Analysis of the geological environment of kimberlite pipes in the Slave craton (Canada)

The purpose of the article is to identify diamond-bearing criteria through a comparative analysis of the spatial distribution of kimberlite pipes in the Slave Craton with varying diamond content based on characteristics such as the age and type of host rocks and the distance to iron formations. Main material. The article analyses the geological environment of kimberlite pipes in the Slave Craton with varying levels of diamond content. A qualitative comparison of the main kimberlite fields was carried out, which made it possible to identify the distinctive features of areas with industrial diamond deposits. A database of 196 pipes was created, which made it possible to conduct a quantitative statistical analysis of the relationships between diamond content and geological environment parameters. It was shown that all commercial deposits of the craton (Diavik, Ekati, Snap Lake, Gahcho Kue) are associated exclusively with the Neoarchean basement (2.8–2.5 billion years old), indicating the decisive role of Late Archean tectonic and magmatic events in the formation of conditions favorable for diamond crystallization. A distinct concentration of industrial diamond-bearing pipes has been identified within potassium granitoid fields, which is consistent with the potassium metasomatism model and the concept of «channelled degassing» in the Late Archean. It has been established that kimberlite pipes are absent at a distance of less than 20 km from the surface outcrops of iron formations, while the largest number of industrial pipes are concentrated at a distance of 100–146 km, which is consistent with the subduction model of diamond origin, according to which BIFs mark the upper edge of a steeply subducted oceanic plate, while diamond formation occurred near its lower part. Conclusions. The results obtained allow us to combine various hypotheses into a single geodynamic model, where the subduction of the oceanic crust at the end of the Neoarchean led to the release of potassium-enriched fluids, potassium metasomatism of the lithospheric mantle, the Earth’s crust, and the formation of diamonds. A comprehensive search criterion for industrial diamond deposits has been formulated, which includes a combination of the following parameters: 1) Neoarchean age of the continental basement, 2) presence of fields of potassium granitoids and potassium metasomatites, 3) location at a distance of ~100–140 km from the outcrops of iron formations on the surface. The application of this approach is important for optimizing diamond exploration and prospecting both within the Slave Craton and in other Precambrian cratons of the world, in particular for identifying potential diamond-bearing areas within the Ukrainian Shield.