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Exhumed conduit records magma ascent and drain-back during a Strombolian eruption at Tongariro volcano, New Zealand

Exhumed conduit records magma ascent and drain-back during a Strombolian eruption at Tongariro volcano, New Zealand
Exhumed conduit records magma ascent and drain-back during a Strombolian eruption at Tongariro volcano, New Zealand
Field evidence from a basaltic-andesite dyke preserved in the eroded wall of a scoria cone at Red Crater, Tongariro volcano, New Zealand, records a history of up-conduit magma flow during a Strombolian eruption, subsequent drain-back and final cessation of flow. The dyke intrudes pre-Strombolian andesite lavas, and the overlying proximal basaltic-andesite scoria deposits associated with contemporaneous lavas, which are, in turn overlain by laminated lapilli-tuff and large blocks. Textural and kinematic evidence of ductile shear recorded in basaltic andesite at the dyke margins records magma deformation imposed by bypassing movement of magma up the centre of the conduit during the eruption, whereas the basaltic andesite occupying the central part of the lowermost exposures of the dyke preserves ductile flow-folds with the opposite (down-flow) shear sense. The evidence indicates that the downward magma flow followed the eruption, and this draining left the central part of the dyke empty (unfilled) at uppermost levels. We discuss the kinematic constraints in the context of the criteria for up-flow of mafic magma and present the factors most likely to result in a final drain-back event. With reference to experimental and numerical work, we propose a draining model for the end of this eruption, and that magmatic drain-back may feature commonly during closing stages of Strombolian eruptions at mafic volcanoes. Drain-back which leaves large cavities in a volcanic edifice could result in hazardous structural instabilities.
Drain-back, Conduit processes, Basaltic-andesite, Kinematic indicators, Dyke emplacement, Magma flow
0258-8900
71
Wadsworth, Fabian B.
07feaf89-6ca5-4a44-a4e7-9356dae8c2a3
Kennedy, Ben M.
6308da42-a9fa-4f03-97bd-9ba994c7ac35
Branney, Michael J.
5261bd6b-5247-4aaf-bdd6-bfcb0a2bf094
von Aulock, Felix W.
b679f865-9860-492c-8fee-b158ba141040
Lavallée, Yan
12649f97-6369-4b78-86e2-fb2b70e2365c
Menendez, Amaya
378704ee-93ff-478f-ba13-83177846dd9c
Wadsworth, Fabian B.
07feaf89-6ca5-4a44-a4e7-9356dae8c2a3
Kennedy, Ben M.
6308da42-a9fa-4f03-97bd-9ba994c7ac35
Branney, Michael J.
5261bd6b-5247-4aaf-bdd6-bfcb0a2bf094
von Aulock, Felix W.
b679f865-9860-492c-8fee-b158ba141040
Lavallée, Yan
12649f97-6369-4b78-86e2-fb2b70e2365c
Menendez, Amaya
378704ee-93ff-478f-ba13-83177846dd9c

Wadsworth, Fabian B., Kennedy, Ben M., Branney, Michael J., von Aulock, Felix W., Lavallée, Yan and Menendez, Amaya (2015) Exhumed conduit records magma ascent and drain-back during a Strombolian eruption at Tongariro volcano, New Zealand. Bulletin of Volcanology, 77 (9), 71. (doi:10.1007/s00445-015-0962-7).

Record type: Article

Abstract

Field evidence from a basaltic-andesite dyke preserved in the eroded wall of a scoria cone at Red Crater, Tongariro volcano, New Zealand, records a history of up-conduit magma flow during a Strombolian eruption, subsequent drain-back and final cessation of flow. The dyke intrudes pre-Strombolian andesite lavas, and the overlying proximal basaltic-andesite scoria deposits associated with contemporaneous lavas, which are, in turn overlain by laminated lapilli-tuff and large blocks. Textural and kinematic evidence of ductile shear recorded in basaltic andesite at the dyke margins records magma deformation imposed by bypassing movement of magma up the centre of the conduit during the eruption, whereas the basaltic andesite occupying the central part of the lowermost exposures of the dyke preserves ductile flow-folds with the opposite (down-flow) shear sense. The evidence indicates that the downward magma flow followed the eruption, and this draining left the central part of the dyke empty (unfilled) at uppermost levels. We discuss the kinematic constraints in the context of the criteria for up-flow of mafic magma and present the factors most likely to result in a final drain-back event. With reference to experimental and numerical work, we propose a draining model for the end of this eruption, and that magmatic drain-back may feature commonly during closing stages of Strombolian eruptions at mafic volcanoes. Drain-back which leaves large cavities in a volcanic edifice could result in hazardous structural instabilities.

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More information

Published date: 2015
Keywords: Drain-back, Conduit processes, Basaltic-andesite, Kinematic indicators, Dyke emplacement, Magma flow
Organisations: Geochemistry

Identifiers

Local EPrints ID: 383927
URI: http://eprints.soton.ac.uk/id/eprint/383927
ISSN: 0258-8900
PURE UUID: f14e09da-d756-49db-be4a-48e38f647b9f

Catalogue record

Date deposited: 12 Nov 2015 09:50
Last modified: 15 Jul 2019 20:57

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