A rare occurrence of a crater-filling clastogenic extrusive coherent kimberlite,Victor Northwest (Ontario,Canada) |
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| Authors: | Bram I van Straaten M G Kopylova J K Russell B H Scott Smith |
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| Institution: | (1) Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, BC, Canada, V6T 1Z4;(2) Scott-Smith Petrology Inc, 2555 Edgemont Blvd., North Vancouver, BC, Canada, V7R 2 M9 |
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| Abstract: | Kimberlite pipes can contain significant proportions of dark and dense kimberlite that have mostly been interpreted as intrusive
coherent (hypabyssal) in origin. This study reports a well-documented occurrence of a fresh intra-crater clastogenic extrusive
coherent kimberlite that is concluded to have formed as a result of lava fountaining. This paper focuses on a dark, dense,
competent, generally crystal-rich, massive kimberlite unit within the Victor Northwest kimberlite pipe (Ontario, Canada).
Using a comprehensive volcanological and petrographic analysis of all available drill cores, it is shown that this unit has
a fresh well-crystallised coherent groundmass and is extrusive and pyroclastic in origin. The proposed clastogenic coherent
extrusive origin is based on deposit morphology, gradational contacts to enveloping pyroclastic units, as well as the presence
of remnant pyroclast outlines and angular broken olivines. This paper, and an increasing number of other studies, suggest
that fragmental extrusive coherent kimberlite in intra-crater settings may be more common than previously thought. The emplacement
history and volcanology of these pipes need to be reconsidered based on the emerging importance of this particular kimberlite
facies. |
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