How to fragment peralkaline rhyolites: Observations on pumice using combined multi-scale 2D and 3D imaging

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Hughes, E.C.; Neave, D.A.; Dobson, K.J.; Withers, P.J.; Edmonds, M.: How to fragment peralkaline rhyolites: Observations on pumice using combined multi-scale 2D and 3D imaging. In: Journal of Volcanology and Geothermal Research 336 (2017), S. 179-191. DOI: https://doi.org/10.1016/j.jvolgeores.2017.02.020

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To cite the version in the repository, please use this identifier: https://doi.org/10.15488/1654

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Abstract: 
Peralkaline rhyolites are volatile-rich magmas that typically erupt in continental rift settings. The high alkali and halogen content of these magmas results in viscosities two to three orders of magnitude lower than in calc-alkaline rhyolites. Unless extensive microlite crystallisation occurs, the calculated strain rates required for fragmentation are unrealistically high, yet peralkaline pumices from explosive eruptions of varying scales are commonly microlite-free. Here we present a combined 2D scanning electron microscopy and 3D X-ray microtomography study of peralkaline rhyolite vesicle textures designed to investigate fragmentation processes. Microlite-free peralkaline pumice textures from Pantelleria, Italy, strongly resemble those from calc-alkaline rhyolites on both macro and micro scales. These textures imply that the pumices fragmented in a brittle fashion and that their peralkaline chemistry had little direct effect on textural evolution during bubble nucleation and growth. We suggest that the observed pumice textures evolved in response to high decompression rates and that peralkaline rhyolite magmas can fragment when strain localisation and high bubble overpressures develop during rapid ascent.
License of this version: CC BY 4.0 Unported
Document Type: Article
Publishing status: publishedVersion
Issue Date: 2017
Appears in Collections:Naturwissenschaftliche Fakultät

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pos. country downloads
total perc.
1 image of flag of Germany Germany 113 72.44%
2 image of flag of United States United States 20 12.82%
3 image of flag of China China 10 6.41%
4 image of flag of Vietnam Vietnam 2 1.28%
5 image of flag of No geo information available No geo information available 2 1.28%
6 image of flag of Russian Federation Russian Federation 2 1.28%
7 image of flag of Taiwan Taiwan 1 0.64%
8 image of flag of Kenya Kenya 1 0.64%
9 image of flag of Hungary Hungary 1 0.64%
10 image of flag of Spain Spain 1 0.64%
    other countries 3 1.92%

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