The Drybones Bay and Mud Lake kimberlites are Ordovician kimberlites located in the Slave Geological Province. The Drybones Bay pipe formed by multiple discrete eruptions, producing several texturally distinct phases of kimberlite, including hypabyssal kimberlite (HK) autoliths, tuffisitic kimberlite (TK), pyroclastic kimberlite (PK) and resedimented volcaniclastic kimberlite (RVK). The recognition of TK suggests this pipe represents a Class 1 kimberlite. The nearby Mud Lake kimberlite is a dolomite-rich HK dyke characterized by macrocrystic and segregation textures. Although the kimberlites are proximal, U-Pb zircon dates indicate they were not emplaced contemporaneously, and geochemical discrepancies that cannot be explained by known magma evolution processes indicate that these rocks formed from distinct parental magmas. Mineralogical and geochemical data is used to evaluate crystallization conditions and diamond potential. New geochemical modeling of compatible trace elements reveals convincing evidence of magma evolution by olivine fractionation, adding substantially to the published research on kimberlite geochemistry. / October 2016