U-PB GEOCHRONOLY OF URANINITE FROM THE SAGAR PROPERTY, LABRADOR TROUGH, NORTHERN QUEBEC

The Sagar property, located within the Romanet Horst in the central part of the Labrador Trough, northern Quebec, Canada is host to a number of mineral showings. Although numerous companies have explored the Sagar property, the geochemistry, geochronology, and genetic history of mineralization is poorly understood. Kish and Cuney (1981) determined an approximate age of 1800 Ma for uraninite deposition on three mineralized samples from the B and Kish showings, and the mineralized erratic boulder field of the Sagar property. The location of the boulder field was determined to be up-ice from the uranium-rich showings.

Here we use secondary ion mass spectrometry (SIMS) to date uraninite from outcrop at the Eagle and Kish showings, and the boulder field, Sagar property. A similar age for uraninite from the boulder field and the showings would suggest that the source of the erratic boulders is the uraniferous showings.

Based on U–Pb ages, the crystallization age of the uraninite from the boulder field and uranium showings is the same (1735 ± 21 Ma). When plotted on a Concordia diagram, all 31 data points are observed to be highly discordant (>5%). Uraninite from the Eagle showing shows the smallest Pb loss and uraninite from Boulder field shows the largest Pb loss.

The age that we obtained using SIMS (1735 ± 21 Ma) is similar to the age obtained by Kish and Cuney (1981). This minimum age of crystallization (1735 Ma) corresponds to the Hudsonian orogeny and suggest that the source of the uraniferous boulders are the Kish and Eagle showings.