Coherent kimberlite at Ekati, Northwest Territories, Canada: textural and geochemical variations and implications for emplacement

The term ‘coherent’ is used in a general non-genetic sense to describe kimberlite characterised by a crystalline groundmass and lacking readily discernable evidence of fragmentation. Coherent kimberlite has been encountered in three main geological settings worldwide: sheet intrusions (dykes and sills), root zone intrusions (irregular pipes) and high-level pipe fills (steep-sided pipes). The EKATI property in the Northwest Territories of Canada (Fig. 1) provides a unique opportunity to study coherent kimberlite from a range of emplacement settings. The majority of EKATI kimberlites are small pipe-like bodies filled dominantly by volcaniclastic kimberlite (VK), including mainly resedimented and lesser primary deposits, as described by Nowicki et al. (2004, 2008). Coherent kimberlite (CK) occurs as minor sheet intrusions, classified as hypabyssal kimberlite (HK), and as volumetrically significant high-level pipe fills, termed pipe-fill CK (pfCK). A recent study of the geochemical trends in a variety of volcaniclastic and coherent EKATI kimberlites (Nowicki et al., 2008) provides insight on the formation of these diverse bodies. Variations in bulk composition of selected kimberlites were found to correlate with the emplacement settings and textural character of analysed samples. In this contribution, we confirm, expand and build on this work.