Weeda Tiraei, BSc

The Kirkland Lake-Larder Lake Gold district is one of world’s largest gold (Au)-producing regions, with over 60 million ounces of historical production. The district is part of the Neoarchean Abitibi greenstone belt in northeastern Ontario and hosts a wide variety of Au deposits, including orogenic and intrusion-related systems. This part of the Abitibi consists of the Blake River assemblage (ca. 2704-2695 Ma), which consists of mafic-intermediate rocks and pillowed lavas/flow, and the Tisdale assemblage (ca. 2710-2704 Ma), which consists of mafic-ultramafic volcanic rocks and intermediate calc alkaline volcanic rocks. Deposited later are sedimentary and volcanic rocks of the Timiskaming group (ca. 2676-2670 Ma), which consists of fluvial polymictic sandstone and conglomerate interlaced with trachyte and intruded by a calcalkalic to alkalic intrusions of the same age. The Larder Lake-Cadillac Fault Zone transects the region and serves as a locus for hydrothermal fluid flow and ore deposition. It controlled the deposition of orogenic deposits in the area. The Tetrahedrite and Telegraph prospects are located between the Upper Canada (orogenic) and Upper Beaver (intrusion-related) deposits, and this study investigates if their formation is more akin to orogenic or intrusion-related deposits. Fieldwork included geological mapping and sampling (n=23) at Telegraph and Tetrahedrite. Petrography, scanning electron microscopy, and whole rock/trace geochemistry helped understand the relationships among sulfide minerals, deformation, alteration, and metal associations. Sulfide minerals at these prospects include galena, sphalerite, tetrahedrite, and chalcopyrite. Preliminary results show that sulfide mineralization is aligned with a foliation that is defined by sericite rather than overprinted by the foliation. Further work will be completed to identify the location and textures associated with gold mineralization. Determining the type of gold mineralization at Telegraph and Tetrahedrite will aid future exploration, because exploration strategies differ for orogenic and intrusion-related gold deposits. Exploration for orogenic gold deposits focuses on the host structures (i.e. fold hinges and shear zones), whereas exploration for intrusion-related gold deposits focuses on the host intrusions and their footprint.