Fluid events associated with gold, uranium, and REE deposits in the proterozoic of northern Saskatchewan, Canada

The Contact Lake lode gold deposit is situated in northern Saskatchewan within the Proterozoic La Ronge Domain of the Trans-Hudson Orogen ($\sim$1.9-1.7 Ga). The deposit is associated with a high angle, reverse shear zone, which crosscuts the central granitic and granodioritic phases of the composite Little Deer Lake pluton. Four temporally distinct stages of veining within the shear zone have been identified on the basis of mineralogical, textural and crosscutting relationships. The four discernable vein types (two devoid of gold and two containing gold mineralization) permit the detailed study of fluids responsible for gold mineralization versus barren fluids, which is critical to gold exploration. High grade gold mineralization is related to stage IV veins. The interaction between the auriferous stage IV vein fluid and the granitic and granodioritic phases of the pluton produced distinct alteration mineral assemblages. The Proterozoic Athabasca Basin in northern Saskatchewan, Canada, hosts several of the largest and richest uranium deposits in the world. The uranium deposits occur at the intersection between Hudsonian-age faults and the unconformity between Athabasca Group sandstones and Aphebian metasediments and Archean gneisses. Uranium mineralization formed at ca. 200°C from the mixing between the oxidizing, uranium bearing basinal brine and the reducing basement fluid which issued along the faults. High concentrations of REE-rich phosphates are associated with uranium mineralization in the Athabasca Basin. The relations among REE-rich minerals, diagenetic clays and uranium mineralization in the basin and basement rocks indicate extensive REE mobility during diagenesis of the Athabasca Basin. The REEs and U most likely were derived from detrital fluor-apatite and zircon in the sandstone, and garnets in the basement rocks. These relations indicate that REEs, and possibly the uranium, were transported as F-complexes. The three stages of ore formation and associated alteration minerals permit the detailed study of fluids responsible for uranium deposition and alteration, which is critical to understanding and refining the model for the genesis of unconformity-type uranium deposits. In addition, the high concentration of REEs associated with uranium mineralization may render these deposits viable sources of REEs in addition to uranium. (Abstract shortened by UMI.