What does it mean when the contract lab reports that the sample was fractionated?
First of all, the age, even though often calculated, is likely invalid. The term “fractionated” indicates that the sample has in some way degassed. This can happen if bubbles form during sampling. It can also happen naturally if gas bubbles form in the aquifer such as during denitrification or methanogenesis near the water table. One indication of fractionation is that Δ4He is smaller than ΔNe. The terms Δ4He and ΔNe are reported in the analysis and indicate the amount of helium and neon in the sample in excess of that in solubility equilibrium with air.
