Argon 38 in Pitchblende Minerals and Nuclear Processes in Nature

The isotopic constitution of argon extracted from four pitchblende samples of different age and uranium concentration has been determined. The ${\mathrm{A}}^{36}$/${\mathrm{A}}^{38}$ ratio was found to vary by over three hundred percent with the greatest deviations from normal occurring in the ores with high uranium content. It is suggested that ${\mathrm{A}}^{38}$ has been produced in considerable quantities in these ores by nuclear reactions involving $\alpha$-particles and/or the spontaneous fission neutrons.