Structural studies on the uranium deposit of the Fay Mine, Eldorado, northwest Saskatchewan

The Fay Mine uranium deposit is composed of veins parallel to the foliation of the paragneisses and paraschists of the Fay Mine Complex, which in turn overlies the Donaldson Lake Gneiss and Foot Bay Gneiss, within the Tazin Group of the Beaverlodge District, northern Saskatchewan. A computer oriented study of 5500 strike-dip measurements of planar features within the Fay Mine reveals that the lowest member of the metamorphic sequence, the Foot Bay Gneiss, is unique in that it exhibits Kenoran (?) structures associated with F1, NW-SE or N-S trending folds. Subsequent to the Kenoran (?) folding, an Aphebian (?) sequence of sediments and volcanics, now represented by the Donaldson Lake Gneiss and the Fay Mine Complex, was deposited. NE-SW trending, Hudsonian, F2 folds then developed and extensive cataclasis was effected. The F2 structures also affected the uppermost, taphrogeosynclinal Martin Formation sediments and volcanics. The major faults of the district are thought to have been initiated either as F2-shear joints or F2-tension fractures and have undergone multiple movement over a long period of time. The pitchblende ± quartz ± carbonates ± hematite ± chlorite veins, classified as 'mobilized stratabound deposits', occur parallel to S2 foliation planes in the crests, troughs, or limbs of F2 folds, wherever minimal plunge is observed. Such deposits may have been generated during regional metamorphism by mobilization of uranium-rich fractions from the originally uraniferous Aphebian precursors of the Fay Mine Complex. Later movement of such major structures as the St. Louis Fault has apparently caused only local deformation and brecciation of the uraniferous veins and has caused no more than limited recrystallization.