Structural and stratigraphic framework of gold mineralization at the Ulu gold deposit, High Lake Greenstone Belt, Nunavut, Canada

Abstract

The Ulu gold deposit is located within the relatively underexplored High Lake greenstone belt in the Archean Slave craton, Nunavut, Canada. The most significant mineralized zone, the Flood Zone, is characterized by brittle deformation, with brecciated wall-rock clasts replaced by quartz + arsenopyrite + K-feldspar, enveloped by a high-strain zone of biotite ± pyrrhotite and calc- silicate alteration assemblages. Its spatial association with ca. 2686 Ma high Fe-Ti tholeiitic volcanic rocks and an interpreted synvolcanic fault is similar to other gold systems in the northern Slave craton. The deposit is atypical compared to the generally accepted orogenic model, as mineralization appears to predate both peak deformation (D2) and peak amphibolite-facies metamorphism (D3). As a result, many of the primary alteration and deformation features have been significantly modified by these later processes. This thesis proposes a refined genetic model for the Flood Zone, suggesting that gold mineralization occurred during a pre-D2 early brittle event, and was subsequently overprinted by later deformation and metamorphism.