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|Title:||Exhumed conduit records magma ascent and drain-back during a Strombolian eruption at Tongariro volcano, New Zealand|
|Authors:||Wadsworth, Fabian B.|
Kennedy, Ben M.
Branney, Michael J.
von Aulock, Felix W.
|Publisher:||Springer-Verlag Berlin Heidelberg|
|Citation:||Bulletin of Volcanology, 2015, 77:71|
|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.|
|Rights:||Copyright © Springer-Verlag Berlin Heidelberg 2015. This version of this article is distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.|
|Appears in Collections:||Published Articles, Dept. of Geology|
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|Wadsworth et al.2015 Drainback.pdf||Post-review (final submitted author manuscript)||2.84 MB||Adobe PDF||View/Open|
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