The Yellowknife Greenstone Belt is host to several world class orogenic gold deposits that have produced over 13 million ounces of gold since 1938. One of the main challenges in the geology of orogenic gold systems is relating mineralization to specific events (e.g., intrusives or deformation stages) that can provide regional constraints on the structures most likely to be mineralized. The most direct way to relate mineralization to geologic events is through geochronology. However, mineralized veins consist of minerals that are very challenging to date (i.e., quartz, sulfides, gold) or whose relationship to gold mineralization is unclear.
In the Yellowknife Greenstone Belt, the one geochemical factor that seems to correlate with gold independently of host lithology is an enrichment in titanium. This relationship has been proposed to occur due to titanium minerals contributing directly to gold precipitation. The replacement of ilmenite with titanite or rutile frees Fe2+ which reacts with bisulfide to precipitate pyrite/arsenopyrite. Destabilization of gold bisulfide complexes through sulfide precipitation then causes gold precipitation. In this process, the age of titanite would correspond to the age of mineralization, providing a geochronometer for gold mineralization.
In this study, we will be conducting U-Pb dating of titanite crystals from the Crestaurum, South Belt and Sam Otto drill sites using the formation of titanite as a proxy for gold mineralization. The first steps in this study will be assessing the abundance and size of titanite. Uranium and lead concentration will be measured in situ using LA-ICP-MS with a preliminary focus on Sam Otto, as previous analyses indicate that titanite in this claim is uranium-rich.