Abstract

Dissolved helium and neon, the 3 He/ 4 He isotope ratio, and tritium concentrations were measured in samples collected from 107 lakes and ponds in central Labrador during 1975 and 1976. Excess 4 He values relative to solubility equilibrium, and tritium- 3 He residence times were used to calculate relative values of radiogenic 4 He flux into each lake as indicators of possible nearby uranium mineralization. The ratio of percent excess 4 He to tritium- 3 He residence time is called the helium prospecting index, I. Diagrams of I values are given for three areas. The area surrounding Walker Lake, which includes the Michelin deposit, and the Kitts-Post Hill area were sampled to test and extend the results of our previous survey in 1974. The agreement between these results and the 1974 results is reasonably good. The distribution of I values in the Moran Lake area, approximately 60 km west-southwest of the Michelin deposit, indicates four favorable zones. Comparison of the locations of these zones with known uranium mineralization is inconclusive at present because exploration in this area is much less extensive than in the other two areas. Dissolved uranium and radon were also measured in many of the lakes sampled for helium. Uranium concentrations are weakly correlated with I values; however, no correlation was observed between radon concentrations and I values.

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