Canadian kimberlites: Geological characteristics relevant to emplacement

Abstract

In Canada more than 770 kimberlites have erupted in diverse tectonic settings over a period of 1000 Ma and over an area at least 5000 km across. The kimberlites represent at least 30 comagmatic fields. One pipe type dominates each of the different kimberlite fields. Even with the discovery of a significant number of new kimberlite fields, this review of recent data substantiates the previous proposal that there are at least three distinct classes of kimberlite pipes which show a correlation with the nature of the country rocks into which they were emplaced. New data show that a variation on the Prairies pipe type occurs when kimberlites were emplaced into competent Paleozoic sediments resulting in steeper-sided pipes infilled with similar pyroclastic kimberlite. New data for each pipe type are summarised and the contrasting characteristics of the three pipe types are considered to reflect fundamentally different styles of eruption and deposition. Apparently uniform, near-surface, olivine- and volatile-rich kimberlite magmas were modified differently during the contrasting emplacement processes resulting in distinct textural rock types, pyroclastic kimberlite (PK), tuffisitic kimberlite (TK) and associated hypabyssal kimberlite (HK) or resedimented kimberlite (RVK) dominating each type of pipe. The substantiated correlation of pipe type with country rock geology could indicate variable constraints on volatile exsolution which affected the nature of the magmatic eruptions in different settings.