Geology and petrochemistry of the Kitts and Michelin uranium deposits and related prospects, central mineral belt, Labrador

The Kitts and Michelin uranium deposits and prospects related to these occur in a belt of Aphebian supracrustal rocks located in the Makkovik subprovince, southern sector of the Nain province of the Canadian Shield in Labrador. The supracrustal rocks were deposited on an Archean basement and are cut by Hudsonian intrusions. The Kitts deposit and associated prospects occur in a unit consisting mostly of basaltic pillow lavas. The deposits occur mainly as stratabound vein systems within both a volcaniclastic unit comprised of argillite, mafic tuff and greywacke and a unit comprised of metabasalt flows and tuffs. Calcium, with or without iron enrichment and oxidation of wall rocks, was associated with uranium deposition. The Michelin deposit consists of a series of stratiform tabular zones of disseminated pitcheblende mineralization within porphyritic rhyolite ash-flow tuffs. All uranium mineralization in the area was emplaced prior to the Hudsonian orogeny, though locally there is evidence for remobilization or recrystallization of some uranium during the later Grenville orogeny. It is proposed that the deposits formed by a diagenetic-hydrothermal mechanism involving the leaching of uranium from an enriched source rock by neutral to weakly alkaline, oxidizing groundwaters under low temperature conditions. Uranium was transported as uranyl carbonate and/or hydroxyl complexes at ppb level concentrations into structurally formed permeable zones in the Kitts-Post Hill belts, and along permeable unwelded felsic tuff layers in the Michelin belt. Precipitation of uranium was controlled by chemical reduction and/or sorption onto Fe-Ti-Mn oxides (Michelin) and possibly organic matter (Kitts) following destabilization of the uranyl complexes