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Geology of the Snap Lake kimberlite intrusion, Northwest Territories, Canada: field observations and their interpretation

Geology of the Snap Lake kimberlite intrusion, Northwest Territories, Canada: field observations and their interpretation
Geology of the Snap Lake kimberlite intrusion, Northwest Territories, Canada: field observations and their interpretation
The Cambrian (523 Ma) Snap Lake hypabyssal kimberlite intrusion, Northwest Territories, Canada, is a complex segmented diamond-bearing ore-body. Detailed geological investigations suggest that the kimberlite is a multi-phase intrusion with at least four magmatic lithofacies. In particular, olivine-rich (ORK) and olivine-poor (OPK) varieties of hypabyssal kimberlite have been identified. Key observations are that the olivine-rich lithofacies
has a strong tendency to be located where the intrusion is thickest and that there is a good correlation between intrusion thickness, olivine crystal size and crystal content. Heterogeneities in the lithofacies are attributed to variations in intrusion thickness and structural complexities. The geometry and distribution of lithofacies points to magmatic
co-intrusion, and flow segregation driven by fundamental rheological differences between the two phases. We envisage that the low-viscosity OPK magma acted as a lubricant for the highly viscous ORK magma. The presence
of such low-viscosity, crystal-poor magmas may explain how crystal-laden kimberlite magmas (>60 vol.%) are able to reach the surface during kimberlite eruptions. We also document the absence of crystal settling and the development of an unusual subvertical fabric of elongate olivine crystals, which are explained by rapid degassing-induced quench crystallization of the magmas during and after intrusion
0016-7649
1-16
Gernon, T.M.
658041a0-fdd1-4516-85f4-98895a39235e
Field, M.
8ecc8fff-737b-48f0-b333-98e230f1206e
Sparks, R.S.J.
68a691b3-ce7a-47fb-929d-c2392048ab60
Gernon, T.M.
658041a0-fdd1-4516-85f4-98895a39235e
Field, M.
8ecc8fff-737b-48f0-b333-98e230f1206e
Sparks, R.S.J.
68a691b3-ce7a-47fb-929d-c2392048ab60

Gernon, T.M., Field, M. and Sparks, R.S.J. (2012) Geology of the Snap Lake kimberlite intrusion, Northwest Territories, Canada: field observations and their interpretation. Journal of the Geological Society, 169 (1), 1-16. (doi:10.1144/0016-76492011-056).

Record type: Article

Abstract

The Cambrian (523 Ma) Snap Lake hypabyssal kimberlite intrusion, Northwest Territories, Canada, is a complex segmented diamond-bearing ore-body. Detailed geological investigations suggest that the kimberlite is a multi-phase intrusion with at least four magmatic lithofacies. In particular, olivine-rich (ORK) and olivine-poor (OPK) varieties of hypabyssal kimberlite have been identified. Key observations are that the olivine-rich lithofacies
has a strong tendency to be located where the intrusion is thickest and that there is a good correlation between intrusion thickness, olivine crystal size and crystal content. Heterogeneities in the lithofacies are attributed to variations in intrusion thickness and structural complexities. The geometry and distribution of lithofacies points to magmatic
co-intrusion, and flow segregation driven by fundamental rheological differences between the two phases. We envisage that the low-viscosity OPK magma acted as a lubricant for the highly viscous ORK magma. The presence
of such low-viscosity, crystal-poor magmas may explain how crystal-laden kimberlite magmas (>60 vol.%) are able to reach the surface during kimberlite eruptions. We also document the absence of crystal settling and the development of an unusual subvertical fabric of elongate olivine crystals, which are explained by rapid degassing-induced quench crystallization of the magmas during and after intrusion

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Published date: January 2012
Organisations: Geology & Geophysics

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Local EPrints ID: 334098
URI: http://eprints.soton.ac.uk/id/eprint/334098
ISSN: 0016-7649
PURE UUID: 9bc662e1-e4c0-4232-8f6c-8a2676834984
ORCID for T.M. Gernon: ORCID iD orcid.org/0000-0002-7717-2092

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Date deposited: 05 Mar 2012 16:25
Last modified: 15 Mar 2024 03:36

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Contributors

Author: T.M. Gernon ORCID iD
Author: M. Field
Author: R.S.J. Sparks

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