Introduction to Special Issue of Bulletin of Volcanology on “Advances in Kimberlite Geology and Volcanology”

Abstract

The volcanology of kimberlite pipes and volcanoes has been a neglected area of mainstream volcanology research, until the last several years. Previously, published kimberlite research focused largely on petrological and geochemical aspects, with few studies on the physical eruption processes, the volcanic facies characteristics and their volcanological significance from the perspective of modern volcanology. To some extent this situation arose because of the constraints of confidentiality associated with the research, which was commonly controlled by major diamond mining and exploration companies in a very competitive industrial environment, as well as a lack of awareness of the opportunites for research amongst the volcanological community. The Canadian kimberlite fields, newly-discovered in the early 1990’s, featured diamondiferous pipes with a greater range of geometries and deposit types, including crater fill deposits, than occurred in the traditional southern African pipes. These deposits were diverse in componentry, texture, and origins and, more often than not, diamond grades varied greatly across the different lithofacies. The variations in diamond distributions within these deposits created an immediate need to develop a better understanding of the factors that control diamond grade distribution and variations in economic kimberlite pipe systems and provinces. Thus, several years ago, the diamond industry began to invite interest from parts of the academic volcanological research community to undertake research on the volcanological aspects of kimberlite volcanoes and pipes. Kimberlite pipes or bodies occur in geographic and age clusters, much like small intraplate basaltic monogenetic volcanic provinces and fields. From what we can tell many kimberlite bodies appear to have been monogenetic volcanoes, although there are also pipe complexes, which consist of coalesced, overlapping pipes, resulting from a succession of eruption events, although the temporal spacing of these is generally unclear. In general, however, each eruption phase appears to have been short-lived, much like many monogenetic volcanoes. Most kimberlite pipes that reached the Earth’s surface were largely explosive in their behaviour, although the Igwisi Hills complex in Tanzania is an exception because lavas have been found in parts of a preserved edifice (R.J. Brown, M.Field and R. S.J. Sparks, pers. comm.). There are few kimberlite bodies or pipes where surface deposits and the supracrustal volcanic edifice are preserved in situ and intact, for documentation and study as is commonly the case with Cenozoic volcanoes of other, more common magma suites. The youngest kimberlite has an age of 32.3 Ma. Thus, for most kimberlites, their volcanic edifices have been eroded. Exceptions include the Igwisi Hills complex in Tanzania, and the Fort a la Corne kimberlite field in Saskatchewan, Canada. For most kimberlite bodies, understanding of the eruption behaviour This paper constitutes part of a special issue: