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Submarine giant pumice: a window into the shallow conduit dynamics of a recent silicic eruption

Citation

Mitchell, SJ and Houghton, BF and Carey, RJ and Manga, M and Fauria, KE and Jones, MR and Soule, SA and Conway, CE and Wei, Z and Giachetti, T, Submarine giant pumice: a window into the shallow conduit dynamics of a recent silicic eruption, Bulletin of Volcanology pp. 1-22. ISSN 0258-8900 (2019) [Refereed Article]

Copyright Statement

Copyright 2019 The Authors

DOI: doi:10.1007/s00445-019-1298-5

Abstract

Meter-scale vesicular blocks, termed "giant pumice," are characteristic primary products of many subaqueous silicic eruptions. The size of giant pumices allows us to describemeter-scale variations in textures and geochemistrywith implications for shearing processes, ascent dynamics, and thermal histories within submarine conduits prior to eruption. The submarine eruption of Havre volcano, Kermadec Arc, in 2012, produced at least 0.1 km3 of rhyolitic giant pumice from a single 900-m-deep vent, with blocks up to 10 m in size transported to at least 6 km from source. We sampled and analyzed 29 giant pumices from the 2012 Havre eruption. Geochemical analyses of whole rock and matrix glass show no evidence for geochemical heterogeneities in parental magma; any textural variations can be attributed to crystallization of phenocrysts andmicrolites, and degassing. Extensive growth of microlites occurred near conduit walls where magma was then mingled with ascending microlite-poor, low viscosity rhyolite. Meter- to micron-scale textural analyses of giant pumices identify diversity throughout an individual block and between the exteriors of individual blocks.We identify evidence for post-disruption vesicle growth during pumice ascent in the water column above the submarine vent. A 2D cumulative strain model with a flared, shallow conduit may explain observed vesicularity contrasts (elongate tube vesicles vs spherical vesicles). Low vesicle number densities in these pumices from this high-intensity silicic eruption demonstrate the effect of hydrostatic pressure above a deep submarine vent in suppressing rapid late-stage bubble nucleation and inhibiting explosive fragmentation in the shallow conduit.

Item Details

Item Type:Refereed Article
Keywords:giant pumice, submarine volcanism, banding, tube pumice, bubble deformation, conduit dynamics, submarine eruption, volcano, marine
Research Division:Earth Sciences
Research Group:Geology
Research Field:Volcanology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
UTAS Author:Carey, RJ (Dr Rebecca Carey)
ID Code:133036
Year Published:2019
Funding Support:Australian Research Council (DE150101190)
Deposited By:Earth Sciences
Deposited On:2019-06-04
Last Modified:2019-07-10
Downloads:0

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