The origin of pelletal lapilli in explosive kimberlite eruptions
The origin of pelletal lapilli in explosive kimberlite eruptions
Kimberlites are volatile-rich magmas from mantle depths of ?150 km and are the primary source of diamonds. Kimberlite volcanism involves the formation of diverging pipes or diatremes, which are the locus of high-intensity explosive eruptions. A conspicuous and previously enigmatic feature of diatreme fills are ‘pelletal lapilli’—well-rounded clasts consisting of an inner ‘seed’ particle with a complex rim, thought to represent quenched juvenile melt. Here we show that these coincide with a transition from magmatic to pyroclastic behaviour, thus offering fundamental insights into eruption dynamics and constraints on vent conditions. We propose that pelletal lapilli are formed when fluid melts intrude into earlier volcaniclastic infill close to the diatreme root zone. Intensive degassing produces a gas jet in which locally scavenged particles are simultaneously fluidised and coated by a spray of low-viscosity melt. A similar origin may apply to pelletal lapilli in other alkaline volcanic rocks, including carbonatites, kamafugites and melilitites.
382
Gernon, Thomas M.
658041a0-fdd1-4516-85f4-98895a39235e
Brown, Richard J.
5b122e28-c030-4e74-8fef-9306680f92a6
Tait, Mark A.
757ee30b-0465-40af-86da-a46f4c4e8c5a
Hincks, Thea K.
9654038a-2f5c-40bc-8f0e-33afc0b1fb71
15 May 2012
Gernon, Thomas M.
658041a0-fdd1-4516-85f4-98895a39235e
Brown, Richard J.
5b122e28-c030-4e74-8fef-9306680f92a6
Tait, Mark A.
757ee30b-0465-40af-86da-a46f4c4e8c5a
Hincks, Thea K.
9654038a-2f5c-40bc-8f0e-33afc0b1fb71
Gernon, Thomas M., Brown, Richard J., Tait, Mark A. and Hincks, Thea K.
(2012)
The origin of pelletal lapilli in explosive kimberlite eruptions.
Nature Communications, 3, .
(doi:10.1038/ncomms1842).
Abstract
Kimberlites are volatile-rich magmas from mantle depths of ?150 km and are the primary source of diamonds. Kimberlite volcanism involves the formation of diverging pipes or diatremes, which are the locus of high-intensity explosive eruptions. A conspicuous and previously enigmatic feature of diatreme fills are ‘pelletal lapilli’—well-rounded clasts consisting of an inner ‘seed’ particle with a complex rim, thought to represent quenched juvenile melt. Here we show that these coincide with a transition from magmatic to pyroclastic behaviour, thus offering fundamental insights into eruption dynamics and constraints on vent conditions. We propose that pelletal lapilli are formed when fluid melts intrude into earlier volcaniclastic infill close to the diatreme root zone. Intensive degassing produces a gas jet in which locally scavenged particles are simultaneously fluidised and coated by a spray of low-viscosity melt. A similar origin may apply to pelletal lapilli in other alkaline volcanic rocks, including carbonatites, kamafugites and melilitites.
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Published date: 15 May 2012
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Geology & Geophysics
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Local EPrints ID: 338939
URI: http://eprints.soton.ac.uk/id/eprint/338939
PURE UUID: f21191bf-5691-471e-b616-f65b83cb6b7a
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Date deposited: 17 May 2012 16:21
Last modified: 15 Mar 2024 04:03
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Author:
Richard J. Brown
Author:
Mark A. Tait
Author:
Thea K. Hincks
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