specific chemical water types. Helium in The Dogger Aquifer contains an excess by a factor of 3 to 4 of helium-3 with respect to radiogenic production and accumulation from the natural decay of uranium and thorium series elements. Calculation of the cosmogenic production and accumulation of helium-3 cannot account for the observed excesses. The excess is attributed to a mantle derived helium magmatic components.
Calculations of the isotopic fluxes of helium out of the Dogger show that the helium residence time and the groundwater residence time in the Dogger Aquifer in 4000 years, with an uncertainty of a factor of 2. This is at least 10 times estimates derived from hydrologic models, and is more consistent with the geochemistry of the water.
Funding SchemeCSC - Cost-sharing contracts
CB2 1TN Cambridge